What is your Turbo Boosting..

What psi are you running your turbo during race or strip application?

well um..i dont have a turbo..itd be nice but hey ..so would a good paying job. if i had one itd be on a drag motor pushing over a bar..i can say that.:cool:

I know someone who runs 24 psi (not all the time) in an '03 WRX that makes over 300hp.

at 24psi he is only making over 300hp? shouldnt that be close if not over 400hp? i have a friend with a bmw 528 with a 3.2l M3 engine fully built and boosted to 28 psi on the street pushing over 550hp. he doesnt race it very often but when he does it goes up to 32psi! he hasnt dynoed it at 32psi yet. should be 600+hp. on 19" BBs LM wheels which are not light by any means and full interior he ran an 11.2 on the quarter. so ill put a vote in for him since i am not boosting:biggrin:

Originally posted by edman24
at 24psi he is only making over 300hp? shouldnt that be close if not over 400hp? i have a friend with a bmw 528 with a 3.2l M3 engine fully built and boosted to 28 psi on the street pushing over 550hp. he doesnt race it very often but when he does it goes up to 32psi! he hasnt dynoed it at 32psi yet. should be 600+hp. on 19" BBs LM wheels which are not light by any means and full interior he ran an 11.2 on the quarter. so ill put a vote in for him since i am not boosting:biggrin:

Have you heard of turbo sizing lately? A tiny-ass WRX turbo @ 24 PSI is moving a lot less air than something like a 60-1 is moving @ 24 PSI.

Personally, I have a safe tune for 1 bar daily on my honduh, and so far I don't have any need to go over that.

10psi now, but after the completely fortified block, 25+ :icon16:

Originally posted by edman24
at 24psi he is only making over 300hp? shouldnt that be close if not over 400hp? i have a friend with a bmw 528 with a 3.2l M3 engine fully built and boosted to 28 psi on the street pushing over 550hp. he doesnt race it very often but when he does it goes up to 32psi! he hasnt dynoed it at 32psi yet. should be 600+hp. on 19" BBs LM wheels which are not light by any means and full interior he ran an 11.2 on the quarter. so ill put a vote in for him since i am not boosting:biggrin:

Somehow I doubt that. He would have to have a full roll cage otherwise they would have kicked him out of the track. You have to have a roll cage if you in the 11s.

Anyhow; both of my GTCs run 13 PSI stock. On my project GTC I plan to run around 21 PSI max on new Garrett GT series turbo. I'll run around 13 PSI for daily use, maybe lower. The GTC will be a street project car. I don't plan to take it to the track very often.

I'm running 7-8 PSI now, I've had it up to 11 though. After I add my intercooler I'm going to run 12-14 PSI.

Damn all you people with your turbos Now I want one! :biggrin:

was at 7 PSI on stock block, now I'm goign to swap and raise the boost for track purpose to about 25 PSI hopefully if everything goes well.

whether or not you believe me that is besides the point Polygon. he has been to the track only that one time. and im sure its because after that run they never let him back without roll cage and everything else.

also yes i know about turbo sizing but i didnt think anyone would be dumb enough to push a stock wrx turbo to 24 psi. i think that is really stupid.

AM RUNNING AT 8PSI AND IN THE FIRST STAGE OF BUILDING MY BOTTOM/TOP END. MY MECHANIC SAID THAT WHEN IT IS FINISH I CAN RUN UP THE MAX HP MY TURBO CAN GIV ME.THEN ALL I HAVE TO WORRY ABOUT IS TRACTION.:bigthumb:

Originally posted by SLEEPERACCORD
AM RUNNING AT 8PSI AND IN THE FIRST STAGE OF BUILDING MY BOTTOM/TOP END. MY MECHANIC SAID THAT WHEN IT IS FINISH I CAN RUN UP THE MAX HP MY TURBO CAN GIV ME.THEN ALL I HAVE TO WORRY ABOUT IS TRACTION.:bigthumb:

Where at in Baltimore are you exactly??

And IF I had a turbo, I'd be boosting 5.5lbs:biggrin:

am in GlenBurnie.where are you located

Originally posted by whtteg
Damn all you people with your turbos Now I want one! :biggrin:

LOL, so get one! Looks like in your mod list you have your stock internals, go for it! With your current mods and boosting about 8 PSI you will do like 235 WHP give or take.

