ok at first you may say no way right? but, think of it this way ok?
1) TPI= batch fire roller 350 9.5:1 compression cheep castiron heads that flow like cra! (230-235 hp)

2) LT1= seq. firing roller 350 10.5:1 compression fairly decent aluminum heads with rev. cool. (270-280 hp)


now never mind the first lt1s 93-94? OBD1 look at first the comp ratios now look the lt1 has seq. fire. well when gm changed the 3.8L v6 from batch to seq. it gained 30hp! same cam! now lets say you give a tpi seq. inj. 30+hp (265hp) now lets even out comp to 10.5:1 off the top of my head say it only gives 5hp(270hp) now to even it up more lets give the l98 some better flowing aluminum heads 15+hp?(285hp) wow??? now think the seq. would really give you mare than 30hp and comp would most sertantly give more than 5hp and the heads hard to say but, I bet they would be better than 15hp. plus the torque the tpi makes would put the lt1 to shame

 

Sorry, but seq inj does not add that much HP. Look at the difference on the LT1 from batch to seq (275 vs 285) and if I recall there were other changes too at that time.

The biggest gain from batch to seq. is beter economy and emissions. The performance gain is not that great. Besides to make sequential totally work, you would have to know how much to trim each injector for "balance" or have an O2 sensor on each primary.

But, when you really think about how "batch" works, the engine does not know the difference. First, the injector is not in the cylinder, its is in the intake port just before the valve. When the injectors fire, they "pulsate" and the air in the column moves in a "wave". The fuel just doesn't splash against the valve while the air remains stationary. The air is actually moving all the time. Thus, even though the injector fires more often when the valve is closed than when open, as far as the column of air is concerned it is firing while the air moving and mixing.

For all the work you would incur (and expense), you'd end up with a lot of money spent for a maximum 10 HP. Not a good bang for the buck IMO. Better off saving your money and springing for a good set of heads.

 

When did GM change the V6's from batch to sequential on 4th gens? All I know is the 3.4L was 160 HP, and the 3.8L they switched to in late 1995 was 200 HP. They have kept the 3.8L ever since.

Also, the 275 to 285 HP switch was when they went to dual cat exhaust in 1995 on California automatic cars, and 1996 for all others.

Whats funny is the L98 aluminum head Corvette made the same horsepower as the iron head L98 in the f-body. I wonder why??

------------------
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=-

 

it may not give much horse but, it would give you that increse through much more of your band not just one spot.

 

Not at all 88. The power band is a function of the induction system and camshaft more than anything else.

If you "converted" a TPI from batch to sfi, I doubt you would get more than 5-10 HP and it would still have the rpm limitations of the TPI system due to the long runners and camshaft.

As I said, you would benefit more from increased gas mileage and reduced emission, but how much...is anyone's guess.

Still not a cost beneficial modification in my opinion. But, give it a go and let us know the results.

 

Look at the 93 LT1. It was still batch fire, yet made a good bit more HP than the L98.

Why?

Better heads.
Higher compression.
Better intake for high RPM.

That right there made almost all the difference in the HP, I'm sure.

 

you fail to see what I am saying. the horse power will be incresed more on its normal band. second have you ever seen both batch and seq. lt1 on a dyno I have and there is a BIG diff. I don't car what motor trend says I belive what really happens. and if you think that fuel loves to stay suspended in the induction system then why does nos say to be carful of the fuel droping out of sus. I am not trying to get snippy but, man some people get excited about nothing.

 

No, your failing to see what we are saying...it'll do basically nothing. The fuel does NOT stay in the air column like a bunch of cars in a traffic light...it travels in a "wave" and is constantly moving. That is the dynamics that is occurring internally within the intake port. But it's your money...go for it and tell us the results.

So how much do you estimate this conversion is going to cost? How do you plan to "marry" the LT1 pcm into the TPI intake? And what do you truly believe you'll gain from this? I can tell you the gain will be less than 10 ft/lbs through out the power band. Sorry but that is truth of what you'll experience for this conversion.

And after you tell us the amount of time and money you spent on it and how much (actually how little) you gained, it will be pointed out that for the same money you could have just installed a cam and had REAL HP.

Actually, the biggest gain you'll get is having the superior LT1 PCM MAF system over what is on the TPI cars. But it is function of the PCM, not the seq. vs batch fire system. If it was TRULY cost effective, don't you think a lot of the TPI MAF cars would go to it that have superchargers? They are the people that would truly benefit because of the higher gm/sec reading of the LT1 PCM MAF system. But why don't they do it? Simple its damn expensive and not easy.

