-
ENGINE RPM LIMIT
There has been an unresolved discussion in the past regarding the maximum RPM limit for our engines. All listings of engine specifications list 2100 RPM as a limit for an engine under load. There is a higher no-load limit listed but this discussion related to an engine under load, such as with the Jake brake or retarder engaged.
Supporting the 2500 limit, based on a statement in the Detroit Series 60 engine owner’s manual that states not to allow an engine on cruise control to be pushed by a downhill slope to exceed 2500.
To determine if 2100 is the limit, or if the owner’s manual statement of 2500 is the limit I communicated with Daimler, Detroit Diesel, Williams, American Fleet and Clarke Power. I also asked the question of Kevin Laughlin and Robert Hitt of Prevost Car and indicated any response would be posted on the PC forum. Nobody responded.
I have asked the individual who stated 2500 is the limit to ask the engineer who told him 2500 is OK to put that in writing, but until we receive something in writing from Detroit or a qualified distributor, or Prevost indicating what the limit for Detroit Series 60 is I would urge all observe 2100 as the engine RPM limit under load, which incudes with the Jake or retarder engaged.
This tread will be re-opened if and when written clarification is provided.
-
4 Replies
-
From Robert Hitt, who provided a very comprehensive discussion about engine RPMs the bottom line is as follows:
[Hitt Robert] 2500RPM is not a good situation for this engine, at around 2300 DDC will code an engine over speed fault at 2500 you will receive the second fault. These will go inactive and be stored in the ECU
They are clearly warning you that 2500 could cause serious engine damage!
At 2500RPM and higher there is the possibility of pistons coming out the side of the block.
-
That pretty much sums it up, common sense will prevail. Another thing Robert mentioned was how the coaches jake brake is setup.
For coach we use low and high 2 cylinders for low and 6 for high this was true until 2007 when we went to the holset turbocharger on the DDC. With the new emissions and aftertreatment.
On these engines both Detroit and Volvo Low is all six cylinders of exhaust braking, when set to high we close the sliding ring on the turbo or block the exhaust gases from entering the turbo. This creates exhaust backpressure and supercharges the cylinders with exhaust gas giving us a very effective engine brake.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
Jon,
I see you conveniently left out the following quote by Robert Hitt:
“Second point, the Allison transmission is a beautiful thing!
Allison has some safety’s built in that will make it nearly impossible to do damage to the engine by downshifting too soon and going over the max allowable RPM of the engine. Using the mode button is your best bet, it will put the transmission in performance mode allowing higher RPM upshifts as well as downshifting sooner”.
-
Per,
Reread your comments in which you choose to refuse to acknowledge 2100 is the RPM limit for the engine. It is your comments that state that 2500 is the limit and as said previously you can drive your coach any way you want to, but we do not want relatively new owners to be mislead by your assertions.
The limit is 2100, and because we cannot fix stupid Allison has built in protections against overspeed something your proclaimed limit or 2500 clearly is.
You choose to cherry pick words and phrases that support your interpretation and while how you drive your coach is irrelevant we do not want our members to think anything other than 2100 is the engine RPM limit under load, which includes when the Jake is engaged.
This thread is closed because no more discussion is necessary.
Log in to reply.