235! naw i don't think so i think more like 260-270. anyway
so when you say "go for it" do you mean it like in a sarcastic way or are you serious because i take what i read on this board serious.you know am looking for good,and educated advice/answers.i try to do the same when replying to a post.:bigthumb:

Originally posted by SLEEPERACCORD
235! naw i don't think so i think more like 260-270. anyway
so when you say "go for it" do you mean it like in a sarcastic way or are you serious because i take what i read on this board serious.you know am looking for good,and educated advice/answers.i try to do the same when replying to a post.:bigthumb:

He was serious and yes he knows alot about turbos so listen to PWMAN if he tells you something.


PWMAN: Money is the issue at the moment lol. But maube in a year or so but I am also saving for a M3 so turbo teggy or M3? Maybe both eventually :bigthumb:

Originally posted by whtteg


He was serious and yes he knows alot about turbos so listen to PWMAN if he tells you something.


PWMAN: Money is the issue at the moment lol. But maube in a year or so but I am also saving for a M3 so turbo teggy or M3? Maybe both eventually :bigthumb:

Maybe he didn't see I said Whp, not just HP. Yeah it would make about 260 to the crank.
Anyway, when isn't money an issue? LOL, unless you are spoiled rich. I'm certainly not!
I don't know much about BMW's, so I can't really say. Of course the beemer is going to be much more loaded with options I'm sure. But there is much more aftermarket for a teg, being that jap imports are the major thing in the scene right now. So I don't know, IMO go for the TEG. Everything for BMW's costs too much.

Originally posted by PWMAN


Maybe he didn't see I said Whp, not just HP. Yeah it would make about 260 to the crank.
Anyway, when isn't money an issue? LOL, unless you are spoiled rich. I'm certainly not!
I don't know much about BMW's, so I can't really say. Of course the beemer is going to be much more loaded with options I'm sure. But there is much more aftermarket for a teg, being that jap imports are the major thing in the scene right now. So I don't know, IMO go for the TEG. Everything for BMW's costs too much.

Well the M3 is supose to run mid 13's stock so I am thinking about it for a daily driver. I could do some simple thingsd to it and be hitting 13.0 or high 12's. It would be nice and it would also be more of a professional looking car but also a sleeper for ppl who don't know the speed of a M3 :evillol: But ofcoarse I would keep the teggy and do something crazy to it.:iceslolan

I think your teg looks pretty sweet.:iceslolan :wink:

Originally posted by PWMAN
I think your teg looks pretty sweet.:iceslolan :wink:

Well thankyou I do too but I also would like a really fast dailydriver that is basically stock too :cool:

Originally posted by PWMAN

I don't know much about BMW's, so I can't really say. Of course the beemer is going to be much more loaded with options I'm sure. But there is much more aftermarket for a teg, being that jap imports are the major thing in the scene right now. So I don't know, IMO go for the TEG. Everything for BMW's costs too much.

me and my dad jus got a 1994 325 I and 1993 325 is for 900...there both smashed but we got them over the winter and swaped motors 1 got hit by a train and the others motor was blown..BMW's well your right the money is so stupid..i header for the i6 -$1200...WRONG im not gettin one...way to much..a nice car but way to much

I WILL be pushing around 6.5 PSI for daily driving, just as soon as I can get that damn thing installed. I wish I had the money to buy an actual kit, instead of doing it piece by piece. Such a pain in the ass.
But after messing with compression, I'll push it to 8, until actual internals are done.
About the WRX...what is the stock PSI? HP is 227 stock, right? Boosting that thing in the 20s without any mods is dumb. My friend's brother blew his up doing that.

Stock WRX boost is about 16 I think. It's atleast 14 anyway.
24 PSI is fine on a stock WRX, the turbo doesn't push much CFM. Even though it's 24 PSI, that doesn't really mean much. And as long as proper fuel tuning is taken care of, the engine stock can handle about 30 PSI I've been told.

