In Reply to: 5-speed owners, does your car do this? (Wierd...) posted by Tim Collins on November 04, 1999 at 00:40:10:
: Ok, maybe I just have NO IDEA what the hell I'm talking about when it comes to car engines, but I've noticed a strange behaviour. Say I'm driving @ 40 MPH. I take it out of gear, and leave it in neutral, so it's just cruising and idling. I would think that the mpg needle would show the top, because I'm using just enough gas to keep a 700 RPM idle and going like 40 MPH, no? It doesn't. It is high, but not at the top. But if I have it in gear and just let completely off the gas, it DOES go to the top (highest MPG, no actual #). Why? Isn't it using more gas to maintain, say a 2500 RPM idle (if I leave it in 3rd) than a 700 RPM in neutral? So shouldn't neutral, 700 RPMs give me better mileage? I just find this really strange... can someone please explain this to me?!
: Tim Collins
: '90 535i 5-speed sharked
The real qustion here is "what is driving that display?". Is it vacuum based (which would require a circuit to drive it to zero when no vehicle motion is detected), is it fuel flow based, or is some other principle being converted to visual indication?