I've seen this question on the PROM board again. I highly suggest you find the post and read it. But, this is not a "cost effective" mod.

[This message has been edited by Glenn91L98GTA (edited January 26, 2001).]

 

I definately have to agree with the L98 being the better engine.

Eventhough we can't turn back the hands of time, think about how much more HP AND TORQUE figures the L98 would have had IF GM had put aluminum heads and bumped the compression to match the LT1.

Also, consider that the TPI setup on the L98's was meant for the 305..

Sure, this is all "what if". But let's just make the playing field a little bit more "equal" between the L98 and LT1. Come on, you can't say that you would choose CAST IRON heads over ALUMINUM..

 

Age, actually I would (prefer cast-iron over aluminum). They are cheaper, stronger, more durable, develope more HP from the same compression ratio and you are less likely to cross thread your spark plugs or gall the heads.

Biggest advantages of aluminum are they are lighter, easily repaired and can allow an engine to use a higher compression ratio. But then, you NEED that higher compression ratio to make up for the losses from converting from cast iron to aluminum.

 

You mean when they changed from the Chevy 3.4 motor to the Buick 3.8 motor in the F-bodys?? , they gained 30 h.p. And actually it gained over 35

And if your talking about the 3.8L itself, it bumped up h.p. when they redesigned the entire engine which became the 3800 GEN II Buick engine.. New heads, big exhaust manifolds, and intake design. It had nothing to do with your sequential theory.

Please show me these dyno results, because I have personally seen well over 20 LT1s dyno of all years, including the 93 F-body LT1s. And there are NO differences based on batch vs seq injection. Actually some of the strongest running LT1s are the 93 due to speed density when they are stock. Even over dual cat cars on occasion.

LT1 heads flow around 20 more CFM @28 inches than the L-98 heads

LT1s have 360 degrees of timing, while L-98 use the conventional dist with only 90 degrees of timing.

Lt1s have reverse flow cooling, which allows 10.5.1 compression and keep within Federal emmisions.

The LT1 intake systems short runner design outflows The l-98 considerabally.. You can run a ton of H.P. though a stock LT1 intake.

LT1s stock dyno 255 RWHP h.p. on average while the 91-92 L-98s run around 225-230 RWHP.

I dynoed 292RWHP on my LT1 with just full exhaust(headers, gutted cat and cat back) and cold air. 3 bolt ons, and I hit 109 mph trap speeds. This is where the LT1 shines over the L-98....meaning stock they are kind of close, but a couple bolt ons, and the lacking heads and intake of the L-98s start to really show.





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

 

I can see that 91gta knows what he is saying but, come on if you think that the first lt1s turn close to the same hp you must not have seen any in person

 

almost forgot where on the entire message did I say I was converting to seq.???? second yes you could do a convertion but yes I agree even if I did get a few more poneys it would not be worth it. not so much cost but, time. I was only saying even it up. and pointing out that lt1s are not all that great. ls1s now that is a motor

 

You forgot one of the biggest advantages to any aluminum part, greater heat disapation, which in a head results in less of a tendancy towards detonation.

 

1985 3.8l mfi vin-3 hp 125 hp @ 4800
1986 3.8l sfi vin-b hp 150 hp @ 4400


this is just some thing I found for specs on a buick centry wasn't what I was looking for but, does show a big diff

 

Z28, the heat works two ways. Yes, aluminum dispates it better thus allow for higher compression, but the cast-iron's heat retention is part of the reason they develop more HP @ the same compression ratio. It's one of those funny things that is not "black and white"...but kind of gray.


88, the most comparable comparison in my mind is when the LT1 went from batch to seq., the gain was only 10 HP and they also went to dual cats as Kevin pointed out.

As for LT1 vs L98, I consider the engines themselves as different. The L98 is a low revving, high torque motor; where as the LT1 is a higher revving, higher HP motor. Personally, I like the power charateristics of the TPI system and I think GM should have continued development of the concept. If I ever total my car, I have plenty of buddies with trucks that already have place "dibbs" on my engine...they like the torque so much.

I always found it funny that GM went from one extreme (long tube L98) to the other (short runner LT1) and then chose for the LS1 a system that appears to be a compromise between the two.

