Why do people switch from TPI to carb?
12-09-2002, 05:50 PM
#1
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Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
Why do people switch from TPI to carb?
Unless we're talking drag strip only, I don't see any sense in it. I'm not very educated on the subject, so I thought I'd find out.
I personally HATE carbs. Probably has to do with the fact that I was a diesel mech in the army and running codes to diagnosis problems is just part of what we did.
I am not currently planning to get rid of my L69, it's a blast, but I am seriously considering buying an IROC with an L98.
I personally HATE carbs. Probably has to do with the fact that I was a diesel mech in the army and running codes to diagnosis problems is just part of what we did.
I am not currently planning to get rid of my L69, it's a blast, but I am seriously considering buying an IROC with an L98.
12-09-2002, 06:01 PM
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Car: 86 Iroc-Z28
Engine: FB385
Transmission: 700r4
A lot do it b/c they claim it is easier to work with and cheaper too. Cheaper, probally, easier, only if you don't want to learn. I was going to do it b/c i did not have the cash at the time i got my crate motor to switch it over to a quality fi set up. Not too many other reasons come to mind when this question is asked! Anyone else?
12-09-2002, 06:29 PM
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One reason I have avoided TPI, ever since I first met it in 85, is because it's so anti-performance... it has a brick wall that you run into beyond which the system as designed simply can go no farther. I'm not talking about FI in general, but rather TPI specifically.
If GM had got wise to its issues a few years earlier, and put something more like the LT1 together sooner, we wouldn't be worrying about how a 400 HP motor struggles to produce 300 HP when you stick TPI on it.
My first experience with it was when, shortly after I bought my L69 car in 85, 2 of my friends were so impressed that they immediately went out and bought Vettes. One with the 4+3, one auto. Both of them got rid of those within 2 years. The guy with the stick car went through several MAFs, an ECM or 2, etc. etc.; seems like every time I visited it was either in limp-home mode or at the dealer. The auto one was slower than my HO car, and the guy was the stereotypical Vette owner who had never had a fast car before and thought that the Vette was some kind of lofty deity on a pedestal to be worshipped by mere commoners like me with F-bodies, and it was really a let-down for him to get spanked by a 305. He didn't take it well at all... he was really kind of a rectum anyway. I don't think either one of them kept their car for 2 years before they ditched them.
I will continue to avoid TPI, continue learn about fuel injection on better platforms, and wait for a better opportunity to buy into the technology.
If GM had got wise to its issues a few years earlier, and put something more like the LT1 together sooner, we wouldn't be worrying about how a 400 HP motor struggles to produce 300 HP when you stick TPI on it.
My first experience with it was when, shortly after I bought my L69 car in 85, 2 of my friends were so impressed that they immediately went out and bought Vettes. One with the 4+3, one auto. Both of them got rid of those within 2 years. The guy with the stick car went through several MAFs, an ECM or 2, etc. etc.; seems like every time I visited it was either in limp-home mode or at the dealer. The auto one was slower than my HO car, and the guy was the stereotypical Vette owner who had never had a fast car before and thought that the Vette was some kind of lofty deity on a pedestal to be worshipped by mere commoners like me with F-bodies, and it was really a let-down for him to get spanked by a 305. He didn't take it well at all... he was really kind of a rectum anyway. I don't think either one of them kept their car for 2 years before they ditched them.
I will continue to avoid TPI, continue learn about fuel injection on better platforms, and wait for a better opportunity to buy into the technology.
12-09-2002, 06:44 PM
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Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
I'm not talking about a platform to produce 400 horsepower. I'm talking for a car with decent low end power, easily driven and so on........daily driver performance car type of thing.
While we're on the subject though, which FI system would you chose?
While we're on the subject though, which FI system would you chose?
12-09-2002, 07:47 PM
#6
Well daily driven street performance can see 6000 rpm ecspecially getting on the highway and what not. And if you keep the same power band the L98 cam runs in it is hard to get a whole lot more power out of it without a power adder. Even the mild 269HR cam I am running likes to pull past 5500. I've seen a power curve showing a straight swap on a motor with a cam similiar to mine from a stock TPI to some aftermarket EFI that looked simmiliar to the LT1 style and it looked like two totally different motors. The stock TPI started the downhill climb at 4500 while the aftermarket EFI peaked at 5500 way up from the TPI one and started falling.
They make larger runners and larger intake ports to replace the stock pieces but that alone is approaching 600 or 700 bucks. Then you have the throttle body also and the price of 8 injectors if you want to upgrade them.
I know it's fun the learn to work with the computer and all the various sensors, but for a daily driver the carb has been a lot less of a head ache for me. Just set the timing on the HEI right and make sure you are running the right jets or rods (depending on carb) and your rolling.
If I had the money for EFI I would go with one of those holley systems in Jegs of Summit like the stealth ram. But that's a lot of money.
They make larger runners and larger intake ports to replace the stock pieces but that alone is approaching 600 or 700 bucks. Then you have the throttle body also and the price of 8 injectors if you want to upgrade them.
I know it's fun the learn to work with the computer and all the various sensors, but for a daily driver the carb has been a lot less of a head ache for me. Just set the timing on the HEI right and make sure you are running the right jets or rods (depending on carb) and your rolling.
If I had the money for EFI I would go with one of those holley systems in Jegs of Summit like the stealth ram. But that's a lot of money.
12-09-2002, 07:50 PM
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Car: 4
Engine: 6
Transmission: 5
I've had pretty good results with the Accel Pro Ram... I'd like to try the MinRam or the Holley Stealth Ram (seems to be alot of "ramming" going on these days, must be the latest buzzword), esp the Holley, that was a kind of cool carb setup back before they put the injector bungs in it. We used to be able to get a pretty competitive-running street rod out of it, sometimes seemed like maybe even better than a single 4-barrel. It has fairly small straight runners, very short, good flow but also good velocity, and the flow is aimed straight at the intake valve, not sideways and almost horizontal like TPI.
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12-09-2002, 07:53 PM
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Car: 1991 Z-28
Engine: 350
Transmission: T-5 (gonna buy the farm)
I would choose a Miniram, or the Holley Stealth Ram. I haven't heard to much on the Ram Jet GM has, but if it is workable, I would take that just for the cool factor.
12-09-2002, 08:07 PM
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Car: T/A / Grand Am
Engine: 383 SBC
Transmission: glide
Axle/Gears: 9" ford 5.67
I was going carb when I built my GTA. A buddy talked me out of it, said tpi was the only way to go for the street. NOT, My car fell flat on its face at 5000 rpm. 9.45s in the 1/8 with a 1.9 60 ft with street tires. That's with a lot of grinding on the plenum and manifold. With the stealth ram, no other changes, 8.86 and 1.9 60 ft. at 83mph. With some chip changes it'll go faster. It don't fall flat at 5000 anymore. Runs out of cam now at 58/5900. I think it's even better on the street.
