How to accelerate in P&G mode?

[monroe74]

Originally Posted by 1993CivicVX

my battery is often too low to start the engine using the ignition

I do a fair amount of EOC. I do tend to avoid it at night, because I'm a little concerned about the headlights draining the battery. Nevertheless, I think there might be something wrong with your charging system. Unless you're doing something extreme, I think you shouldn't often have this problem. I have a feeling maybe you need a new battery. Have you checked the level in it? It could also be something simple like a corroded connection.

Also, with a warm engine, the cranking required to start it should be very minimal. So this might be another clue that your engine isn't running quite right.

Slightly embarrassing to have to push the car in the middle of town and then jump in and bump start it.

Years ago I had a bunch of cars that worked this way. I would routinely look for parking spots that would let me roll downhill. But this was because they were old sports cars in poor condition. A few Fiat 124 Spyders, an Austin-Healey Sprite, an Austin-Healey 3000, and a TR-4. At one time or another, these cars had faulty charging/starting systems.

British car inside joke: Why do the British drink warm beer? Because Lucas makes their refrigerators. (Lucas is the company that makes electrical parts for British cars.)

Anyway, you have a Honda, not a Triumph, and I think you probably shouldn't be having this problem. Like someone said, you can solve the problem with an external charger, but I think that shouldn't be necessary, unless there is something extreme about the way you're using the car (e.g., I assume you don't have a 10,000 watt stereo).

I realize the VX has some special logic which restricts the way the alternator works, but I think you still shouldn't be having this charging/starting problem.

Originally Posted by 1993CivicVX

Maybe there is a discrepancy between our definitions of "smooth" but my car will not pull at 1000 rpm in 5th gear smoothly--it will do it--but I wouldn't characterize the mild vibration and unwillingness as smooth. 1250RPM in 5th gear and the car is very happy.

Yes, the word smooth is subjective. But when I say smooth, I mean really smooth. No vibration or unwillingness. Even down to around 800 or 900 rpm, although it's hard to tell just using the dash tach. This assumes fairly level ground, no passengers, warm engine.

Then again, 1250 is not radically greater than 1000, and the dash tach perhaps isn't a precision instrument, so maybe what you're observing and what I'm observing is not drastically different.

[1fixitman]

I pulse with about 1/3 throttle to 33 MPH then hit the EV(Electric Vehicle only) button I installed to force off the engine(less than 34 MPH) and feather the throttle to achieve a full glide, no arrow condition, but it is a hybrid so it is much easier to do this. The ScangageII is helpful too
Dwayne

[sonyhome]

(OFF TOPIC)

Originally Posted by theholycow

Should we take this over to the fuel meter thread?

Sorry, phased out of existence

Why not?

The OBD2 stuff is out the window, I want OBD1 or plain wire taps for the DelSol. For the CRV & OBD2, I have the ScanGauge.

Couple of notes:

I'm really slow at projects like that.
- This WE I stayed home, and got around to fix my CRV speakers
- ...and cut foam grill blockers for the CRV. Dunno if the foam worked, but got 30MPG @65MPH one way, and 26MPG @74MPH the other way (Short distances, flatish), without overheating apparently. Still warry to use that on long trips.

[sonyhome]

Originally Posted by theholycow

I try to use WOT as much as possible, but my car has a lot of low-end torque and it can be tough to moderate my acceleration at WOT. When I do, I shift at 1200 or 1400 RPM, entering the next gear at about 1000rpm. My pattern is as follows:
1st: A light, quick application of gas gets the car rolling enough for 2nd.
2nd: A quick stab gets the torque-strong car fast enough for 3rd or 4th, which are uselessly close in my car.
Depending on my current pattern, I may skip 3rd.
3rd, if I use it: A quick stab and I go from 15 to 20mph, and am ready for 4th.
4th: Now I get a chance to drop it to the floor for a couple seconds, at which point I'm going 25 or 30mph and am ready for 5th.
5th: On the floor until I reach the top of my pulse, then I begin P&G cycling.

Holycow, that's confirming my intuition is wrong and I need to review my red lights starts. Hondas don't really have much low end torque, they tend to have a longer power band and high-RPM limits with VTEC.

One more reason to hook up a PC to the car, to see where my gas is spent on my commute. i do get a lot of gliding, and I try to sync lights as much as possible.

I'll try to P&G in 5th gear (but I don't like -hum- slow accelerations in traffic).

BTW, I've found yet another way to hypermile: The AAA credit card gives 5% cash back on gas :-P

I not RPMs, flooring the accelerator, the injector duty cycle is close to 100%. So there's a max amount of gas in the piston. Is the explosion complete (gas fully used)? Is there always enough oxygen for the amount of gas pumped in the piston?

[R.I.D.E.]

My Del Sol was not VTEC, and I averaged about 42 MPG.

The worst you can do is hit the brakes.

When you use engine drag (car in gear) you are turning all fuel to the injectors off=DFCO=Decelerate Fuel Cut OFF.

Coasting is great, but if you have to stop or slow down a lot, it may be better to use DFCO. AS long as you can keep engine speed above 1000 RPM you have no fuel delivered to the injectors. Its the same as shutting the engine off without all the restart issues.

