Turbo Boost and FE

[itjstagame]

Nice thread. I can't believe people are arguing over whether turbos increase efficiency or not, that's crazy. Of course I don't have any direct quotes or numbers either but they help with exhaust scavenging and improve thermal efficiency of the engine.

Everyone I know with a turbo gets quite a bit better MPG than the same car in NA form. Of course when they're at the track or driving as fast they can they can get anywhere from 5-15MPG. And then there are STis which seem to always get 15MPG for no reason.

I was trying to find a quote I thought I read about turbos boosting overall engine efficiency to 50% but I think I found the source and it was about thermal efficiency of 2 stroke turbo diesels being 50%. Which btw, are awesome engines and I really think we need them on smaller scales for auto use. I mean a 500cc to 1L should be more than enough power for a car and get quite a bit increase in MPG over a standard diesel.

Anyway, it's true that turbos can be compared to increasing the displacement of an engine and require more fuel, but it's really kind of a displacement on demand, I think the best application would be a 700-1000cc engine that gets awesome fuel ecomony at cruise (neutral pressure), but can take a hit to fuel economy and spool the turbo up to 'act' like a 2L engine when acceleration is needed. Then you would have better FE than a 1.5-2L but just as much power when you needed it.

Good luck in your project, someday I'll build my 2stroke turbo diesel engine out of my spare 550cc mcycle engine and throw it into my CRX. But not having a machine shop or money that time will be never.