Cruise and Engine Brake

[CaptainGizmo]

Just wanted to open a thread to let you know that I’m working with Spartan on an issue with rye Cruise Control.

My config is a 2019 Dutch Star with an ISL (450hp) and Allison transmission. Though I’m sitting on a Spartan chassis, this problem affects the Freightliners as well.

When the Cruise Control is enabled/active, the Engine Brake will NOT go into High even if your speed overruns as much as 25MPH over the set point. The results in your speed running unchecked as you hit a downgrade more than 4%. Once you switch the CC off, the engine brake hits high and the speed starts to decrease.

I’ve identified that the Cruise Control is blocking the Allison trans from downshifting when the CC is active. This has been repeated and Video-recorded under numerous trials.

This is a real problem for us who are constantly going down grades from the Rockies and west; as much as 9%.

I’ve heard of all the “work around”, but frankly, and not accepting this as a normal and safe behavior of the CC parameters.

I’m supposedly going to be doing a field test with Cummins in the near future, in hopes to help with a solution. Whatever happens, I’ll come back and post an update.

 

[sheridany]

@CaptainGizmo
Funny you mention that as I went up and over cajon pass today headed to 58 and while I had decreased the cruise control setting a lot on the downgrade it seemed to hold the speed okay coming down off the pass and both lights were illuminated but I noticed it stayed in the same gears. I wasn’t sure what to make of it so I continued on. So for now is it manual shifting using your rpms as a guide and engine brake as a recommended descent strategy? What about the ascent? Is it downshifting properly?

 

[CaptainGizmo]

@CaptainGizmo
Funny you mention that as I went up and over cajon pass today headed to 58 and while I had decreased the cruise control setting a lot on the downgrade it seemed to hold the speed okay coming down off the pass and both lights were illuminated but I noticed it stayed in the same gears. I wasn’t sure what to make of it so I continued on. So for now is it manual shifting using your rpms as a guide and engine brake as a recommended descent strategy? What about the ascent? Is it downshifting properly?

Listen. Bottom line...the engine and trans work JUST FINE AND AS EXPECTED without the Cruise Control. This is why I refuse to accept this misbehavior with the CC on.

I may be told that “this is for a reason”. However, I don’t accept it because it’s just plain crazy to expect a driver to Compensate in a very unsafe manner when the CC is on.


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[CaptainGizmo]

UPDATE:

Spartan has been meeting with Cummins and Allison on this issue. They want me to take a Cummins tech for a ride so they can data log the switches in Insite and log the J1939 data buss with a CAN tool during this problem.

Hopefully, after the tech ride next Tuesday, we’ll have more info.

After making a video of these events, at least I’m getting some traction and now the experts are agreeing this isn’t very good.

 

[NWIP]

Thanks for keeping us updated on this issue. Haven’t driven our current coach enough to know if we have this issue. On previous coach on FL chassis once speed increased 10mph over cc set point engine brake would engage and speed would reduce to set point.

 

[sheridany]

@CaptainGizmo Any updates on this? Did you do the tech ride?

 

[CaptainGizmo]

@CaptainGizmo Any updates on this? Did you do the tech ride?

Yes we did. It was a brutal day of 60 mph Santa Ana’s with 4 semis overturned on the 15.

We had to wait until they died down enough to get on the grade. Took an hour ride while the Cummins mechanic logged the data from port.

Spartan has been working with the Cummins and Allison engineers ever since. I’ve been told that some of the data they had hoped to get, wasn’t recorded; not sure what the reason was.

As of March 3rd, Spartan continues to keep me updated with a “still researching” email.

I’ll send a tickler and see if anything has changed.


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[CaptainGizmo]

Just got word from Spartan regarding this issue. There's no solution, but at least we know that it is a deliberate setting. Why, they won't say, and it doesn't make sense to me or the mechanics at Cummins. Nonetheless, guess we'll have to move on.




FROM SPARTAN, ON MARCH 18, 2020:
I do want to assure you that our customers safety is our top priority. Any potential safety concern is documented as such and reviewed by our team of warranty analysts and addressed accordingly. I do apologize for the time this has taken to review with both Cummins and Allison, but the transmission preselect condition you’re experiencing has been deemed a normal expectation.

We have investigated this concern with Allison and have found that Allison’s default value is “no preselect with cruise control”. Meaning that if the cruise control is on/set, the preselect feature is disabled from Allison’s TCM and will not downshift the vehicle to assist with slowing the coach. Since this is Allison’s default value, we cannot change the value without extensive testing and will not authorize a change to this parameter.

To eliminate the condition you’re experiencing, you will need to manually disable or cancel cruise control while going down a grade to allow the engine brake and preselect to slow the vehicle.

 

[MapNerd]

Sorry to hear that we didn’t get a better resolution to this, but at least we know and found out without any tragedies happening first. Let it be known, no CC on descents.