Threaded Mode | Linear Mode

Bigmack713 · 11-21-2022, **(Subject: Cm871 bad mpg )**

Hello everyone, I recently purchased a 2010 KW t660, Cummins cm871 , 13 speed 3.55 rears on 24.5 rubber. I'm getting a slow ass 4.2 MPGs loaded. I would like to know what sensors are changed periodically that usually hamper MPGs. Gearing seems a bit off since it did not come from factory with the 11R 24.5 tires. Please advise on the things that can be done to better this. Thank you in advance.

Bengy88 · 11-21-2022, **(Subject: Cm871 bad mpg )**

Has it been deleted? If so pm me. Your gearing is off with 355 and tall rubbers. It would probably do great on long ass straight roads at 100mph. The harder your engine has to work to move the truck the lower your mpg will be. You immediately need to remove your entire egr system and clean everything if not deleted. Rawze has good videos on doing this properly. And if you dont know anything about the trucks history i would change every pressure sensor on it.... Even the oil pressure sensor. 871s are getting older and pressure sensors actually do wear out.

Bigmack713 · 11-21-2022, **(Subject: Cm871 bad mpg )**

To my knowledge , it has been deleted. But I don't know what programming is in it right now, I knew the gearing will be off with those tall tires on it.. what all sensors do you suggest I change? I'm familiar with engine work, but all I had before was Macks , this is my first Cummins and I want to learn what makes it tick. Thank you for your response.

Bengy88 · 11-21-2022, **(Subject: Cm871 bad mpg )**

Ok off the rip invest in a laptop and an inline 6 or nexiq adapter... This is the only way you will ever successfully work on this engine yourself. I can refrence where to get insite in a pm. Most importantly i would change the imap sensor and exhaust gas pressure sensor and make sure the tube to it is clear. Connect the truck to a laptop and I or someone else here can pull your ecm file or teach you how to pull it and make sure its got a good delete in it.... As rawze says... Most arent good so always assume yours isnt. And get some short tires or change those rears lol. You will see and feel a huge difference

Bigmack713 · 11-21-2022, **(Subject: Cm871 bad mpg )**

Ok..I will start there..I will look into getting the nexiq , I've heard they work well.Thanks..also , does this engine have a barometric sensor or is it just on the late model ones?

Waterloo · 11-22-2022, **(Subject: Cm871 bad mpg )**

(11-21-2022 )Bigmack713 Wrote: Ok..I will start there..I will look into getting the nexiq , I've heard they work well.Thanks..also , does this engine have a barometric sensor or is it just on the late model ones?

No barometric sensor on our 871's, 870 and 570 have them. If you go with the NexIQ, only purchase from a licensed dealer, like FleetPride, do not purchase from Amazon, or any other on-line retailer. Many of these are Chinese knock offs and will not work with Insite software. The real units will.

Me, unless you have a mixed fleet of trucks, I would head over to eBay and get one of the $250 Inline 6 readers. I have had mine for years, just used it the other day on a friends truck. The eBay units come with the Insite software, you will need a laptop with Windows 7, it will work on Windows 10, but it can be a real bear to install. I had another member install mine, and he knew what he was doing, and it still took an hour+ to do it. If you use Apple products, you can install their "Bootcamp" software on say a Mac Book Air, that is what I use. Just partition the hard drive and install a clean copy of Windows, it works fine with the Inline 6 reader and Cummins software.

Bigmack713 · 11-23-2022, **(Subject: Cm871 bad mpg )**

I'm guessing both the nexiq and the Amazon unit are read only? Can't change parameters like governed speed or tire size?

Waterloo · 11-23-2022, **(Subject: Cm871 bad mpg )**

(11-23-2022 )Bigmack713 Wrote: I'm guessing both the nexiq and the Amazon unit are read only? Can't change parameters like governed speed or tire size?

You will need Cummins C@lterm for that. And it will work with either unit.

Bigmack713 · 11-23-2022, **(Subject: Cm871 bad mpg )**

(11-23-2022 )Waterloo Wrote:
(11-23-2022 )Bigmack713 Wrote: I'm guessing both the nexiq and the Amazon unit are read only? Can't change parameters like governed speed or tire size?

You will need Cummins C@lterm for that. And it will work with either unit.

Again , thank you .I will start with the basics and keep you all updated.