Airbox Modification

[jsmith]

I understand that Travel Supreme cut an additional three or four inch hole in the airbox and plumbed it to side. Has anyone had such a modification? If so, did it lessen restriction as indicated by the air minder?

2005 Travel Supreme Select, 500HP Cummins ISM

[justaroamer]

On my '06 Insigna 400 ISL, I elongated my 9 slots and gained almost 50% intake volume which approached the volume of the intake duct. It made absolutely no difference in the gauge even with the new filter. I felt better knowing I had maxed out existing design and surely did not hurt.
I always have anual service done at Cummins Coach Care and they told me the restriction is due to the elbow and that at every service, they pull the filter and inspect because many of the 400 ISL's in motorhomes gauge right at the yellow line, even with a new filter.
My '08 with the 600 ISX has the same factory slots as the '06 and my gauge reads below one half. Seems to me the ISX would like more air, go figure. For now I will not enlarge the slots, maybe if I need something to do.
Don't know if what you propose makes a difference, be interesting what others have to say.

[Larnie]

Same problem with our 42' 2008 Envoy 400 ISL. New filter and gauge and it will max out the gauge within 45 miles. Get approximately 6.7 mpg @ 65 mph. Doing some research with a great diesel mechanic and will report back.