Isx15 motor needs more get up and go

[Waterloo]

(04-24-2021 )Cornbreadtrucker Wrote:  Truck is a 2014 579 Peterbilt with a isx15 cummins set at 455hp 1650 torque I had Tramission converted to a 13 from a 9 it’s got 3:42 rears. Motor rebuilt 170,000 miles ago it’s got 673,000 on truck I don’t want a ground pounder I just want little more pulling power and it don’t have to be deleted. Overhead ran 2 months ago.

First, the motor, what is it, a 455st or a 455? I am assuming a 455st. And I am assuming it is a CM-2350 motor? Open a Cummins Quickserve account, you will need the ESN or EIN (Engine Serial/Identification Number) off of the motors data plate, which is found on the valve cover on the driver side of the motor. You will need the EIN to open this free account, and it will give you access to everything regarding your motor, from trouble shooting to complete engine tear down and assembly, along with an entire parts list with part numbers, this is the same information that Cummins uses in their shops, we have full access, use it, do that right now. https://quickserve.cummins.com/info/index.html

Also, regarding the program settings from TMC that may still be lingering in the ECM, if you are going to keep this truck, you will need the Cummins Inline 6 reader and the Insite software, I would recommend ordering that right now, most all of us purchased ours on eBay, around $300 for the kit, here is a link to one... https://www.ebay.com/itm/254353420216?ha...SwG4Be7xPe

Another thing you can do while you await the Inline reader kit from eBay, is take the truck to the local PACCAR dealer and have them update the ECM software to the latest available from Cummins, have them put the standard factory program in, overwriting what TMC has installed. I would do that, as then you have the most up to date software which should turn off any of those terrible settings TMC has installed if they are still there. Now you have a clean slate to work with, and I would not think twice about having that work done, just do it. They normally charge a few hundred dollars, do it.

Your other issue is the gearing in the rear end, I have the same gearing in mine. You can overcome many of the issues if you can keep the rpm above 1500. In mine, I normally run in the 1600 to 1900 range, and use the instant mileage readout, along with the turbo boost gauge to monitor fuel economy. I try to run the boost between 0 and 12 psi, let the engine do the work, not the turbo. I have found that running between 55 and say 63 mph is where I have the most power and fuel economy. DO NOT lug this motor, or you will be in serious trouble, to the tune of tens of thousands of dollars when a liner busts loose and you take out the head. When under a load, KEEP THE RPM ABOVE 1500 RPM!

This is what happens, you lug that motor with a load, say down at 1200 or 1350 rpm, the motor is now fighting against itself internally. This is due to the engine design, when you lug the motor the lateral force of the pistons and rods puts undue pressure on the cylinder, or liner walls. The liners sit on a very tiny ledge, about 3/16th of an inch. The only thing holding these liners in place is the weight of the head and that tiny lip they sit upon. You lug the motor, you are now hammering those liners loose, they fail, and it is in frame time.

With your 13 speed, I would run that in high seventh gear for the best performance. And stay away from the cruise control. About the only time I will use mine is bob tail or in the flats with an empty trailer with a tailwind.

As far as moving away from a traffic lights or stop signs, only fix there is to re gear, 3:55 or 3:70ish, depending on what you are doing. Me, I can live with mine, as I do not care anymore and am not in a hurry, so I live with it and compensate with my transmission. The fuel savings alone is worth it to me to go slow and steady, you can easily shave hundreds a week off of your fuel bill by running like I do, and others here.

Now, the motor itself, I assume you still have the emissions? I hope you do, there are too many butchers out here as Rawze stated, you want a clean slate to work with, and not some butchered up piece of equipment. The EGR tuneup, do that now too, replace the Intake Manifold Pressure Sensor and the Exhaust Back Pressure Sensor. I would assume you will need a proper overhead, or valve adjustment, that is something these outfits like TMC rarely ever do, they are simple to do with the correct tools, there is a video in the video link at the top of the page on how to do one correctly.

Now, the monster in the room, the FUEL PUMP! If that is still painted red, you are driving a ticking time bomb. Myself, I would have it rebuilt, or do it yourself. These pumps are still failing and taking out motors, like boat anchor damage, destroying the block and crankshaft. Nothing to play with, rebuild every 400,000 miles, or sooner. I would do that now too, rebuild it or replace with a new one, so that YOU KNOW exactly when it was rebuilt and can prepare to do it again down the road, do not tempt fate and ignore this pump.

The mandate, myself, I would go see Mr Hagg and let him fix your truck, fix the programming, install the proper gauges, run the overhead, etc... Let him go over the motor. He is located just South of Atlanta in Griffin GA. Mr Hagg is the only shop I would trust in this country to do this work.

Haggai Automotive and Diesel Repair
1228 High Falls Rd, Griffin, GA 30223
Hours: Opens 8AM Mon
Phone: (678) 688-8107

I know, this is a lot to chew on, take it one step at a time, grab this bull by the horns before it bankrupts you. I don't know how old you are, or how long you have been in this trucking or owner operator racket, but these trucks are not the same ones I started with back in the late 80's. Changing oil, greasing them and general maintenance are now a thing of the past, these are complicated machines, but easily understood with a bit of study.

Me, I would take the truck to Mr Hagg, that is your least painful option, but still purchase the Inline reader and software, as that will keep you out of the shops and away from the thieves that populate those places. Many times a sensor will fail, you go the dealer and they will insist it is a bad turbo or EGR Cooler, they can clean you out in a few seconds, when all you needed was a $55 sensor that is easily diagnosed using the Insite software, that kit just paid for itself.

OK, I'm done... We are here to help, take advantage of the years of experience here, and trust me, most all of us have our own horror stories regarding these Red motors, use our knowledge to your benefit, and welcome aboard!