Two questions:

1. Which will spool faster, the GT4088R with the 0.85 AR housing or the GT3582R with the 1.06 AR housing?

2. Which will give the least back pressure at high RPM operation, 4088R 0.85 AR or 3582R with the 1.06 AR housing?

I thought the answers to those questions was easy until I really started looking at the turbine housing flow curves. Now I'm not so sure. Thoughts appreciated.

 

35R usually, I have ran both here, and the difference is almost negligible.(you would be hard pressed to tell a difference) Your trying to split hairs is my point. The bigger question is why run the larger compressor only to choke it up on the top end. Also there is much more to it than just sticking X turbine housing on there. There is no clear answer.

 

What surprised me was that the choke flow is the same for the two.

What I can't quite figure-out is why they're making turbos in different frame sizes that really look like they'll perform almost the same? And there's still the GT37's in between...

The difference I can see is that the 4088 0.85 flows better and offers less resistance during spool. Does that mean that it would actually spool faster than the 35 1.06? Or does that just mean that there's a ton of slip happening? Looking at the compressor maps, the 4088 has a slower rotation speed for a given mass flow and similar efficiencies but with more top end...

Is it possible that the 4088R would spool more quickly and then have the same ultimate choke flow abilities as the 3582R? If that's true, then what's the reason to buy a 3582R other than for the nicer surge line down low?

 

The reason I'm wondering this is because if I put a 3582 on there, then I'm maxed-out in that frame size.

If I go with a 4088, then it's just a matter of swapping exhaust housings in the future to open the top end.

My goal is to make the most total torque. The biggest RMS torque. I don't really care what the peak HP or even peak torque numbers are, or even really where in the rpm range they happen as long as it's within reason. IMO it's the RMS torque in the useable operation range that makes a road car fast or slow...but rotaries are new to me so I could be totally off base here too.

My guess is that up top, the 4088 would be EGT limited by choking the exhaust flow (because the compressor would still be happy), but the 3582 is actually efficiency-limited, maybe even rotational speed limited, AND is choked by the exhaust housing.

I'm still wading through dyno posts on here, but if the 4088 can spool down low and still have the same choke flow up top as the 3582, that looks like the direction I'm going to go.

Engine has a mild street port by the way, don't think I'm going to change that, and it's going to get some internal coatings.

 

You're correct that the 3582 will be efficiency limited up top. But that will only mainly come into play if you raise your boost levels above 20psi. We've run 4094's here with .85 housings and the spool pretty nicely but they tend to be hp limited again because the backside. The one was also on what I would call a mild street port. I wanna say it was low 400's to the wheels at around 2.15P/r on the map. Slower rotational speed is a good thing for the turbo if you can get away with it for obvious reasons. As far as why choose the 35R over the 40R it will spool slightly quicker in most cases. And certainly quicker transient response. But again it's splitting hairs. Have you looked at TO4Z's they somewhat fall between the two, however keep in mind they do not run GT wheels.

-S-

 

zero R,

at about what power level would that gt3582 .82 t3 hotside become a big restriction on a a stock port FD?

i have been considering going with this turbo for no more than 350whp and quick spool for autocross.

 

anyone?

 

WOW.. sick turbos

 

I have a .82 T3 GT35R with a very short runner manifold. On a bone stock reman motor it made about 370hp at 15psi. I later built the motor and put in a decent sized street port. Lost a little on spool up, but gained alot on top. Peak hp was now more like 400, but the hp difference in the 8000rpm range was more like 60hp better with the streetport, as the stock port fell off really fast after the hp peak.


-Andy