What exhaust housing is best

[49-blues]

I'm putting together a stage2 motor with gn-1 heads, TA headers-4 bolt, 12 bolt rear, RJC 325 front mount, 120 lb injectors ,E-85 to about 25 psi, PTE-7175 BB turbo 4 bolt (985 HP), external race gate . What exhaust is better for a mostly street car -a .81 or a .96 housing and why?

 

[bison]

What cam?

 

[49-blues]

224/224 roller with a .587 lift and 1.55 T&D rockers.

 

[bison]

If you were going to run it to it's potential I'd run the larger a/r. 25psi won't be anywhere near the mass flow potential with that cam. Probably solid 9.70 power at 25psi. Running a smaller a/r wont hurt power but will spool faster. You could make about 175hp more if you want to turn it up on the e85. At that point id be running the .96 for sure

 

[49-blues]

how do you measure the airflow in lbs per minute or hour? i ve read you mention airflow ratings on several threads how is this figured out? thanks for your input. i wanted to keep it around 800 hp for the street-i only have forged internals in the motor and dont want to over push it, if it had billet i would go to the larger housing.

 

[bison]

I don't measure it. I base it off of collected data. The big manufacturers have this data available on their compressor maps where all others numbers are based off of customer experiences and data. Fwiw 800hp@6000rpm is about 82lbs/min. 800hp is nothing even with the cheapest of the cheap forged internals. I would not be concerned one bit with a 6500/1000hp engine with these parts.

 

[49-blues]

Thanks- it's a RPE built stage2 off center with new forged crank ,new forged rods and custom stage2 diamond pistons set up to shift around 6400 RPMs.so do you think I would be happy with the spool up if I used the .96 housing?

 

[norbs]

If its race only use the big housing, street go the smallest you can for fun factor, nothing worse than a lazy turbo on the street.

 

[forcefed3.8's]

Why do you say 9.7@ 25psi? I went 8.94@ 26psi with a similar engine and a 3bolt 68mm turbine.
I would run the .81 for spool up until you are in the 8's.

 

[49-blues]

Thanks for the great input!