View Full Version : Kennedy Custom Tunes MPG Gains for LLY's?
I am looking at getting the Kennedy Custom Tune ECM for my '05 LLY, especially with the cost of fuel now as I think the return on cost should be pretty easy with the $4+ fuel costs now. I would like to know what some have seen, especially with the '05 LLY's to make sure I am not getting my hopes up too much. The average since I bought my truck is right at 15MPG but through the winter it drops to high 13's. This is a moderate amount of around town, shorter drives as it is my everyday vehicle (~6 miles to work). My longer runs are usually pulling either a 2500LB jetski trailer or a 3500Lb Boy Scout trailer. I also did take a hit of ~1MPG when I switched to the 265 Revo's, even when adjusting for the difference. All this is hand calculated too.
Thanks for any info.
Mark
More Power
03-21-2008, 13:15
If you haven't already done it, track you fuel economy over several tanks of fuel, then contact JK about his economy tunes. If given an accurate evaluation, JK will likely provide some assurance for the advertised mileage gains. All vendors are on the hook regarding their product's ability to deliver the gains.
Jim
I have the whole history of mileage on my truck except for 1 or 2 tanks. I am confident John stands behind his products. I was wanting to hear from others what they have had as far as long term experience and maybe their before/after #'s. If I could get the 19-20 MPG John states on his site, I would be thrilled but he doesn't say what it was before or what cases that was in. I do a lot of around town driving of trips less that 10 miles - lousy scenario for a diesel but that is a lot of my trips when I am not camping, boating, or out with my son's scout troop. Just curious. Maybe I'll just send JK my whole truck history spreadsheet and see what he thinks.
Thanks.
Philsauto
03-24-2008, 20:47
I have the whole history of mileage on my truck except for 1 or 2 tanks. I am confident John stands behind his products. I was wanting to hear from others what they have had as far as long term experience and maybe their before/after #'s. If I could get the 19-20 MPG John states on his site, I would be thrilled but he doesn't say what it was before or what cases that was in. I do a lot of around town driving of trips less that 10 miles - lousy scenario for a diesel but that is a lot of my trips when I am not camping, boating, or out with my son's scout troop. Just curious. Maybe I'll just send JK my whole truck history spreadsheet and see what he thinks.
Thanks.
I have bought stuff from John, but I went with stock stuff for my programming. They are not all the same. I have the LB7, so what I have experienced may not apply to the LLY but I hope to find out. I got no fuel economy improvement from Edge, set on levels 1, 2, or 3. I installed the Bully Dog Triple Dog and got no improvement on level 1, but picked up 3 mpg on level 2 on highway driving. But around town, I could not detect any difference. I get 13mpg around town (I'm worse than yours with a 3 mile drive to work). On the road, with the Bully Dog on level 2, I get 21-22. The best I got with the Edge was 18.5.
Do you have a Bully Dog "Tri before you Buy" dealer nearby? The Bully Dog website will direct you to the nearest dealer if you do a search. Bully Dog will allow you to install the program for three days or 10 engine starts for free, at which time the program will expire. The trial program is on level 2, which is the one that gave me highway mileage improvements. The other possibility is if you have a local dealer, ask him if he will let you leave a credit card number and try the programmer for 15 days. In exchange you will provide him with accurate information of fuel economy. If he is like me, he'll jump at the chance to get some solid data that may help him sell programmers.
I really want to chase this economy issue as the price of diesel does not look like it is going to come down. I am about to make a 3000 mile trip hauling a two axle enclosed trailer from Hemet, California to Walla Walla, Wa, and on to Seattle, Wa, and then back home. I mapped out my route and checked fuel prices on the internet. The best price I found was in Pendleton, Oregon, $3.78 a gallon. The average I am going to have to pay is over $4 a gallon. I plan to play with the Bully Dog and Edge programmers on the trip to get some mileage comparisons. I would like to market the Bully Dog product based on mileage improvements, but it is a scary thing to do unless you can back it up with personal research.