12-09-2002, 08:57 PM
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Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
I keep running into trouble with my carb setup like fuel evaporation when warm (starting difficult b/c of lack of fuel..done lots of stuff to try and resolve it with only some results), choke always doing something wrong (will be switching to manual soon), and quite frankly I'm a little intimidated by them.....too many small parts!
I had considered making a swap, but decided against it b/c I am at least playing with known factors here.
While my car pulls very well above 3500 rpm (I rarely go past 5500) below 2500 it is pathetic!
Keep 'em coming though, I'm learning a lot.
I had considered making a swap, but decided against it b/c I am at least playing with known factors here.
While my car pulls very well above 3500 rpm (I rarely go past 5500) below 2500 it is pathetic!
Keep 'em coming though, I'm learning a lot.
12-09-2002, 09:25 PM
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I put a carb on my 66 Ferd in 1991, and its been there since. I had an ignition problem, solved with a hotter spark, and the fuel composition changes here more than I change socks, so I had to rejet a few times. Other than that, its been totally reliable, and smacks my TA upside the head when it comes to fuel mileage. And its alot faster too. I've been down the TPI troubleshooting road enough times that I usually know whats wrong just by the way it runs. So far only my newest one hasnt had any electrical problems related to the computer control, but thats just a matter of time. Not to mention what RB said about the wall, it is there and its difficult to work around. I can totally understand why people would want to swap.
12-10-2002, 08:57 AM
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Car: 1999 Pontiac T/A Firehawk
Engine: ***'s Engine
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It's a combination of simplicity and adjustability, That, and my carb will pull to 6500.
If something isn't running right with the carb, you stick your head under the hood a twist a screw that way or tweak a setting this way. Even if it wasn't the right thing to do, you'll at least get a response. Practically EVERY thing on a carb is adjustable if you know what you're doing.
In order to have the same adjustability with Fuel Injection, you MUST run either an aftermarket Fuel Injection setup that can be tweaked in real time with a lap top (big $$$), or get the equipment and learn how to burn PROMs. And doing the chip burning route requires a LOT more time and effort than fiddling with a carb (though I am willing to concede that the end result will probably be better).
Carbs are simple and stupid. Even on Qjets, which a lot of people complain are difficult to work on, I can can change primary jets and rods in 30 minutes. How long does it take to change injectors and burn a PROM? I also only need a small handfull of tools to do the job quickly and easily, and in a pinch it could be done with nothing more than a single flat bladed screw driver (though it would probably take twice as long
)
What carbs DON'T do is adjust for changes in operating condition automatically. In most cases YOU must stick your head under the hood and fix it. If you like twiddling with your car, that's unlikely to be a problem. If you just want to drive it... well...
As an aside, I agree with RB... I don't hate fuel injection at all. However, I have a serious dislike for TPI in stock form... so much so that I sold the TPI setup off my 91 as fast as I could get it off the motor. It'll be staying fuel injected, though, and I plan to use the newest SuperCallaFragilisticRam
when I start getting the motor together.
If something isn't running right with the carb, you stick your head under the hood a twist a screw that way or tweak a setting this way. Even if it wasn't the right thing to do, you'll at least get a response. Practically EVERY thing on a carb is adjustable if you know what you're doing.
In order to have the same adjustability with Fuel Injection, you MUST run either an aftermarket Fuel Injection setup that can be tweaked in real time with a lap top (big $$$), or get the equipment and learn how to burn PROMs. And doing the chip burning route requires a LOT more time and effort than fiddling with a carb (though I am willing to concede that the end result will probably be better).
Carbs are simple and stupid. Even on Qjets, which a lot of people complain are difficult to work on, I can can change primary jets and rods in 30 minutes. How long does it take to change injectors and burn a PROM? I also only need a small handfull of tools to do the job quickly and easily, and in a pinch it could be done with nothing more than a single flat bladed screw driver (though it would probably take twice as long
)What carbs DON'T do is adjust for changes in operating condition automatically. In most cases YOU must stick your head under the hood and fix it. If you like twiddling with your car, that's unlikely to be a problem. If you just want to drive it... well...
As an aside, I agree with RB... I don't hate fuel injection at all. However, I have a serious dislike for TPI in stock form... so much so that I sold the TPI setup off my 91 as fast as I could get it off the motor. It'll be staying fuel injected, though, and I plan to use the newest SuperCallaFragilisticRam
when I start getting the motor together.
12-10-2002, 02:11 PM
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Car: 1991 RS
Engine: 305 TBI
Transmission: T5
Well, if you live in California, you know how much emissions laws can kill you. As much as I want a carb, I have to stay TPI because of these laws. I'm lookin to drop a 350 with close to 380HP into my 1991. TPI of course, I have no choice. I wish I lived in the boondocks like some of y'all, so I can burn fumes with a carb. Until then, I'll just wait for my 350 crate TPI setup.
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12-10-2002, 02:14 PM
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Car: 1999 Pontiac T/A Firehawk
Engine: ***'s Engine
Transmission: T56
Well, I have to pass emissions once every other year here as well. So how do I go about it? Real simple--my car is an 84. It was factory equipped with a computer Qjet. It only takes me about an hour to reinstall all of my emissions equipment for testing, and about a half hour to remove everything afterwards. Now that I've "decomputerized", i expect that time to double... but it's STILL worth it.
12-10-2002, 08:01 PM
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Car: 1991 RS
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 2.73
Don't forget to look at both sides of the coin. Check people's opinons on the carb board to get the whole story. This post in particular is informative:
https://www.thirdgen.org/techbb2/sho...hreadid=102794
Fuel injection is the future, period. But until it becomes superior to carbs by an obvious margin, and much cheaper than they are now, the carb will still have a role in the garages of America.
https://www.thirdgen.org/techbb2/sho...hreadid=102794
Fuel injection is the future, period. But until it becomes superior to carbs by an obvious margin, and much cheaper than they are now, the carb will still have a role in the garages of America.
12-10-2002, 08:15 PM
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Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
The drivability of a fuel injection system is what I find so appealing. I mean I'll be running fine in the morning and evenings, but during the heat of the day, terrible.
I love how easily my fuel injected cars start, no matter what!
I love how easily my fuel injected cars start, no matter what!
12-11-2002, 07:33 PM
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Car: '83 Z28, '07 Charger SRT8
Engine: 454ci, 6.1 Hemi
Transmission: TH350, A5
Axle/Gears: 2.73 posi, 3.06 posi
To sum up why i like carbs over EFI...
