Kennedy Custom Tunes MPG Gains for LLY's?

[mjammer]

Are you running the low tune?

Have you verified speedo with a GPS?

The low tune should leave the DIC just as accurate as it ever was.

Yep, running low tune - assuming I have it right, Low is switched away from the notch on the switch?

I checked the odometer via mile-markers on the interstate - two different straight (Indiana) stretches of 10 miles and it was less than 0.1 miles off. Next time I have my GPS with me in the truck on the interstate, I'll check it that way too.

I will be filling up again this weekend probably of at least 1/2 a tank so I'll see how that goes as it will be without a trailer. The error on a partial tank was 3.4% and the error on two full tanks pulling a trailer was 7.8% and 5.3%, The 7.8% was out of town but the other two were normal place, pump, and filled into the neck.

[mjammer]

I did spot check the speedo with GPS once and if I remember right the speed was reading just slightly high but I need to reverify.

[Kennedy]

The best way to check the switch is open or closed. Open is low tune and closed is hi. For the speedo check (sounds like this is right) I prefer to check at 60mph. There appears to be a bit of variance to the "curve" so it could be dead on at 60mph and 1-1.5 off at 70mph. Drop me a note with your name and I'll check over the tune just to be sure.

[mjammer]

The best way to check the switch is open or closed. Open is low tune and closed is hi. For the speedo check (sounds like this is right) I prefer to check at 60mph. There appears to be a bit of variance to the "curve" so it could be dead on at 60mph and 1-1.5 off at 70mph. Drop me a note with your name and I'll check over the tune just to be sure.

E-Mail on its way to you John.

Mark

[mjammer]

Just got 17.1 mpg hand calculated (DIC was 18.2 mpg, fuleeused said 17.6 but took 18.76 to fill it, hence the error). This was a mix of around town, highway, and interstate.

So far seeing good improvement.

[mjammer]

The best way to check the switch is open or closed. Open is low tune and closed is hi. For the speedo check (sounds like this is right) I prefer to check at 60mph. There appears to be a bit of variance to the "curve" so it could be dead on at 60mph and 1-1.5 off at 70mph. Drop me a note with your name and I'll check over the tune just to be sure.

Looks like I may have been running it in High mode. I just checked the switch and if I understand your definitions of open/closed, it was in high. I assume by closed, you mean grounded. I checked it with respect to the ECM case and where I was running, it was a short/closed. When I switched to the other position, it went open, no circuit. I'll run this tank on the other setting and see how it does.

[Kennedy]

Sounds good, keep us posted.

[mjammer]

Will do. The truck just sat for a week at boy scout camp so not many miles though I did tow tge scout trailer packed to the jilt for ~ 80-100 miles. Sitting about 15.4 mpg at the moment but there was some long slow stretches in camp (1200 acre camp) in 4wd.

[mjammer]

Well, I finally got my guages installed this weekend. I have realized I am not as flexible and able to crawl around an engine and cab like I used too They are in and look good. Drilling and tapping is definetely nerve racking. We'll see what the EGT's and boost looks like along with the mileage.

[mjammer]

Well, I just filled up a 1/2 tank after running at the other switch setting and the DIC was still off ~6.5% on fuel used. I got 15.1 hand calc vice 16.1 DIC mpg. This was with a fair amout of trailer pulling so it was some improvement. I need to look at my detailed records sheet later to compare.

[mjammer]

Just did a long haul pulling a two place jet ski trailer and camping gear. I got 16.3 MPG which is ~1.5 MPG better than similar trips in my log book. Still seeing optimistic DIC readings though (~5.5% off). Overall, I have seen an average gain in my MPG of ~1.1 MPG so for and I haven't had any long interstate trips without a load yet.

[Kennedy]

I'm glad that you are seeing good MPG gains, but confused why the DIC reading is off on the Econ tune.

[mjammer]

Yeah, I can't come up with any reason yet either. Speedo & Odometer is dead on compared to GPS. Running ~1-2 lbs boost and 750-800 degrees at 70 MPH pulling a 2500 lbs two place jet ski trailer on a hot summer day. As expected, it does ramp up the boost on inclines. Maybe it is into the higher tune timing changes often enough to throw it. I haven't had a long steady highway trip without a trailer or anything to see if maybe that would show more consistency.

Mark

[JohnC]

Compare the fuel used on the DIC with the fuel used to top the tank. If it is close and the mileage is close the mpg should be close too.

[mjammer]

Compare the fuel used on the DIC with the fuel used to top the tank. If it is close and the mileage is close the mpg should be close too.

Both the MPG and Fuel Used have the error. Prior to the Custom Tune, it had an average error of 2.5% and now its average is ~5.5%.

[DieselDavy]

John,
Trust Mark on this! I've seen the data base he keeps on this truck. It is a work of art using Excel. We engineers tend to be anal. This data is 6db over anal!
I think if John (Kennedy) could take a look at the data, he would see there really is something different with this tune as compared with others who report no change in DIC performance.
Its funny, I work less than 50' from Mark and I get my updates here rather than stopping by his office!
Dave

[mjammer]

Well I finally took a long trip unloaded/no trailer on the interstate/highway and got 22.5 MPG. This is the highest ever by 1.5 MPG and it was the same route almost exactly. Also, the earlier time was with the OEM 245's and not my 265 Revo's. Great numbers!

Still seeing errors vice the DIC but I pretty much knock off 5% from the DIC to know where I stand.

Overall to date, I am seeing ~1.65 MPG better than before with the 265's and ~0.7 better compared to the 245's. Here is the summary to date:

OEM Avg 15.482 MPG
Stock ECM & 265 Revos 14.522 MPG
Kennedy Tune & 265 Revos 16.180 MPG

[Kennedy]

That's the kind of numbers I expect. How fast were you running? It doesn't take a tail wind, but it sometimes takes a bit to learn what helps and hurts economy. I'll have to revisit the DIC thing a bit later. I hate to mess with success, but it still bothers me that it is off like that.

[mjammer]

The trip was a mix of Highway and interstate so a ~10% 55mph speed limit, 20% 60 mph limit, and the rest 65 mph limit. I typically was running 1-2 mph above the limit using cruise control most of the time. It was mostly flat roads. I was seeing pretty low EQTs too. On the trip down, I was seeing ~625 degrees and coming home I saw about 650 (a little warmer outside and I had the AC on some coming home). As far as the DIC, yep, it is annoying but now that I know the trend numbers, at least I can do a quick calculation so I know where I stand.

[Philsauto]

That's the kind of numbers I expect. How fast were you running? It doesn't take a tail wind, but it sometimes takes a bit to learn what helps and hurts economy. I'll have to revisit the DIC thing a bit later. I hate to mess with success, but it still bothers me that it is off like that.

John,

I have a personal fried that has an 05' LLY same as this one we've been following here on the fuel economy thread. I loaned him a Bully Dog to see if we could improve his fuel economy, which runs around 16-17 on the highway. No improvement. But, he drives very aggressively and very fast, around 80mph whenever he can and does not slow down at all for hills. He is also off and on the gas with his foot. I drove with him down to southern Baja California in my hybrid Honda, and my driving was worth about 5 mpg better than his based on nothing but driving style, no big deal in a Hybrid Accord that managed 30mpg over the 1500 mile trip with 5 and sometimes 6 people in it, but it is a bigger deal on the diesel and he puts lots of miles on it.

My question to you is this: Given that we know how he drives, is there any point to trying anything else, like having you write a custom tune? The truck is block stock, 4X4, crew cab short bed. The Bully Dog downloader is the only thing I have tried to help his fuel economy. He still wants to try something else but I'm skeptical. Do you have an opinion?