In that case, it's reasonable that it'd only be making 300 HP with that much boost. Think about it...a motor pushing 227 HP on 14-16 PSI is quite a small motor...so it can't push too much.

i put the evo in the same boat as the wrx
18psi on the evo and only running low low 13s
my 8psi gonna put me in the 13sec boat.
do you know what 18psi will put me!!
low 11 maybe even a 10sec run
all i know is easy to get into low 13 high 12s
but get very technical after thet because you runout of shit to put on your car and have to start doing some real thinking for a change.:lol: :bigthumb:

Originally posted by SLEEPERACCORD
i put the evo in the same boat as the wrx
18psi on the evo and only running low low 13s
my 8psi gonna put me in the 13sec boat.
do you know what 18psi will put me!!
low 11 maybe even a 10sec run
all i know is easy to get into low 13 high 12s


all i see is a bunch of talk.....get into the high 12 and then we'll talk

Originally posted by Neutrino

all i see is a bunch of talk.....get into the high 12 and then we'll talk

Agreed:pimp:

no turbo here either. Just 100' nitrous.
although got a few friends w/turbo 1. 93' mazda rx7 w/15lbs runs 13.4
2. 00 integra gsr w/8lbs runs 14.4 and my favorite a 94-01 white gsr w/26lbs runs 11.8 w/545whp..all utah times(4500above sea)

100 feet of nitrous? LOL, just messin.
26 PSI GSR only doing high 11's? Sea level doesn't mess it up that much does it? How hot was it out that day?
Around my area cars with 500+ WHP are atleast in the 10's, certainly not HIGH 11's.

I just joined this site, and am not impressed with ya'lls knowledge. You can boost a DSM Stock turbo to 20 psi and not get the same amount of airflow a a t3/t04e with a .60 a/r on the turbine and a .48 on the compresser with a 57 trim wheel. You see, everyone in here should learn that when talking about PSI you must take into count the size of the turbo (compresser and turbine), the a.r's and the trim wheel. Just a note, I am not trying to talk down on anyone here, just trying to inform. A short while ago I did not know anything and I am still learning alot. Good luck with boost!

Posted by LSTurboCivic4DR - 11-05-2003 at 11:08 PM
I just joined this site, and am not impressed with ya'lls knowledge. You can boost a DSM Stock turbo to 20 psi and not get the same amount of airflow a a t3/t04e with a .60 a/r on the turbine and a .48 on the compresser with a 57 trim wheel. You see, everyone in here should learn that when talking about PSI you must take into count the size of the turbo (compresser and turbine), the a.r's and the trim wheel. Just a note, I am not trying to talk down on anyone here, just trying to inform. A short while ago I did not know anything and I am still learning alot. Good luck with boost!


Hmm.... Welcome to AF. . . .I duno much about this turbo thinga mah bobber or the pounds per square of atmospheric pressure they can force into the engine. There are some very knowledgable (forgets spelling?) ppl here. Im sure most ppl do take into account turbo size, a.r's and trim wheel sizes. Its only some ppl that say they have this kit or that kit. . . or talk out of the side of their necks that dont know much... (like me)Either way once again welcome and hope you enjoy your stay.


P.S. I hope you dont think you can boost that dsm to 20 psi as a daily driver. . .And sleeper accord Ima send you a pm.

P.S. I hope you dont think you can boost that dsm to 20 psi as a daily driver. . .And sleeper accord Ima send you a pm.

Why not? The 16G turbo on 1G DSM's are plenty capable. The 14G's on 2G DSM's might over-spin at those boost levels. People run more than 20 PSI on street cars all the time, especially DSM's because the 4G63 can handle it.

LSturbocivic4dr-
Wouldn't the only factor in the amount of air in the cylinders be the PSI though? - Read
The CFM only tells you if you CAN get 20psi, at some arbitrary Rpm. Yea so sure an air tire compressor can pump to 150psi, but only at 50 CFH, thus the psi would not be there once you got to say, 2 rpm :iceslolan . But however, if you have an engine, in which the turbo has adequate CFM to acheive 20psi at high rpm, a higher CFM turbo does nothing for you, unless you want to increase the PSI. So if your ?Running¿ 20psi on ANY turbo at some RPM, then you are increasing its power the same no matter the CFM.
I emphasize the fact that you are RUNNING 20psi, as opposed to just having 20psi wastegates and blowoff's. You have to actually HAVE 20psi throughout the power range. So given that - I don't agree that a bigger turbo will do anything more assuming that he can already Achieve 20psi at rpm's. If thats not what you meant, then I'm sorry for misunderstanding, but thats how I read it.
I think you might have meant what I have stated in the last paragraph; the fact that a t3 probably wouldnt run 20psi throughout the range. But in that case you cant really say your running 20psi if you don't actually get 20psi can you? Youd be wrong if you did. And if you did that, Id say im running 20psi and throw on an electric fan - there would be no difference.
Quote:
"You see, everyone in here should learn that when talking about PSI you must take into count the size of the turbo (compresser and turbine)"

