[Supernova]

Hi Guys, I was just wondering if anybody else has had experiance with poor fuel mileage after a trip to the dyno or if its the fact that the dealer maybe screwed the ecm on my truck.
My truck did return 5.75 us gal mpg for the longest time then after a trip to Atlantic Cat in Moncton NB the truck now is awful on fuel in fact has forced me to park it up. With a total new mpg of just 4.2 us mpg.
The dealer originally in November ran it on the dyno looking for non related issues(a little stumble around 1100rpm) but found nothing, he then adjusted the burn rate on all injectors, flashed the ecm with latest software and then told me that if we put in the heavy haul software the truck will be a better drive and better on fuel. The truck after the dyno session is in their defence a better drive as it pulls like a train but at a cost of almost 2.0 mpg and has boost pressure of almost 60psi. I of course told them about it and they promptly said they would take out the heavy haul software and send me out again to re-check the mpg's. Well after another trip to Cat to remove haul program no difference was noticed! They now have decided that it's got to be Winter fuel and that it's normal for a Canadian truck to be down to 4.4mpg in the winter. I have been doing this work for 7yrs and have never notice winter fuel taking unto 2.0mpg's off your truck and just believe they just don't want to admit fault in case of a compensation claim for lost revenue.
If anybody can point me in the direction of a Cat specialist in Ontario or Quebec that can diaginose a truck instead of plug in and hope the computer tells them whats wrong, I would much appreciate it.
My truck is a 2007 pre emission Peterbilt 379 with c15 acert twin turbo,18 speed, 3.36 rear , 24.5 rubber . I haul light loads in a dry van throughout eastern seaboard.
Need to get this truck back on track asap.

Thanks Guys.

[solo379]

One thing for sure, it's not just a winter. Yes, it's normal to loose up to 1mpg in a winter time, but not 2+mpg. Something is not right here, i'd definatley seek a second opinion, and would start with return to original parametrs. The highest boost i've ever seen on my truck 2004 C-15 is 49psi.

[Supernova]

Thanks for the reply, I agree that winter fuel takes you down a little but like you it does seem excessive. I have posted the question on another forum and the replys are saying its high boost too. I am going to get the cac checked and look for air leaks . It's hard to think winter has robbed me of upto 2 mpg's I think bad tune.
Thanks again.
Supernova

[solo379]

If you got leak in air to air, your boost would be droping, not raising. And considering it starterd after that "tune", i'd start it from there. Tell em to reflash it back to original, and see what's gonna happen. Just make sure everything is back how it was, including fuel to air ratio.

[Supernova]

The Dyno dealer is 120 miles away but has said I can take it to the local cat shop here in town and get them to put the original tune back in, of course no charge. He then went on to tell me I was crazy to go back as it will burn more fuel and that my only problem is Winter fuel and increased idle time, although he could see from the fleet history of the truck that was all nonsense. My idle time over the last 4000 miles is less than 17hrs and was twice that in the summer with AC running.
If I believe what they are saying that would mean on the local rates here where I am located that all C15 owners are running at a loss through the winter months. What a crock of crap .

Thanks for your input sir,

Supernova.

[solo379]

Not a problem. Let us know how the story ends.

[Supernova]

Originally Posted by solo379

Not a problem. Let us know how the story ends.

I returned the Truck back to Cat and they set the truck back to stock original setting (Personality number changed from 53 to 28)
So after another trip out 2300 miles later it would seem that the fuel mileage has returned, The truck now is back to a more respectable 5.3 us mpg average. The terrain on the trip was through the mountains from Scranton Pa through to Pittsburg with a gvw of 78,000lbs so I think its fair to say we did a lot better. Winter fuel will of played a part as would 19 hrs of idle time . In my original post you will remember the Cat dealer told me it would be worse on fuel and I was about to take a big leap backwards from their dyno tune, but I now know that it's simply not true in my application to wind up horse power and boost to increase fuel mileage. I think as for my future plans on the ever quest for fuel mileage and power I need to think a more personal application ecm tune and pay more attention to the simple things like a bunk heater and maybe some new mufflers.
Lesson learnt though... It was better the way it was. So " If it aint broke.. Don't fix it".
Supernova.

[solo379]

Espar could make you wonders! Will pay for itself in less than a year. 19 hours of idling could make a big difference, especially on a such a short trip.

[Supernova]

I wanted to post some results I have had after a tune from Diesel Spec. I decided that enough was enough and I need to either sell the truck for a more efficient aero truck or try a ECM tune.
I can say with no bull that my trip to Smith's diesel in Hampton NB for an ECM tune was the best thing that I could ever do to get the old Pete back in the game and able to compete with newer less aero dynamically challenged equipment. The Owner of Smith's diesel knows the big Cat's very well and put all my concerns to rest. Smith's diesel are the "diesel spec" dealers for the Maritimes and after just a couple of hrs the process was done.
WOW! Night & Day is all I can say. This old girl now hauls ass . The truck is over 600hp and the fuel mileage is around 6.2 us . That's a big change from low 5.0's .
Horespower is a bit of an addiction as is the ever quest for more mpg's and has left me wanting more of it. To quote Mad max, it's all just a question of money so how fast do you want to go?
Yesterday I was loaded at 79,000lb gvw and returning to NB from Quebec , we have some big long mountains to climb up and It just passes all the other trucks with no sweat. It begs the question.... Why didn't I do it sooner.

Ok so after all the good must come some bad right? You quickly find all the weak bits on your truck when you give it some hp. I have installed HD clutch as the oem **** the bed really quickly and the waste gate was a bit seized but nothing too bad . I still have to keep my foot just lightly balanced over the pedal to achieve the best mileage but once up to cruise speed, I just let the truck's torque do the rest.
If you ever had any doubts as to the value of an ECM tune, let this post put that doubt to bed.

Supernova

[solo379]

Originally Posted by Supernova

Hi Guys, I was just wondering if anybody else has had experiance with poor fuel mileage after a trip to the dyno or if its the fact that the dealer maybe screwed the ecm on my truck.

Originally Posted by Supernova

So " If it aint broke.. Don't fix it".

Originally Posted by Supernova

If you ever had any doubts as to the value of an ECM tune, let this post put that doubt to bed.

So, as you see, it's kinda tricky question, with a bit gambling on it. I guess it's all depends....