Pulse and Glide shouldn't work vs. Cruise control - Page 3 - GreenHybrid

ElanC · #22 (**permalink**) 01-12-2006, 09:53 PM

Quote:

Originally Posted by xcel

___Sitting at a stop and then coming to a stop isn’t really a P&G at all. Accelerating at an optimal rate (just below assist) not very fast and not dead slow but with a FAS at just the right moment so that you are actually crawling up to that stop sign ahead will allow the highest FE in that situation. ¼ mile? Screw the Glide. Maybe a 2,100 RPM acceleration rate for about ¾ of a block and FAS all the way in would yield an easy 100 + mpg’s. Where stop lights and signs to be crawled into are concerned, you have to consider a FAS with any IMA based hybrid. Anything else is just wasting fuel.

I don't see the point of FAS when simply taking your foot off the gas pedal puts the ICE in valve-shutoff mode.

NASAgineer · #23 (**permalink**) 01-12-2006, 09:58 PM

Quote:

Originally Posted by xcel

___Sitting at a stop and then coming to a stop isn’t really a P&G at all.

Well, that was just an example. Experiments I did doing P&G between 30-45 miles per hour also seemed to support the theory. My point was just that you have to adapt the technique to the situation at hand.

Another complication is that at least in the HCH-II (I have no experience in any other hybrid), accelerating at anything over 1500 RPM (veerrryyy slow) results in at least a bar or two of assist.

NASAgineer · #24 (**permalink**) 01-12-2006, 10:01 PM

Quote:

Originally Posted by ElanC

I don't see the point of FAS when simply taking your foot off the gas pedal puts the ICE in valve-shutoff mode.

With a true FAS, the CVT is in neutral and the crank is not spinning, so there is less friction loss compared to valve-shutoff mode. The glide will go farther (not sure how much though). To me it's usually not worth the extra gyrations.

xcel · #25 (**permalink**) 01-12-2006, 10:13 PM

ElanC · #26 (**permalink**) 01-12-2006, 10:24 PM

Quote:

Originally Posted by NASAgineer

With a true FAS, the CVT is in neutral and the crank is not spinning, so there is less friction loss compared to valve-shutoff mode. The glide will go farther (not sure how much though). To me it's usually not worth the extra gyrations.

I agree with you on every count.

If you're in a hypermiling competition every ounce of gas matters. Otherwise it's not worth the trouble. There's another issue with the HCH II. When you shift to neutral the ICE powers back up. So there's a loss which you have to make up, both before FAS and when you come out of FAS.

xcel · #27 (**permalink**) 01-12-2006, 10:27 PM

NASAgineer · #28 (**permalink**) 01-12-2006, 10:32 PM

Quote:

Originally Posted by xcel

___Although we may have gone over this already, I have a feeling you will find a particular SoC where you will lose assist on any and all accelerations.

You mean that when SoC gets low enough, assist will disappear? If so, while the low SoC gets rid of the assist, don't you pay for it with the inevitable forced regen that you get at that low SoC?

xcel · #29 (**permalink**) 01-12-2006, 10:40 PM

xcel · #30 (**permalink**) 01-12-2006, 10:52 PM