https://www.thirdgen.org/messgboard/...ML/004958.html


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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Thanks Kevin,
Now I rreeaallllyy cant wait until next month to get my TPI put on. especially since I have a ported plenum and edel brock base. I am in the process of saving up for aftermarket runners. any suggestions/prices.
thanks

 

did the TBI have an open element on it or stock air cleaner and IROC exaust?

 

Hmm, isn't that interesting....

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

the diff in the torque numbers is most likely because of the cam. good gains though. i can't wait to get my heap to a dyno. prolly going in mid february.

lata
tim

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91 Camaro RS-LO3,Auto.
14.301 @ 94.39mph

Check Out The East Coast F-Body Nationals Home Page
www.geocities.com/njspeeder

My MAFB.ORG Home Page
www.mycar.net/mafb/registry/detail.cfm?id=299

 

Stock air cleaner, with a K&N filter. The TPI setup has two K&N filters in the usual configuration. The only mods to this car in both configerations is the stock 85 IROC exhaust.

 

No, the difference is the intake. TPI is very strong in the torque department.

 

i just meant the difference between the stock torque number for the lb9 and the lo3 cam with the tpi on top. it prolly made the torque lower in the power band too, just the nature of the lo3 cam.

lata
tim

------------------
91 Camaro RS-LO3,Auto.
14.301 @ 94.39mph

Check Out The East Coast F-Body Nationals Home Page
www.geocities.com/njspeeder

My MAFB.ORG Home Page
www.mycar.net/mafb/registry/detail.cfm?id=299

 

Didn't your dad also change the rear end gear ratio between the first run and now? That'll make a pretty big difference in RWHp...

 

the stock air cleaner sucks. The intake snorkel is only 1"x2". You should have dynoed it with a 14x3 air cleaner.

 

Did you ever do a dyno pull with the TBI set-up at higher timing than 0* ?? When I changed from 0* to 6*, which is what I run now, I picked up almost 2 tenths at the track and the car ran totally different. I'm not saying that the TPI wouldn't have made more power if they had been equal, but the TBI dyno pull would have been much closer. Also, did you do pull w/o the airfoil in place on the TPI?? Don't get me wrong, I'm not at all discrediting you, or your comparison, I'm just curious, as a 3rd gen enthusiast and the fact that I own a TBI car, what the #'s would have been with equal timing, and no mods to either, and a comparison with both having good aftermarket air filters or I should say open-element on the TBI, because a K&N in a stock TBI air cleaner assembly makes little, if any gain.

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82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page



[This message has been edited by Basett Racing (edited January 25, 2001).]

 

Gear ratio has no effect on horsepower output.

You guys are asking if I did this and that mod. The answer is NO! I said the mods I did. Both engines were "stock" with the only mod being the y-pipe, and cat-back from an 85 IROC. This wasnt a comparison to see the most horsepower we can get from the TBI then switch to TPI. It was to show the difference between a STOCK TBI and a STOCK TPI. Stock meaning as they come from the factory, with the stock timing and everything. I didnt want to s-l-a-n-t the results by doing mods to one that couldnt be duplicated on the other, like an open element filter (not smog legal in CA anyway) or stuff like that. I dont believe the throttle body airfoil on the TPI does much at all, but it was on the throttle body when we got my car originally, and I got another one when I got my 52mm TB, so we left it there.

Edit: s-l-a-n-t is a filtered word??

[This message has been edited by Kevin91Z (edited January 26, 2001).]

 

They will filter anything these days.
I don't think a open element would have made that big of a difference. How many of u guys actually gained anything to the rear wheels with an open element? None I guarentee it. Good job on them dyno results Kevin. Bought time someone did something instead of talking about it.

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

Don't forget guys the TPI was stock too. People keep saying "well you could have done this, this, and this" to the TBI to improve it's numbers, well you could also do alot to the TPI to improve it's munbers. I this it's a very well done, and fair comparison

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

Of course stock to stock TPI beats TBI, they put TPI on the higher performance engines, and they put TBI on the lower engines. TPI can provide a better air/fuel mixture. I still like the TBI system better because of the money and the ease of maintanence. Don't get me wrong I like TPI too, it's a good system, but more hassel, just depends on what you want.

