Fuel Economy on LB7

[20050824|7|006327|000000|216.230.93.198]

I have a 2003 Duramax that was consistently posting 16-18mpg on it. I had it hit 20mpg several times even. The truck has 20000 miles on it and all of a sudden I can't get better then 14 or 15mpg. Any clues? The only thing I changed on teh truck was I went to a 285/75/16 after I wore out the 245/70/16's. The tire size can't make that much of a difference on this truck can it?

[quadrunner500]

I may be able to solve this mystery.

Unless you recalibrated your speedometer when you went to the larger tires, your odometer will be understating the mileage by 11.3%, thus your computed fuel economy is low by the same amount.

[silverback]

quadrunner500 is right, it's the taller tire. One rotation of the new tire is a greater distance then the OEM tire, but the computer doesn't know that. So it's under reporting your miles. I have 265s on my truck and it's one of the reasons I'm leaning toward getting a Hypertech programmer. It can recalibrate your tire height. My Chevy tech says they can do it at the dealership, but it's not persistant (doesn't write to the flash memory) like the after market programmers.
KL

[WanaDmxsub]

The Predator and I think(?) all the other programers, that adjust for tire size, will only adjust your speedo. You will still need to adjust the mileage with currection factors for your tire size.

[DmaxMaverick]

I don't know about Hypertech or Superchip, but the Predator will correct both the speedo and odo. The Juice/Attitude will only display corrected speed on the Attitude display, leaving the OEM speedo uneffected. There is also a buffer available through TruSpeed and one or two others, but they are nearly as much $$ as the programmers. IIRC, there have been some issues with the buffers that cause problems with the ABS and other systems.

[mdadgar]

You probably want to read this (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=007536) thread before you buy a Predator.

- Mark

[DmaxMaverick]

Easy now, StrangeEngine.

Yes. ONE user is having an issue. No doubt about that. I do have doubts as to the cause. Of the many programmers known to be used by members just on this site, to only have ONE issue would surely be a feather in someones hat. I am not conviced that the problem he has is caused by a programmer. There's more to that story than is being told. Certainly, it could be exaggerated by it. I think whatever problem he has would have surfaced sooner or later, Predator or not. Even if it was caused solely by the Predator, every good product will fail at one time or another. Can't tell you how many problems I've had with Holley carb's, and its still the world's leading seller. I've been using a Predator and have had no problems. It works as advertised. Simple as that.

Sorry. No, the sky is not falling.....

[mdadgar]

He's NOT the only one who's had that problem. It is NOT being exaggerated.

It DOES eat the PCM, which then requires replacement.

- Mark

[DmaxMaverick]

Slow down a little. I'm not saying at all that it's a perfect product, nor will there ever be any such thing.

I did not mean the facts were being exaggerated, but it is possible that the Predator had exaggerated an existing condition. It has not been established that the Predator caused the issue.

I read that post on the day it was originally posted and tried to duplicate his results. I could get the error, but only if I didn't install the program per the instructions. A voltage drop, by engaging power hungry accessories, was required. And then, it was only on a cold engine. The glow plugs and heat grid were cycling the whole time. I was able to recover the system by installing the program as per the instructions.

I have not heard of any other catastrophic failure of the PCM while using a Predator. I am still not convinced that the Predator was the cause of his problem. It doesn't sound like it helped it any, though.

My point was, it is not prudent to call foul because of a very limited claim of problems with a product. In the same light, I know of many [former] Ford Pinto owners that didn't blow up, many 70's - 80's GM truck owners that didn't blow up, and several Firestone tire users that didn't blow up. The only thing that blew up was the stories. Warning labels on products are for people that have a reason to not know better....and for idiots.

I would like to know what facts you have that establish that a programmer "DOES eat the PCM, which then requires replacement". The programmer works. That is not to say there will be no manufacturer's defects at some time. GM (or any OEM) is just a subject to those rules as anyone. Just read the forums, here and elsewhere. It's easy to blame a tire manufacturer for a poor suspension design. The bigger dog won that fight.

Don't take anything personal. I didn't mean it that way.

[mdadgar]

You've now heard of a second catastrophic failure.

- Mark

[1BADDMAX]

I've been using the Predator for over a year now and just recently upgraded it to 1.11. I have never had any problems programming with it. I think if you have any problems it's due to weak batteries or some other electrical device draining power while it is programming.

[DmaxMaverick]

You've now heard of a second catastrophic failure. Have I? Not yet.

This is off topic, but you brought it up. Give up some detail. Enquiring minds want to know. Empty claims aren't close to facts. If you make a bold statement that will likely cause a negative effect involving a popular product, especially with a DP advertiser, it's your responsibility to bring the facts to light.

[mdadgar]

Sorry, no. It's distinctly possible that my dealer reads this site.

Diablosport has all the details - you can ask them.

You are welcome to send me a PM about it, but it appears that the PM functionality has been disabled on this board. Bummer.

- Mark