Horsepower increase from tuning stock turbo from 7psi to 14psi

vpr131

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Feb 9, 2012
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Orlando, FL
Hey guys, I was just wondering around how much of an increase in horsepower i would see by tuning my mk3 from 7psi to 14psi. I know everyone says its around 5-10hp for every pound of boost but I was seeing if anyone has had theres dyno'd and tuned and how much it increased after the tune. thanks
 

vpr131

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Feb 9, 2012
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Orlando, FL
thats what i thought. i know a lot of people out there with the stock turbo like mine so i know someone has done it before and knows how much it is
 

suprarx7nut

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Nov 10, 2006
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Using the stock CT-26 at 14 psi is a little more than most would probably recommend. However, if you were to run at that boost level (and risk burning out the ct-26 in a very short time) you'd probably be around 300-375 whp. It all depends on what else you've done.

The boost level is a small part of a very big and complex picture. If you just took a stock motor, threw on a boost controller and set it to 14 psi you'd gain very little. It's a system and you have to continually upgrade the weakest link.

IE:
Turbo elbow
Exhaust
Intercooler piping
Intercooler
Intake
AFM
Boost controller
Upgraded CT
etc, etc...
 

vpr131

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Feb 9, 2012
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Orlando, FL
sorry i forgot to mention i have the HKS PFC FCON which takes away the stock fuel cut. So 14psi would be too much on the stock turbo? ive heard a lot of people run it on that much boost
 

SupraSean

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Mar 3, 2009
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i had an 89 targa that nobody could explain. upgrades were 3" turbo back, solid mounts, egr delete, and a boost controller. this was on a "jdm" 7mgte with a stock ct26. The car made 278whp and 323 wtq at 11psi, made 295whp and 350ft lbs of tq at 12ish psi. car was a freak, ive never had one so stock run so good. Numbers were on a dynojet iirc.
 

rodama5anthony

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Sep 24, 2010
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SupraSean;1817350 said:
i had an 89 targa that nobody could explain. upgrades were 3" turbo back, solid mounts, egr delete, and a boost controller. this was on a "jdm" 7mgte with a stock ct26. The car made 278whp and 323 wtq at 11psi, made 295whp and 350ft lbs of tq at 12ish psi. car was a freak, ive never had one so stock run so good. Numbers were on a dynojet iirc.

stock downpipe and elbow?
 

vpr131

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Feb 9, 2012
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Orlando, FL
Wow 17hp from 11 to 12psi! i havent heard of anything like that before. Did you do anything else besides increasing boost from 11-12?
 

suprarx7nut

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vpr131;1817354 said:
Wow 17hp from 11 to 12psi! i havent heard of anything like that before. Did you do anything else besides increasing boost from 11-12?

Like I said, boost pressure is a small part of a big equation. You can easily have 50whp difference in one psi increase if you change a bunch of other items.

Don't get all hung up on a certain "psi".

Sent from my ADR6400L using Tapatalk
 

supraguy@aol

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Dec 30, 2005
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VPR131-What are your mods?
You have to have some sort of fuel mods in order to 'tune' on the dyno.
If you're talking about a nearly stock setup, then I'd say you won't pass 275hp
 

TRDownShift

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Sep 19, 2010
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Hmm, I guess as long as this is up here... what would you guys say I'll get with a Lex AFM, Ported head, 3in' turbo back, and an intake? I'm hoping for at least 250~260RWHP once the rebuild is done.. and i'll go from there :p thinking about picking up a light weight crank pulley before the rebuild just because there cheap and I hear it's an extra 10~15hp :p

Oh lets say since I'm having the block decked for a MHG I decide to say "fuck it" and have them bore it .020 over while there in there... what would that do? 3.2l 7M :p
 

supraguy@aol

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Dec 30, 2005
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Lightweight crank pulleys are a point of contention; It is said by many that the oem crank pulley(vibration dampener) is necessaryto reduce harmful vibrations. ATI is the only universally recommended crank pulley that I've seen.As for those mods, I would certainly say you can hit at least 260hp on a healthy motor. Even if you don't crank up the boost artificially, you'll be at better than 9psi with a freeflow exhaust and intake.

I did 260 with stock injectors and a MAFT. I strongly suggest you use 550 or 560cc injectors with that Lexus AFM. Otherwise you'll be hard-pressed to tune the mixture anywhere near safe or useful.
 

suprarx7nut

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LEX AFM requires the 550 injectors. That's the whole point of the upgrade. The AFM without the injectors is somewhat useless like supraguy said.

Lightweight crank pulley wont do you any appreciable good, IMO.

I wouldn't bore the block anything beyond what is required. There are PLENTY of ways to gets lots of power from the 7M. Boring out the block is not the best way to do it. This isn't an old domestic motor. ;)
 

TRDownShift

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Sep 19, 2010
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Oh ok, so boring out is a no no :p got it, And I only have the lex AFM because I found it at a junk yard for 5 bucks and I know there like 80 anywhere else :p That and I was running super rich for some reason at the time and a buddy who has a few 3rd gen supra type cars (had a MKIII and now has two 1JZ powered cressidas) told me it would lean it out a bit and help with the rich AFR and wouldn't hurt my car at stock boost :p but it's funny.. wen I put it on I felt a pretty good power gain >.<"
 

suprarx7nut

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Nov 10, 2006
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You'll feel a good power gain, but that doesn't mean it's safe. If your car is running rich, you should figure out why. The lex AFM changes the air signal by about 25%. You're now running 25% leaner than what the stock ECU wants.

If you were/are running rich, it was likely the car's way of protecting itself because something wasn't right. Running too rich is perfectly safe. You may wear out your O2 sensor and catalytic converter, but you wont kill the engine. Running too lean can KILL the motor in ONE pull.

This is all why you'll hear experienced mechanics and tuners say, "It's all about the tune". Normally this is referring to running a lot of power on a motor not necessarily built to be bulletproof. Keeping a good safe tune can get you a looooong ways towards success with any motor.