diesel des

Hi All I am new to this forum and have some questions for all you turbo guys out there. I am involved in a project with a Small DI diesel engine. It currently runs a much larger than stock Garrett VNT turbo, eg a variable vane nozzle turbine. It makes great power and spool is good too. Spool is about the same as stock (Stock is a smaller waste gate turbo) and top end power is way better with the big variable vane turbo. But I am at the limit of this larger VNT turbo now.

I would love to try a compound setup. I have a selection of large turbos that would be about the right size of the LP Big turbo, and also a number of different small turbos too.

But I would like to try using a VNT turbo as the small unit. Eg where you guys would use say a hx35 holset wastgated, I would want to use a Variable turbine turbo and no waste gate. The advantage would be great spool and still great flow at the top end.

So, has anyone here used a Variable vane turbo as the small HP unit? Can it be done without needing a waste gate working in parallel with the small unit?

Thanks in advance.......

RowJ

Not that I know of or have read about!
Don't know much about the turbos you're using, but I would not want to do a compound set up without a WG on the secondary turbo....at least an external WG mounted on the exhaust manifold!

RJ

Gotlift01

I agree with RJ, the secondary really needs to have a wastegate!!



~Nick

diesel des

I was hoping that when the VNT opened up on the small secondery turbo it would have the same effect as a wastgate opening. Why would this not work? Just trying to get my head arround it....

signature600

I will work...but it just depends on waht size it opens up to. As long as it will open enough, I don't think there should be a problem...but it's a big "if" without knowing what the max housing size would be

If you can make it work...it would be real slick,
Chris

gunracer1

can you measure what your drive pressure is right now at full boost and the turbo set to its most open position? i think that would tell you weather it would work out well or not. but my gut feeling is that it would work just fine. as long as you were not just going for some killer set up.

diesel des

Thanks for the help guys. At 25psi boost with currant setup i have 25 psi exhaust manifold pressure. at 30 psi boost im at 35 psi EMP. If i open the VNT right up the boost falls to about 18psi with 15 psi EMP. What are your thoughts. I may be able to weld a wastgate tube into the manifold remotley mounting a wastgate and help the VNT out, but it will take up more space i dont have and need some cast iron welding which is newer good.

All info is great....

gunracer1

sounds like it will work just fine if you can lower the emp that low.

Diesel-Dan

Heck yeah...i don’t think many WG could do that good....i have looked into doing this myself. My only reservation is how to control the VG part of the turbo.....i have heard that some Garrets are Vacuum controlled, some oil pressure controlled, and some electrical. I would think that the Vacuum would be the simplest.....and convert it to reference boost. I have talked to a few on this site about this.......but which turbo do i look for???!!?? Im a Holeset man for obvious reasons!! I think a VGT Secondary in a set of compounds would be killer!!!! Give us some info on the turbo you are using now.....pics? ALSO fill in your sig for us to get an idea of what you got....thanks!

diesel des

Thanks for the info, i think i will give it a try with no wastegate first and see what happens.

Ok this is a VW Golf TDI. Please dont laugh till you have read the rest. Its in a light a2 car from about 1990. The engine is 1.9l and the compression is arround 17:1 on my lattest build. The last run on the rollers put 200BHP to the wheels at about 4400 rpm (About 230bhp crank) and 320 fl/lb (370 at the crank at 2K rpm). I had to reducing the fueling curve at arround 2K rpm to hold the torque back as i could easily slip the 4 puck race clutch with over 400ft/lb torque.

The engin can rev and pull hard to almost 5.5K rpm from 1500 rpm and so in a 2200lb car it goes like a rocket. The turbo is a garrett VNT20. Now, it tops out on flow at about the level im at eg 200 Whp. You guys with your larger engine that is slower revving could easily run 2 VNT 20,s in parrell, or sometthing twice the size. Im not sure what Garret do in larger VNT turbos. But i did see a hx40 VGT once. Maybe that would be a good turbo on the hp unit for you guys compounding. I have a friend here in europe that is a truck mechanic and he works on big cummins engines, so i will ask him what VGT units they use. All most all the 1-10L car-truck engines here in europe are VNT or VGT now.

The garrett units are vacume or electronicly closed. My ecu is coded to control the vacume on the actuator to control boost. Im sure you guys could do something with a stock wastgate actuator though. The secrete with the VNT is that it isnt open or closed, but it needs to move slowly in its mid positions to control the boost best.

Hope that helps.