I got into a flame war on another board...some guys were actually saying if you downshift when stopping on a manual transmission that the car uses NO fuel...I told them it did use fuel just not very much and on some engines the injectors change cycles as well...I don't see how the car can use NO gas at all...who's right?

 

There are tables in the computer called DFCO tables. (deceleration fuel cut off)

You can set the tables to cut any percent of fuel you want on decell since it is not needed. As for NO gas at all, not sure on the exact answer. I would guess you need some enough gas to at least maintain an idle for when you take it into nuetral.

 

Thats exactly what I told them, I know about the deceleration fuel cut off but it doesn't just make the motor quit running all together...at least I didn't think it did.

 

If you downshifted and then turned your ignition off (not recommended), your car would start bucking instead of smoothly decelerating. This tells you that the spark was igniting something, and it wasn't just air. Fuel had to be present.

 

I made that point too and the fact that you can still hear the fawking exhaust which is caused from tiny controlled explosions inside of combustion chambers...anyone have any links or solid info on this cause these people appear as though they're unconvincable.

 

If you watch during closed throttle decel on a scanner, you can see the injector pulse width go to "0". You can feel the fuel kick back on.... on my stock setup I think it was about 1,300-1,500rpm. On my aftermarket ECU, we cut fuel completely on decel. The engine continues to "run".... it is just pulling in air on the intake stroke, compressing it, and then letting the air out on the exhaust stroke. There is no bucking.

 

You are supposed to use your brakes to stop, not your transmission.

 

AND: I don't care if the computer says "honest you are not using any gas, tust me", I do believe that if your gasoline engine was not getting any fuel that it would not be running.

Of course you are using gas. See how long your car will run by leaving it running at idle while you sleep overnite. For goodness sakes.

 

That dude is an idiot. It has to use some gas.

 

It's Friday. On the other hand, if you are "compression braking" like the big rigs, I do believe that they shut the fuel completely off and allow the comprssion to slow the vehicle while in gear. Outlawed in many places because of the noise it makes.

 

aka jake-brake, or tranny brake. And keep in mind that it's there for a different purpose (to brake faster, not to save fuel).

 

Ding Ding, just like I told you on the other board.

 

Is that me you're referring to?

 

Probably the guys on the other message, and you Fred, since your opinions on it are the same

I sent you a PM about a FPSS also.

 

Serene/Injuneer, if I look at the stock Injector Pulsewidth tables, at a PW of 0, the injectors still open for .33 miliseconds.

Doesn't that suggest that it's still going to be putting 'some' fuel in? It's not a heck of a lot, but it seems to pop in a little squirt here and there.

Or does the DFCO tables override the pulsewidth in this case? (Where are the DFCO tables in LT1 Edit anyway? I don't see them anywhere)