Why to people say that a TPI is only has power till 4500 rpm? I don't believe this to be true, it did a lot of testing this summer on this issue. My motor is mainly stock, it has vette heads, stock cam, removed egr walls, headers. I also believe reworking the ECM/PROM helped out a ton. It will pull hard to 5500 rpm then falls flat because of the stock cam. I think people under rate stock tpi. I can pull 13s all day long with this setup. Any thoughts?

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1988 L98
Vette Heads/no EGR
SLP Headers/Y-Pipe
ARAP bin

 

I believe it. TPI is useless over 4500max, and I've ridden in dozens of TPI cars that were the same way. Alot of them thought thier car pulled up higher too..turns out thier butt dynos just needed recalibrating in a high revving short runnered car.



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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

 

Its not that they won't pull up there, it's really where is the best shift point. The torque TPIs make (in the 2000-3700 range) tend to make turning it past the HP peak less than ideal. The best rpm to run is the point that the shift recovery occurs in the next gear. Which with tpis (even modified ones) tend to be below 5000 rpm.

And yeah they can run 13s. Its the torque that does it.

[This message has been edited by jcb999 (edited October 17, 2001).]

 

I guess another question I have is:

which is more important intake velocity or volume? or is it a balance? 2 extremes, superram has volume, lt1 intake has velocity

By changing tpi parts, you are basicly decreasing velocity and increasing volume. Is a stock tpi that choking?

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1988 L98
Vette Heads/no EGR
SLP Headers/Y-Pipe
ARAP bin

 

stock TPI is horrible for anything but a tow vehicle. Fastest intakes are gonna be Miniram or have a carb one converted to EFI with a kinsler TB type of deal or accel elbow thing.

the heads are probably almost worse than the intake. They flow nothing.

the cam is miniscule, you need way more duration and lift to condsider power above what it makes.

those are the engine areas that are pretty brutal. There are many other things that need to be replaced to make the car a performer.

 

What do you consider a performing car? 13s are 13s, doesn't matter what type of intake it has. That's a respectable number for a mainly stock engine. oh I could go out and spend 1000's in parts or buy a 98SS to run 13, but it's more fun tuning what i got.

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1988 L98
Vette Heads/no EGR
SLP Headers/Y-Pipe
ARAP bin

 

Dude! Where the heck were you before???

 

I think ther good till at least 10,000rpms

 

I dont shift till 8,000RPM

 

I dont shift till 8,000RPM

 

I just put one of them TPIs on my 60 over 350 with a custom harness and SD computer and I have a good chunk of change invested in it, but the more I hear about them the more I think I should use the edelbrock intake and holley carb and swap out that computer distributor for a real one. The engine is just rebuilt and hasn't been fired yet

 

There is a lot of truth to this statement. Actually, I was thinking GM should have kept developing it for truck applications.

This isn't a "bad thing", a person just has to realize that TPI promotes low-end torque. This is fine for a street engine where a person doesn't want to rev it past 5,000 rpm and pass cars without having to rev the snot out of their engine.

But if a person wants a car that can also do well at the strip, then intake mods are a must. Superram is great for people that want more top end but retain that torquey feel, Miniram is great for people that want big HP numbers (both can be built to produce power depending on the choice of cams).

I have a friend that just built a 383 with a Miniram, AFR 195s with Competition Porting and 2.05 Intakes. We've been tuning his eprom and I will say one thing, that engine builds a TON of low end torque along with high end HP. So don't let people convince you that a Miniram has no bottom end torque either, it does; depending on how you build your motor.

As for the guys that think a TPI can make useable power above 5,500 rpm...sorry, not true. I have had the pleasure to help tune a good 1/2 dozen TPIs (305s and 350s) in the last few months (most NOT STOCK). They all began to lose power above 5,000 rpm and none would make any beyond 5,500 rpm. 6,000 rpm would just be needlessly reving their engines.

The only engines that I have seen that made useable power at 6,000 rpm was a Superram (and it was dropping) and a Miniram (it was still making power above 6,000 rpm).

 

OH sh_t. Here we go again. Just check out all posts from Bugsbunny and highrev 305 post and you will get the picture that it is true that mostly stock or mildly ported tpi will fall off in power at anything above 4500 rpm's. That's why people have switched to other forms of induction. As for me I will be switching to the LT1 intake setup.

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89 Iroc 350 TPI,
Forged pistions
Comp roller Cam .510 lift 230dur
Flowmaster exhaust
Dart Iron Eagle heads 200cc runners 64cc chambers
MINI RAM SOON!!!!!
stock TPI for now 24# inj
87 Trans Am GTA 350 TPI
had engine fire
SHE NOW RUNS!!!! GREAT!!
Flowmaster exhaust
LT1 Injectors

 

I'm guessing everyone who's craving (or who has) high rpm power, never had the chance to play with BBC's and high (lower numerically) gear ratios.

Lowend torque and the proper gearing is an amazing thing...you don't have to run 6500+rpms to be quick.