Engine/Transmission (1998.5 - 2002) light-load and fuel economy: manifold pressure

[Jdonoghue]

What kind of boost numbers are you seeing driving empty, 50-55MPH?



Why I ask, and what it has to do with fuel economy:

Under light load, the ECM will advance timing up to 3 degrees. As the manifold pressure increases, the less of this timing advance there is, until around 4 or 5 PSI, when there is no 'light load' advance anymore.



My truck ('01 HO, stock turbo with BHAF and no muffler) will see less than 3 PSI on flat country roads driving 50 to 55 MPH.



It would be interesting to see what those with different turbos, twins, etc. have for manifold pressure under similar driving conditions.

 

[johncameron]

I see the same as you. Towind 6K at 65MPH I'm usually under 10PSI. I just made record MPG of 13MPG towing last weekend (-:

 

[Fishin Guide]

I don't cruise at those speeds. But at 60 opr so I am seeing around 4psi. Under that, the gauge is on the peg.



Dave

 

[Huff N Puff]

I normally see about . 7psi to . 8psi on a light cruise. BD monitor can read real low.