General Question

Ltryptophan's avatar

What happens if you keep your foot pressed all the way down on the gas pedal while the car is on and in park?

Asked by Ltryptophan (9112 points ) November 14th, 2010

I know the engine redlines, but what happens if you just keep it pressed down?

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12 Answers

mrentropy's avatar

You blow the engine if it doesn’t have a rev delimiter?

Ltryptophan's avatar

“blow the engine” how so? A rod is thrown? Any number of heat induced failures??? Does the head come flying off? Does it just freeze all of a sudden? Will new cars shut themselves off?

mrentropy's avatar

Let me plumb the depths of my knowledge. Okay, that’s not very far. But if you have an engine with push rods you run the risk of one or more rods being bent.

cockswain's avatar

I’ve worked on cars for years. Here’s what happens: the engine has oil to keep heat-generating friction reduced. It can only reduce so much friction. When you redline it, you are exceeding the ability of the oil to keep friction reduced enough to not generate substantial amounts of heat. The heat deforms/ruins metal parts. Generally the engine will break a rod, or the pistons will expand and seize in the cylinders. In any event, it’s a bad thing unless you are trying to blow your motor intentionally for some reason.

Clear enough?

Ltryptophan's avatar

@cockswain sure. No pyrotechnics? Someone told me a rod could come into the cabin from the engine compartment and injure the driver. I find this hard to believe.

filmfann's avatar

I have broken a couple rods, and you don’t need to worry about that. Red-lining your engine will freeze the engine, and could brake a rod. You do need to worry about that. @cockswain gave a very accurate description.

cockswain's avatar

No pyrotechnics unless somehow a fuel line coincidentally broke and started spraying all over your ultra-hot engine. No reason that should happen unless your luck sucks at that moment. I agree with @filmfann about the rod not flying out of the engine. It is just going to separate into two pieces, but be connected to something on either end still.

LuckyGuy's avatar

For older cars that is true. But with ETC, electronic throttle control, common on vehicles made after 2007, the ECM limits the top speed of the engine. It will hold it at the speed selected by the engineers so that you do not cause damage. Hold it there long enough and some of them will even back the speed down.
Try this trick. In the morning when the car is cold, don’t touch the throttle just touch the key and let go. The engine will continue to crank, start, and run like magic. That is ETC. Big brother is watching out for you.
You’re welcome. ;-)

Ltryptophan's avatar

I blew a rod once. It definitely broke through the block. It left a hole in its wake about the size of a tennis ball. I think that it would not fly into the cabin through the firewall regardless.

LuckyGuy's avatar

I threw a rod on my 500 Kawasaki by revving it to >12,000 rpm. I was lucky it did not take my leg off. Scary.

cockswain's avatar

@worriedguy No shit? Good to know. I used to be able to work on engine problems on cars. Not anymore, too many electronics to easily troubleshoot.

@Ltryptophan I’ve never seen a rod blow through a block either. I thought those were thick enough to withstand that sort of event. I guess I was wrong. That rod must really be moving to knock a hole in it. Now that I think about it, older ones were generally cast iron or aluminum alloys. Maybe some newer ones are made of a weaker metal (which is probably lighter or dissipates heat better).

jerv's avatar

One thing that some people here seem to be overlooking if that even many older cars have rev limiters. I mean, I’ve hit the limiter on my ‘85 Corolla and it has a carburetor, albeit a feedback carb with an O2 sensor. I also did that with my ‘87 Corolla (same 4A-LC engine), an ‘89 Golf, and a few other pre-OBDII cars.

Another thing that I haven’t seen mentioned is the dropping of the bottom end onto the pavement. Oil breakdown is not pretty, and broken down oil tends to be expelled from the engine in bad ways, along with a few other things.

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