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1989 Pontiac Firebird Formula LO3 Auto
-180 degree stat
-Hooker Cat-Back
*****Possible summer '01 mods*****
Open Element, Auburn Posi, Keyless Entry, wonder Bar off the IROC, 4th gen seats, T/A tail lights

1985 Camaro IROC-Z LB9 Auto
http://www.geocities.com/krt80/

 

Whats high performance about this engine???? Its the same TBI engine except with a TPI intake on it. The same TBI cam, the same TBI heads, the same TBI pistons, crank, etc. I think it just proves once and for all that on the 170 HP TBI vs the 205 HP LB9, it wasnt the small exhaust causing the restriction. Its the design of the TBI unit itself.

Andy's car made 175 HP on the dyno back in December of 98, and he's got headers, open element, etc. But we think he has other problems with his engine, like a worn out timing chain.

 

No, the difference is in the long TPI runners that enhance low and mid rpm torque.




[This message has been edited by Dan W (edited January 26, 2001).]

 

Then how do you explain the 17 HP gain from 158 to 175? Whether you say the TPI enhances the flow or TBI restricts the flow, its two sides of the same coin.
We took the eng. to 5000 RPM's the hp dropped after 4200-the tq. nose dived after 3000.



[This message has been edited by Kevin91Z (edited January 27, 2001).]

 

Well I'm shooting off the hip here but I'd be willing to bet that your motor does not make power in and was not tested in the high rpm range. There for that power gain was in the mid rpm range.

Dont you know how and why the TPI intake or any other long runner intake works?

 

When I said they, I meant GM.

 

Not at the flywheel, but it certainly does at the rear wheels, and you did measure at the rear wheels didn't you? If gear ratio made no difference then you would also have the same reading in 3rd gear as you did in 4th, since the only difference between 3rd and 4th is the gear ratio... The shorter gears give you more mechanical advantage, therefore more horsepower makes it from the flywheel to the wheels. That's why calculating hp at the flywheel from known numbers at the rear wheels is an estimate at best.

 

Yeah, a non operative fan switch. By the end of the run, the coolant temperature was 240 degrees, and only God knows how hot the air was that the open element was pulling in off the headers. Without a cowl induction or ram-air hood, open element filters only are effective when the car is moving and not just collecting blazing air in the engine compartment.

 

No Andy, changing the gears does NOT change the RWHP.

Yes, it will change the amount of torque going to the rear wheels, but since hp is a function of torque AND SPEED, the hp will not change. Although you can put more torque to the ground in 3rd gear, you are doing so at a LOWER SPEED (the speed of your wheels -where the measurement is being taken.)

All the dyno really measures is how quickly your car can accelerate a known mass (the roller). If you do it in a lower gear, the car will accelerate the mass more quickly, but at an overall lower speed, and a lesser total amount of acceleration. If you do it in a higher gear, it will accelerate both at a higher speed and a greater range.
1st gear: 1000 RPM-5000 RPM ~ 5mph-25mph
4th gear: 1000 RPM-5000 RPM ~ 20mph-100mph
So what I am saying is that the difference in torque is offset by the difference in speed.

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'83 Trans Am. 400 CID, 224/234 crane cam, Summit aluminum roller rockers, hand ported intake, home bored 2.09" (53mm) throttle bodies, MSD 454 injectors(75 lb/hr), Holley 255LPH fuel pump, custum modded FPR w/Vacuum port added, Edelbrock TES headers, empty cat, SLP 3" stainless steel cat back, stock ECM & chip. Borg/Warner T-5 World Class, 12" Corvette rotors and clipers, GTA 16" wheels, South Side Machine subframe connectors, 1LE sway bars, 3.45 ring and pinion, Alpine sound.
Best E.T. 13.532
Best MPH 102.24

 

