Request for Data from TheHolyCow

[R.I.D.E.]

Fuel consumption will be constant in any gear at 20% throttle and 2000 RPM only when the manifold vacuum reading is identical, and only for a short period of time.

regards
gary

[monroe74]

Originally Posted by R.I.D.E.

Fuel consumption will be constant in any gear at 20% throttle and 2000 RPM only when the manifold vacuum reading is identical

If throttle setting hasn't changed and engine speed hasn't changed, what would cause manifold vacuum to change? I think at any given throttle setting and engine speed, manifold vacuum should be pretty constant.

It's true that if you want to be very scientifically precise about things, there are other factors that need to be considered, like atmospheric pressure, ambient temperature, and engine temperature. Probably also the chemical composition of the fuel. But all those things are likely to not change much, especially within any given brief interval. So I think it's OK to simplify things and more-or-less ignore them. But maybe you're thinking of other factors that I've overlooked.

and only for a short period of time

You seem to be saying that even if throttle setting, engine speed and manifold vacuum all remain constant, that after "a short period of time" there is something else that is going to cause fuel consumption to change. I can't imagine what that would be, so I hope you'll explain what it is.