Gageraid wrote:
I want to know more about it, unless it's just some stupid feature that there isn't anything to know about.
I had bothered Musclez before to see what RPM's it went to in the green area. Kind of weird it doesn't start even lower in the RPM range.
Since you are so obsessed with trying to get the very best mileage, maybe you need to install a vacuum gauge. Back in the eary 60s some of the cars came with them as an option. I had a 62 Chev with 3 on the tree and overdrive and a factory optional vacuum gauge. Of course you drive by trying to keep the most pressure , maybe worth checking into. I assume they still make them
I'd almost bet that the "Eco" gauge is based somewhat off of the same principal
Just in case you don't fully understand how they work Vacuum Gauge
Though little understood, the vacuum gauge is probably the best single indicator of your engine's health you can get.
A Little Background
When your car is idling-whether it's fuel injected or carbureted-the throttle plate or plates are restricting the amount of air the engine can breathe in. The pistons are attempting to "suck" the mixture past the throttle. (Of course, in reality, it is atmospheric pressure that is attempting to "push" air into the engine as the pistons travel downward on their intake strokes.) When throttle is closed, vacuum is high in the intake manifold, from the throttle plate(s) to the combustion chambers. By contrast, at wide open throttle there is relatively little restriction to outside air entering the intake manifold, so vacuum in the manifold is very low.
A vacuum gauge reads pressure differences from atmospheric pressure, so the reading is zero in our "normal" sea of air. By convention, vacuum gauges in the US read "inches of Mercury."
Reading the Gauge
Unlike a fuel gauge, the vacuum gauge will keep you entertained with its instantaneous, wide-ranging movements.
When you floor the accelerator pedal, you can watch manifold pressure (another word for vacuum) swing from strongly negative to nearly zero (atmospheric pressure). When your engine is "on the overrun," like using engine braking down a steep hill at high RPM, you'll see really high vacuum readings. Naturally, turbocharged and supercharged will show very different results, with readings swinging into the positive at high speed. IAP's vacuum gauge is not designed for turbo or supercharged vehicles.
Your vacuum gauge is also a sort of "poor man's" fuel mileage indicator; when vacuum is low, you are burning more fuel. Absolute readings are not as useful as changes over time. That is, if you establish baseline readings under a variety of circumstances, you will know what to look for if your engine begins to deviate. Everything else aside, a high vacuum reading tends to indicate a healthy engine.
Login
Register
FAQ
Search
