What gets damaged when the engine is over-revved?

He didn't do any damage. Probably did the thing some good to get revved up a bit. The computer cuts the engine off if you truly get to an over-rev situation. 45mph in third gear is nothing. Hell I was up near 70mph in third a couple of times today having fun getting on the hiway...

Steve B.

Are you sure? It sounded horrible at those RPMs, like a hair dryer with marbles in it

If it sounded that bad at those speeds, it wasn't anything that he did.

I didn't catch what kind of vehicle that this was, or the vintage. Is it diesel? They can sound pretty nasty at times.

Other than that, I'd check fluid levels to ensure that your not running low, including the gearbox. Also make sure you're using the right weight of oil, and go thicker in hot areas and thinner in very cold areas.

Find out what the redline is and buy a cheap tach to see what that sounds like when shifting. I bet the guy didn't go past it, maybe not even near it. I learned to drive around 1970 when cars still mostly had engines that were comfortable with being shifted at 2000 RPM or even less, making me too worried now about running these small engines up anywhere near their redlines. Some smaller engines are easily damaged by shifting too soon and lugging them; it can cause detonation or bearing damage from heavy loads at low RPM. Some of the earlier English imports were wrecked that way when North American drivers traded in their Fords or Chevies for Austins or Sunbeams.

Dan

Well thanks guys. I do feel better about the situation. At least I know it didn't get damaged.

Thanks

-phaeton

Ditto...well said.

Good ol' Sun Super Tach II is around $40. Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

How do you know what a hair dryer with marbles in it sounds like?

Seriously though.. he did no damage. If something broke from doing that it was about to fall off anyway.

Steve B.

I doubt anything was about to fall off. It sure sounds to me like this guy did do some damage. The fact is when an engine is worn it is much more susceptible to damage from high rpms than when it is tight. Some people have the knack and can drive an extremely worn engine for 100K miles. Other drivers would wipe the same engine out in a couple 100 miles and those drivers will be the ones that claim something was about to fall off anyway. Of course there is nothing to be done about it now. Next time the OP will put the guy in the passenger seat when he want someone to listen to a noise.

-jim

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That's nice but the OP doesn't have an extremely worn engine. He has a 99 Ranger with 150k miles. He obviously babys the truck and takes good care of it. That engine is far from extremely worn.

40MPH in second gear in the truck would be around 5krpm which is just to the peak HP mark. If doing that broke something it was about to break anyway

Steve B.

Well which is it? One second you have the engine in excellent condition and the next it is on it's last legs? Revving to 5k can damage some engines that otherwise would last a good long time if driven like the OP does. Your claim that whatever happened would have happened anyway is more than likely incorrect. And it also doesn't sound like anything broke as you claim. It sounds like he now has some piston slap that he didn't have before. He might have driven that engine another 100k without that ever happening.

-jim

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No where in any of my posts did I say that his engine was in excellent condition nor did I say it was on its last legs.

Your claim that whatever happened would not have happened anyway is more than likely incorrect.

I never claimed that anything broke. I said that ***if anything broke*** it would have broken pretty soon anyway. If you think that a couple minutes of minutes of 5k operation is going to do 100k of damage to the pistons well... I wish you a speedy recovery.

Steve B.

You said "the engine was far from extremely worn". And you said if it now has engine damage that was going to happen anyway. So one second your saying it is in excellent condition and the next your claiming it was about to crap out anyway.

Neither of the those statements are likely to be accurate. But you said them to dance around the simple reality that high RPM could do damage. And that damage is quite likely to be of a nature that would have not occurred otherwise.

But you are either claiming that something broke or you are just dismissing as fantasy the obvious signs of damage the OP has now reported. You claimed whatever broke would have anyway. The reality is that it is possible that things can happen at 5k RPM that will never ever happen if you stay well below that RPM. You are obviously oblivious to that possibility. You have absolutely zero proof that whatever happens at 5k would happen anyway. You just made that up. The fact is that some of the engine components were subjected to loads that are double or more of what they would have been if the OP had been driving the vehicle himself and that clearly would have never happened anyway.

What I think is you don't know what you are talking about because you keep saying things that are so completely wide of the mark. The type of damage that may have occurred is not 100k of damage. It is just as likely it is the type of damage that would have never happened in a 100k if the OP was driving. You don't seem to be able to even grasp what that means.

I don't claim to have any more than a guess as to what is now wrong with the engine or what caused it. But, I do know it is possible that it is related to driving it at 5k in second gear - it is obviously also possible it is unrelated.

