Turning off your car at 55 mph


#61

In all seriouness, I don’t mean any of my comments on this thread to be combative. It’s simply that if I don’t know or don’t understand something then I WANT to understand it.

I don’t get fuel pump operation having anything to do with converter lockup.
If a car is coasting at 60 MPH with the key in RUN and engine off then where does the ignition pulse come from to cause the ECM to trigger the pump relay?
If the converter is locking the engine with an operative fuel pump then it will not be coasting as the engine will instantly start running with the key in RUN.
How does one attain speed and disable a fuel pump without some creative wiring?

Just for the heck of it I can do this on my Lincoln this week. The inertia switch is right behind the drivers door. Five feet of wire pigtail, a switch, 5 minutes of time, and I can kill the pump at speed so I’ll try that just because I’m curious.
I’m just having a hard time seeing as how this would affect converter lockup but I’ll give it a shot anyway and will post back.


#62

At 3000 rpm his engine is turning 50 revolutions per second. That’s 50 times each piston is at top dead center. Considering that the camshaft stopped almost instantly when the timing belt broke, that’s 50 times each piston could be slamming into an open valve. Human reaction time is 3/4 of a second or so, assuming he’s not tuning the radio, texting, waving to a pretty girl or cleaning out a nostril at the time. The chances of stopping the engine before it bent a valve is 0%. He has no chance of saving the engine from disaster. He’s wasting his time, and ours, with this question.


#63

Perhaps you’re reading too much into this? You turn the key back one click–the ignition, fuel pump, etc. are off. Whatever remains engaged is due to purely mechanical forces at this point. I would expect the torque converter to unlock, but since the system is designed to operate powered, who knows what initially happens?

I do know that in my 1994, which is SOMEWHAT modern, has a lockup TC, and a computer-controlled engine and tranny, that the engine and transmission seem to stay coupled for at least 10 seconds at highway speeds. This can be verified by looking at the tach (which continues to operate), or by turning the key back on, at which point, the engine will resume running.


#64

“Human reaction time is 3/4 of a second or so, assuming he’s not tuning the radio, texting, waving to a pretty girl or cleaning out a nostril at the time.”

That cracked me up :slight_smile:


#65

Does it matter that my car is a Kia Mini van with a funky engine?


#66

The Buick Dynaflow and Chevrolet PowerGlide were completely different transmissions than the GM Hydramatic. The Hydramatic was, at that time, a 4 speed unit with a fluid coupling between the engine and the transmission. The Dynaflow and the PowerGlide had a torque converter between the engine and the transmission. The Dynaflow depended on torque multiplication rather than gears as did the Chevrolet PowerGlide until 1953. In 1953, the PowerGlide became a 2 speed unit that would start in low and shift to direct drive when the selector was placed in drive. If you wanted to start a Buick Dynaflow or a 1950-52 PowerGlide Chevrolet in low range, you had to manually select Low.

As I said in my quote, not being able to pushstart the Hydramatic happened in 1959. The cars equipped with this transmission in the GM line were only the Pontiac, Oldsmobile and Cadillac. In 1961, the Hydramtic was changed for some models and became a 3 speed unit that was called the “SlimJim”. It had a torque converter. I don’t know if GM cars equipped with this transmission could be push started or not. Interestingly, the Pontiac Catalina had this “SlimJim” transmission, while the upper Pontiac lines (Star Chief and Bonneville) had the older 4 speed GM Hydramatic.

To confuse the issue even further, in the Ford line, Ford and Mercury introduced an automatic transmission in 1951 that was made by Borg Warner. However, the Lincoln in mid-1949 introduced the Hydramatic transmisson made by GM. I’m not certain when Lincoln stopped buying its automatic transmissions from GM, but I think it was after 1953. The point is that automatic transmissions are different.

One more little interesting note: The GM Hydramatic plant suffered a disaterous fire in 1953. Some Pontiacs were equipped with the Chevrolet PowerGlide. The PowerGlide did have a “park” position on the shift quadrant–the GM Hydramatic did not. My uncle had a 1953 Pontiac that had the Chevrolet PowerGlide transmission. I believe that some Oldsmobiles may have been equipped with the Buick Dynaflow, but I’m not certain about that.


