Into the @m*m^2

[Precisionw900]

How can you guys run at such low boost levels?. My 870 will make 20psi at the lightest touch of the pedal. I’m still learning this isx and it’s habits as it’s a new truck to me. In the process of doing a egr tune up and have tried to contact Mr. Hag for tuning without any luck. I would like to make sure everything checks out

[Rawze]

if it has delete programming in it then it could be over-boosting all the time.


Besides that, you have a flying brick... if your worried about fuel economy then you should not have purchased the least fuel efficient truck money could buy.

[Precisionw900]

(01-05-2021 )Rawze Wrote:  if it has delete programming in it then it could be over-boosting all the time.


Besides that, you have a flying brick... if your worried about fuel economy then you should not have purchased the least fuel efficient truck money could buy.

I agree with you no doubt on a w900 being inefficient but this truck stays local with very little use above 60 mph. It was a low mileage, well taken care of and fit what I was looking for.

I’m just new to the isx as all I’ve ever dealt with is the L10’s m11, n14, and a little with a ism. I took your advise and working on a egr tune up right now. The truck cane from Cali so of coarse it had an after treatment system on it. Once removed I had my local Cummins dealer install what he said would be latest update of factory tune for cpl 8285. Should I assume truck is running in top order with just that ? I appreciate any and all feedback. Teach me some thing Rawze. I’m trying to learn all I can.

[Rawze]

(01-05-2021 )Precisionw900 Wrote:  I’m just new to the isx as all I’ve ever dealt with is the L10’s m11, n14, and a little with a ism. I took your advise and working on a egr tune up right now. The truck cane from Cali so of coarse it had an after treatment system on it. Once removed I had my local Cummins dealer install what he said would be latest update of factory tune for cpl 8285. Should I assume truck is running in top order with just that ? I appreciate any and all feedback. Teach me some thing Rawze. I’m trying to learn all I can.

One thing that helps is to keep the RPM above 1500 when you need power. ISx enigne wear much faster when your heavy on the foot below 1500rpm or so.

[Chamberpains]

Am I reading that correctly. You removed the egr system and then had a Cummins dealer update the ecm? If so, you probably have a bad delete or are running the truck in a derated state. Both of which are not good at all for the engine.

Very few people know that there are ecm parameters that need to be edited while the ecm is live or in other words after the base programming is done and while connected to the active ecm. And even less people know what those parameters are... you need to have that engine programming looked at by someone who knows what they are doing. Mommaburt comes to mind. But I don't know how much he's on here anymore.

As far as keeping it below 20 psi while driving. Well that easy but hard to do. Its all in that appendage hanging off the right side of your hip. YOU need to learn how to drive with less throttle and using the proper gear.

When pulling ANY kind of grade the 1st thing you should do is let up on the throttle and gear down. And keep gearing down till you get the right gear that puts you in the 1500-1900 rpm range using approximately 50% of the throttle pedal and gets the boost under 20 psi. Yes, you will lose a fair amount of speed. But the name of the game is engine longevity and burning less fuel NOT winning that imaginary speed race up the hill. You get more of the engine longevity and a little of the MPG gain driving this way. It took me months to learn how to do it and about a year for it to sink in and be the only way I drive a commercial engine pulling heavy weight. It is well worth learning how to operate a truck this way. The huge savings is in what you don't spend in maintaining the equipment because you stopped pushing it to its limits constantly, if ever again. And I do mean huge amounts. Like 10's of thousands of dollars a year in maintenance and down time you DON'T have to shell out. It adds up quick and you get more time to focus on other problems within your chosen business model.

[Rawze]

As far as boost levels go, even when not pulling, that style of big-nose truck will be hard pressed to keep under 10 psi boost going down the highways on flat ground at 60 mph where an aero truck would be sitting at mostly zero (and using a lot less fuel) because it is not fighting those stacks and front end.

Sometimes when I get into a strong headwind, I will see a constant 10+ psi boost where i would typically not see any, just to maintain speed. A square-nose truck would be seeing 20+ in those same conditions. - My fuel mileage drops from 8 down to high 6's, so I can just imagine how bad it would be for someone trying to pay the fuel bill on a truck that did this all the time.

[Precisionw900]

Sorry guys been away from the forum for awhile. Sorry chamberpains I was unclear.
The truck egr is still intact and in good working order, I plan to keep it that way. What I meant is the truck had an aftermarket aftertreatment system added at some point in its life since it was a Cali truck. That system was removed. Before I found this forums and knew any better I had the Cummins dealer update ecm with factory tune to hopefully alleviate any possible emissions tunes in place. Knowing what I know now I have spoke with running rough who has agreed to look it over for me.

Rawze you absolutely correct with it being a square nosed brick. It’s loaded heavy and usually running below 60 mph so fuel mpg is not top priority. The best thing I’ve done so far was getting rid of that terrible meritor 10 speed and installing a new Eaton 18918b, with 3.42 tears it has worked out well. 1600-1700 rpm at 60-63 mph in 17th running loaded. Empty in 18th runs about 1375-1425 rpm at 65-68 mph and I can keep boost around 10 psi and keep it below 15 or so when empty.

I have always been a conservative driver because I have to pay the bills and I’m all about making something last.