engine brake vs exhaust brake or both?

[Steve Ownby]

Originally Posted by dengraham

Just to offer more confusion they are telling me I have a turbo brake which its not an exhaust brake with a lever nor a compression brake.

This is a form of exhaust brake. Specifically Cummins uses a variable geometry turbo and the turbo can be used to act as an exhaust brake. It is part of the engine ECM software. Cummins started using VG turns in '03 on some engines but the use as an exhaust brake was started several years later.

[dengraham]

Steve,
Thanks for the response. I was surprised to see it on an ISL but it works well. On my previous ISL I had the compression brake with hi and low but I always just used the low because hi was really a lot of braking power that I never neeed. I understand the turbo normally compresses air into the engine and I guess the turbo then can direct the compressed air into the exhaust. I have seen a video of the turbo but I still don't understand how it slows down the engine... but it does.

[laurier]

Originally Posted by crah

An engine brake is far superior to an exhaust brake. 2 total different things and they both coordinate with the transmission. Not sure what exact engine you have but sounds like you have an exhaust brake. If you have a cummins isc or isb you will have and exhaust brake. A cummins isl can have and actual engine brake with a high low switch, and some isl models also have and exhaust brake. If your coach is the coachmen in your profile, you probably have an exhaust brake. I'm not certain on the cat engines but I'm sure others will chime in. Both will reduce brake usage but the engine brake being the better of the two.

Could you tell me what ISC, ISB and may be ISM stand for?
Are they different types diesel motors or just related to howm many HP?
I do have I believe a ISM . Is it a turbo type? Not much acceleration, probably because of the full MH weight.

[Steve Ownby]

Originally Posted by laurier

Could you tell me what ISC, ISB and may be ISM stand for?
Are they different types diesel motors or just related to howm many HP?
I do have I believe a ISM . Is it a turbo type? Not much acceleration, probably because of the full MH weight.

The "IS" stands for Interact System, which is Cummins name for the electronic engine control system used by the company. The last digit identifies the Basic engine block which in turn will identify the displacement of the engine. There was generally a non electronic engine which used this same identifier in past years.
1. ISB was 5.9 liter, later 6.7 liter.
2. ISC is 8.3
3. ISL is 8.9
4. ISM is 10.8
5. ISX13 is 13
6. ISX15 is 15

Diesel engines due to their inherent characteristics don't accelerate in the same way as gasoline engines. I have heard it described as "gathering momentum". That being said, an ISX15 in a 26 k motorhome would be a rocket sled! If course, generally the ISX goes in a coach weighting 45k.

If you have an ISM you should have a true "Jake" compression brake with a high/low switch and an on/off switch. In my opinion, it's one of the diesel engines best suited to motorhome service.