When I asked about different mods, I wanted to know, for my own knowledge, how different mods affected HP on the TBI engine.
Now, about the timing, you said "Stock meaning as they came from the factory" but actually, this is not a truly accurate or fair comparison, due to the fact that this is still a L03,with LB9 timing and a TPI unit installed. 6* timing is factory on a LB9, meaning that the engine would have different heads, different exhaust, and on most engines a different cam (I know,some TPI cars have the peanut cam). This engine was designed from the factory to be this way because this was the so called High-Performance version of the 305, the TBI engine was 0* due to a highly restictive exhaust, poor cam, poor flowing heads and the fact that the base engine, or base V8 in our case, needs to be able to run on 87 octane (try running 87 octane with the timing you have now, and you'll see what I mean). Putting better exhaust on a L03(which has been done to yours) and advancing the timing to 6* makes a very noticable difference.So in inclusion, the only REAL way to have tested the TPI unit against the TBI unit would have been to have a TBI engine with stock EVERYTHING e.g exhaust, air filter, gears, and timing, and then bolted on a TPI unit and left EVERYTHING else alone, or Vise Versa, put a TBI on a TPI engine with the same controls -- no changing timing, no air-foil, no K&N's -- that would have been the ONLY way to have an unbiased, totally equal comparison, or with no S-L-A-N-T, as you said. The reason I'm pointing this out, is to inform people who may not know that if both of your dyno pulls would have been done with the same timing and gears, the difference would NOT have been as much. The TPI would have probably still made a little more HP, and it would have definetly made more TQ, I've never doubted that, but it wouldn't have been as much. If someone read this and went out a paid a considerable amout of $$$ for a TPI unit, and they were already running 6* timing, and had an open-element air filter, gears, exhaust, etc. on their TBI car, I think they would be very disappointed, especially if they were racing the car on the clock at a track, because a guy just driving a car on the street would feel a difference in TQ and the car would be a lot more fun to drive, but I just don't think the numbers would be what he expected on the clock, plus he would have an induction system that would cost much more $$$ to upgrade than what he had before. Now once again, I'm not saying this to discredit, or to discount your research in any way, please don't think that, I'm only saying that if someone bolts on a TPI, and they've already changed timing, gears, exhaust, etc. and expects get 17HP and 70ft lbs (especially that much TQ), he's going to be very disappointed. JMHO

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82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

 

I think u guys need to lay off Kevin a little bit. The guy did what everyone talks about doing all the time on this board. He has actual proof now of the 2 different injection system and the numbers they put out. I am sure that if TBI put out more tq then the TPI did, he wouldn't be having so much controversy over his dyno numbers. Kevin, u did a good job man.

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

Basett Racing:
We spent the time and money to go out and do the testing. Can't you just take it at face value without trying to disect it. If you can come up with actual test results to back up your theory please do so and post them here so all can share as we have done.

Thank you, Don & Kevin

And Thank You Eric for your support.

[This message has been edited by Dyno Don (edited January 27, 2001).]

 

Tom 400 CFI: Okay, I'm getting confused. hp is a function of torque AND SPEED. Right, but I thought it was engine speed, not wheel speed. It's hp = tq / 5252 x engine rpm isn't it?

 

Andy, your formula is correct, but the formula isn't restricted to just the crankshaft of an engine, it can be any shaft, including the ones coming out of your axle housing. The dyno is still measuring torque (by measuring the acceleration of the drum) and speed, the speed of the drum. Just as an engine dyno measures crank torque, and crank speed.

But here is the difference. On an engine dyno, you measure crank torque, and perform the formula you have at every RPM to calculate the hp at that RPM, until you have the entire curve.

The chassis dyno is doing the same thing of the rear wheels. It is measuring torque as it speeds up. However the difference is that at the same time it is measuring the torque and speed of the rear wheels through the acceleration of the drum(hp), it is also measuring the RPM of the engine. NOT TO CALCULATE HP THOUGH! To calculate hp, it counts the RPM of the drum. It is reading the RPM of the motor to corrilate that engine RPM with the hp currently being calculated at the rear wheel. That is what gives us useful tuning info.

Do you get what I'm saying? All the calculations and measurements are done at the drum, which is driven by the rear wheels. But readings of the engine's RPM are being taken so we can see where in the ENGINES rpm range the DRUM is measuring a given amount of torque or hp. It is useless to us to know that 300 hp is being used to accelerate the drum past 156 drum RPM. Know what I mean?

One last thing. Lets say you have an engine that produce 300hp @5000 RPM. At that RPM it is producing HPx5252/RPM= 315ft/lbs of torque.
In 4th gear(to keep the math simple) with a 3.00:1 axle ratio(to keep the math simple) your wheels would be turning 1666.6 RPMs (5000/3.00)
But they would also be delivering 945 ft/lbs of tq (315x3.00). Now do your formula;

HP=(tq/5252)xRPM (945/5252)x1666.6 =300hp
See?

The loss generally associated with RWHP is from friction in the drive train. because of that, the rear wheel torque would actually be less that in my idealic hypothetical situation(by about 15%) therefore the RWHP would calculate out about 15% lower.

