Thread: VE-T twin scroll setup

Since your compression is that low, you should be able to have a heap more timing in there.

E.g. My 16,000km VET makes 200psi across all cylinders with VE cams. 18* timing at full load.
e.g.2 Tuned GTiR with same turbo, 150-160psi across all cylinders, 28* timing in same zones.

Once you've taken off the MSD and fixed the boost leaks, my suggestion is to crank the base timing up to 21deg. Still, the way it intermittently drops timing to 3-6* is just wierd...

I am going to up the timing back to 19*. I figured the new setup would flow a lot more and would possibly detonate on higher timing levels.

This is the same exact dyno as before. I have put on about 1500 miles since the setup went on. But with no mishaps with the engine I am going to start looking at other possibilities before saying the engine is the problem. Car runs great, gets great mileage, burns no oil, and driveability is good.

Ok so here's some things I have found out about the setup I decided on.

The manifold is great, awesome upgrade, you can use the VE cams without any issues with reversion.

The dual wastegates are awesome too, they flow a ton and don't recirc back to the exhaust system. Creep-free, loud, and sound great!

The turbo is awesome, very responsive. With the VE cams I hit full 15psi at 4000rpm, and with the VET cams I hit at 3700rpm in 4th gear on the dyno. The exhaust housing I am using though... is not as good. Basically the bottleneck in the system is the housing. A .78 divided housing is not really a .78ar housing. When you add the two sides together you get .78, but the problem is; When you have two pulses going through the turbine housing, they only go through 1/2 the housing. So it really performs like a .39 in spool and like a .48ar in backpressure.

The heavy backpressure takes its toll on overall performance. I'm sure the car could still make 500whp+ on high boost pressures, with a very very strong and wide powerband. The issue you have when running this small of a housing is with Volumetric efficiency. Though you do see gains in turbine efficiency (you will make more power because of this) you will not see any gains in volumetric efficiency because you will never ever come close to crossover.

FYI crossover is when boost pressure is equal or more than backpressure, and in this situation you can reach very high volumetric efficiencies and can make a ton of power.

When in crossover, the engine will perform almost like it is NA. Flat torque, and very peaky powerband generally, until you reach the flow capabilities of the setup. At which point the power will level off.

With the .78 housing, you are only using half the housing. So .39ar is really what a .78ar is. a 1.06 can spool like a .63, but will flow double what the .78 will. If you really want a TS setup, get a borg warner (or similar) with a t3 divided housing in a 1.06 or slightly bigger. The GT35R has a T4 option for TS, and has a 1.06 housing. This would be the way to go.

Apparently there is a 1.06 housing available for the GT30R, but it is only available overseas as far as I know.

Once again, learn from my mistakes. The .78ar housing will need about the same amount of boost as the .48ar to make power. It may perform only marginally better, but will require a crapload of boost. A log manifold and a .63ar performs very close to the .78 and tubular manifold.

If you have an SR20, don't even mess around with the .78 unless it is a full-out race car and can run lots of boost. Just stick with a .82. Not a .63. A .82 to make the best power. It is the smallest housing you can run on a GT30 sized turbo to reach crossover.