And yes if that is the way you drive then it would happen to you anyway. But for someone who has always kept the rpm below 3k it is likely the OP might have been able to drive that a good long while without ever getting any of the symptoms he now has. I can assure you that if you take all the 10 yr. old Ford Rangers on the road with 120K+ miles and subject them to the same treatment some of them are not going to hold up and for most of them that do crap out it is unlikely that whatever happens would happen anyway. If I was of a suspicious nature, I might suspect the service manager was aware of this and hoping to be able tell the guy at the end of the test drive that the engine is fried and that sure is a shame since you are out here in the middle of nowhere.....

-jim

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NO he isn't! Sheesh.

He said that a 150k mile engine isn't a generically nearly worn out engine that was on its last legs. However, it could still have had some impending catastrophic failure (spun bearing, loose connecting rod bolt, etc.) Hell, a brand NEW engine can have a failure like that!

The latter would have failed anyway, but revving even a very worn engine to its normal power peak isn't going to break anything.

The point is your statements are meaningless in the context of the question asked. The reality is yes there are many engines out there that have impending failures just waiting to happen if the engine is revved to 5k. Yes, some of them might even be new, but most aren't. In many cases if someone drives them and holds the rpms down to below 3000 rpm the engine can run and outlast the rest of the car. That was the issue the OP was interested in and the issue that you want to completely avoid. So yeah I'm twisting the words, but that's because they weren't even close to responding to the question asked. Don't you think an evasive answer deserves a little needling? Bullshit about spun bearings and loose connecting rod bolts doesn't contribute anything to answering the OP's question.

The OP wants to know if it is possible the damage he now has might not be there if not for the way the dork in South dakota drove his car. And the answer is yes, that is possible. It is indeed possible to have an impending disaster and to completely avoid that disaster by simply never revving that high. That can happen and that does happen, albeit probably not to you. The notion that anything that happens at 5k will always happen anyway is false. There are lot's of things that could happen at 5K that wouldn't happen anyway. There are definitely also some things that would happen anyway, but that is irrelevant. That is the point -> you give an irrelevant answer and then you shouldn't whine when it's ridiculed.

So in your view it's a moral question - any engine that can't stand to be revved to 5k should be destroyed as soon as possible like they shoot horses don't they? As far as your concerned the OP has no right to be driving such a vehicle.

-jim

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And I happen to disagree COMPLETELY with that claim. The difference in real component stress between 3k and 5k rpm is not that large. If it fails at 5k, its going to fail soon at 3k too. Or even at idle.

Unless the noise he took it in for was a spun bearing or failed rod bolt, fer cripes sake! Remember he took it TO the shop BECAUSE OF AN ABNORMAL NOISE.

In your opinion. I disagree. If 5k is below the redline of the engine, there is nothing that could possibly fail at that RPM that isn't going to eventually fail at lower RPM anyway. If you can think of a real-world example that proves otherwise, I invite you to do so.

Any engine that can no longer operate in its NORMAL operating range is not safe to be on the road. So yeah, in a sense I guess it is a moral position.

Wrong, Some loads increase geometrically all increase at least linearly. So your talking an increase of 67%-200% on a new engine in perfect shape. And some loads increase as clearances increase. So an engine with more clearance on bearings, pistons, cylinder and rings will experience heavier loads on some components at the same rpm. And a little bit of oil mixed with the air and fuel increases the likelihood of high speed detonation. So all added together the additional real component stress could be exceedingly large. The reality is the failure point is often just that - a point. If you stay below that point it won't fail.

Wrong.

And then afterwards he drove it half way across the country with this mythical spun bearing or loose rod bolt. Yeah that makes a lot of sense.

The redline is not something handed down by God to Moses and written on stone, which is what you apparently believe. The so called redline represents the point at which damage occurs that would not otherwise occur. What you are to dense to see is that I am telling you is the redline of a particular engine with 150k miles on it might well be 3000 RPM. This is not only possible it is even likely. That engine may last a good long while if it is driven below that 3000 RPM, but may fail in short order if you start to drive it above that. That by definition makes 3000 rpm the redline for that engine.

Just run engines past redline and see what happens - what more proof do you need?

Some people can buy a used car at 150k and drive it for another 100k and the engine is usually not the component that eventually does it in. And then there are others who buy a car with 150k and they will consistently wipe out the motor in 500-1000 miles. And that also just happens to be the guy who shifts out of second gear at 5000 rpm. Now someone would have to be completely stupid, deaf, dumb and blind not to not be able to put the facts together to see what is going on there.

