Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Too much of a good thing --15 minute gravity drop

endurance · 10-05-2010, 12:32 AM

I guess I'm lucky with the start of my commute, in that I drop from 7400' in elevation to 5800' in my first 9.5 miles every day. Right now on an average day I can touch the gas once if no one is around, just enough to get from a rolling stop to 30mph on one flat spot after a stop sign. If there's traffic, I usually have to use gas to get from 30-45 for a merge (mountain highway with a 45mph speed limit), but without traffic, I can roll up to merge speed fairly easily, just late in the ramp.

My question is just how much should I tempt fate with this gravity drop. It takes a good 15 minutes and that's a lot of time to waste with an idling engine. I want to start playing with EOC, but obviously with that big of a drop, I'm on and off the brakes for short pulses several times a minute with the twisty mountain roads. I saw the thread on adding a PVC vacuum reservior from 2008 and that's very tempting, but even if I extended my number of brake applications from 2 to 6 or 7, I'd have to recharge my vacuum every 1-2 minutes to maintain safe, solid brakes. Is it worth it? Are there any other alternatives, like maybe figuring out some kind of 12v vacuum pump? I just hate the idea of not taking advantage of this tremendous geographic advantage since I'm definitely paying for every drop of gas to get to the top of this mountain.

10-05-2010, 12:32 AM	#1 (permalink)
endurance Master EcoModder Join Date: Sep 2010 Location: Foothills near Denver Posts: 279 RSX2fast4mpg - '02 Acura RSX Type S 90 day: 38.22 mpg (US) bubbatrucker - '98 Chevrolet K1500 90 day: 18.1 mpg (US) Thanks: 15 Thanked 25 Times in 17 Posts	Too much of a good thing --15 minute gravity drop I guess I'm lucky with the start of my commute, in that I drop from 7400' in elevation to 5800' in my first 9.5 miles every day. Right now on an average day I can touch the gas once if no one is around, just enough to get from a rolling stop to 30mph on one flat spot after a stop sign. If there's traffic, I usually have to use gas to get from 30-45 for a merge (mountain highway with a 45mph speed limit), but without traffic, I can roll up to merge speed fairly easily, just late in the ramp. My question is just how much should I tempt fate with this gravity drop. It takes a good 15 minutes and that's a lot of time to waste with an idling engine. I want to start playing with EOC, but obviously with that big of a drop, I'm on and off the brakes for short pulses several times a minute with the twisty mountain roads. I saw the thread on adding a PVC vacuum reservior from 2008 and that's very tempting, but even if I extended my number of brake applications from 2 to 6 or 7, I'd have to recharge my vacuum every 1-2 minutes to maintain safe, solid brakes. Is it worth it? Are there any other alternatives, like maybe figuring out some kind of 12v vacuum pump? I just hate the idea of not taking advantage of this tremendous geographic advantage since I'm definitely paying for every drop of gas to get to the top of this mountain.