#67

Like I said in an earlier post, when the clutches bleed down your 88 dakota’s engine will not keep turning. When they bleed down, thats it, you can push it, pull it, drop it from the sky if you feel the need, the clutches will not re-apply.

Try reading ALL the posts before you go pointing fingers.

transman


#68

Tardis,

I dont think you understand completely but you are right about what you said. Like I said in an earlier post, the engine will spin for a short period of time until the clutches bleed down. Seconds, I cant tell you how many seconds for each individual transmission because I never even thought about experimenting with this and dont know of anyone else who has so I could look at their results. Its all in the fluid flow through the converter. Remember, the fluid CHANGES DIRECTION inside the converter. You have a dead engine being driven by the transmission so it wont be long at all before the clutches bleed down. Normally on an automatic transmission, the engine turns faster than the transmission all because of the fluid flow in the converter. Its sort of a cushion. This is why you can sit at a red light with the transmission in gear and the engine running and your foot on the brake. You need the speed of the engine to cause the flow in the converter to spin that turbine. With a dead engine you dont have that. This is why you cant even push start an automatic and this is where some folks on the board here are getting hung up at.

There are certain people here who would like nothing more than to try to discredit me. Thats ok though, that doesnt bother me at all, they just dont understand. Not everyone understands this topic. All I can do is try to explain it as clear as I can but sometimes I dont do that right off the bat and thats my fault for not being as clear as I should. You do seem to understand it more than others on the thread though.

transman


#69

Indy–Despite the side discussion on automatic transmissions, I hope that you absorbed the message from several earlier posts, telling you that shutting down the engine CANNOT prevent damage from a snapped timing belt on an interference engine like yours.

Let me repeat the message a few more times:
Your friend is wrong.
Your friend is wrong.
Your friend is wrong.

If you think that the engine is funky now, just wait until that belt snaps–without warning.


#70

Well this has little to do with the OPs question but it should answer some of the other statements made. I took my van out this evening and going down a short hill, I turned of the engine. It held the van back until I got near the bottom when I turned on the ignition and went up the next hill. So I tried it on a longer hill. Same results, with no loss of steering or brakes. It actully held me back so much that I I had to turn it back on to keep going. In either case, I did not have to use the starter. I do not reccomend turning the engine off and coasting to a stop, either with an automatic or a manual. I might add that I drive nothing but automatics, and only had one transmission failure in 60 years of driving, that was a '59 Ford that I bought used. Also I brake with my left foot and always have.
Would someone tell Transman!!


#71

Tardis,

I dont think you understand completely but you are right about what you said. Like I said in an earlier post, the engine will spin for a short period of time until the clutches bleed down. Seconds, I cant tell you how many seconds for each individual transmission because I never even thought about experimenting with this and dont know of anyone else who has so I could look at their results. Its all in the fluid flow through the converter. Remember, the fluid CHANGES DIRECTION inside the converter. You have a dead engine being driven by the transmission so it wont be long at all before the clutches bleed down. Normally on an automatic transmission, the engine turns faster than the transmission all because of the fluid flow in the converter. Its sort of a cushion. This is why you can sit at a red light with the transmission in gear and the engine running and your foot on the brake. You need the speed of the engine to cause the flow in the converter to spin that turbine. With a dead engine you dont have that. This is why you cant even push start an automatic and this is where some folks on the board here are getting hung up at.

There are certain people here who would like nothing more than to try to discredit me. Thats ok though, that doesnt bother me at all, they just dont understand. Not everyone understands this topic. All I can do is try to explain it as clear as I can but sometimes I dont do that right off the bat and thats my fault for not being as clear as I should. You do seem to understand it more than others on the thread though.

transman


#72

I did my own test tonight to see how many seconds it takes for the clutches to bleed down on this particular vehicle. I tested the vehicle at 4 different speeds by shutting off the ignition and counting how many seconds it takes before the internal clutches inside the transmission bleed down and release.

Subject vehicle: 2009 Ford Crown Victoria 4R70W transmission.

20mph: After shutting off ignition it took 2 seconds before the clutches bled down and I completely lost power steering AND power braking and the vehicle coasted neutrally.

40mph: It took 3 seconds before losing power steering and power braking.

55mph: This was indy’s question @55mph. It took 4 seconds before losing power steering and power braking.

