ShinerBock wrote:
Anecdotal? How many engines have collected data showing that a 500 hp 6.7L in a marine application will have reduced B10 and B50 life percentages over a 200 hp 6.7L that goes into a medium duty truck? How much power did you run to know that breaking point of internals? I am going to guess a big fat zero, and if so then what are you basing your statements on?
Still waiting for you to show me evidence the same engine at 500hp with no life reduction over a 200hp variant, which defeats every engineering principal. I'm guessing you have a big fat zero :D
Saying B50 and B10 together is redundant - throwing tech jargons doesn't make you sound smarter...
If you actually tested any turbo diesel engine you would know what this has to do with durability and what drive pressure and high EGT's does to internals. The fact that you don't know speaks volumes.
A VG turbo creates high drive pressure along with thermal stress and is added solely for emissions purposes. This combined with bad timing spikes will blow gaskets and damage other internals. A correctly sized fixed geometry turbo will not only have considerably less drive pressure and produce a lot less heat, but it will make more power with less boost.
Just replacing the stock VGT with a correctly sized fixed geometry will allow you to create more power while reducing stress and heat on the engine internals. However, since these engines are designed and tuned to meet emissions, a VG turbo must be used even at the detriment of the engine.
Here is a good video by Gale Banks going over what I am talking about. It is on a new L5P Durmax, but the same concept still applies to the Cummins 6.7L since it uses a similar turbo setup. LINK
Did I say I don't understand how variable geometry works? Or that I need a lecture on it?
I asked you to back up your statement that 2 of the same engine, with the same VG turbine + compressor, why the lower hp version won't live longer.
Do you agree since the compressor is the same, at lower hp we're operating at a lower pressure ratio? Do you agree a lower pressure ratio means lower EGT with the same intercooler? Do you agree lower EGT, plus lower intake air mass / density, means lower EGT and therefore longer life? If you say no I want to see equations backing it up...
I don't care if you didn't ask. I gave my credentials because it was obvious you did not have any.
EDIT: Correction, the marine engine 6.7L (which abides by less stricter emissions requirements and therefore uses a larger fixed geometry waste-gated turbo) is at 550 hp/1,250 lb-ft, not 500 hp like I stated above.
A good engineer always backs up statements with principals, calculations, laws of thermodynamics, etc. A bad engineer, or tech, relies on "years in the industry" in the absence of sound reasoning.
As a consulting ME, I always tell them: a GM car salesman can be in the industry for 40yrs, and can't find a filler cap on an LS7.
You should know diesels on sport yachts last 5,000 hrs. In standby generators - 20,000 hrs @ 1500 rpm. A gasoline boat engine averages 2 - 3000 hrs. The same engine in a forklift last 20,000+ hrs.