Talk to me about torque

[Toltec]

Despite the title, sorry couldn't help myself, a serious question even if I do not have a specific application in mind.

If an engine produces a peak torque of, for example, 400Nm at 3000rpm would it be safe to assume that the engine would be able to reliably withstand the same torque at higher rpm?

To put it another way if you could re-tune the engine to move the same peak torque up to 4500rpm to produce 50% more power would you expect the stock internals to take this happily?

I know there would be some other effects such increased fueling and cooling to consider, but I am trying to think what other changes apply. The cylinder pressures will be higher, what else?

[anonymous-user]

Simple answer: No

Can't be bothered with the long answer, but in short, the engine will be "thermally" limited as well as "mechanically" limited. Torque, at a higher speed is more power, this is more heat, this heats up the bits in your engine more, this reduces their material properties. At some point it all goes pear shaped..........

[Toltec]

Re-reading that I worded it imprecisely by implying the power at 4500rpm would be increased by 50%. That would require the torque on the unmodified car to have dropped by 2/3rds so the power at 4500rpm was the same as at 3000rpm. Lets say the change in power at 4500rpm is more like 15%.

The effect of the extra heat loading is going to depend on efficiency of the transfer to the cooling system. If the cooling is sufficient for the coolant input temperature to be maintained the engine will stabilise with some components at higher temperatures. That will reduce their mechanical limits so I guess it isn't that simple.

Thanks for the reply, helped me think that through

[aw51 121565]

Don't forget that the engine oil is a significant contributor to engine cooling. So maybe higher spec oil (to cope with the increased oil temperatures that might be expected) and an oil cooler (if there isn't one already, and maybe with thermostat?) might be needed .

[TomN94]

A quote I stole from somewhere years ago, is remotely...in fact, almost not at all relevant to this, but it mentions torque.

“Understeer” is when you hit the fence with the front of the car. “Oversteer” is when you hit the fence with the rear of the car. “Horsepower” is how fast you hit the fence. “Torque” is how far you take the fence with you.