2020 Cummins IKE pull

ShinerBock wrote:

stsmark wrote:


I was wondering the same thing, it’s like the EB just gets shut off. Seems like it would be tough on some part of the drivetrain. Also if it just shutoff what’s holding the truck back from accelerating if not the brakes?
I find it interesting that neither of them point out how cool that brake hp indication is.

Engine braking at 3,500 rpm is what is trying to hold the truck back when it is off. It cannot with engine braking alone so it starts to gain speed past 35 mph and then the exhaust brake kicks back on to slow it back down to 35 mph then cuts off again. As you can see at of the video 5:56 of the video. Exhaust brake is off, it starts to get to 37 mph and then it kicks back on to slow it down to 35 again.

You can hear the exhaust brake. It's remaining constant. The exhaust brake/engine brake is really the same thing. While the engine is being driven from flywheel it is braking. The degree of braking varies with the speed of the engine and the amount of restriction in the exhaust. The exhaust brake is simply the turbo adjusting to create more restriction in the exhaust. It's like if you had an engine driving a positive displacement water pump and you had an adjustable nozzle on the end of the water hose. You could change the power demand on the engine by opening and closing the nozzle. The engine on these trucks is acting as an air pump and the adjustable turbo is the nozzle.

I'm not saying the exhaust brake is switching on and off when the gauge is displaying a value. I'm suggesting the wheel brakes are being applied to help with braking during the time that the gauge is displaying a value.

stsmark wrote:


I was wondering the same thing, it’s like the EB just gets shut off. Seems like it would be tough on some part of the drivetrain. Also if it just shutoff what’s holding the truck back from accelerating if not the brakes?
I find it interesting that neither of them point out how cool that brake hp indication is.

Engine braking at 3,500 rpm is what is trying to hold the truck back when it is off. It cannot with engine braking alone so it starts to gain speed past 35 mph and then the exhaust brake kicks back on to slow it back down to 35 mph then cuts off again. As you can see at of the video 5:56 of the video. Exhaust brake is off, it starts to get to 37 mph and then it kicks back on to slow it down to 35 again.

FishOnOne wrote:

4x4ord wrote:
I went back and watched the 4:00 minute mark of that video. I wonder why the gauge reads up to 240 reverse horsepower a while then drops off to 0? It almost seems as though the gauge starts reading at about 37 mph and it pulls it down to 35 mph then quits displaying. Could it be that while the gauge is displaying a number the wheel brakes are being applied.

240 reverse HP would definitely be slowing the truck. 175 reverse HP at the crankshaft should be enough to hold speed on the steepest part of the hill.

That was my take on what happened. But as always I could wrong.

I was wondering the same thing, it’s like the EB just gets shut off. Seems like it would be tough on some part of the drivetrain. Also if it just shutoff what’s holding the truck back from accelerating if not the brakes?
I find it interesting that neither of them point out how cool that brake hp indication is.

FishOnOne wrote:

ShinerBock wrote:

FishOnOne wrote:
So to summarize:

Brake Applications:
Ram: 0 (Auto Brake assisted-unproven theory by Ford fanboys)
Ford: 5
GMC: 9

Time:
Ford: 10:20
Ram: 11:32
GMC: 11:47

MPG:
Ram: 2.5 mpg
Ford: 2.4 mpg
GMC: 2.4 mpg

There, I fixed it for you.

I would still love to see how these trucks do at 80F or even 100F.

I agree with testing at 80F or 100F but I doubt the order of performance would change.

And now your ok with reporting the computer mpg when you have always reported major errors with these systems.

TFL reported the brakes were part of the braking system so if you don't like that or agree with it go debate it with them like you do the Australian.

I feel the result will be similar to last years test if it were 80F.


I have stated before that I don't think the computer is accurate with a lot of stop/starts of the engine. The more start/stops are in the tank average, the more it is off based on my experiences. I have also said it is fairly accurate going from point A to B without turning off the engine.

I like to report all the data(good or bad) and let the people decide for themselves instead of only giving them part of the information because of some bias. Mr Truck has reported many inconstancies before and I doubt this would be the last. After all, he also stated the truck/trailer's brake lights were on and yet they were not.

4x4ord wrote:
I went back and watched the 4:00 minute mark of that video. I wonder why the gauge reads up to 240 reverse horsepower a while then drops off to 0? It almost seems as though the gauge starts reading at about 37 mph and it pulls it down to 35 mph then quits displaying. Could it be that while the gauge is displaying a number the wheel brakes are being applied.

240 reverse HP would definitely be slowing the truck. 175 reverse HP at the crankshaft should be enough to hold speed on the steepest part of the hill.

That was my take on what happened. But as always I could wrong.

Yes Westbound on Stevens Pass is fairly steep. You for sure want to be at the right speed when entering the right sweeping portion at the bottom of the steepest part.

You should try using your cruise control when you are descending in 3rd. I like 3rd with rpm's up near and at 3k, lots of braking power there!

I went back and watched the 4:00 minute mark of that video. I wonder why the gauge reads up to 240 reverse horsepower a while then drops off to 0? It almost seems as though the gauge starts reading at about 37 mph and it pulls it down to 35 mph then quits displaying. Could it be that while the gauge is displaying a number the wheel brakes are being applied.

240 reverse HP would definitely be slowing the truck. 175 reverse HP at the crankshaft should be enough to hold speed on the steepest part of the hill.

Cummins12V98 wrote:
"I would still love to see how these trucks do at 80F or even 100F. "

Even pushing 100 trans does not get any higher, fan kicks in and drops to the 190's. This is pulling 33k combined on a steep long grade in the Rockies.

Looks really good!

Although I've never towed 30k with my truck, I have towed 16k all over the place in BC, which has steep mountain grades everywhere as anyone who has been here knows. The only time I ever have to use the service brakes is to lower my speed to catch a lower gear (my truck is a manual) because I've misjudged the steepness of a grade and need to slow down to avoid over revving the engine in the lower gear. Once it is in that gear (3rd is usually the right gear for really steep passes), I rarely if ever have to touch the brakes. Usually I end up having to give the truck some throttle because it's slowing down too much. Travelling with my wife's uncle behind us on Stevens Pass in Washington a couple of years ago, he actually thought my trailer was not plugged into the truck because he saw no brake lights descending the West side. I had another lady frantically wave me down in bumper to bumper traffic one time also claiming that I had no brake lights on my trailer, when in reality I wasn't using the service brakes at all.

Having experienced the exhaust brake in the Cummins for several years now, I truly believe that it was only the exhaust brake working in the video and not the service brakes on the truck.

ShinerBock wrote:

FishOnOne wrote:
So to summarize:

Brake Applications:
Ram: 0 (Auto Brake assisted-unproven theory by Ford fanboys)
Ford: 5
GMC: 9

Time:
Ford: 10:20
Ram: 11:32
GMC: 11:47

MPG:
Ram: 2.5 mpg
Ford: 2.4 mpg
GMC: 2.4 mpg

There, I fixed it for you.

I would still love to see how these trucks do at 80F or even 100F.

I agree with testing at 80F or 100F but I doubt the order of performance would change.

And now your ok with reporting the computer mpg when you have always reported major errors with these systems.

TFL reported the brakes were part of the braking system so if you don't like that or agree with it go debate it with them like you do the Australian.

"I would still love to see how these trucks do at 80F or even 100F. "

Even pushing 100 trans does not get any higher, fan kicks in and drops to the 190's. This is pulling 33k combined on a steep long grade in the Rockies.