Fuel economy - PeachParts Mercedes-Benz Forum

dozer · #10 07-28-2008, 07:20 PM

Quote:

Originally Posted by ForcedInduction

Right. I can basically turn my turbo off when cruising, it makes only 0-2psi of boost and has little more restriction than a non-turbo engine.

I'd think that a change of turbo settings or geometry would improve your MPG then.

If your boost is zero at cruise, then you're not using the 'free' exhaust energy to overcome the less-than-100% VE, correct?

In another post, someone mentioned running around 5psi at cruise. That sounds like about the optimum point for best economy.

Since I drive almost all rural 2-lane, in mountain-country; I spend a lot of time at very low throttle...i.e. just maintaining say, 40mph, against wind-resistance...because there's another curve coming up soon where I'll have to brake.

So I've always been interested in setting things up to get boost at very low power-settings. Yet I need a turbo system that works well at near full power as well; because every 10 curves there's another mountain to climb...

In lieu of the $$$ VGT's that I can't afford, I've often wondered about experimenting with a tandem turbo setup. Something tiny from a sub-2L, in tandem with either a stock 617 turbo, or even a slightly larger one (to keep backpressure down at the upper-end of the power/rpm range).

My first guess is to use backpressure to control the gates that'd switch between the two turbos...but I've really not thought it all out in detail yet.

So many experiments to try, so little time....