Quote:
Originally Posted by tehsocks
Hey, i have an 85 camaro (v8 5.0L 305ci) NOT an economical car by any means but its fun to see what it can do.
It can do consistent 30's on the highways and thats good. but thats aside the point.
I recently installed a vacuum gauge (hooked upto manifold vacuum), and my understanding is that when i have most vacuum im using the least amount of gas, correct?
Well I find that when im idling i have 22, and when i put my car into OD and start driving around, when i accelerate my vacuum goes all the way down to 14-16ish. and its horrible. But if i put it in 1st, rev to 3500rpm, and cruise around in 2nd at 3000-4000rpm. I have 22-24 vacuum.
And when i let off the accelerator in 2 or 1 my vacuum goes off the scale high which i also assume is good. But this doesnt make sense to me. I thought OD was the most economical thing you could do. But thats not what im getting from my gauge.
Ive tried doing this for about 100km's on this tank and i seem to be getting my normal gas mileage, so it doesnt seem to be using any more, and doesnt seem to be using any less.
But am i correct, is this how i read teh vacuum gauge, and does this seem odd to any of you? Ive never heard of revving high to get good mileage before.
(redline is 5000rpm)
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What I'm hearing,and this has been touched on,is that in low gear,the engine sees little load,so it can operate at higher rpm with little throttle opening,hence the higher vacuum.--------The vacuum gauge,as an economy device was intended for carbureted cars to help you keep out of the power-valves and prevent secondary throttles from opening.With the primaries nearly wide-open,the volumetric efficiency is good,mixing is good,and high turbulence in the intake runners(also good).All good for mpg.