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MTSteve · 07-24-2017, 12:42 PM

Thanks so much, macandphyl. I certainly didn't go over that--not really even that close. It's funny, that's a number I've been looking for and couldn't find. I finally called Cummins and the person helping me gave me (after a long search) 3300 rpm, which I couldn't believe was accurate--my tach doesn't even go that high. But I left it at that. Might call them back, though.

The real lesson is that I was slow with my foot. That I can fix.

capnqball · 07-24-2017, 11:22 PM

My 6.7 B series Cummins has a normal red line range at 2600-2800 rpm. On downhill exhaust brake usage I will see as high as 3200-3250 at which time it will shift up a gear, like it or not. I will not let it get that high normally and have only experienced it happening once in the three years plus of usage. Seeing these higher numbers when the coach was new, I checked with several Cummins CSR folks at different times and was explained to me that my engine will actually go to 4200 rpm for a period of 13-15 seconds, at which time exceptionally bad things happen. This goes to show you that these engines will take a lot more rpm than what we will normally see in our usage even if we tried. Just my $.02.
Happy travels all.

Happycarz · 07-25-2017, 02:18 AM

My 2006 Cummins ISL400 engine is governed at 2000 RPM when on the accelerator pedal.

Coming down a hill with no throttle, if I gain too much speed in any of the gears, it will upshift to next gear at 2650 RPM.

As you approach 2500 RPM's, stab the service brakes a short time to slow you down a bit. Let the RPM climb and repeat.

gatorcq · 07-25-2017, 05:32 AM

If you were to overspeed, the ECM would prevent you from re-starting, after you shut it down.
Your Service service light would be on. You can call cummins to verify this.
AND while you are online, asked THEM what are your engine limits.
WOT no Load, WOT w Load
Temperature Limit, ETC.

You can also call your Chassis manufacture too, as they have all of this info.
By the way, this is my first line and second line of knowledge as they ARE the experts.

RKins · 07-25-2017, 06:15 PM

Does the OP have an exhaust or engine brake? No mention of that in the speed reduction dilemma.

Ray,IN · 07-28-2017, 09:32 PM

Quote:

Originally Posted by MTSteve

"Downhill is another story, you should do everything
in your power to never go above 2600 rpm on an ISL."

Governed speed for my engine is 2100/2200 rpm. So shouldn't I not exceed that, in all cases? (In the future I sure won't.) Or are you saying "in reality" I don't have to really worry about damage until 2600 or so?

Thanks to everyone for their responses. I really appreciate the help and the insight.

You should have received a Cummins engine user manual with your MH. It has a section explaining in detail how this all works. Some of the replies do not coincide with my Cummins engine manual, several are almost verbatim. IF everything is operating as it should, overspeeding your engine is not likely.
I will say, it's not a good feeling (pucker factor exponential) when descending a steep grade and the TCM commands an upshift to protect the engine from overspeeding the first time you have the experience. Sure taught me to pay close attention.