Continuous operation near red line

OK, I'll go first!

Sustained high RPM, full load--top ring/cylinder wear.

Sustained high RPM, low load--con. rod fatigue cracking, unless the rod design/material/stresses are well researched.

20 years ago one of the first tests of a 'new' engine design was 100 hours at full power. If it got through this then generally it was capable of passing the full durability, eventually.

However, the rumour was that most of our engine failures on the dynos occurred at high speed low load which was part of the running in procedure.

So, if you are running full load, should be OK. No load, reputedly more difficult.



Cheers

Greg Locock

Greg, do you recall what the failure mode typically was for the dyno failures at high rpm, low load?

Not really, but top end I think, probably pistons burning or seizing. Remember, this was before fuel injection.

At around the same time most production engines that failed during their dyno test was due to seized mains.



Cheers

Greg Locock

There shouldnt be any problem running the engine at full power all the time. Provided that you service the engine as recommended in the manual.

Just like Greg said, WOT test for 100 hours. Nowadays we do it for twice or thrice time longer. I do have to admit that we encounter more problems at higher RPM high load operation if compared to the high rpm low load. We encounter many things like thermal, wear, fatigued, lubrication, coolant, stress, etc. All those must be rectified before we release the 100-105ps/liter to the market.

As for the high rpm low load durability test, the failures encountered were the smaller parts like oil strainer, brackets, fuel rail, etc. The amplitude at the natural frequency appeared to be larger at no load+high rpm if compared to high load+high rpm. The vibration level for those small parts are high that it caused fatigued problem if continously subjected to that condition.