Have you read the product review here:
http://www.thedieselpage.com/reviews/jkecm2.htm
I'll be right up front on the MPG. I make no promises, but I regularly hear "best ever mpg" reports. My 2005 would run 17-18 at best using everything short of what I list below. It now runs well over 20mpg. I've seen 22+ pretty consistently. Here are a couple of keys to maximizing mpg from any tune:
65mph or less (wind is the biggest killer)
No lifts (wind again)
No wide tires
Good quality fuel and additive
Synthetic lubes
Less trips (warming up takes fuel)
That said, my 2005 LLY despite being a larger truck is my best mpg producer. My tune is responsible for the single largest gain.
As for the Tri-Buy thing, I do not recommend it. This will leave skeletons in your ECM. You can't put code changes into an ECM and expect it to dry up and blow away after a period of time...
John, what kind of difference do you notice pulling with your tune? I know MPG's are never promised, but have you noticed any MPG towing difference.
My towing is so varied it's hard to say. When I go out on a long tow I carry my Aux tank which only allows approximations. Carrying 90 gallons aux and 34 gallons main (never able to use it all of course) I run over 1300 miles. This puts me in the 11+ range towing my 2002 on car trailer which puts me around 20k combined with a LOT of tongue weight. This is running at 5 over posted speed most anywhere that road conditions will allow, and has been done on trips to the DP Pull off, Weekend on the Edge, etc. so we are talking 75mph and up across teh Divide, etc.
I towed this load once in state, and if memory serves it was around 14mpg. I think my tractor on trailer in state runs around 15mpg at 17k-18k combined.
Philsauto
03-27-2008, 12:47
John is towing heavier than I did on this trip but I have my fuel mileage for the first leg, Hemet to Walla Walla Wa towing a two axle 12 foot U-haul (low profile) with about 4,000 lbs in it. I estimate my total weight at about 13k. My average mileage with the Bully Dog on level 2 was 16.8mpg, hand calculated, 1100 miles. My best mileage, between Fallon and Winnemuca , Nevada was 18.7 but that is about ideal terrain for economy, perfectly flat, no head wind. I bucked a head wind from Adelanto to Fallon and mileage was 16.3.
I decided to try towing on level 3, and quickly decided that was a bad idea. I made a decision to pass a truck on a pretty steep grade, kicked it in the pants, and roared around the truck. The Allison did not like the treatment, the Edge kicked in and defueled, I lit the check engine light and set a code P0700. I had to pull over to the side and shut down, clear the code, and take off again, which of course gave time for the truck to pass me again. Now that was a waste! I decided towing on level 3 is not a good idea and backed down to level 2.
In general I am extremely pleased with 16.8 avg mpg while towing. I kept the speed around 60-65, as the towing limit in California is 55 and the limit on all of Oregon's back roads is 55. A CHP pulled up next to me on 395 when I had the cruise set on 62. I figured it was a waste to back off, he would either let me go or ticket me for 62, but I guess he decided I was within a reasonable allowable speed.
Cheapest price for diesel was $3.91 a gallon. Ouch!
Thanks for the replies. I had read the article John as well as everythig else I could track down. The only reports I had seen posted besides the article was Rinkers. It sound slike it might be time to take the plunge.
Just sent one down the road last week:
"On the way back from leaving I got 20.5 hand calculated." (unsure the vehicle speed)
Mileage before: Between 15.5 and 16.5 going 70. the best I ever got going 60 and babying it was 18.3
Sounds like this might be a good use of my tax rebate. Got to keep the economy going, right?