I think carbs adapt to modifications alot better than TPI does and a carb is alot easier to work with as far as tuning, etc.
Although, carbs are probably not quite as good as TPI for fuel mileage and use in the cold (winter?)
BUT... no contest, 4 Barrel all the way!!
I've also noticed that (correct me if im wrong) carbuerated cars tend to have a nastier, rumblier (that even a word?) idle
I think carbs adapt to modifications alot better than TPI does and a carb is alot easier to work with as far as tuning, etc.
Although, carbs are probably not quite as good as TPI for fuel mileage and use in the cold (winter?)
BUT... no contest, 4 Barrel all the way!!
I've also noticed that (correct me if im wrong) carbuerated cars tend to have a nastier, rumblier (that even a word?) idle
Last edited by Air_Adam; 12-11-2002 at 07:35 PM.
12-11-2002, 08:35 PM
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Car: 88 Trans Am GTA
Engine: 5.1L Gen III
Transmission: T56
Axle/Gears: 3.70
True but you can, with a lot of tunning, run a lot run a bigger cam with a much better idle, Also with roller cams you can get a ton of lift with a lot less duration. How many people do you know can drive a dual tunnel ramed carbed car everyday too? The stealth ram is prob. my fav. intake. On the other side though is there are alot of people w/ tpi that have surging idle issues, etc. that never go away.
Basically if you get a tpi car keep it tpi, IMO its not worth stripping out a good factory fuel inj. for perfermance or for pure lazyness. If you want a carb buy a v6 rs and put a built 383 in it, or convert a tbi over, your insurance will be cheaper and your not mutilating a good factory car. I'm not a purist **** but it kinda pisses me off when people make a chevelle ss a pure 8 sec. monster. Sure its cool and all but they could have done the same thing with a straight six and three on the tree and put on some emblems and stripes. Nothing is left of the original car anyway. What I'm saying is don't trash a good car, trash a sh**ty one when you can.
Basically if you get a tpi car keep it tpi, IMO its not worth stripping out a good factory fuel inj. for perfermance or for pure lazyness. If you want a carb buy a v6 rs and put a built 383 in it, or convert a tbi over, your insurance will be cheaper and your not mutilating a good factory car. I'm not a purist **** but it kinda pisses me off when people make a chevelle ss a pure 8 sec. monster. Sure its cool and all but they could have done the same thing with a straight six and three on the tree and put on some emblems and stripes. Nothing is left of the original car anyway. What I'm saying is don't trash a good car, trash a sh**ty one when you can.
Last edited by Roostmeyer; 12-11-2002 at 08:38 PM.
12-11-2002, 11:31 PM
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Car: 1999 Pontiac T/A Firehawk
Engine: ***'s Engine
Transmission: T56
Originally posted by gruveb
I love how easily my fuel injected cars start, no matter what!
I love how easily my fuel injected cars start, no matter what!
Apparently to some people, the difference between 2 and 4 cranks in the morning is a life threatening problem. I have no trouble EVER starting ANY of my carb cars as long as the battery is good, and I just don't see the problem here.
And yes, I only have to wait about 5-10 SECONDS after starting before putting the Oldsmobile in gear and driving, and I don't have to even wait THAT long with the Camaro or the Vette.
This whole thing got spread by people who simply couldn't figure out how to set a choke properly. There's no other explanation.
Yes, FI does have advantages over carbs, but I don't feel that starting or cold driving is a major one. (In fact, my LS1 has a tendency to "buck" when cold, something neither my ZZ4 nor the Vette does).
12-11-2002, 11:44 PM
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Originally posted by 99Hawk120
I'm so tired of hearing that.
Apparently to some people, the difference between 2 and 4 cranks in the morning is a life threatening problem. I have no trouble EVER starting ANY of my carb cars as long as the battery is good, and I just don't see the problem here.
And yes, I only have to wait about 5-10 SECONDS after starting before putting the Oldsmobile in gear and driving, and I don't have to even wait THAT long with the Camaro or the Vette.
This whole thing got spread by people who simply couldn't figure out how to set a choke properly. There's no other explanation.
Yes, FI does have advantages over carbs, but I don't feel that starting or cold driving is a major one. (In fact, my LS1 has a tendency to "buck" when cold, something neither my ZZ4 nor the Vette does).
I'm so tired of hearing that.
Apparently to some people, the difference between 2 and 4 cranks in the morning is a life threatening problem. I have no trouble EVER starting ANY of my carb cars as long as the battery is good, and I just don't see the problem here.
And yes, I only have to wait about 5-10 SECONDS after starting before putting the Oldsmobile in gear and driving, and I don't have to even wait THAT long with the Camaro or the Vette.
This whole thing got spread by people who simply couldn't figure out how to set a choke properly. There's no other explanation.
Yes, FI does have advantages over carbs, but I don't feel that starting or cold driving is a major one. (In fact, my LS1 has a tendency to "buck" when cold, something neither my ZZ4 nor the Vette does).
Anyone that cant get a carb car to be reliable , have good throttle response or get decent mpg put of it while they arent on it isnt trying hard enough.
Last edited by evil t/a; 12-12-2002 at 01:40 AM.
12-12-2002, 01:28 AM
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I have to agree with evil t/a and 99hawk120. Carbed cars start FASTER than TBI when they're hot and about the same when they sit overnight.
I bought my Cutlass early in the summer and I've put about 18000km on it since I got it. I've never once had it not start up right away. Its a stock LG4, the quadrajets been rebuilt about 3 years ago according to the guy i bought it from.
When its hot it starts about as fast as i can turn the key and let go. When its been sitting 3 hours or longer i press the gas once and then turn the key and it fires within 1 second. If it sits somewhere longer than half an hour but less than a few hours i give it a quick turn of the key and then tap the gas and it starts right up. Now thats its cold out (i live in Canada) when the car sits overnight I give it 2 pumps and it still takes less than 2 seconds to start.
Compare this to my friends 87 half ton with the same motor as mine but it has TBI and it takes about 3-4 seconds everytime no matter what. Almost all the TBI engines I've seen do this. My moms new Olds Alero takes longer than my car to start.
I don't really mind TBI for an almost stock street car cause its almost as simple as a carb and doesn't require much maintenance but I think its a bad excuse to say they start better cause they don't.
I bought my Cutlass early in the summer and I've put about 18000km on it since I got it. I've never once had it not start up right away. Its a stock LG4, the quadrajets been rebuilt about 3 years ago according to the guy i bought it from.
When its hot it starts about as fast as i can turn the key and let go. When its been sitting 3 hours or longer i press the gas once and then turn the key and it fires within 1 second. If it sits somewhere longer than half an hour but less than a few hours i give it a quick turn of the key and then tap the gas and it starts right up. Now thats its cold out (i live in Canada) when the car sits overnight I give it 2 pumps and it still takes less than 2 seconds to start.