[This message has been edited by Tom 400 CFI (edited January 27, 2001).]

[This message has been edited by Tom 400 CFI (edited January 27, 2001).]

 

I for one appreciate the trouble you went through to dyno the motor and show the difference between the induction systems. This is very good data (or at least would be if someone could scan or type in the actual results with rpm's and test conditions).


I however differ on your opinion about dissecting data... I think the whole point for obtaining data is to analyze it in an effort to understand the why's and how's. I'm forming conclusions here about your testing that could provide useful in both theory and practice.
Again, I humbly ask, please post the actual dyno information with barometric pressure, temp and humidity.

 

Thanks, Dan. Disecting the facts is why the car was dynoed in the first place, right???

------------------
82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

 

I wont be able to scan the dyno graph until I go back to work on Monday.

 

"I think the whole point for obtaining data is to analyze it in an effort to understand the why's and how's."

I dont agree. What I see here and on the other board is a bunch of TBI guys crying about the end result of the test, and trying to theorize away the difference in power between the 2 engines. GM did not rate them at the same power. Do you realize that? Doesnt this test coincide with those numbers from GM? Whats this crap about TBI cam? My 86 TPI TA had that same stupid cam. So did a friends 87 TPI. Why are we arguing about timing? They set it at the factory setting. You say the heads are different, the exhaust is different, and in some cases the cam is different. Do you know that the timing is the same even though the cam isnt on the TPI cars? Didnt mention that, did you?

You people arguing over the results are a joke. Take a look at the factory HP and TQ ratings sometime. What I see with this test is similar results. Those of you busy trying to add HP to the TBI results and subtract HP from the TPI results need to come to the realization that even GM knew they didnt make the same amount of power. I am gonna LMAO if the weather testing results come in and theres no difference there either. Whats the next plan of attack, how the older tires gripped the drum better on the dyno? Typical, cant take results for what they are. Ill bet even if there was absolutely NO differences that you are all complaining about you would find something stupid to discount the results.

Right outa the 1988 Pontiac sales brochure, read it and weep:

Gosh, looks like 20HP and 70ft-lbs of torque, what a concept!

 

I've never doubted TPI or its abitilty to make power. Its the fact that it is much more expensive to modify, nothing else. TBI can be used with almost any of the 100s of carb intake with a simple adapter. How much would it cost for a person without hookups to do a TPI swap? $400? At least? would that be that much better than an Edelbrock TBI intake and open element for $250? I dunno. maybe someone can dyno it some day. What if they wanted to go 383 later? how much is a superRam? $900? Mini Ram is $1200. How much is a single plane carb intake and used 454TBI? $300?

 

Gm rated the HP differently, duh huh?? GM also put different heads, exhaust, timing, and on MOST, not ALL, a different cam on the TPI engines so, of course, they were rated higher. I am not disputing that a TPI 305 (LB9) is stronger than a TBI 305 (L03), nor am I disputing that a TPI unit will not make more power than a TBI unit, if you would READ my other posts, you will see that is what I said. I am not crying over the numbers, I'm sure that what Kevin said they got on the dyno is true - I'm not doubting that at all.


Timing has everything to do with an engine's performance, take a 500 HP engine that runs its best at 36* TOTAL timing, and retard it or advance it 5-6 degrees and dyno it, or just drive it, the difference is like night and day. The reason I mentioned it was like I said in an earlier post, I gained almost 2 tenths (.018 to be exact) by changing my timing from 0* to 6* on my LO3. Everyone that is trying to make their L03 run faster is running higher than 0*, or at least I hope they are!!


No, that is EXACTLY what I would like to see!!!

To Kevin and your dad: Once again, I not trying to discredit, or discount you or your research. My hat goes off to you or anybody else that is a car enthusiast and goes out and actually works on their own cars to make them perform better. Also, I have always enjoyed reading your posts and appreciate anyone who gives advice to people who don't have knowledge about our cars.

