Here we go again... EOC & automatics

[wagonman76]

Originally Posted by Nevyn

Let me know what comes of that! I have a '93 Lumina Euro with the 3.1 MFI, and would love an answer!

Also note: I work in Bloomsburg - nice to see a (relatively) local!

That would be cool to know. Not sure if youve got the 440T4 or the 4T60E. Ive got both.

[Christ]

Isn't the Lumina Euro equipped with the 3100 60* engine?

My wife's car is a 3.1... they're different. Not sure if they use the same tranny though.

[Nevyn]

No, the 3100's didn't come in until '95. My intake header says "3.1 LITER MFI" cut right into the aluminum. It matches the engine in the car it replaced, which was a '92 Grand Prix SE.

The transmission on it is the 4T60-E (according to the tranny pan under the car).

It does have a 2-stage catalytic converter on the Euro model, but single exhaust - means I have 2 little cats (kittens?) instead of one large one. Only one O2 sensor though, go figure.

Didn't get a chance to test engine-off, in-gear at lunch.

[Christ]

ah... note my ignorance about the 3100 engine.

You should (possibly) have 3 cats, actually... 2 pre-cats, and a normal cat.

Although, GM might not have done this.

[Christ]

Digging up graves here, but I actually just did this with my wife's car tonite coming down E-Ville mountain.

Result:

I shut my wife's GP off with the engine braking (0 throttle @ 2500 RPM) in 2nd range (about 40 - 50 MPH) (Automatic transmission) and waited 5 seconds. I then turned the key back on, and hit the gas, and the car accelerated.

What this means, is that the torque convertor restarted the engine. The tach wasn't working with the key off, and I couldn't hear if the engine was still spinning, but it did restart with no effort (nearly zero feel) when I turned the key back on. No jerking, etc.

I'm not sure if the engine speed actually died all the way down or not. But I do know that I didn't crank, and never took the car out of gear or put it into another gear. Left it in 2nd range the whole time.

[Oval_Overload]

I'm thinking the in-gear, engine off thing is the way to go, though I don't have any hard evidence because my Ford dealer closed.

I think that installing a kill switch will take a lot of the lurch out of the restart, at least on my car, because the ECU won't have to boot back up on restart.

[Christ]

I didn't see even a slight delay in the restart, honestly. I hit the gas as I was turning the key, and it seemed like the engine just picked right up.

Rebooting a car's ECU is NOTHING like rebooting your home PC, or even your cell phone. It doesn't have a GUI, or any of the "cool" features that anything else has. It uses a very minimalist OS, which only contains the information necessary to run the software, and it's hard-coded in flash memory. Literally 1/60th of a second is plenty to start it back up.

Imagine your digital wristwatch... you put a battery in it, it's ON. Right now. No waiting for the software to become aware of what needs to be done, in a flash, it's there, working, telling you the time. (It's the wrong time, but that's something different.)

Now, as to whether the ECU will appreciate being turned on and off constantly, is a thing to consider. Over time, heating and cooling cycles help to cause "Tin Whiskers", a phenomena common to circuitry, where a circuit will grow a "hair" of tin that connects to another circuit and shorts it. Often, they will short, destroying the whisker, and not damage anything, but occasionally, they will destroy a circuit completely.

Another thing to consider is that over time, circuit lines wear away. They actually get thinner with use. What eventually happens, is that the line gets too small to deal with the current present in the line, and it eventually breaks the circuit. This is also not repairable, as it usually occurs on inner planes first, and could only be fixed by making an identical, external circuit on the board, using the VIAs that were connected to the broken circuit line.

By all means, leaving the ECU on for the drive instead of constantly shutting off/restarting will definitely prolong its life, but even in the event that it's dead, for most cars, its' a matter of going to a junkyard and paying $60 for a new one. When you consider the average of something like 3 starts a day that a car goes through, over the life of nearly 23 years that one of my cars has on it, that's A LOT of starts and stops that the ECU has gone through, and it still works. Even cut that time down to a couple years between replacements, and you're still on a good mark.

Spend $10 on a switch and a relay, and you're even better off, nearly never having to replace either, and saving the ECU all but the initial starts of each trip.

[RH77]

I tried the same on an off-ramp last week, and it did indeed restart. What I noticed was a considerable amount of slowdown with turning engine components. I had to restart early (just keyed-on) to maintain a reasonable speed. My process of shifting to neutral seems to work better for me (E-Off, or E-on).

Plus, I prefer having ABS, Airbags, and the SG -- which is all powered down in this scenario. I still have a kill switch in the dash, I just need to rewire it.

The biggest thing to remember with the kill switch is remember you used it! On coast-down (with engines using DFCO), at a pre-determined RPM, the ECU will ask for the injectors to start again -- you may lose TC lockup or experience some interesting side effects, including the need to pop to N and use the starter.

RH77

[Christ]

yeah, but you have to remember the whole purpose of me doing that experiment was verifying that the engine would keep turning, and the OP wanted to know if it was OK to do so during downhill coasting.

Some modulation can be achieved, as earlier noted, by using the accelerator pedal while the engine is off. This lessens the effect of engine braking to an extent.

A combination of WOT, E-off, trans in gear, would be the scenario necessary for most efficient easyon/easyoff coasting in an Auto.

[Intrigued]

Originally Posted by Christ

BTW, If you have a dead battery, coasting at 25 mph will start your engine in an automatic car... just like pop-starting a manual. (Except certain models, as is the case with all automatic "quirks")

Back in the dark ages, when I was a teenager, my Dad and I push-started his '57 Chevy to start it once. It had the 2-speed PowerGlide. It took to almost 35 mph to work, but it had pretty tall gears!