I think it could be better stated that - you have to take into account the size of the turbo in relation to the amount of psi your running and the amount of air your engine can use at that psi at your racing rpm. And if your turbo can't achieve the designated psi at the designated rpm then your turbo will not actually be running that psi throughout the power band, and thus you could benefit from a larger turbo - But otherwise not.

HTH
Buzz1167
Jon N

Posted by PWMAN
Why not? The 16G turbo on 1G DSM's are plenty capable. The 14G's on 2G DSM's might over-spin at those boost levels. People run more than 20 PSI on street cars all the time, especially DSM's because the 4G63 can handle it.

I know they can..... Maybe I should have clarified . Lets say 20 psi every day on a stock 80k mile motor. . . I know a little about dsm's.... not a whole lot.... but enuff to get me by. Nuff out of me time to hit the shower and sleep.

Stock WRX boost is about 16 I think. It's atleast 14 anyway.
24 PSI is fine on a stock WRX, the turbo doesn't push much CFM. Even though it's 24 PSI, that doesn't really mean much. And as long as proper fuel tuning is taken care of, the engine stock can handle about 30 PSI I've been told.

I have a buddy with a stock 2002 wrx and it pushes 13.8 psi.

LSturbocivic4dr-
Wouldn't the only factor in the amount of air in the cylinders be the PSI though? - Read
The CFM only tells you if you CAN get 20psi, at some arbitrary Rpm. Yea so sure an air tire compressor can pump to 150psi, but only at 50 CFH, thus the psi would not be there once you got to say, 2 rpm :iceslolan . But however, if you have an engine, in which the turbo has adequate CFM to acheive 20psi at high rpm, a higher CFM turbo does nothing for you, unless you want to increase the PSI. So if your ?Running¿ 20psi on ANY turbo at some RPM, then you are increasing its power the same no matter the CFM.

Wrong, Wrong, Wrong. Boost is just a measure of resistance of the motor. Boost is uncomparable between turbos. 20 PSI from a DSM turbo and 20 PSI from a T3/T04E is NOT the same. Power is airflow, not boost. Bigger turbos move more air than smaller turbos at the same amount of boost, and make more power, period. If this wasn't true, why do supra guys make 400 RWHP BPU with stock twins @ 19 psi, and then they go and bolt on something like an Sp74 @ 19 PSI and make 700 RWHP? It's because PSI is meaningless when comparing 2 different turbos.

Wrong, Wrong, Wrong. Boost is just a measure of resistance of the motor. Boost is uncomparable between turbos. 20 PSI from a DSM turbo and 20 PSI from a T3/T04E is NOT the same. Power is airflow, not boost. Bigger turbos move more air than smaller turbos at the same amount of boost, and make more power, period. If this wasn't true, why do supra guys make 400 RWHP BPU with stock twins @ 19 psi, and then they go and bolt on something like an Sp74 @ 19 PSI and make 700 RWHP? It's because PSI is meaningless when comparing 2 different turbos.

I could not have explained it better myself.

How do you flow more air, with the same internals, in the same space, without increasing the psi?
I think you probably read the first part of my post and stopped reading?

Edit: oh I didnt respond to the question. Here we go,
My answer to this (your quote)
"why do supra guys make 400 RWHP BPU with stock twins @ 19 psi, and then they go and bolt on something like an Sp74 @ 19 PSI and make 700 RWHP?"
Is becuase the supra engine can consume more than the rated CFM of the stock twin turbos @ 19psi @max rpm, and the reason it makes power is (My quote)
"your turbo can't achieve the designated psi at the designated rpm then your turbo will not actually be running that psi throughout the power band, and thus you could benefit from a larger turbo"

I bet if you strapped on a PSI guage on one of those stock supras running 9000rpm (or whatever they run), the PSI would no longer be 19.