 

I believe this is the biggest falicy there is about the TPI. Being designed for a 305.

You think they designed the TPI to go on the f-body? You also think the f-body is the flagship GM car?

EHH!!! WRONG. They designed it for the vette. The car that is ALWAYS the test bed for what gets dumped over to the f-body.

It is designed for a 350.
It just works well on a 305 even when you add a lot of mods.

Just logically think it through.

Oh another thing with aluminum heads. You have to bump the compression up on them vs. iron heads to get gains out of them. I cant remember exactly why but it has something to do with the quench time, etc. blah blah...

------------------
-86 IROC
Vortech stuffed EFI 406 in progress
-=ICON Motorsports=-
Cluelessness: There are no stupid questions, but there are a lot of inquisitive idiots.

 

LOL Yeah, I guess your right

Hey 88 350TPI, it seems like you know plenty about the LT1s. Can you give me some advice on how to make mine go faster??

 

Hey Guido, long time no talk. I've been meaning to send you an e-mail.

I can't remember the EXACT reasons, but heat was a major factor. It was in some older magazine article about heads and it had something to do with the heat retained by cast-iron heads (along with a bunch of other engineering mumbo-jumbo). It was also from this articel (and other things that I have read, including a few people on this board), where I noticed that "hotter is better" when it came to developing more power...within reason. It is when I actually tested the effects of a hotter T-stat (now that I am burning my own eprom), that I confirmed for myself that a cold t-stat is not necessarily a good mod.

I should add, that I forgot another advantage of aluminum; the softer metal makes it easier to port.

 

Hey Guido, it was designed for a 305

Chevy was planning on dumping the 350 from the vette too and using a 305 instead. Just so happens they changed their mind but the intake was already done.

The heat in the combustion chamber also helps produce power. Aluminum dissipates heat faster than cast iron, and therefore sucks more heat out of the combustion chamber. This costs you some HP in the form of lost heat, but you can run higher compression and gain some of that back. Its hard to say if the loss is worth the gain, but IMO its probably close enough not to worry about.

 

Glenn, the 93 F-body speed density batch-fired LT1 was rated at 275 HP. The 94 F-body MAF sequential fired LT1 was rated at 275 HP. 95 stayed at 275 HP for the 6-speed and non-California automatic LT1's, and the CA automatic LT1's got the dual cats and 285 HP. In 96, all F-body LT1's got dual cats and 285 HP. I do not know the HP ratings for 92-93 Corvette LT1's and 94-96 Corvette LT1's, but I think it was 300 HP. I'm not aware of a difference between 92-93 and 94-96 HP numbers.

 

Thanks Kevin. Not following the evolutionary changes of the LT-1 extremely carefully, I was aware in the early 90s there was an increase from 275 to 285HP, a change from batch to seq, a change from SD to MAF and a change from single to dual cat all within a year or two.

Canada gets slightly different cars in certain areas because certain parts (lower mainland of BC) must meet California's (actually lower now) emission standards. Being 5-7 years ago, I remembered all the changes roughly occurred at that time, but the biggest contributor to the 275 to 285HP was not the batch to seq injection but some other mod; which you reminded me of the single to dual cat.

Thanks for the clarification of when various changes were made, and that the change that contributed to the 275 to 285HP was the dual cats and not the batch to seq. injection. (or the SD to MAF for that matter). Though, I do understand that the 4th Gen MAF is a vastly superior system for "tuneability" at the PCM level. Hope to get a chance to play with a 4th Gen MAF system one day.

 

guys the lt1 is not that much stronger than the l98. we are talking about a diffrence of 2 to 3 tenths at best. I beat them at the track all the time. there are some that have the same mods that i ahve that run about the same at the track. while they do have higher trap speeds i kill them through 1st bad enough to beat them. The l98 is a beter engine for the stop light derby. the superior torque of the l98 gives you an instant car length lead over the lt1 guys. how far do you guys race? where i am from the 1/4 mile is all we race to. Some times i am actualy pulling on lt1's through the entire 1/4 they may run similar and some times slightly higher trap speeds but i am infront so far that i got to 100 mph before they did. let me put it this way if i raced a pro stock car that shut off at 100 mph he would be pulling on my for the entire 1/4 mile even though i had a higher trap speed. it is just the fact that he hit 100 mph 300 ft into the race and finished the 1/4 before i ever got to 100. the trap speed is not every thing. just because some one runs a higher trap speed does not mean they are pulling on you in the traps and it does not mean they would ever be able to pull on you.

