Fuel Injector shut-off while Coasting - Page 4 - Fuelly Forums

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Old 07-10-2011, 06:51 AM   #31
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Re: Fuel Injector shut-off while Coasting

THC is correct- cutting fuel pump power is not the best method.

When I pull my fuel pump fuse (to depressurize the fuel system so I can safely change my fuel filter) my car will start and run for 2-4 seconds. It will even "try" to start with the next 2-3 attempts of cranking.
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Old 07-10-2011, 10:40 AM   #32
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Re: Fuel Injector shut-off while Coasting

Shutting off your fuel pump is an awful idea. Don't do it.
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Old 07-11-2011, 03:19 PM   #33
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Re: Fuel Injector shut-off while Coasting

There may be a few cars that don't disable the injectors when coasting in gear above 1000-1100 rpm's but that's not the case with most.
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Old 01-03-2012, 01:14 PM   #34
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Re: Fuel Injector shut-off while Coasting

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Originally Posted by mtbiker278 View Post
my car is an auto with five gears. A first on the civic. I do notice that it likes to hold the gear while deccelerating. It'll get down to about 800 rpms before down shifting when coasting.

So are you guys saying that it is more likely that OBD1 cars do this and not so much newer ones? I know metro said his was OBDII. Is there a way to find this out without having to call a honda engineer?
My Accord has a 5-speed automatic and what I've noticed is that while deccelerating the lock-up is still engaged through 5:ft to 3:rd gear down to about 15mph and 900-1000rpm before releasing the lock-up. You can feel the engine locked to and braking the wheels constantly and through every downshift at low rev as you describe at about 900rpm. At the same time I have monitored through an OBD2 interface that the fuel system is in open-loop mode which tells me that the fuel is cut off. I'm very excited to find out if the scangaugee I have ordered will read 999mpg during decceleration. This is when lock-up is engaged to start with. If the engine is cold or you have throttled yourself out of lock-up just before coasting this will probably not work.

Maybe we have similar transmissions.
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Old 01-04-2012, 09:40 AM   #35
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Re: Fuel Injector shut-off while Coasting

It sounds like the current software on the scangauge does report DFCO. Otherwise you have to go by the loop reading with older ones.
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Old 01-05-2012, 11:14 AM   #36
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Re: Fuel Injector shut-off while Coasting

I received the scangauge^e today and installed it. It works just as i hoped it would. The instant L/km shows 0.0 when I let the foot of the throttle from high speed all the way down to 13mph (22km/h). If I coast in N the fuel consuption depends on the speed. The higher the speed the better the fueleconomy is .

I haven't done the fill up calibration yet, it will take som more driving for that, but the values I'm getting seem reasonable.
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Old 01-13-2012, 06:57 AM   #37
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Re: I've noticed something

Quote:
Originally Posted by philmcneal View Post
i keep telling people, sure you won't have the power of a manual transmission but you can still save gas. Just abuse N and don't use your brakes.... but NOOOOOOOOOOOOOOOOOOOOOOOO people think I'm rubbish....


enjoy paying for the gas sucker. If you haven't noticed, in D there's a potenial truth that somehow the gasoline engine is still feeding power THROUGH the torque converter which in turns go to the wheels. With it in N all power to the torque converter is now CUT and enough gas is pumped into the engine to prevent stalling.

By putting it in N you elminate the middle man, doesn't matter if D coasts as well as N, there's still resistance from the torque converter!.
Fixed.

A torque converter is bolted to the flexplate (in a manual car, called the flywheel), bolted to the back side of the crankshaft. You have the rotating mass of the TC spinning which gives momentum unless you turn the ignition off and let the engine stop. You have to imagine a torque converter as a giant fluid filled metal doughnut. Spin the fluid inside, the metal fan-like vanes direct the fluid towards the input shaft and that is what spins the transmission and eventually, the wheels. It's a fluid coupling, not a physical connection. Now then you have lockup torque converters which can physically grab the input shaft and these are very close in efficiency to a regular manual transmission. Feels like letting out the clutch, if driving an automatic normally feels like driving with your foot resting on the clutch pedal.

That is how it's always felt for me since 1994, when I taught myself to drive standard, by myself, in the dead of winter, by buying an '86 Lynx with a 4-speed for $60 at an abandoned car auction. I rode my bike to the auction, wasn't planning to buy a car. I actually bought two, but the '80 Civic 1300DX I got had a thrown timing belt. I did actually drive that Civic. I would leave the clutch out, and crank it in gear long enough to get up to 4-5mph and then I'd jam on the clutch and coast 40-50 feet at a time. That's how I got it out of the impound lot and across the street to a mechanic shop to have it checked out. You can't do that in modern cars. Thought it was something simple, it wasn't. Fix was $700 on a $40 very rusty car, I scrapped it. But I kept the Lynx, sold it later for $350 still with no brakes and no muffler.

I do want a manual shift car for my next car. It's hard to do that though, with the wife demanding a family type vehicle, and I prefer cars with enough metal around me to not die when I get broadsided by Escalades and Land Cruisers. I may have found a solution in Mexico. They made the Chevy Celebrity down there like they did up here in the USA. But the ones in Mexico ALL have a manual transmission. 4-speed through 1986, 5-speed through 1989. Not a single automatic unless it was imported from the USA. Only downside is they're all V6 models, but at least it's only the 2.8L and with that overdrive 5-speed in a lightweight non-AC Celebrity coupe, it should do quite well. Coupes thru 88 only though so I'm torn between the 87-early 88 speed density and the late 88-89 MAF version as they didn't make the coupes in 89 and those late 88 coupes with the MAF system might be hard to find. Then again I like four doors, I have been called a four door ***** before and it won't be the last time.
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Old 01-30-2012, 06:31 PM   #38
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Re: Fuel Injector shut-off while Coasting

I have a 2009 Ford Focus five speed and when I coast, the rpm bounces around between 1000 and 2000. This happens most of the time under all weather conditions. A Ford tech took it for a ride with his computer and his determination was that the catylitic converter was telling the engine that it needed more oxygen to burn off pollutants, so the engine was speeding up and running very lean to pump more oxygen. I'm not satisfied with that answer. If that is true, it still ticks me off that it does that. So, if I never coasted, the pollutants would never get burned off? And what would keep the converter from telling the engine to speed when the car is in gear? Anyone else experience this?
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Old 01-31-2012, 03:52 AM   #39
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Re: Fuel Injector shut-off while Coasting

I agree, that doesn't sound right. It sounds like the tech didn't want to get involved in a very difficult troubleshooting process that won't make much money.

Can you test-drive a similarly equipped 2009 Focus to show him that most don't do that?
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Old 02-01-2012, 06:41 PM   #40
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Re: Fuel Injector shut-off while Coasting

I haven't found a stick to test, yet. I'll probably have to try an automatic.
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