Gasoline vs. Diesel Turbo longevity
Gasoline vs. Diesel Turbo longevity
(OP)
I was wondering why it seems that a cummins turbodiesel can go around 400,000 miles before it's first overhaul but gasoline turbocharged engines in some cases have problems doing having that before their turbos experience some sort of failure?





RE: Gasoline vs. Diesel Turbo longevity
Assuming, for the sake of discussion, that both are "built to last", then we can take into account some operational concerns. The typical diesel engine sees more steady-state operation, over a narrower RPM range, than its gasoline cousin. This allows engineers to size turbos more accurately for a diesel application. This equates typically to more stable EGT temps, and lower turbine shaft speeds. Both of which aid in turbo longevity.
Regards,
Bryan Carter
RE: Gasoline vs. Diesel Turbo longevity
Gas engine exhaust temps: 1600-1800 deg F
Diesel engine exhaust temps: 800-1300 deg F
RE: Gasoline vs. Diesel Turbo longevity
RE: Gasoline vs. Diesel Turbo longevity
Most "turbo" cars seem to be driven within an inch of their lives a lot of the time.
Cheers, Pete.
RE: Gasoline vs. Diesel Turbo longevity
RE: Gasoline vs. Diesel Turbo longevity
The durability is designed in by the designing engineers, not by the choice of fuel.
Also, turbochargers serv 3 different functions in each engine type.
For heavy duty diesels, it typicaly serves to improve fuel economy and reduce engine weight for a given HP rated engine
For a petrol engine, it typicaly serves to increase the HP of a given engine design.
For an aircraft, it serves to compensate for volumetric efficiency losses at high altitude
Regards
pat
RE: Gasoline vs. Diesel Turbo longevity
There are mandated rebuilds (e.g. TBOs) at specified engine-time intervals which are well short of the effective hours-of-operation equivalents for the mileages being discussed.
While I do not doubt that component robustness and general quality are high in aeronautical applications (and cost os often little or no object!), we might also remember that light weight and packaging can be factors in design.
RE: Gasoline vs. Diesel Turbo longevity
1) Turbochargers for spark ignition engines are really only functional at near-full to full throttle openings -- i.e., while accelerating or climbing hills. Diesels, on the other hand, have turbochargers that are not throttled and essentially work all the time. The turbos increase peak hp on gas engines and "cruise" hp on diesel engines.
2) The mandated rebuilds in aircraft are only for commercial aircraft. There are less and less piston aircraft in that particular category.
Having said that, it should be noted that the typical turbocharged aircraft engine probably won't make it to the tbo number, which may only be 1200 or 1400 hours anyway.
RE: Gasoline vs. Diesel Turbo longevity
Low stresses, lots of metal(in the right places)=long life.
RE: Gasoline vs. Diesel Turbo longevity
I also think that the people who are buying the gas turbo's maybe pushing the engine over it limits. Diesels like gas have rev limiters on them, and seeing as the diesels stroke is much shorter than that of a gas engine, it is much harder to push that button. But it is a familiar case to see someone young and foolish pushing a turbo charged car to its limits. Sooner or later, something has to go.. I find it is more of a connecting rod than a turbo problem..
You also have a hard time finding a young person buying a diesel because they don't offer that option in little cars..
Chappy
RE: Gasoline vs. Diesel Turbo longevity
apparently you're in the US?
RE: Gasoline vs. Diesel Turbo longevity
And even though it's purely subjective, I just don't enjoy the sound or smell of a diesel engine. An engine that sounds like it's full of marbles and belching out clouds of smoke that reminds one of a fire in a coal mine... just isn't sexy.
"That's right baby. 1000 lbs of torque and 12 horsepower. This puppy screams all the way up to it's 2800 RPM redline. Yep, she's a real monster. You want to hold the glow plug button in, or shall I?"
Just doesn't have the same ring to it.
Regards,
Bryan Carter
RE: Gasoline vs. Diesel Turbo longevity
I agree, the large diesel engines are simply designed to last.
Macangus
RE: Gasoline vs. Diesel Turbo longevity
RE: Gasoline vs. Diesel Turbo longevity
What's the purpose of a BOV? It's to relieve pressure in the intake track when the throttle is rapidly closed. That's when it hit me, diesel engines don't have a throttle. They use fuel to modulate RPM and power output. The turbo on a diesel is not subjected to the same resonance and pressure changes as in a gasoline (petrol) engine. Which, of course, is easier on the turbo's bearings and shaft. Maybe that could be it...
Regards
Bryan Carter
RE: Gasoline vs. Diesel Turbo longevity
RE: Gasoline vs. Diesel Turbo longevity
Knock has been shown to strip away the boundary layer of gases that protects the piston and can eventually damage it. It also causes the flame front speeds to jump from the order of centimeters per sec to meters per sec with a corresponding increase in crank and rod loads.
The diesel cannot preignite! No crazy above design crank loads, no piston softening/ annealing etc. Well, until the owner turns up the injection pump and adds propane injection etc etc. and melts the pistons!