Compare this to my friends 87 half ton with the same motor as mine but it has TBI and it takes about 3-4 seconds everytime no matter what. Almost all the TBI engines I've seen do this. My moms new Olds Alero takes longer than my car to start.
I don't really mind TBI for an almost stock street car cause its almost as simple as a carb and doesn't require much maintenance but I think its a bad excuse to say they start better cause they don't.
12-12-2002, 07:42 AM
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Car: 1989 IROC-1
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Originally posted by 99Hawk120
I'm so tired of hearing that.
Apparently to some people, the difference between 2 and 4 cranks in the morning is a life threatening problem.
I'm so tired of hearing that.
Apparently to some people, the difference between 2 and 4 cranks in the morning is a life threatening problem.
What is a big deal though is taking a trip through the mountains and stopping for a picnic and having vapor lock! Or running to the store at 9 at night b/c your daughter is sick and having your carb's choke lock up on you.
With that in mind, everything can have trouble and leave you stranded.....if it's got **** or tires you're gonna have trouble.
Bort, what type of FI system are you going to?
12-12-2002, 08:39 AM
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Car: 1999 Pontiac T/A Firehawk
Engine: ***'s Engine
Transmission: T56
I've been stranded a couple of times because of starting issues with carbs. I drive two carbed vehicles regularly and 2 to 4 cranks in the morning is NOT a big deal.
Starting issues you won't have when the carb is in good tune and good condition. A carb with a choke set wrong or in poor tune CAN be a nightmare to start in cold weather. That doesn't mean carbs suck, it means there is something WRONG.
FYI, under EVERY CONDITION, my Qjet starts faster than my buds TBI. That of course does more to reinfoce that TBI sucks than anything else, of course... the "better starting" really only applies to dry flow injection systems like TPI, LT1, LS1...
What is a big deal though is taking a trip through the mountains and stopping for a picnic and having vapor lock! Or running to the store at 9 at night b/c your daughter is sick and having your carb's choke lock up on you.
#1: Intank electric pump. What is this vapor lock you speak of?
#2: I had that exact same problem happen. Well, I don't have a daughter, so it wasn't exactly the same... but you get the idea. Anyhow, there's about 6 million ways to fix this, when my car did it I simply removed the choke plate from the carb. I've only had it happen once... and you know when it did? On 2bbl Dualjet that had never been rebuilt with 120,000 miles on it. I've seen TPI with a heck of a lot more problems before 60,000. And in fact, this just reinforces my earlier statement about these problems only happening with a carb that is in poor shape or poor tune.
Starting issues you won't have when the carb is in good tune and good condition. A carb with a choke set wrong or in poor tune CAN be a nightmare to start in cold weather. That doesn't mean carbs suck, it means there is something WRONG.
FYI, under EVERY CONDITION, my Qjet starts faster than my buds TBI. That of course does more to reinfoce that TBI sucks than anything else, of course... the "better starting" really only applies to dry flow injection systems like TPI, LT1, LS1...
What is a big deal though is taking a trip through the mountains and stopping for a picnic and having vapor lock! Or running to the store at 9 at night b/c your daughter is sick and having your carb's choke lock up on you.
#1: Intank electric pump. What is this vapor lock you speak of?
#2: I had that exact same problem happen. Well, I don't have a daughter, so it wasn't exactly the same... but you get the idea. Anyhow, there's about 6 million ways to fix this, when my car did it I simply removed the choke plate from the carb. I've only had it happen once... and you know when it did? On 2bbl Dualjet that had never been rebuilt with 120,000 miles on it. I've seen TPI with a heck of a lot more problems before 60,000. And in fact, this just reinforces my earlier statement about these problems only happening with a carb that is in poor shape or poor tune.
12-12-2002, 11:44 AM
#25
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Car: 1989 IROC-1
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99Hawk,
Everything can break and everything has problems. I still maintain that for a daily driver with moderate performance fuel injection is the way to go.
One of the biggest problems I have in my 84 Z is that on warm days all of the fuel boils out of the carb when I shut down. I've tried everything to keep this from happening.....little luck.
Everything can break and everything has problems. I still maintain that for a daily driver with moderate performance fuel injection is the way to go.
One of the biggest problems I have in my 84 Z is that on warm days all of the fuel boils out of the carb when I shut down. I've tried everything to keep this from happening.....little luck.
12-12-2002, 12:40 PM
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Car: 1999 Pontiac T/A Firehawk
Engine: ***'s Engine
Transmission: T56
Originally posted by gruveb
One of the biggest problems I have in my 84 Z is that on warm days all of the fuel boils out of the carb when I shut down. I've tried everything to keep this from happening.....little luck.
One of the biggest problems I have in my 84 Z is that on warm days all of the fuel boils out of the carb when I shut down. I've tried everything to keep this from happening.....little luck.
12-12-2002, 03:34 PM
#28
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Car: 1989 IROC-1
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Originally posted by 305LG4Cutlass
The only benefit of FI is gas mileage and emissions.
The only benefit of FI is gas mileage and emissions.
An obvious sign of intelligence north of the border!
:hail: 305LG4Cutlass
12-13-2002, 08:27 AM
#29
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I switched from TBI so Im not real educated in this subject. I thought about switching to TPI but $$ and performance made me change my mind. Carb kinda sucks sometimes.....runs bad until warm but after its warm its fine. No problems starting my carbed car in winter like some day 
If chevy would have got it right like ford did with EFI I would have jumped all over that in a heartbeat. Not to come off as a ford guy but ford EFI kicks TPI ***. 6k is easy in a 302 fix body. my dads 95 GT pulls to 6.5k no problems....ive heard TPI is good till 4500 and I know my TBI sucked after 4500...so far ive turned 5500 with my carb and it pulled good even with my lame heads and ***** cam.
If chevy would have got it right like ford did with EFI I would have jumped all over that in a heartbeat. Not to come off as a ford guy but ford EFI kicks TPI ***. 6k is easy in a 302 fix body. my dads 95 GT pulls to 6.5k no problems....ive heard TPI is good till 4500 and I know my TBI sucked after 4500...so far ive turned 5500 with my carb and it pulled good even with my lame heads and ***** cam.
12-13-2002, 09:37 AM
#30
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It Depends on how much money you have.
A TPI setup like the StealthRam is probably the best all around choice, in my opinion, if you have the $$$. I mean the WHOLE THING. Holley's little kit for $2400 that comes with everything from a NEW ECM to the fuel pump. you tune it with a laptop, it can control boost compensation, it will net good fuel economy, and its adaptable to almost any mod simply because you can tune it yourself with a laptop. one of these kits and one of ATI's intercooled superchargers can provide well over 20 MPG and 600 RWHP. provided you have the $$ to dump into your bottom end as well.