More irrelevant bullshit. How does normal peak power (whatever that might mean) have anything to do with anything. Or are you back to your morality thing? If an engine doesn't have a shot at winning Daytona it doesn't deserve to be allowed on the road?

That is what I figured. At least you now are being halfway honest, but only an idiot would think that shifting in 2nd gear at 5k rpm is NORMAL. So you think the guy had the right to destroy the OP's engine on moral grounds? He was after all doing the OP a big favor - right?. It was all done out of the goodness of his heart, because he was hoping to give the OP a really good deal on a new engine. I don't think the courts would agree with your moral position. How are you going to demonstrate that you are a danger to yourself or others just because you drive like the OP does without exceeding 3000 rpm?

-jim

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| > And I happen to disagree COMPLETELY with that claim. The difference in | > real component stress between 3k and 5k rpm is not that large. | | Wrong, Some loads increase geometrically all increase at least | linearly. So your talking an increase of 67%-200% on a new engine in | perfect shape. And some loads increase as clearances increase. So an

This is a stupid argument.

If the engine specifications state that 5000 rpm is within the operating range of the motor, then running at 5000 rpm in first or fourth gear is ACCEPTABLE. IF it fails within it's normal operating range it WAS defective.

It doesn't matter that the owner may have never experienced the defect during their use. The engine was run withing ACCEPTABLE limits. It FAILED. It WAS defective.

So the owner has no right to ask the guy to shift at a reasonable RPM? Or to expect that a technician that test drives his car will handle it with the same care he does?

See this is the problem. Their are a lot of these idiots out there who think they have the moral right perhaps even the moral duty to destroy someone else's property just because they deem it to be defective. And unfortunately they often do just exactly that.

First when asked if it causes damage they will lie and say "No, It causes no damage". Then when confronted with that lie they will respond "it doesn't matter because we have the moral right to do damage because it's defective anyway". And some of them will even go so far as saying the owner has no business driving in a way that doesn't cause damage.

So the owner has no right to keep his so called "defective" vehicle and drive it for another 100,000 miles? Is that how it works?

-jim

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On Jul 3, 4:50 pm, "Calab" wrote:

The guys who convert auto engines for use in aircraft or boats often test their conversions by running them under load at redline or very near to it for a long time to see what it'll take. Some are pretty much stock, some have cams to get peak torque at a higher rpm. These engines typically run for hundreds of hours at these loads and rpms, and are found to be in unexpectedly good condition when torn down. Redline, I think, is a point that leaves considerable margin to protect both the engine and its manufacturer from idiots. Both boats and airplanes are hard on engines, because at cruising speed they're operating at anywhere from 65 to 90% of max hp, while a car might need 25 or 30% in cruise. Big difference. Most of the problems with these conversions are making sure the thing has enough cooling capacity, especially in aircraft. A certified aircraft engine is expected to last anywhere from 1400 to 2400 hours, depending on the model, and auto conversions (for uncertified aircraft) should last 600 hours or better. A current certified aircraft engine, the Thielert Centurion, is a converted Mercedes diesel that produces 135 hp from

2.0 litres, at 2300 propeller rpm, which is reduced at least 2:1 from crankshaft rpm, so we know that the crank is turning at least 4600. And that engine is rated at full power, continuous, at whatever altitude you want. 135 is max sea level power. The engine is certified for 2400 hours of that treatment. See it: They also get 350 hp out of a 4 litre model. When a dork abuses an engine, he accelerates hard, repeatedly. He'll cause detonation, which scrubs or cracks pistons, breaks rings, cracks heads, and causes wide temperature swings that warp and break things. He'll decellerate hard, sucking oil past the rings. He probably won't look after the engine, either, feeding it cheap gas and never changing the oil. The crankcase will sludge up and so will the lifters. He'll start it at -20 and go right away, on summer-weight oil, which won't pump worth a hoot at that temperature and his engine starves for lube. Stupid, all of that, and it's no wonder his engine comes apart. But I still don't like running so close to redline. I've flown a Glastar with a converted Subaru 2.2L, cruising at 4600 engine rpm and redlining it at 5600 in max speed flight. Sure doesn't sound like it's enjoying itself, not after the Lycomings I cruise at 2200 or 2500 rpm or my Old Continental A-65 that's happy at 2100. But the Subaru doesn't come apart, either. Strong enough to take producing max hp at max rpm, for some time. Years ago I built a boat in which I stuck a converted Chev 283 and cruised that at anything up to 4800, which I think was beyond redline. It didn't mind at all. It was still running well when I sold it.

Dan