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Old 09-30-2009, 06:35 PM   #55 (permalink)
Jammer
Chevy and CB Radio Lover
 
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Join Date: Sep 2009
Location: East Kentucky
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Quote:
Originally Posted by Old Mechanic View Post
If you are using the engine to slow the car down going down a steep slope. you are using no fuel with the ignition on due to DFCO as Pale stated.

Example:

You crest the hill (top) and start down. The hill is very steep so you downshift with your foot off the gas. No need to turn the engine off. It's not using any fuel anyway. Steering and brakes work normally.

If you can not slow down enough using the gears and your are worried about the engine revs getting too high, apply the brakes momentarily to kill some speed, but keep the car in gear with your foot off the gas pedal. You are getting infinite mileage when your foot is off the gas and the slope is keeping your revs up in any gear.

As you approach the bottom of the hill you have two choices. If you have enough time use EOC (engine off coasting). If you don't have enough time, put it in neutral and let your speed increase some (Maybe 10 MPH). You want to use the speed to get you as far up the next up slope as possible without danger or a ticket.

Its a lot like a roller coaster, but you have to be safe with your maximum speed.

If the speed limit is 50 MPH, your highest speed would be at the bottom of the hill, and your lowest speed would be right before you reached the crest of the hill. This is just like a roller coaster. I use the roller coaster as an example because it can go very far without any power at all, after its first climb under power.

regards
Mech
Thanks again. I mean no offense, after all your the mechanic, but I can not see where downshifting down a mountain with the engine running results in NO fuel being burned. After all I think the DFCO cut off is around 2,500 RPMs, so I have to assume gasoline is burning to that point. I guess I am curious if it is possible to go EOC down hill by gearing down to slow down with the key in the off position, or will this idea end up burning gas some how? My mind is real fuzzy on this one.

Also there seems to be a limit to braking during EOC in my Cobalt XFE, or is that my imagination? As far as I can tell if I am going a long distance in EOC my brakes work fine for a few pumps then do not work until I start the motor back- which can be extremely dangerous around these curves here. I am still learning how to do all of this safely, but I no longer have the fear I did back when I first tried it and had trouble.

I do plan on getting some home insulation and taping it around the battery in the trunk and see if that helps my battery to charge/keep a charge or not.

My best.
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