i'm up in the airr about what t70 to get as far as exhaust a/r . whats the rest of you all running ? i'm thinking either a .68 or a .84 . i want fairly quick spool since this is a street car . bbut my redline is only 5500 so i don't want sumthing thats gonna take till 4000 to spool . this is a fun daily driver , back roads where quick spooling coming out of a turn is nice but still got enough to pull to redline . so again i ask whats everbody running an what rpm's are you getting full spool at ?

 

Use a .68 for a 5500 rpm setup but really depends on the motor its on. 305 or mild 350's should stick with the .68 IMO. It will spool quick.

I have twins on my 401 so if you think of it as a 200" motor running one T70, with .68's it was spooling by 3000-3200 rpm. It would see a few psi boost by 3500-3800 range. Now a single T70 on a 305-350 would be in the lower 3000 or high 2000 rpm range which is perfect for a street car.

 

Go with the .84 a/r, you will spool quick with a fairly decent stall (2400-2800) plus it will leave you room to grow if you ever decide to up the ante. The amount of RPM doesn't dictate how fast you spool, how much air you move during the RPM does...

 

thanks guys , i'm leaning toward the .68 for the faster spooling i just wasn't sure if it would be to small . thanks guys you've both been a big help

 

If you go that small be sure to monitor your EGT's and air temps. I am running a .96 a/r, and with the stock stall speed converter the turbo still spooled pretty damn fast. Once the converter went in it was instantaneous. This is why I recommended the .84 a/r. Either way, should be a sweet ride when your done...

 

thanks for the heads up , i'm talking with pro built transmission right now about what a good stall speed would be
for this setup

 

i'm planning on running a meth injection kit from cooling mist . i had one on my srt4 an it worked great so hoefully the egt's an iat will be good but i will moniter it tho .

 

Backpressure would be higher with the .68 but I understand you have a 305 TBI car thats getting the turbo? With a small cube 5500 rpm motor, I dont think the .68 would be a problem. .84 would not be a bad choice either...its a happy medium between most .68 or .96 options out there. Those seem to be the most popular sizes for P-trim type turbines.

Alot of guys run .96 T60-T70's on bolt on L98's and they work very well. Spool fairly quick, but a L98 350 has a good bit more air flow going through it than a 305 car

 

i'm gonna go with a t4 so making the merge pipe should be easy . a t 3 seems to small for two 2 -2 1/2" pipes to merge into . tha should help with sum back pressure but i understand the .84 would have less . see the .84 spooling a little slower could also have the advantage of hooking up better ... see my delima . i don't think either is bad but whats gonna fit my driving the best .

 

Freaky go with the .84. Only first gear and launch will see the benefits of the .68. Almost ever shift you make will only drop you about to 3k ish RPMS. So for 2nd 3 and 4th your not gonna benefit from the .68. I have a 305 tpi and my t76 .80 ar exhaust side and its spools fast.

 

twin turboroc what rpm does that t76 full spool at ?