cooke95 Report post Posted October 11, 2011 Saw here recently of a "reprogram" for the Cummins 400 ISL that will upgrade to 425 HP. Is it that easy? How about problems because of the reprogram. If none where can we get it? Share this post Link to post Share on other sites
wolfe10 Report post Posted October 11, 2011 Suggest you give Cummins a call with your engine serial number. Cummins 800 343-7357 Share this post Link to post Share on other sites
cooke95 Report post Posted October 12, 2011 Thank You Shall Do! Share this post Link to post Share on other sites
larryanelson Report post Posted December 5, 2011 Newbie I have a Cummins ISL and Allison 3000 trans in my Country Coach 38' with a tag axle.. I had a private shop set my up to get better mileage, which I gained 7 to 8 tenth MPG over the last 40,000 miles, and I have 395 HP to the ground . They said I would get better MPG initially and I was hoping but at $3.80 per gallon every little bit helps. There are very few grades that the trans will shift lower then 5 gear in the western part of the US Canada and Alaska, Larry Share this post Link to post Share on other sites
hermanmullins Report post Posted December 5, 2011 Larry, Welcome to the Forum. If you don't mind me asking, what did it cost for the shop to reprogram you ISL? I am assuming that you had a 350 HP Cummins? What were you getting in MPG before the reprogram? At present time I am getting 6.7 to 6.9 MPG from my 400 ISL and a increase of almost 1 more mile per gallon might be worth looking into. Thanks Share this post Link to post Share on other sites
larryanelson Report post Posted December 6, 2011 Herman As I said in original post I have a ISL 400HP. I am getting 390 HP at the pavement. There is a loss of horse power through the Transmission and differential etc. This 390 HP was on a dynamometer. Before the tune I was getting in the low 7MPG. Just returned from Boston and Washington DC, the fuel mileage for the total 7600 miles was 8.1 MPG. I am towing a Jeep Liberty. I try to maintain between 60 to 65 MPH and the correct tire pressure on the coach and the Jeep. It cost a Grand 3 years a go, I have heard that they have had an increase.. Performance Diesel Inc St George, Utah. Larry Share this post Link to post Share on other sites