Buzz1167
Jon N

Boosted 331 is correct. Psi means nothing, it's the amount of air flowing that is important. There have been a couple people that have put t3/t4's on srt-4's that are still running the stock boost levels that are pushing over 100hp more at the wheels. The 16g in my car is very efficient and quick spooling, but doesn't push a lot of air. Anyway, 15 psi in the srt and hopefully 16-20psi out of the h22 when I'm done. I'm thinking of going with a t66 on the accord, 500+ whp will be no problem.

Its hard to argue with someone who compliments my argument. Your saying that at 15psi the srt can comsume more air than a small turbo can provide, so when you tack on a bigger turbo, you get more power becuase it can provide closer to what the engine can consume at 15psi. I completely agree with that statement as I said In my first post. What the first part of my post said was that if you engine could Not consume as much air as the turbo could provide then a bigger turbo would not help. You have not given an exclusion to this point as of yet. But rather you have given many examples of engines that can use much more air then the turbo can provide.

This is how the air is working, and I think youll agree to even this.
As you increase the PSI your engine is sucking the same VOLUME (the volume of the cylinders) of air, but there is "more air" in that volume becuase it is compressed. This translates into needing more CFM to attain that psi. And that cfm increases as the rev's get higher (becuase your taking in more volume at higer rev's). So if your running at something conservative like 4 or 5 psi, a t3/t4 might be able to provide that much air. However all the examples you give me are of 15+ psi, where the engine is obviously capable of taking more air than the stock turbo(or a small turbo) can put out. So really even though you think your proving me wrong, your actually just justifing the second part of my post, Witch since you didnt bother to quote the second part, Im betting you didnt bother to read it either.

So here we go
1) "Psi means nothing, it's the amount of air flowing that is important."
If psi meant nothing then we wouldn't judge anything by the psi, we'd have 65CFM blowoff's instead of 15psi blowoffs. The entire reason you get more power is becuase the Delta pressure is 15PSI(or whatever you are running) and the air tries to equalize itself in the cylinders thus "sucking" it into the cylinders.

2) "There have been a couple people that have put t3/t4's on srt-4's that are still running the stock boost levels that are pushing over 100hp more at the wheels."
I bet if you take the time to calculate the volume of air capable of flowing into the cylinders at the stock psi, and the amount of air the srt-4's can consume at that psi level while running something like 7-8000rpm (whatever it can run to) that the amount of cfm the stock turbo can put out isnt enough, and thus the bigger turbo can help it, whitch is why you see power gains.

3)"The 16g in my car is very efficient and quick spooling, but doesn't push a lot of air."
Yes your right, it doesn't, so that means if you try to get alot of psi from it, that it won't be able to create that psi at rpm, and thus your wont actually acheive that psi at however fast your going. And thus at that PSI you could benifit from a larger turbo. However at some psi level(something low), it WILL be able to create enough psi and at that psi your wont benifit from a larger turbo.

I have never said that if you want to run 20psi that you don't need a large turbo, nor does my first post say that. Either you don't understand or you don't care and just want to say I'm wrong.

I'll say it again, the pressure drop from the IM to the cylinders is what causes air to flow from one place to another (any person who knows the dynamics will tell you that). So if the PSI is not there, then less air is pulled into the clyinders, then you don't make as much power. The only way to get more PSI is to push more air, so if your not pushing enough air, then your not making enough psi, and so your not making enough power. The only purpose of being able to flow more air is so you can increase the pressure level, or so you can maintain the pressure level as the consumtion increases.

Buzz1167
Jon N

I shouldn't say psi means nothing, but all it is in fact is a measurement of the pressure of the air. The fact is though that what matters is how much air is being pushed into your cylinder. You can take a 16g and a t3/t4 and run them at the same psi, and the t3/t4 will push more volume of air. It's the same reason why cars that have don't have an intercooler or have a SMIC or TMIC go with a FMIC. It doesn't increase your psi, in fact in some cases it makes it harder to build boost, but it increases the volume of air flowing into the intake. I'm not trying to say you are wrong at all, you have made some very good points.

