A diesel experiment

[Sludgy]

My truck has a manifold pressure sensor and a variable vane turbocharger. At low manifold pressure, the turbo vanes tighten to increase the exhaust gas velocity, and this spins the turbo harder. This reduces turbo lag, but it also adds exhaust backpressure.

My proposed experiment is to put a one way valve in the sensor line to keep the sensor reading high pressure. The ECU should open up the vanes, reduce the backpressure and slow down the turbo. I think this might improve FE.

What do gassavers think?

[omgwtfbyobbq]

I'm gonna guess this will do nothing, or hurt FE.

[Lug_Nut]

Just take the turbo completely off if the desire is to reduce back pressure.

No, your proposal won't help fuel mileage.

[Sludgy]

Originally Posted by Lug_Nut

Just take the turbo completely off if the desire is to reduce back pressure.

No, your proposal won't help fuel mileage.

Why do you say that? It seems intuitive that pumping losses in the engine would be a lot less, and FE would improve.

[omgwtfbyobbq]

Any advantage gained from reduced back pressure would be lost because you couldn't cram as much of a charge into the cylinders at a given rpm, and would have to spin the engine higher, which means more friction losses. Pumping losses on the exhaust end are relatively small because the exhaust charge is higher pressure than the outside air, and will flow out pretty well. Being able to make more power allows for a smaller engine, which by nature of it's design, reduces pumping losses.