Anybody thought of doing a compound set up with a little t3 turbo and a large frame t4 or a t6? Maybe run 7-10 psi on both to average out to 14-20psi total. That way you could spool "supercharge" fast but hav bad *** top end with low drive pressure. I know it's been talked about before but I haven't seen it done yet in the gasser truck world. It would be cool to have the little guy at full boost by the time the big one takes off, Around the 3500rpm range.

 

I know kyle was wanting to try it but dont think he ever did...trouble is the pressure ratios get multiplied, not added, so boost gets very high very quickly. And the hot side would be complicated with at least 2 wastegates to route exhaust flow. Also the smaller turbo would end up choking the big one up top, and the big one keeps the little one from spooling as fast as it otherwise could, so you loose on both ends, but should gain tons in the middle. The engine size and size of the turbos determine where that "middle" would be in terms of power.

 

I think just not cost effective.
If you are gonna buy two turbo might go ahead a do twins.

 

Twins are an idea too. But I think with proper waste gate sizing there shouldn't be a big choke point. The drive pressure could be high but once the gate opens it should drop the pressure and send it all to the large turbo which should be sized big enough to flow well along with its own gate. If you pipping is short from the atmosphere turbo and the Houseing is large then it should slow down the small turbo much at all. A big 88-91mm over a little 60, the 60 should be able to drawl all the air it needs. The outlet of a 91mm is around 3"s right? An the actual wheel size of a 60mm is 2.3". Sounds to me like plenty of airflow.

 

Do it,

diesel guys are doing it with 70+psi and 1400+whp and 2K+ tq.

hell its even done on small 2.5 6 cyl nissan engines, and they ran high 8's

 

thats where i'm bringing this from is the diesel world. i think it would be awesome in the gas burner ls world.

 

My girlfriends father runs this on his pulling tractor with 3 turbos. He runs a 600ci alcohol engine at 112 PSI. Makes good power.

 

Here's a good build of a compound set up from the import world. My compound turbo set-up - DSM Forums
I was think about it too, just dont have the funds for it.

 

the thing would be to cap it at 20psi or so. but, if you could make it hold 60psi it would be one fast ******* ls motor. lol

 

Sounds like what you're talking about is more of a "sequential" set-up than a "compound" set-up. It would be great I think, to have a small divided housing "baby" turbo that would spool <1,700 rpm with the help of a diverter valve to block off one side of the housing until you hit your peak boost for that turbo then opened up to allow full flow. You'd need a few waste-gates/diverter valves and a control mechanism for the exhaust routing to bring the larger turbo in for the mid and top-end, and allow for the proper amount of bypass of the small turbo.