High revs damaging?

[willie45]

Hi

I'm pretty rubbish at mechanical stuff and I also am new to automatic transmissions. I have just noticed that if I'm a bit nifty with the accelerator that my rev counter will soar into the red level.

I had thought there would be some sort of limiter to stop this from happening and was a bit surprised there wasn't. Probably my stupidity.

Anyway, I'm not a boy racer but I am guessing there will have been a handful of times when the needle's gone into the red for a few seconds. I doubt this has been for more than 5 -10 secs max and probably still under 5k rpm so only the first red part.

Surely this will not have damaged any of the engine? If it had would this show up on the computer they use in garages to check the engine?

Last I seem to recall that they floor the pedal for a full minute when checking diesel emissions at MOT. Is this right and surely this would really stick the revs into the red zone?

Anyway thanks for reading and all answers most gratefully received. I really am clueless as you will gather so I'm looking to clarify the above.

Thanks again

Willie

 

[whitenemesis]

Mercs are limited to well below the red line if revved in neutral.

 

[Dieselman]

Not diesels.

 

[whitenemesis]

Probably 'cos the diesel red line is much lower anyway!

 

[Dieselman]

Probably 'cos the diesel red line is much lower anyway!

No, it's because all diesel have to rev freely to the governor for smoke test purposes.

 

[sinewave]

...................and the Governor is therefore the limiter!

 

[Dieselman]

...................and the Governor is therefore the limiter!

yes, and...?

 

[sinewave]

Just clarifying for whitenemesis!

 

[Dieselman]

Just clarifying for whitenemesis!

It must be me being a bit thick, please explain.

 

[willie45]

All this seems to be above my understanding I'm afraid, so what's the story re my revving it into the red on a couple of occasions. Should it do it or should it not? Also should I worry about having done it or not?

Thanks

 

[Dieselman]

It can't damage anything as the governor will cut in before the revs go high enough to do so.

I take it your car is a manual gearbox, in which case your revving it high will be slowing down your acceleration as you have gone well past peak torque and power.

 

[whitenemesis]

From the OP " I also am new to automatic transmissions" ...

 

[willie45]

Yes it's automatic.

Willie

 

[prm]

Don't worry about it, these engines are built to take any amount of revving.....in fact it does them good every now and again to give them an Italian tune up.

 

[willie45]

LOL thanks for the advice prm. I'm not keen to make a habit of it but good to know unlikely to have caused any harm

Willie

 

[DSM10000]

The red line is there for a reason, the manufacturers have set this as the maximum safe engine speed so why worry about reaching it?

As DM explains the inbuilt governor will prevent you over reving the engine and causing damage but as he also points out high engine speeds on a diesel are generally counterproductive as you have passed the maximum part of the power curve and torque peak so you will not go any faster just burn more fuel until the governer kicks. Is that correct DM?

 

[Deleted member 65149]

With a petrol engine you have to avoid over-revving when cold because oil hasn't yet reached everwhere. I've always hated diesels (especially when following them ... cough cough ..... or listening to them starting) but because they use a fuel/oil mixture I assume that cold revving is less of a problem. Anyway, the odd second or two into the red isn't usually a problem. Just don't try driving in the red for any distance or everything will overheat and your already noisy diesel engine will get even noisier ... for a few seconds before it stops!

 

[Uncle Fester]

I've aways liked diesels for their torque, and pulling power, and nower-days they are more or less as fast as the petrol models.
They can be a bit noisey, but I do like the sound of a diesel engine (the bigger the better)

24V71 Detroit - YouTube

(shame about the OTT American fella, but one hell of an engine)

Or of course a nice V12 2 stroke diesel?
http://www.youtube.com/watch?v=pOVJG1DgwJs&feature=related

Anyhoo, I digress, It was my understanding that you could not over rev a diesel engine due to the govenor limiting the fuel/revs, and of course coupled to an auto box, that too will change gear at the optimum time to gain the best accelleration.

Please let me know if I'm mistaken.

 

[grober]

It may also reflect your rear tyres have momentarily broken traction if the increase in revs is not matched by an increase in road speed. Easy to do with today's high torque diesels