Ram HD 1000 lb-ft MPG loop

RoyJ wrote:

I didn't say emissions was a non-issue, I asked what proof / reasoning you have that a lower engine tune doesn't ALSO yield longer engine life?

Again, we're talking 200hp vs 300hp, both emissions certified.

I have been trying to tell you, but you don't want to listen. You keep thinking that just because an engine has higher power output then it will have lower longevity and the reason why the manufacturers charge more is because more warranty repairs. This is absolutely FALSE based on assumptions.

RoyJ wrote:
I challenge anyone who makes a statement based only on their "experience".

I'm an engineer, who believe in numbers, equations, models, and laws of thermodynamics. And if you really have the experience you claim, you'd have no problems backing it up.

That's how we design / invent things you techs then put on a test bench, press a few buttons, and brag about how many years you've done that :P

For being an engineer, you certainly did not know how an engine worked earlier. I have also been trying to tell you how it works, but you refuse to listen.

RoyJ wrote:
What you described is exactly "66% throttle". You realize TP doesn't imply rpm right?

At a constant rpm, if I fuel at just over 66%, with proportional air mass density, then I achieve 66% power output.

I'm asking you, holding ALL other constants (cold start, maintenance, etc.), do you agree one engine at 66% power output last longer?

That is NOT how it works in the real world with the trucks in question, and we don't make our B10 and B50 projections based theories that don't apply to the real world. I will explain at the end why we did not see any significant reduction in B10 and B50 life with higher power level engine below and why we actually saw the opposite even though it was not really a significant percentage.

RoyJ wrote:
Read what I wrote above. I don't doubt you know what the breaking limit is, but you don't seem to understate how material properties / engine life behave under that breaking point.

Yes, we can give a rough estimate on the failure point of the internals because we tested the failure points in the test cells. Heck, it is even common knowledge in the aftermarket world on how much the stock internals of a 6.7L can take. Why, because of actual real world experience.

RoyJ wrote:
You get defensive when your statements are challenged, and the only backup you have is "I worked, I saw, I know".

Pot, is that you? This is kettle.

RoyJ wrote:
And your logic is based on not completely understanding what you saw - you see some numbers from the test bench, spoke with a few engineers, but you can't explain why things happen.

I completely understood what I saw and its real world application, not some 66% theory based on your zero experience or knowledge with said engines or class 6-7 trucks.

Let me first try and tell you why we saw no significant reduction in reliability in real world scenario testing by explaining what the real world scenario of these trucks are. I will use the truck Mich800 said he drove, a 26k GVWR Freightliner M2, which is the truck that started this debate. Lets use real world scenarios of how this truck is utilized given both power options, a 325 @ 2,500 rpm/750 lb-ft @ 1,600 versus a 200 hp at 2,500 rpm/520 lb-ft @ 1,600 rpm.

If the truck that Mich800 was driving was the 200 hp version and an automatic then it was probably mated to an Allison 1000/2000 transmission. The 325 hp version engine has to be mated to the costlier Allison 3000 transmission along with costlier drivetrain to handle it.(<--- one of other reasons for multiple power levels).

Now I am not sure if you have ever driven one of these trucks with both engine variants of engines, but I can tell you that there is a huge difference in drivability especially when you start adding weight. Even without much weight on the truck, the 200 hp version of this engine requires a lot of foot to the floor at high rpms just to get it to move at any reasonable speed while the 325 hp version does not require that much. Remember that both these engine make their peak hp at 2,500 rpm

Loaded is even worse with these two. If loaded to max 26k GVWR, it takes a over 200 hp just to move that much weight at 65 mph(which is the speed most of these trucks are governed at) up a 2% grade hill. So the 200 hp engine would be foot to the floor under heavy load pegging it's governed speed of 2,600 rpm on just about every incline. The 325 hp version not so much. Since it makes 750 lb-ft at 1,600 rpm, we can do the math to deduce that it is making 228 hp at 1,600 rpm allowing the truck to perform the same work with less rpm and it does not require the driver to push the pedal to the floor putting the engine under max load most of the time. In these conditions and truck applications, the 325 hp version is much more reliable.

However, on the flip side, a higher hp engine has issues in city environments since it is not under as much load as the lesser hp engine and therefore does not get the exhaust hot enough for emissions compared to the 200 hp engine which is closer to its peak load more often in these conditions. This causes increased EGR usage and more frequent regens in the higher hp engines so the hp is decreased in these applications so the engine has a chance to get closer to peak load more often due to emissions like I have been saying. The addition of SCR/DEF does allow higher power variants to be used in urban applications more often, but it was still better for the lower power versions in these applications especially for cost reasons since you don't have to extra for the added power and drivetrain to support that power.

We data-logged hundreds of thousands of real world driving hours with many drivers and many conditions to know how these engines will be used, and to know what power level was best for each condition. This also how we determined that cold start, maintenance, and driving conditions(especially when the engine is not spec'ed right for the application) had more of an effect on engine longevity. In all actually, since the lower hp versions were generally speced on trucks that did a lot of city driving with a lot of stop/starts, they had a slightly worse B10 and B50 rating than the higher hp variants that were mainly speced out on trucks that drove more on the highway with more miles than stop/starts.

So there you have it, the reason why I said that we did not see any significant difference in real world applications between power levels and why I say your 66% theory doesn't mean jack in the real world application of these trucks. It is also also false to assume that a higher power rated engine will break down sooner because truth is, the lower hp engine is likely to break down sooner when used in an application meant for a higher hp engine while the higher hp engine would likely break down sooner when used in an application meant for a lower hp engine. If you want to read a little more as to why certain power levels are used in certain applications and to know I am not just telling you BS, then these articles may help.

Spec'ing Medium-Duty Powertrains for Optimum Performance

Tips for Spec'ing Engines and Transmissions

So..... were is your proof that the higher hp engines will not last long in the truck applications and that manufacturers charge more for higher horsepower versions to cover higher warranty costs? You talk about making unchallenged statements and people assuming they are true. You have no room to talk with these kind of false assumptions.