That is indeed disappointing. I had high hopes for that setup and at one point was pretty sure it's what I wanted to build. Can you please explain what it is about them that causes it to come up short?

 

^^^ that certainly explains it!

i believe the issue comes up from the T4 turbine housing that is used. As a turbine wheel gets smaller and smaller, the vector direction of the exhaust gas that hits the turbine wheel will change from more tangential to more radial (aka on-center) or vice-versa. I think for this reason of turbine geometry, the standard S200, with the t3 divided inlet would be a better performer for the small turbos, and using a t4->t3 adapator would make a lot of sense

 

Yeah it does.. Gotta love that.. Well the kits up for sale, and I'll fix this issue and look forward to learning as much as I possibly can.

 

Thanks for the explanation Geoff. That makes sense.

 

so, no loss on low/mid end, no loss on spool, just more top end? just the turbo change from 30r .82 t3 to 35r 1.06 t4?

 

I went from .82 T3 GT3076 to .82 T3 GT35R to 1.06 T4 GT35R with lots of changes between the GT30R and first GT35R setup, but not very many between 35R single scroll to twin scroll setup.

To re answer the question, more tq earlier, more peak tq, more tq at redline, more HP everywhere (the HP line of the 30R setup never is above the HP line on the 35R).

Scorke

 

good to hear scorke

 

Scorke, while interesting, the 0.82 A/R GT30 isn't known to provide very good spool.

Did you ever have the 0.63 A/R housing on it as that seems to be the better matched housing for the GT30s. Seems like the GT30 turbine just can't get the flow out even with the larger housings.

FWIW, there is a local Nissan guy that went from a T3 0.78 divided GT3076R to the 1.06 A/R T3 housing. No loss in spool at all.

 

^^03whitegsr - i gotta disagree with your assessment, while the .63 a/r does work well, if the engine is properly modded, the .82 should provide almost identical spool with far greater powerband.

exactly what your nissan guy saw

 

Yeah that doesn't make much sense that the .63 and 1.06 T3 would do ok but not the .82.

 

How does it not make sense?

Through some research you can find SAE references stating to size a single scroll at ~0.6 of a twin scroll.

1.06 * 0.6 = 0.64 interesting how the 1.06 TS falls right in line with how the 0.63 single scroll seems to work quite well.

That 0.78 TS is just tiny and chokes the hell out of the motor as it flows roughly like a 0.47 A/R housing. You go too small and efficiency drops like a rock, giving no better spool and choking it everywhere on power. If you want to compare TS to 0.82 single scroll, better go up to ~1.35 A/R, which I have a feeling will show considerable spool losses and minimal HP gains over the 1.06 divided housing.

From what I've seen, if you aren't running very aggressive cams with a fair bit of overlap, the 0.63 housing makes nearly the same HP but spools faster, providing a broader powerband. Yes, it gives up a little up top, but it offsets that with gains down low. With more aggressive cams and head work that can take advantage of the additional flow, the 0.82 offers worth while gains but I don't think that kind of work matches up with most GT30 setups.

This also seems to be similar to the TS talk about how drive ability is not apparent on the dyno as the difference will only be 100-200 RPM yet the overall feel is night and day difference between the two.

Also, as far as the Nissan guys go, it seems like many of them use the T25 based GT30s with the 56mm turbine. They tend to use the odd combination of GT2840s and GT2835 too. I know the T2 based 0.86 or what ever it is housing is pretty popular over there on those setups.

 

If you do a Twinsrol, you want a T4 1.06AR. T3 is too small. Trust me.

 

^^^^ agree with the garretts.

BW likes the 1.00 on S300SX and 1.15 on S200SX

 

That depends upon the turbo and intended application. Drifto's 1.06 TS T3 HTA3076 doesn't appear to be suffering ...

https://www.evolutionm.net/forums/ev...e85-33psi.html

I've driven this car, and I wouldn't change a thing.

 

^^drifto's turbine housing doesnt actually exist for people who want to buy one.. ive tried to buy more of these from him and he cant get them. But yes the T3 footprint is NOT the limiting factor - its the housings and wheel combinations.

While were on the topic of this i should probably post up pics of the crazy fabrication job we just did to a turbine housing to use a prototype turbo on my R14 for time attack -- modified a T3 twinscroll hsg, with dual-flapper internal wastegate and 4.5" marmon flange outlet, to be a T4 twinscroll, IWG eliminated, with 4" vband DP in the 42R location