shawnoc2003

Three issues drive the decision between twin turbos vs. single:

1. packaging
2. performance (low end power is typically OEM preferred for driveability)
3. cost (single turbos are generaly cheaper)

There are some older single turbo cars out there (Pontiac TransAm, Buick Grand National...etc), but as you shrink the engine compartment and lower the hood packageing becomes even more difficult.

complacentsee

But with FSI it completly changes the ball game.

shawnoc2003

Do you mean fuel directly injected into the cyinder (Audi's FSI)? or the new GM diesel that is coming out.

The next generation of V8/V6 diesel engine is supposed to have the exhaust ports in the intake valley (which will simplify a single turbo configuration and lower costs) and the intake ports on the side of the engine. Not sure if this is out yet or not.

complacentsee

Yep. That is exactly what I was talking about. I believe I saw a BWM (I think it was a V6 diesel BMW with a single turbo in the genter valley) that had the "inverted" configuration. I'm not sure why it wasn't thought of long ago. (on the deseil side) Once you take fuel injectors out of the equation you don't need to have the intake/fuel inectors pointed down.


With the huge push for fuel economy. I think this may be the future of turbo vehicles.

shawnoc2003

GM looked at a while ago; however it was deemed too cost prohibitive due to underhood temperatures (the upper area of the engine compartment is pretty stagnant).

Newer materials, back then, are now commercialized so they're thinking it can be achieved. We'll see how it fairs when it debuts. My understanding is that its going to replace the Isuzu Duramax engine that's in the current GM trucks.

I agree though that in time, we'll see this happen with gas engines as well. Just imagine how easy it would be to change the turbos in the S4 if it were in the valley.

Of course the other path is Eaton's supercharger in the valley which is heavier but more modular.

complacentsee

Yeah. Looking at the MB with the integrated supercharger, water to air inntercooler, and intake manifold are a really sweet design.

shawnoc2003

Yeah, the compressor efficiency is pretty close to an equivalent turbo (except on the top end). Just a lot of weight really high up in the engine compartment.

Just what an Audi needs huh, more weight up higher over the front wheels