If it were me, I'd definitely go with the G series. Gotta remember ATP is selling you their exhaust housing with that gtx so there is a little bias there .Dunno if you ever seen their turbine housings, but the tolerances are pretty damn loose compared to the Garrett housings aswell.

 

Interesting.. I didn't know that, although the g30 660 T4 is a ATP housing, i don't think Garret makes them. Not sure though.

 

yeah I dont think garrett makes them any divided housings for anything other than the 4 series and larger

 

that's true, the g42 does have a divided housing, i figure they found minimal difference in their R/D, not enough to warrant the cost and or effectiveness of divided housing on their already high performing small/mid sized g series options.

 

I expect the G30-660 in the 0.82 to spool faster and have better transient response than the GTX3576R in the divided 1.06. The G30-660 is a turbine wheel size smaller (60mm vs 68mm) and the 67mm compressor is two sizes smaller (71mm then 76mm). And the turbine housing A/R is a size smaller, 0.82 vs 1.06. The GTX3576R being in a twin-scroll housing would make up for the 1.06A/R vs open 0.82, but it's not going to make up for the downsized turbine and compressor wheels of the G30-660 in spool-up. Plus in transient, the G30-660 has way less rotational inertia, so it'll be much snappier on/off throttle. And the GTX3576R is a 650whp turbo, so 100whp more than your target.

Garrett had a T4 twin-scroll internally wastegated housing planned for the G25 from the very beginning. I imagine to compete with the EFR 7163 T4 twin-scroll internally gated housing. But it hasn't made it to production yet. It is a complicated casting. Just for reference, I'd expect the G30-660 to spool up about 200rpm faster than the 770 and of course have a little snappier response.

 

Thanks guys, i'll update you all with the progress of this build as it continues, I don't know how many other f series guys have run the g25/g30 but I don't think it's been documented much here. I'll be ordering the g30 660.

One new consideration, my IC piping is 2.5in diameter whereas the g30 outlet is 2in. How will the missmatch diameters affect the setup? I can adapt the 2in -> 2.5in piping no problem but I figure there would be a trade-off of sort, just don't really know what.

 

Burns Stainless sells aluminum narrow angle diffuser/transitions. You want the long taper with the 14deg included angle. 14deg is the max for a diffuser before you start getting relatively big pressure drop.

https://burnsstainless.com/collectio...=8778931667035

 

UPDATE: I received the G30660 and man this sucker is tiny! I am having a hard time believing it will even make 500 on e85, it is so small!

 

Excited to see it when you're done!

 

I hit 480 @15 on the g25-660 w/recirculated dump. Small turbo but holds to 9k rpm n spooled up around 3700 rpm. Don’t think you’d have an issue hitting 500