The FACTORY Tpi's biggest restrictions, so im told, are its runners. they are tuned to a specific velocity to produce good VE% and cylinder pressure in the mid-range area. overcoming this restriction means bigger runners. or a new TPI setup.
Carbs, on the other hand, can be tuned fairly easilly. but they can get expensive too. new carbs are what now? $400? $650 for the HP series? yeah thats alot cheaper than $2400. But my biggest problem with a carb now is the fuel economy factor. I was a devoted carb fan until I got myself a Holley EFI setup. The ability to modify your "fuel map" and "spark map" via laptop computer sold me instantly on efi. there is nothing better than saying "hey look im rich up here but lean down here... ok its fixed!" and "hmm theres a little spark knock up here so lets... ok all done!"
You just cant do that with a carb. you can change power valves and jets and drill out PCVRs and air bleeds and throttle bodies all day and not even come close to the tunability of an aftermarket EFI setup. or even a factory one for that matter.
I can go on all day. lets finish with this:
My engine, with a carb, did the following:
13 MPG highway, 10 City. 420 RWHP with 6 PSI of boost. below 2500 RPMS the car was a dog, simply because the carb was "extra big" to allow the blower to pull air past 5500 RPMS. this also killed my throttle response and driveability.
My engine, with Holley's Commander 950 EFI throttle Body Injection did this:
21 MPH highway, 18 MPG~ city. 440 RWHP with 6-7 PSI of boost. Car now has excellent throttle response and idles better. got back most of my "lost" low end torque, but that also had to do with the stall change.
A TPI setup like the StealthRam is probably the best all around choice, in my opinion, if you have the $$$. I mean the WHOLE THING. Holley's little kit for $2400 that comes with everything from a NEW ECM to the fuel pump. you tune it with a laptop, it can control boost compensation, it will net good fuel economy, and its adaptable to almost any mod simply because you can tune it yourself with a laptop. one of these kits and one of ATI's intercooled superchargers can provide well over 20 MPG and 600 RWHP. provided you have the $$ to dump into your bottom end as well.
The FACTORY Tpi's biggest restrictions, so im told, are its runners. they are tuned to a specific velocity to produce good VE% and cylinder pressure in the mid-range area. overcoming this restriction means bigger runners. or a new TPI setup.
Carbs, on the other hand, can be tuned fairly easilly. but they can get expensive too. new carbs are what now? $400? $650 for the HP series? yeah thats alot cheaper than $2400. But my biggest problem with a carb now is the fuel economy factor. I was a devoted carb fan until I got myself a Holley EFI setup. The ability to modify your "fuel map" and "spark map" via laptop computer sold me instantly on efi. there is nothing better than saying "hey look im rich up here but lean down here... ok its fixed!" and "hmm theres a little spark knock up here so lets... ok all done!"
You just cant do that with a carb. you can change power valves and jets and drill out PCVRs and air bleeds and throttle bodies all day and not even come close to the tunability of an aftermarket EFI setup. or even a factory one for that matter.
I can go on all day. lets finish with this:
My engine, with a carb, did the following:
13 MPG highway, 10 City. 420 RWHP with 6 PSI of boost. below 2500 RPMS the car was a dog, simply because the carb was "extra big" to allow the blower to pull air past 5500 RPMS. this also killed my throttle response and driveability.
My engine, with Holley's Commander 950 EFI throttle Body Injection did this:
21 MPH highway, 18 MPG~ city. 440 RWHP with 6-7 PSI of boost. Car now has excellent throttle response and idles better. got back most of my "lost" low end torque, but that also had to do with the stall change.
12-13-2002, 11:54 AM
#31
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The Stealth Ram isn't TPI... it's not a kind of TPI, has nothing to do with TPI. It's port injection, but the similarity ends there.
TPI stands for "Tuned Port Injection". Remember that phrase, it accurately describes the physics of how it works. As air rushes down into a runner, and the intake valve suddenly closes, the air has inertia, and kind of smacks into the back of the valve and stacks up; this produces a positive (higher than ambient) pressure. TPI's design is that the runners are of a specifically chosen length, such that the acoustic pressure wave (could be otherwise referred to as "sound pulse") generated by one intake valve's closing event travels back up that valve's runner, into the plenum, and then down the next runner with an open intake valve, and that the time it takes to make the trip causes it to reinforce the intake event at that next cylinder (as well as all the others, but they don't matter), and thereby it "compresses" a little extra intake charge into that cylinder. The length is of course dictated by the speed of sound, which is roughly 1100 feet per second at room temp & pressure, slightly different inside the motor, but still roughly one foot per millisecond. So, as we all know, the length of a TPI runner is 22" including the base; that makes the distance from one intake valve to another by way of the runner & plenum to be about 4'; which means the valves are about 4 milliseconds apart at the speed of sound. That's 1/250 of a second. 4 cylinders fire during one crank revolution, so that means that the RPM at which this reinforcement is at its maximum, occurs at somewhere just below 250/4 per second, which is roughly 60 revs per second, which is roughly 3600 RPM. Look at the torque curve of a TPI motor, you'll see a HUGE peak there. Now you know why. The runners are acoustically "tuned" (the T in TPI) to produce it.
The penalty for this blessing is two-fold. One, in order for the runner to effectively transfer the sound pulse, the runner needs to be as small as possible. That's TPI's famous flow limit. The runner diameter is just large enough to meet the flow requirements of the engine at the "tuned" RPM, but no higher, as there is no need for flow beyond that RPM anyway due to reason #2.
The second penalty is much worse even than the first. After this pulse of air movement bounces off the valve and travels up the runner, it partially evacuates the runner, leaving a negative pressure behind. This half of the pulse also travels up the runner, into the plenum, and down the "next" runner in the firing order. If the intake valve happens to still be open when this pulse arrives, it has the opposite effect. If the engine RPM is well below the "tuned" RPM, the arrival of this pulse is insignificant, because the intake valve that's open at the moment it arrives is open for so long that the short-duration pulse doesn't have much effect on cylinder fill at all. But, if the engine RPM is above the "tuned" RPM, the negative-going pressure wave from one cylinder's intake valve closing event doesn't have time to reach the next valve in the firing order, instead it affects the cylinder 2 cylinders later in the firing order; and at this higher RPM, the length of the pulse is significant compared to the total intake valve open time. The effect is, of course, negative: this negative-going pressure wave subtracts from cylinder fill at RPMs in that range. This occurs from about 5000 RPM on up.
