Community Forums

KIX · 02-12-2013, 08:14 PM

I just re-read the #1 post that reported gear shift is at 2200rpm on an ISC. My ISC shifts ~ 1550rpm. My understanding is that if there's not much load then there won't be much boost either. Could Jeff's whole problem lie in the high shift point?

Mike Canter · 02-12-2013, 08:37 PM

Shift rpm depends on load and how hard you have your foot down on the floor. I would suggest that your loaded wide open throttle shift point is higher than 1550 rpm because your peak horsepower is at a higher rpm than that. If your ISC shifts at only 1550 at full load with a WOT then that would indicate that you have a problem

KIX · 02-12-2013, 08:53 PM

Quote:

Originally Posted by Mike Canter

Shift rpm depends on load and how hard you have your foot down on the floor. I would suggest that your loaded wide open throttle shift point is higher than 1550 rpm because your peak horsepower is at a higher rpm than that. If your ISC shifts at only 1550 at full load with a WOT then that would indicate that you have a problem

I didn't get from any of the OP's posts that he was operating at WOT. And, I agree that under WOT it will shift at a higher rpm. I was just offering a suggestion and I'm no where near as positive as you seem to be.

Mike Canter · 02-12-2013, 09:24 PM

The specs on that motor show that 2200 is right about at the WOT shift point. In 2001 the engine is governed to a max of 2500 rpm. The newer motors where governed down a little lower to 2200 rpm. It is easy to be positive when you are reading the Cummins spec sheets on the motor. I just thought it was a little confusing to throw in a 1550 rpm shift point and to say that the OP's problem could be because of a too high of an rpm when it is within specs.

KIX · 02-12-2013, 10:04 PM

Quote:

Originally Posted by Mike Canter

I just thought it was a little confusing to throw in a 1550 rpm shift point and to say that the OP's problem could be because of a too high of an rpm when it is within specs.

Mike, I didn't say his problem was due to shift point. Re-read my post #29. I simply posed a question.
And still.......how do you know from the posts in this thread that he is operating at WOT?

wb7auk · 02-13-2013, 04:48 AM

Quote:

Originally Posted by Mike Canter

If the boost sensor is bad then you will get a Check Engine Light.

Only if it is not working at all, if it just reads very low no light.

Mike Canter · 02-13-2013, 05:00 AM

KIX the only way you would get a shift at 2200 rpm would be to be at WOT or very close to WOT.

Art, the diagnostic computers also use logic that would expect a certain resistance or voltage through a sensor and would detect a sensor that was not totally failed but was partially failed.

wb7auk · 02-13-2013, 05:08 AM

Art, the diagnostic computers also use logic that would expect a certain resistance or voltage through a sensor and would detect a sensor that was not totally failed but was partially failed.[/QUOTE]

Mike, if this was true then none of the MP-8 and other such chips would function as that is one of the things they do, tell the computer the engine
has less boost than it really does.

Mike Canter · 02-13-2013, 05:13 AM

There are numerous ways to do that without setting off the check engine light. It is done all the time when chipping cars. The most common way is with software so the diagnostic part still works.

wb7auk · 02-13-2013, 05:27 AM

I agree there is more than one way to skin a cat as they say.

larry koenn · 02-13-2013, 05:41 AM

Ok all this is great - but I would get a spray bottle of soapy water - get the wife to hold the pedal at 1200 and spray it all down and find a posible leak - if there is one

rssnape · 02-13-2013, 05:57 AM

I don't know about these engines but as the turbo is a mechanical device the only way for the ECM to limit its output is with a waste gate valve to dump the excess boost. I would suggest that there could be a problem at the waste gate if it indeed has one. It could be stuck partially open.

Jeff753 · 02-13-2013, 06:54 AM

Quote:

Originally Posted by rssnape

I don't know about these engines but as the turbo is a mechanical device the only way for the ECM to limit its output is with a waste gate valve to dump the excess boost. I would suggest that there could be a problem at the waste gate if it indeed has one. It could be stuck partially open.

All great info and much appreciated. I will also check the waste gate. ( I have a PAC brake). I presume there will be some linkage. I don't really recall if I was wide open throttle shifting at 2200 RPM. I may have been since I was trying to force higher boost. I will check again on the 20th when we pull out of Disney. When I reported the 14# boost/2200 RPM SHIFT and 109 temp manifold I was just providing some info for the experts like Steve and Mike. I didn't even know the manifold temp was incoming air.

I presume I can soap test at 1200 RPM with no load? I will also closely inspect CAC when I can get the DW to clear out the closet floor

I thought the coach was just doggy since I had no other to compare it to. I lose 10 mph on cruise on Florida hills

so knowing I may get more boost is encouraging although finding the problem and fixing it may be expensive. I will pull the filter and closely inspect hoses and see if I can find what a waste gate looks like. If I cannot find it and fix it I am taking it to cummins anyway. Perhaps I should have mentioned earlier Cummins told me I have a leak in my lift pump ($600) that I need to get fixed also but I was under the impression the lift pump only works at start up. Perhaps that is also my boost problem?

Anyone have a preference with cummins south at either Ocala, Tampa or Orlando? I've used Ocala once and thought they were fine.

Again thanks for all the great post!!!

Jeff

RustyJC · 02-13-2013, 07:08 AM

Quote:

Originally Posted by larry koenn

16.7 C is about 60 F

An ambient air temperature of 16.7C is 62.06F since degF = (9/5 * degC) + 32. The 32 has to be added to reflect the offset between C and F temperature scales - the freezing point of water is 0C or 32F

A differential temperature of 16.7C does NOT require the addition of the 32 degree offset; therefore, a differential temperature of 16.7C is 30.06F, as stated correctly by Cummins.

First things to check for low boost:

1. Plugged air filter
2. Plugged fuel filter(s)
3. Leaking intercooler piping (from turbo to IC and from IC to engine)
4. Cracked/leaking exhaust manifold
5. Stuck wastegate on turbocharger.

Rusty