As far as my srt-4 engine goes, the stock block and crank are used on the mopar sponsered car driven by Shaun Carlson and he is pushing around 950whp at 44psi with a T88. I would have to say 15psi from a 16g is far below what the engine wants or needs.

I think i did a much beter job of expaining my point in the offspring turbo post "Do different turbos mean different amounts of boost". I see you agree'd with me there, so I guess were finally on the same page. :biggrin: Its hard to explain myself becuase as far as i can tell, your all saying the same thing I am, but you (when I say you, i mean everyone collectively) keep saying your disagreeing.

Your (now I mean you 93hybrid) -first line
"The fact is though that what matters is how much air is being pushed into your cylinder."
Is just what I said before, except in so many words. The PSI dictates the amount of air you can fit in the cylinder, and the CFM tells you how many times you can do that per minute, so if you've got enough cfm then the psi will be sustained, however if the turbo is too small for the amount of psi, then the pressure will not be sustained and youll loose pressure the higher in the rpm ranges you go.

The only problem i have with your statement is this one:
"You can take a 16g and a t3/t4 and run them at the same psi, and the t3/t4 will push more volume of air."
Kind of, the t4 will push more air than the 16g, but only after the 16g has maxed out. Whitch is easily possible if youve got a high revving, or high boost situation. If your running at max 5000 rpm and 5 lbs of boost, they would both be putting out the same amount of air (but the wastegate on the t4 would open up becuase it would be trying to create too much volume (witch would increase the PSI), while the 16g would be barely making it.) So the t4 would have greater capability if the boost were to go to 10psi, the 16g wouldnt be able to make 10psi at 5000rpm, and the t4 probably would. So in the first case you'd want the smallest turbo you can get becuase of turbo lag, but if it isnt big enough (like if you go to 10psi) then you wont have boost at the top, and you could benefit from the t4. (whitch is just what I said in my first post).
Keeping in mind that those figures are all just random stabs in the dark, I have no idea what a 16g can push and the size of the engine matters too.

P.S. the entire reason i posted my first post, is becuase you can't assume that bigger is always better. If your only going to be pushing 5psi then you don't need to over do it, becuase you'll only be sacrificing turbo lag. Or with any psi, if you follow the rules I was trying to outline, youll have a turbo that is big enough but not too big.
It was also in response to lsturbocivic4dr, becuase he seemed to put the wrong enphasis on things, and I was trying to fix that. Yes a t3 can put out more flow than a stock dsm turbo, but thats not the entire reason it makes more power. The reason is becuase the stock dsm turbo set to 20psi, is never going to achieve 20psi when your racing in upwards of 8000rpm, its going to drop off as soon as you start going. So are you really boosting to 20psi with that turbo? NO! unless your only counting the 100-2000rpm range, which you aren't. (that is the main part of my argument) However The t3 makes more power becuase it CAN actually get to 20psi ( maybe not that high, but definatly higher then a stock dsm) when your racing at 8000rpm.
Thats why bigger turbo's give you more power, not becuase so much of airflow, but the ablility to maintain psi (witch is the offspring of having that airflow.)

What really got me going was this atrocity (I can see it already, Im just kidding dude, alright)
"20 PSI from a DSM turbo and 20 PSI from a T3/T04E is NOT the same."
20psi is EXACTLY the same from a dsm and a t3/04e, the properties of air don't just magically change becuase youve got a bigger turbo. The fact of the matter is that "20 psi from a dsm turbo" isn't 20psi PERIOD. Just becuase you set your wastegate and blowoff to 20psi doesnt mean the turbo can magically make 20psi. I don't know alot of the turbo sizes; but I know that there is no friggen way a stock dsm turbo will actually hold 20psi in a racing situation. Itll have 20psi for about a second before all the pressure is consumed by the engine and cant be replenished with its tiny CFM rating.

