Coasting with an Auto

[Compaq888]

be sure to post the results of how many N bombs it takes to kill the tranny.

[GasSavers_DaX]

Originally Posted by Compaq888

be sure to post the results of how many N bombs it takes to kill the tranny.

"How many licks does it take to get to the center of an auto tranny?"

I've N-bombed twice before from what I believe to be about 3500 RPM's (didn't have a tach back then). If I decide to do it I'll be bouncing off the rev limiter. Go all out.

[philmcneal]

so with an auto tranny coasting with engine off in N ... say your going 10-15 mph and you decided to put it back into D. Would the engine magically start up again (roughly hense the name bombing) that would be cool! Or you have to key on?

I noticed some Volkswagaons have a DSG (its a manual transmission controlled by the "best manual driver in the world" i wonder if the computer is smart enough to bump start the engine smoothly...

too good to be true stop dreaming~~

[Compaq888]

The vehicle has to be in N or P in order to restart.

[zpiloto]

DaX:

I've N-bombed twice before from what I believe to be about 3500 RPM's (didn't have a tach back then). If I decide to do it I'll be bouncing off the rev limiter. Go all out

It would be cool if you could record the audio and post it so we could hear the full effect.

[rh77]

I did it with a Pontiac Grand Am a few years ago. Basically you're traveling along at any speed and shift to N. Then Rev it up bumping off of the rev limiter -- that's the loudest sound. Then shift to D. You'd think it was a big production, but it isn't, really. Then oddly enough, the transmission makes little noise. The engine just bogs down while the tranny catches and figures out the right gear like if you were to rev up a car with a clutch and let it out slowly. Then the car acts normal with a downshift for power acceleration unless it's been fried.

RH77

[zpiloto]

Can some one help me with why it destroys your auto transmission if you coast in neutral with the engine off. I've never seen the inside of a transmission and looking around on-line it doesn't really address the issue it always get side tracked into legality, brakes and PS. The torque converter is a fluid coupling and with it in neutral the axel is still hooked up to the transaxel so the gears are still spinning around no harm there. But when you shut the engine off it shut down the pump. Now where is the pump pumping fluid to? Even when the pump is off the gears will still have fluid from when it was on and there is no load. So does a coast of 30-60 second at speeds under 50 MPH cause that quick of a heat build up? and what parts are geting damaged? I can see where if you flat towed it cold for miles it would cook everything.

[n0rt0npr0]

With no fluid *pressure* the auto transmission disengages completely. There is absolutely no way for this engine off coasting in gear or out to destroy a tranny.

However IF you have an electronic transmission, IT WILL most likely confuse the **** out of the tranny. Thats why Compaq888 was having a hard time with his in the first place. It's all because of the way they designed the "fuzzy logic" ....either the engineers factor in that the driver won't use engine off coasting (ie, compaq888) or they will factor in engine off coasting (ie, 2001 olds intrigue)

[psyshack]

I coast our 05 Accord 5AT all the time. ICE off,, ICE on. restart engine and dump it in drive.

[Compaq888]

Originally Posted by psyshack

I coast our 05 Accord 5AT all the time. ICE off,, ICE on. restart engine and dump it in drive.

your tranny must be designed differently than mine. I'm still getting good mpg with coasting in D. Whenever you let your foot off the gas the tranny goes automatically into neutral, the reason the car slows down so much is it's connected to the engine. When you put the lever in N you actually disengage the tranny from the engine and you get a longer coast because your engine is not slowing down the tranny.

It's actually pointless to just stick it in N and coast because the engine still injects fuel. If you're going to stick it to N you better shut off the engine to save fuel. On my car if it's in D and I coast the fuel injection shuts off till like 1000-1100rpm then comes on to prevent the engine from stalling.

You can find out a lot by reading a FSM for your car. If you have one look in the Electronic control section.