Compound turbo setup.
 

Anyone considered this?
Been thinking about this recently and not seen much in the subaru scene, mostly big cummins diesels and drag machines in the USA.

What's the downsides?
Anyone with more experience in this sort of thing?

I work for a Volvo Truck And Bus dealership, Volvo used a compound turbo once and that was one time too many. :wall:

Overly complicated, don't get me wrong no less reliable but when things go wrong they are a lot more expensive to repair.

They soon dropped the idea and thankfully didn't use it again.

what's a compound turbo system?

Its like a pre turbo a smaller one, scania trucks have it and its good until it goes wrong, if first one fails it take out the other turbo with it.

how does it differ from a twin turbo setup?

A compound turbo is a smaller turbo that blows into the main turbo, a twin turbo setup is quite different.

You actually have the bigger turbo at the intake then it feeds a smaller one.
A twin turbo is 2 identical turbos hence the twin bit.
There's a hatch in America that's been done with a gt35 I think but I don't know what the smaller turbo is.

a compound turbo

https://i68.photobucket.com/albums/i...urbo_large.jpg

ok, so now i'm learning something here. i always thought in a twin turbo system...the smaller turbo, boosting on low revs, feeds into the larger one. but clearly the small one shuts off at higher revs and the larger one takes over, but this small one does not boost into the larger one. instead it boosts via it's own conduit.

does VW's supercharger plus turbo system works like a compound or like a twin chargring system??

or rather a bi-turbo setup then. the system which has a small and a big turbo.

I think to run a compound setup you need an external wastegate between the two also. This guy explains it pretty good.