Vacuum Gage on Automatic Transmissions Autos?
 

Hi I am new and interested in getting some Fuel feed back instrumentation before I start Moding my cars. Does a Vacuum gage help if you have an automatic transmission? Or is it more of a "shift indicator" for a manuel?
Thanks
Ivan

I have a vacuum gauge installed on my 1997 Corolla (1.6L, 3 speed automatic). It is useful for giving me an indicator of how hard my engine is working (and thus how much extra fuel I consume).

I find myself holding the transmission in 2nd gear for better acceleration as my 3rd gear is pretty much a freeway only gear. (Imagine a 5 speed, that only has gears 2, 3 and 5) When in "D" it will shift from 1st to 2nd at 11 MPH and 2nd to third at 25 MPH, unless I over-ride it. I use the vacuum gauge to make sure I am not pushing too hard on the gas pedal before my upshift.

Thanks
 

Ok thats great to know. I do think that unless I am flooring the gas pedal my truck and car both shift a little early. So my question is now: Do you find that you are able to get better gas millage when you override your Auto?
If so how much?
Thanks again for your reply.
Ivan

Slow or fast acceleration can result in bad MPG
 

I would like to remind you that I have a 3 speed. If I don't over-ride the auto my acceleration is really bad, so it takes me a lot longer to get up to the good gas mileage speeds (35-55 mph in my car). I am a student, and I have a job, so I find myself doing a lot of short trips on city streets. I have only been keeping my fuel log since January, so I can't tell how much of my improvements in MPG are from driving habits/mods and how much is from warmer weather. I might try to do some experiments on this.

I think delaying the up-shift is a trade-off that can hurt or help gas mileage depending on how it is used. My car's early shift to 3rd gear (at about 20-25 mph) lugs my engine out something fierce, so I have to press harder on the gas pedal to only move slightly faster. I usually delay it to whatever cruising speed I choose (35-55 mph). I look farther up ahead on the road to make sure it is worth it for me to accelerate faster (waste gas) to cruise longer (save gas) versus going slow the whole time (get OK but not great gas mileage). I use my Scanguage almost all the time, it would be impossible to know if there was a difference without it.

I think downshifting manually is better for gas mileage, because I still have control over the throttle (compared to flooring the gas to make the car downshift on its own, like you mentioned). On some hills, I have to downshift manually.

I tried an experiment where I would barely accelerate for a whole gas tank (1 mph faster every 5 seconds or so). This actually resulted in worse gas mileage than driving normally.

Does anyone know if the shift points in an automatic can be adjusted? That would be great.

Shift points can be changed on an automatic but you need to find a tuning program that will work with your cars PCM or a place that sells custom chips. I'm not sure who makes one for a Toyota but for most GM and some Dodges and Fords HPtuners can edit the settings.