Renze
Elite Member
Cummins 5.9 12V heads cracked often in excavators at 6-8000hrs. They thermically didnt like the on/off load cycles. I had it once on a wheel loader too, but that was at 17.000hrs so that engine had already earned its keep.
The early QSB 4 valve lasted only 8000 hrs in a wheel loader in 190hp configuration. It lasted 20.000hrs in one size smaller, at 155hp.
When stretching the limits in automotive engines, you dont get punished for the few seconds every day this power is used to overtake or sprint away at a traffic light. But in commercial, or industrial duty where these engines run at peak power often and long, under-engineering for the given duty cycle, gets punished hard.
Thats why a Landrover gets 370hp from the 4.4 liter V8 Diesel, a DRW Ram gets 370hp from a 6.7 ISB, and a dumptruck gets a similar power from an ISX12.
If you take a look at Fendts new flagship the 1050, it packs a 12.4 liter MAN engine with a specific output of 40.3 hp per liter, where the 939 has a specific output of 50hp per liter... Because in heavy use, these 7.8 liter engines at 390hp were burnt up and ready for rebuild at 5000hrs.
Engineering limits can be stretched, but only if development of engine metallurgy and engine oils keeps up the pace. And historically, it shows that the market allways demands faster than metallurgs can keep up with.