To Madmax: What I posted was never personal to Kevin, you, or anyone else, but you chose to half-read my post, disregard everything I said, and draw your own conclusions that the reason I posted it was the fact that I think the TBI is a better induction system, and I'm trying to make up excuses for it. That is not the case, I'm simply saying that everybody that has TBI cars are running higher than 0* timing and 95% of us are running open element air cleaners which DO make a very significant gain in performance, I've raced my car at the track and changed the air cleaner and timing there and got 2.6 tenths and 2.1 MPH from those mods. According to the NHRA accepted formula to estimate RWHP from weight and MPH, that is a 13 HP gain. This is an estimate, but it has been proven to be accurate to about (+/-) 5 %. This IS how we run our cars, and this is why I would have liked to seen a comparison with equal timing. Remember, absolutely NO differences!! Like I said before, I KNOW the TPI would have made a gain over the way we run our cars, but I don't think it would have been as staggering of a difference with - READ - all things being EQUAL.

To all: This is my last post on this subject, our boards don't need to be filled with bickering and argueing. I have already drawn my own conclusions about this test, and being confident in what I have proven at the track with my car and the results others have got with their cars, I just can't call this a completely equal comparison. If you agree with me, good, if you don't agree with me, still good - That is YOUR opinion, this is MINE. If you're going to quote me and object to what I say, that's fine, but READ what I said and object to that, but don't half-read my post and assume what I'm thinking.

------------------
82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

 

I remembered that when we last dynoed the car in June, we removed the air cleaner lid, bypassing the filter. Would that simulate an open element filter? Who knows.

We never touched the timing on the TBI engine because my dad ran it on 87 octane. It was never his "race car" like you guys have made with your TBI's. I dynoed the car after I first got it, in December of 98, and it was bone stock with 195k miles or so on it. With the only things I changed being a K&N air filter and Mobil 1 10w-30 synthetic oil, it was 150 HP and 200 TQ. In January 99, I added a 180º thermostat and Turbo City 185º fan switch, and my dad put on a stock exhaust from an 85 IROC he had sitting on a shelf in his shop. Yah it was probably 14 years old at the time, haha. I got my 91 Z28 back on the road in February 99, and have been driving it ever since, while my dad took possession of the 92 RS in question. The car became his pleasure car, until he sold his 81 El Camino, then it became his daily driver. As I said, the timing was never touched because he ran it on 87 octane. It was verified to be at 0º sometime during this time, and was checked before it was dynoed again in June of 2000, still at 0º. The gain after the exhaust, which included the y-pipe, cat, and cat-back, was 8 HP and 20 TQ. The y-pipe was modified to fit the stock exhaust manifolds. I forget when, but sometime in September or October of 2000, the stock 1992 10-bolt 3.08 open rear end was replaced with a 1989 9-bolt 3.27 posi rear with disc brakes. The fuel pump was changed at the same time, to a 55 PSI pump. My dad originally planned to put in a 350 TBI engine, because he knows TBI very well, having swapped 4 of his cars to it, from carb'd. But after seeing the gains I was getting from my TPI engine, he decided to go with TPI. In December of 2000, after months of research, he attempted to run the TBI engine with a 7730 TPI computer for fun. He modified the stock TBI harness, but the experiment was a failure. I wrote this in a thread then that didnt get a lot of replies. So rather than spend the time converting the harness back to TBI, we went ahead and pulled the TBI intake and dropped the TPI intake on. Then in January of 2001, we dynoed the car to see the difference.

Now, for the variables: The last TBI dyno was around noon on June 10th, 2000. It wasnt hot, but it was warm, probably around 80º-85º outside. The TPI engine was dynoed on a different dyno, on a cool January 24th evening around 7pm, . The outside temperature was about 60º-65º. Yes you can argue all you want about the rear end, and the temps affecting the output, but do you really think it affected it 17 HP worth? How about that 70 TQ? I'd say there is a 5 HP and 5 TQ margin of error.

Now, thats the complete history of what we've done. Hopefully I'll have the dyno graphs up on Monday night.

 

Good stuff Kevin. I dont think anyone here is trying to say that the TPI setup doesnt make more power than factory TBI. I for one am just suprised about the torque gain... I was expecting a 30-40 or so gain and you doubled it... thats great... I just want to figure out why.

 

.018 huh? Compared to what? How many runs? What was the weather? Post some timeslips so I can see if the 60' times were different. What other mods during that time, like different fuel or synthetic oil, new plugs? Anything like that? See where I am going with this? I can tear that .018 apart just like you are trying to somehow find out why the 2 results were so much different. I think you missed my point by not reading what I said. So, plain and simple, here it is:

The purpose was to compare a stock as delivered from the factory TBI to a stock as delivered from the factory TPI.

