If I am running 7lbs out of a Minnam stage 2...with a T3/T4..and someone else is running a ASR with say a T25 intercooled system at 7lbs..Are the horsepower gains the same, being at said 7lbs...Now I know the time to spool up and Size of exhaust and all that contribute..but Straight up 7lbs vs 7lbs...The SAME?????Educate me

Moderator ya say...

Well to make a long story simple... Your turbo is bigger than his which gives you a higher or flow rate and efficiency compared to his smaller turbo.. which he probably has less lag than you have..

I am too stressed to go deeper... sorry man.. that's all i can muster... right now.

in short no, one turbo can flow more air (cfm) at the same psi as another turbo... so it will make more power, there is more to this , like trading off spool time, efficiency etc...

Thnaks...Thats what I thought but wanted to makesure I was on the right track.

OH BTW...What does moderator skills have to do with the Question???? Its all good.:)

actually yes they are the same. 7psi is 7psi, since it's relative to atmospheric pressure... but if you're talking about output by 7psi of the different turbos there's a difference. A bigger turbo @ the same boost moves more air than a smaller one. But 7 is 7.

in short no, one turbo can flow more air (cfm) at the same psi as another turbo...so it will make more power, there is more to this , like trading off spool time,efficiency etc...


But the flow is related to the engine characteristics (displacement, VE, RPM, etc.), which isn't changing here.

I do agree, however, that a particular flow and pressure ratio would probably put you in different spots on the respective compressor maps, and therefore give you potentially different efficiencies.

depending on the setup, one of you may be spending more energy creating that boost than another.

and also depending on the setup, one of you may be creating more heat in the intake air than another.

so, no, 7lbs is not just 7lbs.

Ideally, youd have a zero friction turbo with perfectly optimized impeller that would add very little heat to the air etc. etc.

7 psi on the boost gauge...thats what I mean..If I see 7psi at the manifold...Thats my question..I understand compressor maps and Bigger turbos produce more air..but At the manifold 7psi regardless of compressor is 7psi..right??

Hey,
Offense needs to be taken... I would figured through your moderator duties you would have read something like this that's all..

It's also like the scoobie newbie thing... or the number of post... they don't tell you the full scope of who that person is...

Later...

since my wrx is running only 7 psi right now... I bet your RS at 7 psi would embarrass me..

I think the real matter is where in the RPM range would 7psi come in the most handy? Build your turbo around that understanding and your 7psi turboed RS would probably be able to beat a similar 7psi turboed RS.

Edited out. Because I was very intricate, but very wrong. Doh!

Boost is basically the restriction of air flow into the cylinder. If Turbo A and B are both making 7psi at 5000 RPM on the same motor, they are flowing the same volume of air. The engine can only ingest a certain VOLUME of air at a given RPM, and boost is just the restriction created from the turbo trying to cram the air down the engine's throat (in layman's terms of course.) :) Sure, the turbos might be rated at different air flow rates, but the same engine and the same boost will ingest the same CFM (Volume of Air) at a given boost. All you can effect would be the MASS of air, as a result of the turbo's effeciency at said boost level...and therein lies your answer to power. If you can bring a higher MASS of air into the engine, in theory (given the right MASS of fuel and timing) you'll make more power.

There's also other issues like exhaust backpressures, pressure drops, yada yada yada.... just depends on how deep into the subject you want to get.

I think you all have the right idea, but the terminology is all wrong.

Regards,
Trey
Cobb Tuning

Thanks Trey....Thats what I wanted to know...Knowledge is POWER brother..:D:D:D

thank you trey.
my intuition was telling me that things were as you say. But I didnt want to declare it in case I missing something.

I'll just add for the laymen in here, that you get more air MASS into the engine by having it be COLDER.

a more effecient impeller size/shape will heat the air up less.

oh well trey beat me to it.

its kind of like the "which is heavier a ton of feathers or ton of bricks" question.

psi = lbs per square inch. its a measure of pressure a force over an area. so 7psi is 7psi period.

but like trey said the turbo's characteristics come into play. Maybe a lot of the confusion comes into play when people dial in their boost controller to 25psi and say there u go, the turbo is flow 25 lbs per square inch from the time the wheel starts moving. I am sorry but only mine does that ;)

jmott i am sure you mean the air colder and not the engine ;)
i kinda think lots of people know that tho. hence the whole cold ain intake system that is so popular. colder air is denser air (molecules are packed closer together). But then that is the akin to the function of the turbo; pressurize the air above atmospheric level.

[Decided not to beat a dead horse]

7psi is 7psi but the Ttoosmall will not flow as much air as the t4t3. If you were talking about two turbines of different makes but of the same size then there wouldn't be much difference. That being said... the Ttoosmall would have to pump about 11~13psi to keep up with small t4t3 at 7psi and the t4t3 would still push more air on the topside of the rpm range!

did you even read what Cobb tuning posted?

no.. because after about the thrid reply things got kinda boring!!

=MAP's, one at 200f and the other at 5f do not yield the same power potential; i.e. you with an inefficient turbo beyond its range and him with a high efficiency turbo and a huge IC core with dry ice on it...



SLR-