I need to replace my air filter too, would you recommend an OEM or the Uni-Filter Foam? I was checking my Total Power supply and it is low too. Might need a bigger rebate ;)
I prefer the Uni as noted in my Tech Tips. You might consider teh air box shrouds from www.coolmyduramax.com as well. I've been hoping Chris would make a set to work with the Mega filter as well. I would definitely suggest waiting to cut the box until you get the shrouds though as my mods are a bit aggressive for his shroud containment.
mark45678
04-06-2008, 06:21
I am running JK performance/tow tune , I see 1 mpg better towing and about the same empty. I do think it would be better but its hard to keep your foot out of it . Run really good compared to all other edge products I have had in the past. Low end TQ gains are really noticable when your towing
Well, I just ordered the custom tune ECM so we'll see how things go. Hopefully I can get it in and installed before a trip I have to Kentucky in a few weeks pulling a trailer for a boy scout trip. Looking forward to it. I also picked up a guage package seeing I was going to be crawilng around the engine and dash anyway.
I just got the UPS notice that my ECM and Guages are on the truck for delivery. I think I might be coming down with something and need to go home sick from work ;) It might be the ECM Install Flu :D
ECM is installed. A pretty straighforward job other than just learning my way around the engine compartment and dash. Note to all, don't install it when it is almost 90 and humid - lots of sweat dripping all over :p
I'll be filling up the truck tomorrow to start tracking the mileage (after I step on it hard once or twice on my way there just to see how the performance feels before I go back into fuel miser mode). ;)
Just as an FYI, here is the averages I have seen to date on my truck. I'll keep you all posted as I start getting data on the Kennedy ECM tune. First tank fill-up was this AM and I will be pulling a trailer on a 700 mile round trip next week so we'll see how it does.
Miles Gallons Avg MPG
OEM Avg 20961.7 1360.7 15.405
With 265 Revos & w/o ECM 15128.5 1039.4 14.555
With 265 Revos & w/ECM 0 0 0.000
Lifetime Average 36089.6 2400.1 15.037
DieselDavy
06-22-2008, 17:39
Mark,
Any reports for us now that you are back from your first trip?
Dave
I have done a couple tanks and have seen some improvement. I did two tanks pulling a 3000# boy scout trailer as well as my truck bed full of gear and 6 people in the truck. I got an average of 15.2 MPG on those tanks. The closest similar trip I could find in my log I got 13.9 MPG. My current tank is lookig good too but will need to wait til I fill it up.
One thing on the down side so far is the DIC MPG estimate is way off as is the estimated fule used. Both are running off almost 6% as compared to hand calc and fule pump readings. We'll let it go a tank or two to see if this changes otherwise I'll get John's opinion.
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.
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.
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.
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.
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
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.
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.
Sounds good, keep us posted.
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.
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.
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.
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.
I'm glad that you are seeing good MPG gains, but confused why the DIC reading is off on the Econ tune.
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
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.
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
08-08-2008, 09:35
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
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
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.
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
08-15-2008, 07:30
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?
He could well see some benefit, but it's hard to say. Experience tells me to stay away from this one. The quest for improved fuel economy requires driver participation and understaning to be effective. At the very least he'll need to use cruise control to steady his speeds. Slowing down will also definitely help.
Phil,
My first recommendation, besides obviouslt telling him to take it easier on the throttle, would be to install a set of guages. It becomes obvious when you are pushing the engine harder than necessary when you see that boost ramp up and the EGT's climb. Once he sees that, it might help him change his ways, then go for the custom tune. Also, I would hard wire his to the economy tow mode so he can't play with the performance setting because he would love that power too much to stay out of it :D
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.
Did you get a flash update from your dealer? I did in June 07 and since then, my DIC fuel used/mpg has been off by roughly the same amounts as you post... I run 100% stock. I've been back to the dealer numerous times since, but all they do is shrug shoulders and tell me that there is no new update from Chevy.
cheers & beers,
Chris
No changes recently from the dealer. It hasn't been in since I got the Kennedy Tune put in and I have the OEM ECM module for when I do
I thought I would post an update. Here is how the numbers are looking to date:
OEM Avg 15.482 MPG
Stock ECM & 265 Revos 14.522 MPG
Kennedy Tune & 265 Revos 16.172 MPG
I have ~4700 miles on the ECM to date and have been very please with the improved mileage and it will get up and go with much more gusto if you want it too, especially if you flip to the high perf tune.
