6G Celicas Forums

The engine is completely stock, thats why i stop at 10psi.

Interesting. OOBE said that 8 PSI was the max on stock internals. No issues whatsoever though?

No issues at all, it depends on the injection and especially the ignition tuning how much a 7A will handle without braking something. I tuned my 7A to run with an afr of 11,5:1 at full boost and retarded the timing a lot. It's absolutely important to watch engine knock while tuning.
8 psi is pretty safe on a good tuned 7A, 10 psi is the max i would give a stock engine over a longer period of time, maybe 12-13 psi with an water injection.
If you want to go higher you have to lower the compression and get some stronger internals...

WTF? I NEVER said that 8 PSI was the max on stock internals. I've had mine to 15 PSI.

The "mechanical engineer" guy was the one that said that. I was the one that broke that myth here years ago about the 7A-FE not being able to handle more than 7 PSI.

I do know stronger internals are eventually necessary, I just thought that point was past 8 PSI.



OOBE, you lied to me! Okay, good then. What I'm really looking for is not necessarily a max, but a good point for a DD. What do you run daily?

So both of you guys, push the hell out of your engines so Ferdi has plenty of study material!

This post has been edited by SwissFerdi: Nov 9, 2009 - 5:11 PM

awesome look at that odometer move!

Ferdi,

With good tuning, 10 PSI on a good size turbo is nothing for this engine. You can run it daily. Even with the piston I hurt in the dyno, I was still boosting 15 PSI daily until the car overheated because of a failing radiator fan last week. The broken piston never got more hurt than what it was when I overboosted 18 PSI at the dyno, which is when it broke. The dyno read 222 WHP when the piston broke and I wasn't even on WOT. Who knows if the engine saw over 250 horses. The dyno read that, but the engine might've made way more. That's asking a lot. These are replacement pistons, so they might be weaker than Toyota pistons.

Remember that different turbos give you different power per pound of boost, and the weather conditions affect power A LOT, which is a very important fact that most people forget or fail to realize. In my case, just one PSI in the lower boost range on my turbo counts for ten wheel horsepower according to the dyno, and that's on 85 degree weather at night with a lot of humidity. I might get more on a cool day, which never happens in this island. I also have a bigger turbo, custom intake manifold and bigger throttle body...and also a more efficient intercooler with a horrible two PSI pressure drop. These items were not installed last time I dynoed, so I cannot compare the numbers. Everything changed. Who knows how much these items helped the engine or took away. I couldn't baseline unfortunately.

At 15 PSI, I'm probably getting a bit more than ten wheel horsepower per pound of boost, since the turbo is in its sweet spot on higher boost. Taking this into consideration and given the acceleration rate and how the car feels, if I follow that 10 WHP/PSI ratio, who knows if I'm probably at 250 WHP as of now...ignoring that the head is warped and that the piston is hurt. It's very possible, since the AFR stayed religiously the same from 7 PSI to 18 PSI and the power was being made consistently.

If it wouldn't have overboosted, it wouldn't have broke a piston and I ASSUME I would be around that power level, give or take. A smaller turbo will give you less obviously. So after my experience, I can say that with a good tune, you can boost a bitty more than 200 WHP daily with no problems.

This post has been edited by OOBE: Nov 9, 2009 - 6:15 PM

That's great to hear. 200 WHP would be PLENTY for me, especially coming from...80ish WHP? Realistically, I'd like to say I'll be able to work on the engine once I start this turbo install...but more than likely, I'll still need to learn. Simplistically, I'd like to bolt the stuff on and get it tuned to a reliable standpoint for DD where I won't have any problems. I do want my money's worth in power right away, obviously.

This post has been edited by SwissFerdi: Nov 9, 2009 - 6:01 PM

Well, the most important thing is to find a good tuner, and either use an e-Manage, or an AEM FIC, or better yet, a stand-alone EMS, because you NEED to be able to control timing if you want the engine to last. I've broken a piston three times in six years. The first two times were because of detonation, not boost level or leaning out. This engine advances timing a boatload when accelerating. You will not believe it. I wish I would've recorded when my tuner took timing readings with a very expensive digital timing light. It was unreal and we were surprised that the engine lasted through all that abuse with such advanced timing throughout these years. By the way, I just sold my e-Manage last week. It worked awesome, but I need more control of the engine because I'm aiming for good numbers now since I'm going with forged internals.

I'd love to find somebody local that knew their way around a 7A-FE, or at least a turbo'd version of a Japanese 4-banger...my mechanic might have a hookup though, or know himself actually. I imagine those systems are pretty expensive? Well worth it though, obviously.

So basically, if the timing's off, the spark won't go off relative to the correct piston position and it'll just run like crap?

This post has been edited by SwissFerdi: Nov 9, 2009 - 8:09 PM

The spark will go off regardless, and there is no such thing as correct piston position. It depends on the engine and what you want to do with it. The point is that if the timing is too advanced, you'll get detonation. Detonation kills engines inside. There are different kinds of detonation. That's why you need high octane fuel or meth/water injection to run high boost. No need for someone to know about 7A-FE engines. My tuner is a 3S-GTE expert, but he has never touched a 7A-FE before mine. It's all about knowing the principles of tuning.

Okay. I was just thinking in relation of the piston in the chamber moving toward the spark or away from it...if that makes sense.

This post has been edited by SwissFerdi: Nov 9, 2009 - 9:05 PM

Detonation would be the the spark igniting the mix b4 the piston is a TDC(top dead center)...thus teh crank forcing the piston up and the mix forcing it down(bad mix )

The mixture is always ignited before TDC , detonation occurs when the mixture is very hot and pressure rises extremely fast in the cylinder due to a to much advanced ignition timing, this ignites small parts of the mixture.
Pre-Ignition would be the really bad thing thats forcing the piston down when it want's to go up...

well i ment wayyy before haha...Detonation=heat...pre-ignition=timing

This post has been edited by CelicaST_CALI: Nov 10, 2009 - 11:40 PM

Hafkai, another question...you're running the stock transmission right? I'd like to do a manual swap before I turbo, and I'm wondering if the ST's C52 (?) will hold the power, or if I should just get the GT's S54.

Ferdi,doc told me he had a 4agze with a c52 and 225 running through it fine..

> Nov 9, 2009 - 8:02 PM
> SwissFerdi
> '97 ST Hatchback
> From Fort Myers, FL
> I'd love to find somebody local that knew their way around a 7A-FE, or at least a turbo'd version of a Japanese 4-banger...

We'd All love to find a professional to do it.

> So basically, if the timing's off, the spark won't go off relative to the correct piston position and it'll just run like crap?

Learn to tune Yourself ?
www.efi101.com

How far away is Port Charlotte ?

EFI-101
Fundamentals of High Performance Engine Tuning
Using Aftermarket Electronic Fuel Injection
Port Charlotte, FL (Relentless RPM)
http://www.efi101.com/schedule.php?cat=EFI&country=USA

Regards;

OOBE, i've only taken 1 degree per psi of boost. I'm running at 9 psi.

Appreciate it, but $500 for two days of class? Holy crap!

This post has been edited by SwissFerdi: Nov 11, 2009 - 4:06 PM