In a nutshell, this is what's wrong with long-tube runners for performance, or more specifically, horsepower. Horsepower does not exist, as such; it is a quantity that's calculated from torque and RPM. You can get a high HP output from an engine either by having huge torque at some moderate RPM, or moderate torque at high RPM; but since torque is simply a measure of CID and cylinder fill, unless you have some way of increasing the fill beyond 100% which is only possible with some kind of "power adder", it isn't possible with a straight N/A motor. So, the only way to get high HP out of a N/A motor is by producing significant torque, i.e. near complete cylinder fill, at high RPMs.... which TPI is deliberately designed to defeat.
That's whay a motor that makes 355 HP with a carb, or that would make similar numbers with a Stealth Ram or a MiniRam or ProRam or any other system that doesn't depend on tuning, will only put out 240 HP with a TPI on it.
In short, TPI should have been used in trucks, it would be absolutely perfect; but cars like ours should have been equipped with something more like the LT1 intake. The MiniRam in fact was exactly that, except for that it pre-dated the LT1 by many years. In other words, it took GM that long to catch on, or at least to reach the same conclusion. Too bad GM didn't wise up sooner: 3rd gens would have had some actual power, and the F*rd guys would have been wondering what they were going to do to keep up alot sooner than what has happened. Incidentally, their intake looks kind of alot like the MiniRam or LT1, as far as its design.
This is why I'm not interested in being bothered with trying to make TPI fast. I choose not to butt heads with the laws of physics. So, I will choose a carb over TPI; but I might choose some other form of FI over a carb for some applications, too. Dislike of TPI is not the same thing as dislike of FI, or love of carbs.
TPI stands for "Tuned Port Injection". Remember that phrase, it accurately describes the physics of how it works. As air rushes down into a runner, and the intake valve suddenly closes, the air has inertia, and kind of smacks into the back of the valve and stacks up; this produces a positive (higher than ambient) pressure. TPI's design is that the runners are of a specifically chosen length, such that the acoustic pressure wave (could be otherwise referred to as "sound pulse") generated by one intake valve's closing event travels back up that valve's runner, into the plenum, and then down the next runner with an open intake valve, and that the time it takes to make the trip causes it to reinforce the intake event at that next cylinder (as well as all the others, but they don't matter), and thereby it "compresses" a little extra intake charge into that cylinder. The length is of course dictated by the speed of sound, which is roughly 1100 feet per second at room temp & pressure, slightly different inside the motor, but still roughly one foot per millisecond. So, as we all know, the length of a TPI runner is 22" including the base; that makes the distance from one intake valve to another by way of the runner & plenum to be about 4'; which means the valves are about 4 milliseconds apart at the speed of sound. That's 1/250 of a second. 4 cylinders fire during one crank revolution, so that means that the RPM at which this reinforcement is at its maximum, occurs at somewhere just below 250/4 per second, which is roughly 60 revs per second, which is roughly 3600 RPM. Look at the torque curve of a TPI motor, you'll see a HUGE peak there. Now you know why. The runners are acoustically "tuned" (the T in TPI) to produce it.
The penalty for this blessing is two-fold. One, in order for the runner to effectively transfer the sound pulse, the runner needs to be as small as possible. That's TPI's famous flow limit. The runner diameter is just large enough to meet the flow requirements of the engine at the "tuned" RPM, but no higher, as there is no need for flow beyond that RPM anyway due to reason #2.
The second penalty is much worse even than the first. After this pulse of air movement bounces off the valve and travels up the runner, it partially evacuates the runner, leaving a negative pressure behind. This half of the pulse also travels up the runner, into the plenum, and down the "next" runner in the firing order. If the intake valve happens to still be open when this pulse arrives, it has the opposite effect. If the engine RPM is well below the "tuned" RPM, the arrival of this pulse is insignificant, because the intake valve that's open at the moment it arrives is open for so long that the short-duration pulse doesn't have much effect on cylinder fill at all. But, if the engine RPM is above the "tuned" RPM, the negative-going pressure wave from one cylinder's intake valve closing event doesn't have time to reach the next valve in the firing order, instead it affects the cylinder 2 cylinders later in the firing order; and at this higher RPM, the length of the pulse is significant compared to the total intake valve open time. The effect is, of course, negative: this negative-going pressure wave subtracts from cylinder fill at RPMs in that range. This occurs from about 5000 RPM on up.
In a nutshell, this is what's wrong with long-tube runners for performance, or more specifically, horsepower. Horsepower does not exist, as such; it is a quantity that's calculated from torque and RPM. You can get a high HP output from an engine either by having huge torque at some moderate RPM, or moderate torque at high RPM; but since torque is simply a measure of CID and cylinder fill, unless you have some way of increasing the fill beyond 100% which is only possible with some kind of "power adder", it isn't possible with a straight N/A motor. So, the only way to get high HP out of a N/A motor is by producing significant torque, i.e. near complete cylinder fill, at high RPMs.... which TPI is deliberately designed to defeat.
That's whay a motor that makes 355 HP with a carb, or that would make similar numbers with a Stealth Ram or a MiniRam or ProRam or any other system that doesn't depend on tuning, will only put out 240 HP with a TPI on it.
In short, TPI should have been used in trucks, it would be absolutely perfect; but cars like ours should have been equipped with something more like the LT1 intake. The MiniRam in fact was exactly that, except for that it pre-dated the LT1 by many years. In other words, it took GM that long to catch on, or at least to reach the same conclusion. Too bad GM didn't wise up sooner: 3rd gens would have had some actual power, and the F*rd guys would have been wondering what they were going to do to keep up alot sooner than what has happened. Incidentally, their intake looks kind of alot like the MiniRam or LT1, as far as its design.
This is why I'm not interested in being bothered with trying to make TPI fast. I choose not to butt heads with the laws of physics. So, I will choose a carb over TPI; but I might choose some other form of FI over a carb for some applications, too. Dislike of TPI is not the same thing as dislike of FI, or love of carbs.
12-13-2002, 03:57 PM
#32
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<b>it's not a kind of TPI, has nothing to do with TPI.</b>...
your absolutelly right, but as far as holley is concerned, they consider it(stealthram) a TPI setup. I know its rediculous, and some of the info on their site is wrong, but its how holley labels it. I think they do it because it replaces the existing TPI easilly enough, and they want existing TPI owners to think its a better form of TPI.
whatever the case, i labeled it TPI because thats how holley labels the stealthram.
and one more thing...