Try this. use a lower gear than you would use normally. Once you reach the point where more throttle really doesn't do much of anything, you have reached the best point for economy. Wot will use more fuel than this method. The ideal throttle percentage should be about 70%, could be less but not much more.

If you need greater acceleration use a lower gear. If you don't need greater acceleration, use the highest gear that you possibly can. When you want to maintain speed use the highest possible gear as soon as practical.

An example.

Light ahead is red and I know I will have to stop. I downshift through the gears as my engine speed approaches 1000 RPM.

5th gear down to 1000, then 4th down to 1000, etc.

To determine what RPM your enigne stops fuel shut off, just let off the gas in 5th gear and wait until you feel the surge when the fuel supply returns. In my car its about 860 RPM, but it is higher if you have the AC on. You can do the same in any gear, but it will tell you when the fuel shut off ends as far as engine RPM.

People do get frustrated with me when I spend a lot of time coasting to the light that is red. They fly by me and slam on the brakes, and sometimes they block my path through the light when I get there right at the point where it turns green. In that case I just keep using DFCO. I don't care what the other drivers do, I wont waste the gas idling or the gas it took to get to speed, when I throw it away braking for the light.

Remember DFCO is the same as shutting the engine off without the restart hassles, as long as you have to slow down more than you would coasting.
Coasting is alwats better as long as you do not have to use the brakes. Then DFCO is better.

regards
gary

[R.I.D.E.]

Also when using DFCO make sure your foot is not applying any pressure on the gas pedal or DFCO will not engage.

regards
gary

[cinnapatch]

What is P&G? No idea in North Carolina.

[dosco]

Originally Posted by cinnapatch

What is P&G? No idea in North Carolina.

Pulse and glide. A driving technique wherein you maintain an average speed - say 65 mph - by "pulsing" to 70 mph and then "gliding" (with the transmission in neutral) to 60 mph. Repeat.

There are variations on this theme. When gliding, the engine can be left to idle. The alternataive is to glide with the engine shut off, called "Engine Off Coasting" or "EOC."

I also have a 1999 Camry, mine has an automatic transmission. It is not possible to EOC because it will damage the transmission.

You should try P&G, I have a mixed commute from home to work, about 50% highway and 50% city, I'm getting about 33 mpg.

I noted your gaslog, if you have 90% highway commute, you could get much better mileage. On my last highway trip in the Camry, I achieved about 45 mpg using P&G driving.

[theholycow]

Originally Posted by sonyhome

I not RPMs, flooring the accelerator, the injector duty cycle is close to 100%. So there's a max amount of gas in the piston. Is the explosion complete (gas fully used)? Is there always enough oxygen for the amount of gas pumped in the piston?

The computer won't let it run that rich. I have never managed to see more than 50% duty cycle. At low RPM, flooring it doesn't increase the duty cycle much vs. partial throttle. If I am light on the gas at a given RPM I might see 8% duty cycle, and if I floor it I might see 12%.

Originally Posted by R.I.D.E.

When you use engine drag (car in gear) you are turning all fuel to the injectors off=DFCO=Decelerate Fuel Cut OFF.

Coasting is great, but if you have to stop or slow down a lot, it may be better to use DFCO. AS long as you can keep engine speed above 1000 RPM you have no fuel delivered to the injectors.

If you need greater acceleration use a lower gear. If you don't need greater acceleration, use the highest gear that you possibly can. When you want to maintain speed use the highest possible gear as soon as practical.

Quoted just to reiterate. That was very well said. I would replace "may be" with "surely is".

Try this. use a lower gear than you would use normally. Once you reach the point where more throttle really doesn't do much of anything, you have reached the best point for economy. Wot will use more fuel than this method. The ideal throttle percentage should be about 70%, could be less but not much more.

Are you talking about your Honda in specific, or all cars? From actual measurements, I can tell you this is not universal. In my VW, injector duty cycle goes down when I go from 80% (maybe 70%, maybe 90%, my foot is just not that accurate) to WOT. I'm at a loss to explain it. At first I thought maybe the fuel rail pressure goes up at WOT, allowing a shorter duty cycle to feed in more fuel; but I can't argue with the gas pump, and using WOT (instead of that 80% target) has improved my FE.

To determine what RPM your enigne stops fuel shut off, just let off the gas in 5th gear and wait until you feel the surge when the fuel supply returns.

Also, note that the surge is barely perceptible, you really have to be looking for it, at least in my vehicles. It is gentler than, for example, the torque converter locking in my truck (which itself is almost impossible to feel).

[sonyhome]

Originally Posted by R.I.D.E.

My Del Sol was not VTEC, and I averaged about 42 MPG.

When you use engine drag (car in gear) you are turning all fuel to the injectors off=DFCO=Decelerate Fuel Cut OFF.

RIDE, thanks, I like your explanation!

However, for the CRV, it seems there is no DFCO, unless the Scangauge is wrong. Downhill in "D", I see 0.8GPH used, and up if the grade is steeper and the engine RPMs go up. Shifting to "2" or "1" increases consumption too (slower speed higher RPMs, duh! and no DFCO?).

What Del Sol model year were you driving? I have a '93 Si (D16z6 1.6L SOHC VTEC engine), there is also the S (1.5L non VTEC) and VTEC (160HP 1.6L DOHC VTEC). The S has the best fuel economy...