For this application (where minimum lag is a priority) probably so, but I'm of the belief that if one were going to use a T4 flanged turbo and wanted to a housing that size, he just may gain more from using a smaller turbo than he loses.

 

The purpose of a larger hotside is to reduce backpressure. Backpressure is more or less a function of power (air mass flow). My point is I do not believe you're going to make enough power with 91 octane + water/meth mix to cause a .82 A/R hotside to be a limiting factor. There is a point whereby going larger costs more in spool time than it gains in power potential, and I strongly believe you're in that category if considering anything larger than .82 A/R for a 2.4L engine that is going to be most mechanically efficient at midrange rpm, with a moderate sized turbo, and with limited octane.

 

Reason why I asked is that people are making serious power above 620 with the .63 a/r open exh housing. I would figure that a T4 .58 will be slightly bigger releaving slightly more back pressure than the .63

I have two housings in my possession and not sure which to use, I have a T4 .58 and a T4 .68 I have been told that there is a 300rpm lag differance between housings. Whats is your take on this?

 

So in a nutshell what you are saying is that the .82 A/R hot side is the largest I should need to go given the modifications that I have and the RPM vs. spool times that im trying to achieve.

Sorry for sounding so redundant.

 

Ted, thank you for all of your help. I understand all of what you are saying by mass airflow (im going to school for mech. eng.) Only reason i was pushing mike towards a .82 was because of the FWD aspect of this car. It doesnt need to spool right at 3K. That would result in a LOT of hopping around. Plus, keeping reversion down at idle will keep the tuning aspect a bit easier on the longer duration cams. I told him to order both a .63 and a .82 and see what works best. hell, he might even be better off getting the .5x hotside that comes with the turbo.

Now back to Rod/stroke ratio. What do you feel is max RPM for this motor. Road Race seems to think 8.1K is fine...i was worried about going over 7.5K. Rod/stroke ratio is somthing i need to learn more about, you know of any threads/sites that have good explainations?


and...
thanks for hatin. Sorry for asking knowledgeable people about somthing you prolly have no idea how to do. I wanted to learn, i figured this section would get the most traffic/chance of a correct answer.

 

Thanks for all the help guys.