I don't mean to come off as an ass, its just hard not to get frustrated while trying to explain myself 15 different ways. :banghead:

Buzz1167
Jon N

Stock supra turbos can feed 19 PSI to the motor solidly to about 7000 RPM's, but since you don't seem to be getting this, lets compare a T66 and a T76. Both running 25 pounds of boost at the manifold, they will both hold that easily to 8000 RPM's. What do you think is going to make more power? The T76 is physically moving more oxygen into the motor at 25 psi than a T66 does. Boost is a measure of restriction placed on the turbo by the motor, and a T66 is working harder and not pushing as much air into the motor as a T76 does, in laymans terms. PSI does not dictate how much air you can fit into your cylidners, PSI is a measure of restriction on the motor. If your theroy was correct supra guys would never run anything bigger than an SP67, because that will hold 30 pounds of boost to redline easily, and if your theory was right that would make as much power as a T88 holding 30 PSI to redline.

Once again boosted, you are correct. Look at it this way, you have a hose that is 2.5" in diameter and a hose that is 4" in diameter. It takes a lot more air to make the 4" hose the same psi as the 2.5" hose. It works the same way with a turbo.

Buzz, I'm 100% behind you and I feel your frustration. They don't quite get it though. The other thread you mention sums this all up really nicely, and in more simple terms.

Let me try.

You can set up a 16g and a t3/t4 to run at 15 PSI. Fine. Now bear in mind the when you 'SET' a car to 'RUN' at 15 PSI it is the 'LIMIT' that will be reached before the wastegate initiates. 15 PSI is the maximum. Now maybe at 4000RPM the 16g can run at 13PSI and the t3/t4 at 15 PSI. Close enough. But when you reach 5000RPM, the 16g may only be able to handle 8, and the t3/t4, 14. KEEP IN MIND THAT EVEN THOUGH THE TURBOS ARE STILL SET TO RUN AT 15 PSI, THAT IS THE MAXIMUM AND THEY AREN'T REALLY PUSHING THAT MUCH PRESSURE INTO THE CYLINDERS.

PSI is very effective when comparing turbos. You just have to be careful you use it in the correct context, because you boosted331 are not and it's contributing to the confusion. When you select a turbo, note the the PSI it is actually able to create. Because any size turbo can be set to 40PSI, but it takes a 'LARGE' turbo to reach that.

Come on guys. I'm an idiot with cars and I knew that.

You are wrong about the 16g and t3/t4. My turbo spools up 14 psi all the way to redline. It actually spikes to about 16, sometimes more. The person I was refering to that has over 100hp more at the wheels has theirs set at 14 because the computer will pull timing if it senses much more boost than that. Anyway, the only reason they are getting 100 more hp at the wheels is because they are pushing a larger amount of air. Psi is a relative term, it doesn't tell you how much air you are pushing, it just tells you the pressure it is being pushed at.

I guess i just dont get it, at a set psi, there is only so much air that the engine can use at an rpm; adding more air in there doesnt make it use more, it only increases the pressure. The only reason possible for making more hp is if the engine is using more air, and when you increase the psi, it does use more air. But if you increase the cfm it doesnt help the dynamics of it any. The only thing causing air to go into the cylinders is the fact that there is 15psi outside the cylinders and less in the cylinders, the amount of air isn't in the equation as long as the psi on the loosing side stays constant.
BTW, measuring the pressure at the mainfold, before the manifold, at the turbo, and in the manifold are all different pressures. I'm talking about RIGHT before it goes in, and if you can't measure that then, theres no way to calculate my perfect turbo, and this was all just hypothectical, but the math is right.
The psi before the intercooler is higherer than the psi after the intercooler, just like the psi before the intake manifold if different than the psi in the throttle bodies, right at the valves and in the cylinders. I doubt anyone has scientifically measured the real pressure, and I doubt a common guage would even be accurate enough, especially since its a person who as to read it (usually).


"Once again boosted, you are correct. Look at it this way, you have a hose that is 2.5" in diameter and a hose that is 4" in diameter. It takes a lot more air to make the 4" hose the same psi as the 2.5" hose. It works the same way with a turbo."

Who said anythign about increasing the volume where the air is placed? Of course you can get more power by doing that. Becuase the air being subtracted will have a lesser effect on the surrounding psi, so the 15psi will stay for longer on each intake stroke. We wern't adding any other variables into the equation, only turbo size. If YOU WERE, then maybe thats why we were disagreeing.

"Stock supra turbos can feed 19 PSI to the motor solidly to about 7000 RPM's, but since you don't seem to be getting this, lets compare a T66 and a T76. Both running 25 pounds of boost at the manifold, they will both hold that easily to 8000 RPM's."