70mph: It took 4 seconds before losing power steering and power braking.

At 55 and 70mph, turning the ignition back on AFTER the 4 seconds elapsed resulted in NO ENGINE RESTART. Turning the ignition back on BEFORE the 4 seconds elapsed resulted in immediate engine restart.

As I stated before, the clutches will bleed down and release, in turn releasing the engine from the transmission.

transman


#73

Some Oldsmobiles did have Dynaflow transmissionns. I know, I worked for them at the time.


#74

In my test today, The engine kept running, but I don’t know how long. Definately more than 10 seconds. I couldn’t read my watch and drive safely.


#75

This is actually an old prank, you shut off the engine at this speed, and the exhaust backfires. Thus scaring the drivers around you, who would think they are being shot at.

It’s obviously a very stupid prank, and it might actually just blow a big hole somewhere in your exhaust system.
And all the other things about no power steering and power brakes at a pretty high speed would happen. Not a good experiment.


#76

Indy, when you’re in park with the engine at idle and turn the engine off, the engine goes around a few times before it stops, due to it’s momentum. When you’re turning off the ignition at speed, even if your transmission isn’t turning the engine, the engine is going fast to begin with. It make make 10s if not hundreds of turns.

A broken timing belt can seriously damage the engine within a fraction of a turn.

To put it in perspective, your engine makes about 20+ turns EVERY SECOND on the highway. Unless you can leap out of your car in that tiny fraction of a second and grab the crankshaft as soon as the timing belt snaps, you’re not saving it.


#77

when I turn off the ignition, the fuel pump quita also, so there is no explosion. When I got to the bottom of the hills, I turned the ignition on and went up the other side of the hill.


#78

I agree with transman, tried this on my 87 Marquis this morning but only one test as I felt it was to dangerous. Had vehicle at 60 mph, shut engine off with key, after 5 or 6 seconds power steering lost. Turned key back on and dead engine with all dash lights lit up
Had to put it in neutral to restart.

Now if you were to do this on my 59 T-bird you could do the old backfire trick as this tranny has a front and rear pump, where the rear pump would be driven off the output shaft of the tranny providing pressure to keep the clutches engaged and keep the engine spinning.

On modern automatics with only a front pump you cannot tow the vehicle with the drive wheels on the ground as no lubrication would be available and damage may occur. You could probably get away doing this for a very short distance maybe a block or two without damage.

Now with a vehicle with both front a rear pumps you COULD tow an automatic with certain restrictions. I have the original owners manual for the 59 and it states" If you need tow to the vehicle with the rear wheels on the ground, “DO NOT” exceed 35 mph and a maximum distance of 50 miles. If you did have to tow this way you had to “MAKE SURE” it was in neutral or the engine would start spinning when towing speed reached 20 - 25 mph.

Now on my 59 I did this test different to prevent a back fire. Car was going at 25 mph, put it in neutral, and shut engine off. Turned key back on, Dropped it into “L” and it fired right up.


#79
         This has little to do with the original post But I tried the test again tonight on a rather long hill.  I turned the ign off at the top of the hill and 24 seconds later, because I was approaching the stoplight, I turned it back on and it started immediately. One of these days, when I fand a loooong hill, I'll try it again.

#80

This kind of test defies all mechanical logic and while I’ve never performed a test like this or even had reason to do one I did perform the test on 2 vehicles this evening.

While I did not get too technical with this I performed the series of tests at varying speeds and no stop watch; just a rough estimate.
First car was my Lincoln with the 4R70W. At various speeds the engine is not rotating within seconds of turning the key off. Even when turning the key back a few seconds later the engine does not fire up. If there was engine rotation then it would of course.

One test involved disconnecting the inertia switch and hanging a pigtail and switch into the car cabin to shut off the fuel pump, although I fail to understand what that has to do with anything. Same thing, no engine rotation.

Second test was a 4th gen Camaro with the 4L60E. At various speeds and within a few seconds no engine rotation.

The tests were all performed at various speeds between 30 and 60 MPH. If the converter is locking the rear axle to the engine then I’d like to know why the engine does not fire right back up with the key in the RUN position.

With both cars the brakes and steering was not bad at all for a non-running engine. A bit stiffer than normal but no big deal.