VMSpc reading of intake manifold temperature

[Rambling Man]

I am starting a new thread to get input on my intake manifold temperature readings. Before our last trip in the MH I hooked up my VMSpc to our new to us 2010 Holiday Rambler Scepter. Our Scepter has the red 425 ISL complete with the diesel particulate filter and other emission controls mandated by our government gurus in Washington.

When we left the house I was immediately concerned because the Intake manifold temp was not tracking 25 to 30 degrees above ambient temps. In fact the manifold temps hit 150 to 155 and turned my VMSpc gauge to yellow. Having read on this forum that several others routinely measured about 30 degrees above ambient and seeing mine hover at better than 50 degrees above ambient worried me for two days as we traveled from Louisiana to Missouri.

I stopped at a Cummins Dealership in Springfield, MO and presented my situation. After a small bit of discussion, it was decided that I didn't need to worry, that my ISL was functioning properly. The explanation was this:

I have the ISL with all the emission controls attached. One of the emission controls is an EGR (Exhaust Gas Recirculation) valve that dumps warmer than ambient exhaust gas back into the air intake system. This causes the intake manifold to run warmer than a pre emission control engine. The engine technician tried to locate the temps where the ECM would throw out a warning and could not immediately locate, but he thought it was close to 200 degrees. According to him, no de-rating of the engine will take place until after 200.

Based on his recommendation and the performance during our 2000+ mile trip in 90 to near 100 degree ambient I am going to change the parameters in VMSpc upward to keep the yellow warning from showing up and bothering me while driving.

Does anyone on this forum agree or disagree with what the technician told me? By the way my 425 ISL only has about 400 hours and under 15000 miles on it.

[Dutch Star Don]

Rambling Man.....I posted what I was seeing on my non smog ISL during my average driving. I'm a short/light DP at 36" and about 31000 pounds. I'm guessing my numbers would absolutely be lower than yours with a smog motor. I hope I didn't cause you undue stress with my numbers. Yours sound like what they should be.

[Rambling Man]

No stress Don and I didn't want to imply that at all. I did want others to hear that there seems to be an expectation for the pre smog and a different expectated reading for the post smog ISL and to report my findings. I do hope to hear from others with a post smog ISL and to find out that my readings somewhat match theirs.

I have a 40' side radiator MH weighing in at about 37,000 lbs. I have to learn what is normal for my MH if I am to feel comfortable taking off across the country. I think the VMSpc is a great tool and used it with my previous bus, a 2001 Ambassador.

Wiley