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90 iroc l98
last season best corected 13.62 @102
mods
full exhaust, AFPR, pulley, jet stage 1 chip, billet servo, 52mm throttle body and a few other little things.

 

That is about the stupidest comparison Ive ever heard.

Cmon guys, everyone knows the 334TBI is the best engine ever made. I was thinking about talking my dad into putting a 334TBI into his 68 Camaro that he races at the track.

It runs 9.70's in the 1/4 now but I told him that if he put a TBI on top of it that it would run 8.70's.

 

Guido, it is not a false statement. The tpi was designed for the 305. And you are right it was designed for the flagship vette. Gm had planned to drop the 350 and the vette was going to be a 305. Last minute changes kept the 305 and the tpi was forced to choke a 350.

 

Wow, you guys really take this stuff a little too serious. I have really enjoyed working on both of these engines. They are both great designs. But, I would have to say the neatest one we have got to work on is a 89 IROC. It now has the updated L98 ( ZZ-4 ) crate motor. Amazing how much it looks like a LT1 on the inside. It also has AFR heads and a Mini-Ram intake now. Not too bad for a stock bore and stroke engine... 12.10 @ 119 mph. Still even has the old T-5. I would just hope my latest tinker toy comes close.
Some of you guys really know your stats on these motors. I guess I just sleep too much.



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1988 Trans Am. Carburetor fed LT1. T-5. Ready to rock and roll. No runs yet though.

[This message has been edited by RedRaider88 (edited January 29, 2001).]

 

88red I'd like to hear a little more about that minram combo. Im no where near those times on motor alone, and am trying to peg it down to if it is the computer or not. I will soon put it on a dyno with a wide band o2 and see if it is the program.

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87z 383,afr 190's, crane hyd roller(224/230-.509/.528,112 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, strange 12 bolt, tremec 5spd, , 1,3/4" slp headers.

 

It's kind of sad to see people arguing over the relative merits of two discontinued motors(each has distinct pluses and minuses). It's also kind of sad to see how easily GM gives up on promising concepts without fully developing the potential.

It is very nice to see that the aftermarket is not as quick to discard a good idea. Judging by the number of businesses specializing in "TPI", and developing new products for it, the Tuned Port Induction still has considerable life left in it.

 

It is really hard to compare these two engines. We are dealing with apples and oranges here. The main point he was trying to make was that if you put a SPFI unit on a TPI, jack the compression way up, and other stuff like that, the L98 would surpass the LT1.

I dont agree. This is practically bench-racing horsepower figures.. Whats good on an Lt1 will not necessarily work good on an L98..The motors are designed to be different. L98=Tons of Torque at lower RPMs. LT1= Good torque throughout the power band. Intakes are way different..Too different to even compare.

The L98s Hp Rating of 235/245 or whatever is somewhat miss-leading compared to the LT1s 275/285. The thing that is going to make your car fast is TOTAL TORQUE not just some peak number. A car could have 500Ft/lbs of torque at any given RPM and only have 100ft/lbs everywhere else in the RPM range, but a car that makes a nice Flat torque curve around 400ft/lbs for the whole power band, would be a faster car. No doubts.

This is almost the case here. (I am not trying to imply that an L98 has more "total torque" than an LT1) but, it is pretty close. Closer than the 40-50 Hp difference in engines leads us to believe.

I have raced several stock 4th gens when my car was stock and I have beaten many of them and also lost to some. So, I believe that a L98 car and a LT1 car are getting similar amounts of total power to the ground.

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

 

87z-ya... yea. No problem on the info. Just let me know what you wanna know. The low down as it stands right now is: Mini-Ram is port-matched to the AFR 195 CNC and ported heads. They have the comp. valve job and were angle cut to 57cc. The bottom end is a stock bore and stock stroke ZZ4 350. SLP Cold Air Induction. AS&M 52mm TB. 4th gen 10 bolt with 4.10 gears. After market control arms and torque arm ( who's ?) All of that with launches only in the 3000-3500 rpm range. 12.10 @ 118.9 mph. Not bad.
Anything else... just let me know.

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1988 Trans Am. Carburetor fed LT1. T-5. Ready to rock and roll. No runs yet though.

 

You guys forget to look at TORQUE. The L-98 has even more torque than an LS1!!!!!!!!