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DDlighttruck · 07-22-2017, **(Subject: 2003 ISX suggestions needed )**

2005 IH 9900i with an ISX 500 hp, 13 speed, 3 axle truck. Motor was replaced last year with an '03 model, 450 hp. I bought the truck from a friend of mine who had it probably 7-8 years, and was the one who had the motor done. I believe he said the only difference was the turbo actuator. I've been running it OTR about 6 weeks now. I am a brand new O/O, and this is the first ISX I've driven, we do have a KW with an ISX I've driven for a couple hours.

So a few things- I believe it's got some turbo cough. Sometimes when under load accelerating, usually just once, sometimes when you take your foot off the throttle to downshift, usually only once or twice.

Turbo boost drops off when pulling a hill under load. It'll go to about 30 psi, then as you're pulling drop to around 15, might go back to 30, then back to 15, sometimes it loses enough boost/rpm you have to downshift and repeat the cycle.

I had it run on the dyno on Thursday at Cummins. They said fan on it was putting down 330, fan off 350 hp. They said spec was 340 hp fan on, so it was a little low. They said the exhaust gas pressure was bouncing around while they pulled it and recommended a borescope to check the nozzle.

I didn't have time to get more work done. They say I can reflash it to 500 hp, 1650 tq stays the same. I had originally booked it in for an overhead, but they said if you're coming in for power loss, do the dyno first to see if you are actually short power. So ok I said lets dyno it.

I'm youngish and want to run hard, I want excellent fuel mileage, I want to be able to pass uphill loaded and I want it to be reliable, all which don't go hand in hand. I'm not really interested in deleting anything just yet, but I would like more balls. I don't know what turbo coughing means for turbo health, but I'm hoping for some guidance on where to either focus my energy or money. I can fix a lot myself but some I don't mind paying for. I'm still thinking an overhead should be my next step, but a turbo inspection isn't a bad idea either.