Thread: Difference Between .86 & .64 A/R GTI-R t28

End of discussion. .78ar vs 1.06. Which one is which?



The red is 25psi on the 1.06 housing. the blue is 25psi on the .78. You can see that after 4000rpm the 1.06 makes a ton of torque, and is slightly faster. If I had started the pull sooner with the 1.06 I would expect torque to be even closer, but I started the run later on the 1.06 and the turbo wasn't even building 1psi of boost yet.

The response difference on the street was incredible. the 1.06 owned the .78 in response as well, granted this is a twin-scroll setup.

Just throwing this out there, because some turbos are DESIGNED to run best with certain housings. a .82ar GT30R turbo will perform all-around better than the 1.06ar version, despite the fact that there is a big difference in AR size. Just something to keep in mind. They don't exactly give you turbine data specifically for each AR size.

Looks like your right. I did some research and found that the gtir turbine housing does not fit the s14/s15 wheel. they are both 53.8mm but the gtir wheel is a 79 trim and the s14/s15 is 62 trim.

the larger ar i would think would make more power like in the graph but comparing the larger ar to the smaller ar the response like the torque is going to be much greater on the smaller ar vs the larger ar , for drag if you had the cams that will fill in the mid range the larger ar will make more power but be less responsive

Just remember that any increase in volumetric efficiency will make the engine perform like a larger version of itself. A 1000cc motor with 80% VE will only perform as well as an 800cc motor at 100% VE. And they will spool the turbo about the same in most cases.

So think of it this way, if putting a larger housing on the turbo will increase the VE on the low end, then response will remain nearly the same. But top end power will be better. Same spool, same response. On that small of a turbo I highly doubt even in autoX that you will ever be below 3500rpm. I say if you want the best response, ditch the GTiR turbo and get a disco.

If you get a disco, get the .86ar housing. It will be extremely responsive.

i agree the disco is probably the best turbo as far as response goes the larger .86is going to yeild you greater power while still maintaining quick responsive spool, cant beat that.

Just to update you guys. I got this all installed this week and its great! very responsive and reaches full boost at about 3K and seems to have a great deal of power. I appreciate all the help this community as been through all the years and in a couple of weeks I'll take it out to the 1/8th and well see what happens! Thanks again
-Jason