The guages also really help me monitor the suttle changes when I am driving to help me find the acceptable speed vs. MPG throttle setting, especially when I am pulling a trailer. You can quickly see when you are pushing it harder by watching the boost and EGT temp climb.
Time for another update. Here is how the numbers are looking to date:
OEM Avg 15.482 MPG
Stock ECM & 265 Revos 14.522 MPG
Kennedy Tune & 265 Revos 15.929 MPG
I have ~8800 miles on the ECM to date. I am still very happy with the tune as far as mileage gain and drivability. I periodically pull trailers and it is much smoother and easier with the tune. Of course, every now and then I just have to flip the switch to performance tune for a few miles and :D
Have you been able to duplicate the 22+ mpg on any other trips?
Have you been able to duplicate the 22+ mpg on any other trips?
Nope, haven't been able to duplicate it but I also haven't been on a trip like that sinc either. I have only done one long, no trailer trip since then and it was in the dead of winter over Christmas to the upper peninsula of Michigan so it wasn't the best of weather. I did get 18 & 18.6 on that trip.
I am still seeing the DIC being off. I was looking at it recently and was wondering, is the tank size stored in the ECM ans it seems like the Fuel Remaining is off from reality as if it thinks it has a 30 gallon tank vs 34 or something.
Mark
Have you been able to duplicate the 22+ mpg on any other trips?
John,
I just got back from a trip up to Boundary Waters (Ely, MN) and got great mileage. Over 4 fill-ups and 1575 miles I averaged 20.98 mpg. This was with 5 people and gear in the truck and running at to a few MPH over the speed limit most the time. :)
Mark
Just another update after several summer vacations with the truck including hauling Jet Ski trailers and Boy Scout Trailers around.
OEM Avg 15.482 MPG
Stock ECM & 265 Revos 14.522 MPG
Kennedy Tune & 265 Revos 16.251 MPG
This is over 14K miles now with the ECM.
Nice job John! Thanks
Its been awhile since i did an update. The tune is still going strong.
OEM Avg 15.482 MPG
Stock ECM & 265 Revos 14.522 MPG
Kennedy Tune & 265 Revos 16.146 MPG
This is almost 21K miles now with the ECM.
About time for some new tires. Will probably get Michilen LTX M/S II's in 235/85R16's to see if that bumps the mileage a little more.
gimpyhauler
05-10-2011, 13:01
'07 Sierra Classic, Duramax. I don't have the full data yet but I have some observations. I haven't put on enough miles yet to truly establish my fuel savings. BUT, it appears I'm getting better mileage, so far. Stick it on level 4 (Holy S_it setting) and put your foot down, it's a scary level of power. I leave it on level 2 normally for better mileage and am very pleased.
Fresh change of Delvac 1, and bypass filter at 91k on odometer. Previous change was 68k. Loyal WI to Pierre SD via I90 running at 5-6mph over posted 70 and 75mph speed limits. As usual I had across 20mpg going until I hit the MN line. The speed, the climb up from the River, and the following open terrain and wind hammered me down to where we were down to 17mpg by the time we hit Pierre. I know if I would slow down it would come up dramatically, but with a 10+ hr drive I just want it to end. Besides we'll make it up on the trip home running with the wind right?
Trip home saw Easterly winds. :mad: MPG never got a chance to recover much. Sat at 17 pretty much all the way. Once in WI and running under 65mph it started coming back and ended up at 17.4 for the trip.
With 1200 miles on the oil change pull the stick and it still looks like honey. I have a large tune at my disposal with a flip of the switch, but seldom use it these days. A modest 50HP tune gets the call 99% of the time. DIC fuel used and economy is quite accurate with this tune, smoke is non esxistent in most all cases, and it's just nice to drive...
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