<b>unless you have some way of increasing the fill beyond 100% which is only possible with some kind of "power adder", it isn't possible with a straight N/A motor.</b>
heh your right but i want to point out that tunnel ram manifolds can create VE%'s of over 100% in a N/A motor.
its the same sort of theory. the air has a weight, like water, at high speeds. it floods into the cylinder because of the momentum. like a mini "invisible" supercharger. but otherwise, i dont think any TPI motor has seen a VE of over 100%. but i could be wrong.
your absolutelly right, but as far as holley is concerned, they consider it(stealthram) a TPI setup. I know its rediculous, and some of the info on their site is wrong, but its how holley labels it. I think they do it because it replaces the existing TPI easilly enough, and they want existing TPI owners to think its a better form of TPI.
whatever the case, i labeled it TPI because thats how holley labels the stealthram.
and one more thing...
<b>unless you have some way of increasing the fill beyond 100% which is only possible with some kind of "power adder", it isn't possible with a straight N/A motor.</b>
heh your right but i want to point out that tunnel ram manifolds can create VE%'s of over 100% in a N/A motor.
its the same sort of theory. the air has a weight, like water, at high speeds. it floods into the cylinder because of the momentum. like a mini "invisible" supercharger. but otherwise, i dont think any TPI motor has seen a VE of over 100%. but i could be wrong.
01-09-2003, 10:23 PM
#33
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Oh yeah!! well my car dosent have either CARB or FI. It's got a kick a$$ fission atom spliting burn up the street and make your carb and FI look like **** engine. C'mon guys, why so much words wasted on my crap is better than your crap... one thing I will say... if carb is so much better than fuel injection (in a few mans opinion). Then why do all the new cars have fuel injection?
01-09-2003, 10:39 PM
#34
I don't see many wasted words in this thread. Mostly great insight into different ways of delivering fuel to your car. More information than you can get is most car magazines.
01-10-2003, 07:36 AM
#35
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Well Considering I just got done doing the TPI to Carb switch heres my Views
Money, Simplicity, Convienence, and Performance
People have been telling me "Oh your messing up" blah blah blah
The car hasnt ran that good since I bought it never aches for power and has that cool little body torque to it now. and yes it soundss alot more powerful then it did with the TPI. For me the TPI was to expensive. I work on computers all day, I dont want to fool with the cars.
Money, Simplicity, Convienence, and Performance
People have been telling me "Oh your messing up" blah blah blah
The car hasnt ran that good since I bought it never aches for power and has that cool little body torque to it now. and yes it soundss alot more powerful then it did with the TPI. For me the TPI was to expensive. I work on computers all day, I dont want to fool with the cars.
01-10-2003, 08:16 AM
#36
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Interesting view points...
Mine is, "if the car started out FI why back up to a carb?" I would also like to state, that in my book TBI doesn't really count as FI. Suffers from the worst of both worlds.
Lastly, two of our prominent members (1 admin and 1 mod) on sethirdgen converted from carb to FI. Both are very happy with their new results.
Mine is, "if the car started out FI why back up to a carb?" I would also like to state, that in my book TBI doesn't really count as FI. Suffers from the worst of both worlds.
Lastly, two of our prominent members (1 admin and 1 mod) on sethirdgen converted from carb to FI. Both are very happy with their new results.
Last edited by Lounge Lizard 6; 01-10-2003 at 08:19 AM.
01-10-2003, 05:08 PM
#37
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I was thinking about trying to swap TBI in place of the carb on my LG4 just for gas mileage and possibly passing emmissions easier (shouldn't be a problem, but my friends TBI 305 passed with a gutted cat and smoking valve guides so im thinking TBI might help). It would probably be quite a bit of money and work for the swap though and then i have to put up with longer starting times than I have with the carb right now and worrying about the in tank fuel pump dying on me.
01-10-2003, 05:30 PM
#38
Everyone bashes TPI but whos got more power stock? In the factory cars TPI is the king of HP/TQ. And RPMS aren't everything. So the TPI RPM limit is not the biggest problem with the cars. Aftermarket setups eliminate this issue. RPMs are one of the reasons behind the import people arguments that higher reving engines are better. Sure they can run up to 7000rpm or what have you, but does that accomplish what the V8's do at 5500RPM? Hell no it doesn't. I think for every day use TPI rocks. But I do admit that TPI sucks to troubleshoot. There are PROS and CONS on both sides. I will leave it at that. Whatever you prefer is whatever you prefer.
01-10-2003, 05:45 PM
#39
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Originally posted by Ancel Zero
if carb is so much better than fuel injection (in a few mans opinion). Then why do all the new cars have fuel injection?
if carb is so much better than fuel injection (in a few mans opinion). Then why do all the new cars have fuel injection?
01-10-2003, 05:50 PM
#40
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Car: 97 Z28
Engine: LT1
Transmission: A4
Axle/Gears: 3.73
Originally posted by 87WS6
Everyone bashes TPI but whos got more power stock? In the factory cars TPI is the king of HP/TQ. And RPMS aren't everything.
Everyone bashes TPI but whos got more power stock? In the factory cars TPI is the king of HP/TQ. And RPMS aren't everything.
01-10-2003, 07:26 PM
#41
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Car: 86 Corvette, 89 IROC, 1999 TA
Engine: 350, 350, LS1
Transmission: 700r4, 700r4, T-56
Axle/Gears: 3.07, 373, 4.10
i went with carb when i built my car because of easy adjustability and i needed a affordable way to utilize my engines power curve which tops out just under 6500..
01-11-2003, 10:15 PM
#43
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Car: '83 Z28, '07 Charger SRT8
Engine: 454ci, 6.1 Hemi
Transmission: TH350, A5
Axle/Gears: 2.73 posi, 3.06 posi
87WS6 - You think that just because the TPI cars had more power from the factory that that automatically make them better than the carbs? Ooh man.... You obviously haven't seen the stock L98 with an L69 intake manifold and carb.. made 20hp over what the TPI made AND was an easier driver on the street. I'm not attacking you, but what you said was kinda unfair to the carb'd cars.
At first, i shunned my Z28 for having a 4 barrel and not a TPI, but since then, i am very happy that i did get a 4 barrel car because i think that the 4 barrel is less complicated to work on, its easier to make lots of power for less money and when you drop the idle down to about 500 rpm... even with my stock '79 Camaro 350... it litteraly sounds like a big block, and i have yet to see that done with a stock TPI.
At first, i shunned my Z28 for having a 4 barrel and not a TPI, but since then, i am very happy that i did get a 4 barrel car because i think that the 4 barrel is less complicated to work on, its easier to make lots of power for less money and when you drop the idle down to about 500 rpm... even with my stock '79 Camaro 350... it litteraly sounds like a big block, and i have yet to see that done with a stock TPI.
Last edited by Air_Adam; 01-11-2003 at 10:19 PM.
01-11-2003, 10:45 PM
#44
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Oooh......it's getting hot in here...
RB83L69 made ALOT of good points. TPI WAS NOT designed from the factory with HP in mind. Fuel economy, better all weather performance FOR THE AVERAGE CAR BUYER.....
