okay, this is something i came across in the kills forum, but for some reason i cant post there so it goes in here now. the argument was about the wrx and whether it sucks or not, and someone brought up the point that "it only makes 227 hp out of 14 lbs of boost and thats terrible because if i did that on my si it would make 300 hp blah blah blah". well the undisputed arguement to that point was, and this is not a direct quote, "well thats just because its a small turbo. sure if you put a T3/T4 on your si itll fly. you just dont understand the concept of flow and cfm". ok basically what theyre saying is that a bigger turbo flows more at the same psi. okay....does anyone else see something wrong with this? lets suppose you have your wrx running 14 psi or whatever. then you swap a T66 on there but leave the wastegate at 14 psi. what will happen? well, besides having a lot more lag....NOTHING! once it spools it will pull no harder than before. a larger turbo is CAPABLE of flowing more at the same pressure, but it cannot simply force more air into the engine without boosting with more pressure. another example: lets take your T66 now and slap it on an 8 liter viper engine (i think theyre 8 liters, but its irrelevant, theyre huge). now i dont know what the figures are, but lets just say that a stock wrx flows 300 cfm at full boost at 5000 rpm. with the T66 it will flow the same on the wrx, but with the T66 on the V10, at 14 psi (i dont even think this is possible, but bear with me) you would be flowing more like 1200 cfm at 5000 rpm. follow me here? so ya the turbo is capable of flowing more at the same psi, but its only going to flow more on a bigger engine (or with bigger cams...). so the only real reason the little SI's engine makes so much power out of so little boost is because of the high compression ratio. you lower it to the same 8:1 c/r the wrx has and itll be making about the same power as the wrx. sorry if this was hard to follow, but i had a lot to say. if im wrong please correct me, and if you want you can flame me too. no holds barred!

 

retracted previous statement


[Modified by ELUD THS, 10:40 PM 9/4/2002]

 

correct ME if i'm wrong, but you're wrong
A bigger turbo can provide more power at the same level of boost because
1) it can be more efficient, producing that boost at lower temps which means more horsepower

2) (and this is the big one) if the turbo can flow more, especially on the exhaust side, then there is less restriction in the engine's path so every pound of boost that is made produces more horsepower. I can specificaly think of APEXSER's customer's car (or whatever he changed his name to ) where they made a huge jump in power just by switching from a .63 a/r exhuast housing to a .82 a/r exhaust housing.


-Xerxes

 

Agreed, and owned. Bye n00b.

 

So are you saying that a smaller turbo at 14psi will flow the same as a larger turbo at 14psi on the same engine?

Correct me if I am wrong, but I think that is incorrect. The larger turbo will flow more.

 

You need to learn more about turbos my friend.

Its very hard to understand what your saying here, but Im gonna suggest you buy the book Maximum Boost by Corky Bell.

This is completely wrong. The Trim on the compressor blade controlls how much air flows into the motor.
What is considered so much power from an Si's motor? Low boost isnt fun.