Have you ever figured it out, or do you just look at guages and say its close enough? 25psi is a pretty extreme number, How do you know what a T66 ot T76 can hold to 8000rpm (like wheres your info coming from).
I bet if you compared a t66 and a t76 running 10psi, that they would be the same.

Buzz1167
Jon N

hmmm interesting... I run 24 PSI on pump gas and 27 PSI on 118 octane torco race fuel. 10 PSI after a fortified block??? :grinno: The number one consern for any force inducted engine is spark knock, pre-deatonation. I Don't care how much your block is fortified if your pre deatonating your fuct. BTW i run that boost through a stock block, stock heads, stock pistions, stock crank, stock connecting rods, ect. the only thing I have done to my engine as far as inside it is change valvesprings. The trick is to watch your knock sensor readings....and alcohol injection :naughty:

hmmm interesting... I run 24 PSI on pump gas and 27 PSI on 118 octane torco race fuel. 10 PSI after a fortified block??? :grinno: The number one consern for any force inducted engine is spark knock, pre-deatonation. I Don't care how much your block is fortified if your pre deatonating your fuct. BTW i run that boost through a stock block, stock heads, stock pistions, stock crank, stock connecting rods, ect. the only thing I have done to my engine as far as inside it is change valvesprings. The trick is to watch your knock sensor readings....and alcohol injection :naughty:
Dude you can't compare these things, your engine was built for a turbo. These are N/A engine being boosted, they were never meant for it from the factory.

You are trying to say that a t66 and a t76 at the same psi will push the same amount of air? You are joking right? You obviously don't understand that if something has a larger inner diameter that it takes more air to make the same pressure as something that has a small inner diameter. PSI means nothing unless you are telling me what kind of turbo you are running plain and simple.

Dude you can't compare these things, your engine was built for a turbo. These are N/A engine being boosted, they were never meant for it from the factory.

The only difference between the N/A 3.8 and the turbo 3.8 is the turbo motor had 8.0:1 compression and the pistons has a steel skirt. The things that matter such as a crank, block, conecting rods, main caps,etc are the same. Built for a turbo or not pre-deatonation should still be your number one consern.

The only difference between the N/A 3.8 and the turbo 3.8 is the turbo motor had 8.0:1 compression and the pistons has a steel skirt. The things that matter such as a crank, block, conecting rods, main caps,etc are the same. Built for a turbo or not pre-deatonation should still be your number one consern.
OK but does it have forged crank/rods/pistons? I bet the crank and rods are forged, pistons don't have to be contrary to popular belief. I've seen cast pistons do 30 PSI, but you better have forged rods.

OK but does it have forged crank/rods/pistons? I bet the crank and rods are forged, pistons don't have to be contrary to popular belief. I've seen cast pistons do 30 PSI, but you better have forged rods.

My car doesn't have a forged crank. The rods are, but neither the pistons nor the crank are forged.

You are trying to say that a t66 and a t76 at the same psi will push the same amount of air? You are joking right? You obviously don't understand that if something has a larger inner diameter that it takes more air to make the same pressure as something that has a small inner diameter. PSI means nothing unless you are telling me what kind of turbo you are running plain and simple.

I never said that, who are you referring to?
Psi still means something. In fact psi is everything, if there were no psi, thered be no boost. You cant push more air into the cylinders if the psi doesnt increase, its a law of physics. Witch is the basis for the argument that there is maximum cfm that an engine can consume at a certain psi level, becuase there is, you can't push more air than there is space, or the psi increases. And since the psi is constant, you cant; plain and simple. A different turbo might be more effiecient and make the air colder, but if the cfm rating is above the inputable amount it becomes wasted.

Buzz1167
Jon N

OK but does it have forged crank/rods/pistons? I bet the crank and rods are forged, pistons don't have to be contrary to popular belief. I've seen cast pistons do 30 PSI, but you better have forged rods.


not form the factory. i have stock cast rods, stock cast iron crank and stock cast iron caps. Also im not a one person case alot of people run the kind of boost I run. Too much pressure can hurt your motor but pre-deationation will just rip it to shreds. I would worry about that before I would worry about making the block stronger espiscally just for 10-14 PSI of boost.