Few questions for easy, $0.00 modifications

[palemelanesian]

Originally Posted by FLAteam

-Engine off Neutral (on my automatic!) twice. It was kinda scary. Found out I don't have power steering. Seemed to help, but not much more than engine on Neutral (but I wouldn't know...my speedometer was at 0 and I don't have a Scangauge).

You should turn the key back to the ON position as soon as the engine stops! That's very unsafe not to! Your ABS, airbags, and any other electrical systems are turned off at that time! Besides, you're not registering any of the miles traveled, so your numbers aren't reflecting reality.

[Mr. Pig]

In my Cavalier, per my ScanGuageII, when coasting in drive at around 55mph I see around 55-60 mpg, if I pop it in neutral I see around 125-130 mpg. I'm having trouble understanding how the fuel cutoff could be using zero fuel. If there was no fuel at all, the engine would die and effectively have to be bump started to get going again, which isn't possible in an auto. Perhaps it is just cutting fuel to a point that it is running super lean? Or is my GM vehicle just not the norm?

[palemelanesian]

The Scangauge is likely not reporting it correctly. It's only guessing - there's no code in the OBD-II protocol for fuel cut. It just guesses by the light load and rpm.
If it's in gear, your car's momentum is driving the wheels, which in turn are rotating the engine. That's how it stays turning with no fuel. If you're in neutral, the engine will require fuel to keep running, so there's no fuel cutoff in that case.

[theholycow]

Originally Posted by Mr. Pig

In my Cavalier, per my ScanGuageII, when coasting in drive at around 55mph I see around 55-60 mpg, if I pop it in neutral I see around 125-130 mpg. I'm having trouble understanding how the fuel cutoff could be using zero fuel. If there was no fuel at all, the engine would die and effectively have to be bump started to get going again, which isn't possible in an auto. Perhaps it is just cutting fuel to a point that it is running super lean? Or is my GM vehicle just not the norm?

What was the tachometer reading?

If it's still in gear and the wheels are turning the halfshafts are turning the diff is turning the driveshaft is turning the transmission is turning the crankshaft, what's the problem with reducing the fuel until zero fuel is injected? As long as fuel is resumed before the RPM drops below idle speed, no restarting will be required.

A Cavalier isn't exactly the showcase of all the latest in modern technology; I suppose it's possible that it might not support DFCO, though I'd guess that it's more likely that it just wasn't revving high enough. 1000 rpm is the number everyone says for DFCO and it's definitely the borderline point for my VW, but I'm not sure that it's the same in all vehicles.

Pale: I hope your guess is wrong. I am planning to buy a SG and I'm counting on it being able to report actual fuel consumption volume. If it can't, I need to come up with some other gauge to do it.

[palemelanesian]

Test for DFCO: Do a controlled coast-down in gear with the engine on. Mark the distance/time results. Do it again in gear with the engine turned off. If the results are similar, you have DFCO. If the engine-on coasts longer/farther, you don't.

[GasSavers_RoadWarrior]

Ford EEC computers are meant to do it down to 1800 rpm on auto transmissions, I guess that's about where the transmission stops driving the motor.

[theholycow]

1800 is pretty high for DFCO to quit.

Mmmmm.....1800.....

[FLAteam]

well, I just filled up 10 gallons and got around 35.5 mpg. However, i filled it up super-slowly...so maybe next time it'll be higher.

[theholycow]

I found a free mod that is very easy and might help hypermilers with automatic transmissions. The link is about tuning for racing, but the same mod can be applied to us with one minor change:
http://www.autospeed.com/cms/A_1304/article.html

It says to adjust the cable so that your transmission will be more responsive, downshifting with less gas pedal input. However, if you adjust it in the other direction, you'll be able to use larger throttle opening at lower RPM.