I like TPI personally. I've owned and wrenched on plenty of carbed cars, and I remember having similar arguments defending the performance of the "lowly" Q-Jet. ( Best carb for all around performance and EVERYDAY reliability IMHO )
I've also wrenched on a bunch of CCC Q-Jet apps, like the '83 L69 F-Body, but most of mine were in G-Body's, pretty much identical.
Compared to the CCC Q-Jets, emissions wise, there's alot less to worry about with TPI...less clutter in my opinion. More stuff for previous owners to screw up on the CCC Q-Jet cars...so you never know what you're getting when you get that new 'project' car.
One thing though, carbs, by nature, are 'mechanical' devices, and as such they NORMALLY require more attention to keep them right...most times this is not a big deal.
I think a MAJOR factor that contributes to alot of 3rd gen F-Body owners who convert to carb ( as far as TPI is concerned ) is the fact that TPI 3rd gens now have a good bit of age and miles on them. And again, previous owners can do devious things. On TPI cars, they usually seem to be more likely to have high miles, because the owners just drive 'em, and when they act up, they sell them or trade them in.
It's all perspective IMHO...
If you buy a TPI car, and have troubles, maybe harder to DIAGNOSE troubles, and you don't take the time to correctly diagnose the SYMPTOM to find the actual problem, replacing this sensor and that sensor at random can get annoying and expensive REALLY quick. That can be very discouraging. And a carb can seem alot less initimidating than fuel injection.
RB83L69..... I know you've heard the old saying... "...90 percent of all carb troubles AREN'T."
Alot of people will blame carbs for ignition and other related problems, and this happens with TPI as well.
So to sum it up, if you want a carb, swap it in...makes FI parts cheaper and easier to find
This is like asking Why some people like Chevy's and some Ford's......let's not go there.
Later
I like TPI personally. I've owned and wrenched on plenty of carbed cars, and I remember having similar arguments defending the performance of the "lowly" Q-Jet. ( Best carb for all around performance and EVERYDAY reliability IMHO )
I've also wrenched on a bunch of CCC Q-Jet apps, like the '83 L69 F-Body, but most of mine were in G-Body's, pretty much identical.
Compared to the CCC Q-Jets, emissions wise, there's alot less to worry about with TPI...less clutter in my opinion. More stuff for previous owners to screw up on the CCC Q-Jet cars...so you never know what you're getting when you get that new 'project' car.
One thing though, carbs, by nature, are 'mechanical' devices, and as such they NORMALLY require more attention to keep them right...most times this is not a big deal.
I think a MAJOR factor that contributes to alot of 3rd gen F-Body owners who convert to carb ( as far as TPI is concerned ) is the fact that TPI 3rd gens now have a good bit of age and miles on them. And again, previous owners can do devious things. On TPI cars, they usually seem to be more likely to have high miles, because the owners just drive 'em, and when they act up, they sell them or trade them in.
It's all perspective IMHO...
If you buy a TPI car, and have troubles, maybe harder to DIAGNOSE troubles, and you don't take the time to correctly diagnose the SYMPTOM to find the actual problem, replacing this sensor and that sensor at random can get annoying and expensive REALLY quick. That can be very discouraging. And a carb can seem alot less initimidating than fuel injection.
RB83L69..... I know you've heard the old saying... "...90 percent of all carb troubles AREN'T."
Alot of people will blame carbs for ignition and other related problems, and this happens with TPI as well.
So to sum it up, if you want a carb, swap it in...makes FI parts cheaper and easier to find
This is like asking Why some people like Chevy's and some Ford's......let's not go there.
Later
01-11-2003, 11:06 PM
#45
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You would think that with the "tuned" tpi setup that on the street it would be great. (and it is... right?)
But when you wana lay down some rubber @ 6000 rpms cant forced induction "over-ride" the "top end limitations" of the TPI runner? You would think forcing the air through would make it much more RPM capable, provided the heads/cam were setup like that.
Which makes me wonder about TPI / Procharged applications...
isnt it sort of the best of both worlds? Tpi street driveability / Fuel economy + 6000 Rpm Power from intercooled boost.
Does that make any sense at all?
But when you wana lay down some rubber @ 6000 rpms cant forced induction "over-ride" the "top end limitations" of the TPI runner? You would think forcing the air through would make it much more RPM capable, provided the heads/cam were setup like that.
Which makes me wonder about TPI / Procharged applications...
isnt it sort of the best of both worlds? Tpi street driveability / Fuel economy + 6000 Rpm Power from intercooled boost.
Does that make any sense at all?
01-11-2003, 11:24 PM
#46
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for me TPI sucked
After the computer in my Formula 350 quite working properly I considered bolting on a carb. My car was still fast and seemed to run fine even though I could unplug any of the sensors without any major change in the cars performance. The only problem was my car now got a whopping 5 miles per gallon ! ! ! A few months later I broke several crankshaft bearings. Now 3 years later the complete tuned port set up including my L-98 heads sits on a shelf in my garage. I have so far been unsuccesful in my attemts to sell it.
(by the way, even when my L98 ran great it lost all its ***** after 4000 RPM's. A good performance engine should atleast pull until 5,500 RPM)
(by the way, even when my L98 ran great it lost all its ***** after 4000 RPM's. A good performance engine should atleast pull until 5,500 RPM)
01-11-2003, 11:34 PM
#48
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It seems to me, based on RB83L69's post, that forced induction would override any benefits the TPI setup would have cause it would simple force air in under boost and therefor the whole concept of Tuned port runner become irrelevant cause the forced induction would always create positive pressure behind the valve.
01-11-2003, 11:44 PM
#49
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TPI seemed like a good idea
The whole problem with the Tuned Port Injection was that it could pass enough air through it. The runners were to small, the throttle body was to small, the plenum was to restrictive. You just couldn't get the necessary volume of air through the system. The best thing about having a TPI engine is that it just sounds cool, especially to people who don't know what it is. I just liked saying "My car has Tuned Port Injection."
And many people were impressed by that.
And many people were impressed by that.
01-11-2003, 11:51 PM
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correction
Sorry, in the last post I meant to say " TPI couldn't pass enough air through it ".
But everyone who has owned one already knows that.
Without modifications to the intake you just couldn't make the horsepower numbers most people wanted. And I never really understood why the L98 heads had such small cumbustion chambers, what are they 58cc? couldn't GM have used 64cc heads with different pistons to keep the 9.5/1 compression ratio ?
But everyone who has owned one already knows that.
Without modifications to the intake you just couldn't make the horsepower numbers most people wanted. And I never really understood why the L98 heads had such small cumbustion chambers, what are they 58cc? couldn't GM have used 64cc heads with different pistons to keep the 9.5/1 compression ratio ?