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Old 07-08-2010, 12:09 AM   #1
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FAS vs. P&G

hello, my name is cris, and i am new to hypermiling.

i was curious if the FAS P&G combo gains over just regular P&G would outweigh the extra wear on the powertrain by repeatedly shutting off and re engaging the electrical system as well as bump starting the engine. i am not using the starter, and wear on the clutch is, i believe minimal, as i simply engage it just enough for the ICE to turn and fire up on its own. yet still i wonder because i am constantly repeating this procedure on a 60-40mph P&G. it does seem like the wear on components is adding up rapidly. what do you guys think? thanks.
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Old 07-08-2010, 07:03 AM   #2
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I don't FAS on short P&G cycles. I try to save it for longer glides. If I'm doing 60-40 P&G on level land I probably don't FAS.

Remember, idling in neutral vs. shutting off is a matter of time, not distance; so 30 seconds at 20mph represents the same amount of fuel as 30 seconds at 70mph. When I first started FAS I did not stop to think of that and I had trouble deciding when to do it...I was trying to go longer distances when I really just needed to do it by time.
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Old 04-11-2011, 03:07 PM   #3
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Re: FAS vs. P&G

What is FAS and what is PG? I'm new and the lingo spoken here can sometimes read like a foreign language. Any help?
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Old 04-11-2011, 03:18 PM   #4
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Re: FAS vs. P&G

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Originally Posted by Arky View Post
What is FAS and what is PG? I'm new and the lingo spoken here can sometimes read like a foreign language. Any help?
here's the whole 9 yards...http://www.gassavers.org/showthread.php?t=7428
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Old 04-11-2011, 06:02 PM   #5
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Re: FAS vs. P&G

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What is FAS and what is PG? I'm new and the lingo spoken here can sometimes read like a foreign language. Any help?

To answer your question Matt:

FAS means Force (or Fuel) Auto Shutoff...like many of the new hybrids have. When the car comes to a full stop it shuts the engine off.

PG means Pulse and Glide, which in basic terms say the speed limit is 60mph you'd accelerate (pulse) to say 65mph, then coast (glide) down to 55mph, and do this over and over...increases your mileage assuming you have HRR (high rolling resistance) tires or at the very least properly inflated tires.
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Old 04-11-2011, 06:06 PM   #6
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Re: FAS vs. P&G

Welcome, Cris. What THC said. At high speeds, glide times are minimal, so FASing isn't very productive. You'll pulse 8 seconds going from 40-60 mph, and only get 8-16 seconds of glide time - a 1:1 or 1:2 P/G ratio.

The slower you go, the longer your glide times, proportionally. P&G from 25-40 mph is something like 8 sec pulsing, and 24 secs gliding, a 1:3 P/G ratio. P&G from 15-30 mph is 8/40, a 1:5 ratio, and 10-20 mph is 3/30, a 1:10 P/G ratio.

So, shutting down your engine 50% of the time helps, but shutting it down 75%, 83%, or 91% of the time gives you far more benefits.

Your cost/benefit ratio will vary. I've saved $1700 in gasoline costs by hypermiling, more than enough to buy several clutches and starter motors, and I haven't replaced any of either since I started hypermiling.
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Old 04-11-2011, 09:37 PM   #7
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Re: FAS vs. P&G

I've had poor luck with P and G but that's mostly attributed (so I think) to the lean burn function. At steady state cruise on flat ground (of which there is little here in Maine) and 35 mph, I can see 75-95 mpg on my gauge.
However, EOC and shutting down at stoplights seems to help a lot. I used to do more EOC during all down hill runs, but I've found once the engine is warm I do better leaving it running/DFCO down hill because most hills don't allow me to use the extra bit of momentum I sustained by coasting in neutral with the engine off. Some do, and I still EOC down those. Coming up to almost all stop lights I EOC to a stop. Then I start it with the key. If the light changes, I bump start with the clutch. I've gotten pretty good at reading the intersections I go through a lot... and make sure in double lane sections that I let the guy behind me race around me (because I'm traveling slower than he is) and charge up to the light. He sets off the light (mostly sensor lights around here) and I roll through it slowly.
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Old 04-12-2011, 05:36 AM   #8
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Re: FAS vs. P&G

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make sure in double lane sections that I let the guy behind me race around me (because I'm traveling slower than he is) and charge up to the light. He sets off the light (mostly sensor lights around here) and I roll through it slowly.
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Old 04-14-2011, 12:13 AM   #9
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Re: FAS vs. P&G

Thanks for the answers. I didn't even realize it but I've been doing the FAS quite a bit lately. I do love it when some idiot passes me to get to a stop light, then trips the sensor and I coast right through the light. There are two of those at the bottom of hills on my way to work that hit all the time.
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