RoyJ wrote:
You stated a 200hp version doesn't result in any increase in durability. When you make a statement, be ready to defend it. And no, "I worked in the industry" is not a defense - rather, it's lack of defense.
Actually what I initially stated that was that the difference between each rating had more to do with emissions and up selling to another hp level rather than reliability.
Working for an actual engine manufacturers, personally tuning/moding, and wolring with many tunners in the industry works as a defence for me especially versus some one who has absolutely none and is basing their assumptions on zero experience. I am sorry that you take the word of no experience over someone with experience, but it kine explains a lot.
Again, I can ask you the same thing. Back up your statements that the reason for the power decrease between the GVWRs is for reliability and not emissions.
Here is actual Ram engineer saying exactly what I am trying to tell you.
LINKRoyJ wrote:
Do you always give lectures thinking no one knows as much as you?
Re-read what I said - saying B10 AND B50 together, is redundant. In this context, if B10 goes up/down, then obviously B50 does as well.
No, not always. Only when someone is trying to tell me I am wrong and they have absolutely no idea what they or talking about or have any real world experience on the matter. They never actually tested engines to see what they can handle or pushed them to their absolute limits to see where their weak link lies yet they like to tell others how the cow eats the cabbage.
RoyJ wrote:
Here's my reasoning - I hope you agree an engine at cruise, making 50hp will last longer, in hours, than an engine at WOT redline, correct? I don't think I need to prove this one - it's basic powertrain engineering 101.
The 200 hp engine is essentially a 300 hp engine at 66% throttle. Factoring emissions and thermal constraints, the engine at 200hp may experience even less than 66% of the thermal/mechanical stress.
So logically, how does the 200 hp engine NOT last longer?
No, that is incorrect. A 200 hp is NOT a 300 hp engine at 66% throttle. They both achieve their peak hp at the exact same rpm. The difference is how much fuel being delivered, injection timing, VG vane position at peak, and air being added. How the engine is being used along with maintenance, and how many cold starts the engine has has more off effect on engine internals than a power range from 200 hp to 300 hp or even up to 500 hp.
As I said, the internal of a 6.7L can handle way more than what the turbos built for emissions and HPFP can force upon it. If something is built to withstand 800+ hp, then what does it matter if you send 200 hp through it or 300 hp. Neither will have any major effect or at least enough of an effect on longevity to make any significant difference.
RoyJ wrote:
Once again, no one compared a VG turbo vs fix geometry. We're comparing a 200 vs 300-320 hp highway spec ISB, which both have VG turbines.
Based on this setup, the 200hp version always have lower EGT, IAT, ECT, and piston / exhaust valve temp (based on lower EGT). Agree? Therefore, the 200hp engine lasts longer.
No, it will not always have lower EGT or IAT. The EGT and IAT are mainly effect by the intake and exhaust which is made by truck manufacturer along with the turbo efficiency. Cummins does not make the intercooler, the intake, or all of the exhaust. EGT and IAT will not rise that much between power levels until the limit of the turbo's efficiency is reached.
Remember, high EGT is caused by no having enough air for the amount of fuel being injected. If both are using a turbo that can easily expel enough air for say 500 hp without EGT's getting too high, then there will not be that big of a difference between in EGT's. In short, the turbo's efficnecy has a lot to do with the temps of the engine as I have been trying to say. That is why the 550 hp Cummins has a fixed geometry waste gated turbo and the on road has a VGT.
As far as ECT, that depends on how hard the engine is working in rpms and whether or not turbo can expel exhaust gases quick enough. Since a 200 hp and 300 hp Cummins both achieve their peak hp at the same rpm....
RoyJ wrote:
Also, there is no magical hp "limit" of an engine assembly. Everything is on an inverse curve - the higher the hp, the lower the lifespan, up to the absolutely breaking point (represented by the metal's UTS @ that working temperature). You can't say "an ISB has a working limit of 750hp", metallurgical fatigue limit doesn't work that way.
Yes, and this is what I am tring to tell you about the internals of the 6.7L. The breaking point is way more than 200 hp, 300 hp or even 500 hp. Internally, the weakest link are the head bolts, to around 550 hp, but the rest can handle over 800 hp all day every day. How do I know? Because I seen it in the test cells.
RoyJ wrote:
Re-read my writing instead of trying so hard to prove me wrong. I'm using logic based on engineering. Not once did I say "I say so because I've worked at XXX for XX years".
Remember, we're all trying to learn here, not to say who's right who's wrong...
You mean logic based on zero experience or knowledge on how much the internals of a 6.7L can actually handle