Get that? Was it 100% fair, eh I dont think so. I would have taken the airfoil off. To set the timing 6 degrees advanced, well... do you know what the factory setting is? Looks like it to me. It was never the point to MOD the TBI and compare it to a stock or modded TPI. Thats what you are talking about, advancing the timing to somehow optimize the factory setup. Hell, the TPI responds well to a timing advance too, mine likes to run at 10 or 12 rather than 6. So they should have advanced it too. I'd bet that would negate your .018 increase by increasing the 1/4 time of the TPI by .018 too.

Im done here too. Seems like many are too hard headed to see the facts in front of their face. Ive always been one to accept whats there, and if you wanna mod what you have, by all means go ahead. Is it better? Depends on what you want and what you can afford. I still dont have FI on one of my cars which is carbed, because quite honestly the minimal gain I would get isnt worth what it would cost. Nothing wrong with modding the TBI, just more things you have to overcome to get power since you are in fact starting with less. Take a look at a bone stock LS1 which will trounce modded TPI's all day long. Throw a couple minor mods at it, and try and find a TPI that can even keep up. Good luck. With a TBI there is much more to overcome to even get to that level... I think there is one I know of on this board that ran in the mid 13's? Its not because TBI is worse, its because it had less power and less performance oriented parts to begin with. Simple. This test proves that. Simple. If I were you, I would look at the results and try to find out where the TBI is suffering in torque (I already know where the difference is) and attempt to fix that if you want that sorta torque. A better idea would be to go for a HP increase instead because of how the system is setup. TQ will just come along for the ride.

 

I'm sure the .018 was meant to be .180
.018 is eightteen-thousandths.
.180 is eightteen-hundredths.
and
.2 is two-tenths.



[This message has been edited by Tas (edited January 29, 2001).]

 

After I talked to Don about his swap i came on to check the post he mentioned......i couldn't believe the size of this topic....and it's kinda funny how people don't read everything before they start making comments...It was a stock to stock comparison, and the numbers don't lie.

For everyone talking about how expensive TPI is for this or that, and how much it costs to change your car to TPI..... WHY NOT JUST BUY A TPI CAR TO BEGIN WITH? I mean, you see guys on the boards all the time talking about dropping 350's in their V6 F-bodies and we all tell them it's not worth it...just buy a V8 car....similar situation here. It's far cheaper to start with a TPI car than convert.

 

thats smart. ya. lets all sell our 305 tbi's and go buy tpi 350 cars. we would have all the power we need. we would be happy then and stop trying to mod our cars. that sounds like a very viable, and logical. maybe even valid suggestion. um, no.

 

If I would have know what I know now 3 years ago about this engine. I would have bought a 305 TPI or 350 TPI. Sorry guys, but them numbers don't lie.
BTW: Swapping to TPI may be expensive but you have to look for deals out there. I have seen TPI setups for CHEAP on ebay and from people that have wrecked their cars and just want to get rid of whats left.
COBRAKILLER has an aftermarket TBI and intake on his 355 right now and he runs a 13.5 (I think) and this summer when he swaps to TPI I am going to bet that he runs a better time then a 13.5, but we will just have to see eh Tom?
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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

[This message has been edited by 91Bird305 (edited February 03, 2001).]

 

This really IS hard proof that TPI makes more power on a mild engine, there's no way to dispute that, Kevin was pretty thorough with what was done, and how it was tested. I however am still not goin to TPT because it's better suited for lower rpm torque. The dyno results back that up, it's a torque biased induction system. This is great for street cars, and drag cars. I'm setting my car up (slowly but surely) for road racing. I need high rpm power, not low end torque. The shorter runner lengths of a dual plane, let alone a single plane manifold are much better suited to this task. The only way to get that from TPI is to go with a mini-ram, even a super-ram has longer runners than a dual plane. Mini-ram is out of the question for two reasons: 1) not emmissions legal, and I want my car to be street legal. (well, at least close enough to fool smog check techs.) 2) The damn thing just costs too much. For probably 80% of people here, TPI would be the better way to go, I'm just not one of them. There are 3 reasons for not going to TPI over TBI. 1) You can't afford to do it for one reason or another. 2) You are building an engine designed for high revving power, not off the line grunt. 3) You just love the expression on TPI guys' faces when you tell them they just got beat by a TBI