New Guy
 

I'm introducing myself to anyone who wants to read what I have to share. My back ground is as follows:
I've been a certified automotive; medium and heavy duty truck; marine and generator technician for over 35 years.
I worked for a Detroit Diesel and Allison transmission distributor ship for 23 years. We sold and serviced Detroit Diesel, Perkins, Hatz diesel engines along with Allison transmissions and Kohler Generators. We also serviced trucks, trailers, yachts, fishing vessels, fire apparatus and motorhomes. I was afield service technician for about 14 of my years there.
Prior to working there I worked for a trucking company and after working there I have been employed with a municipal fleet maintenance facility maintaining everything from the weed eaters to the Airport Heavy equipment with every public works department there is. We also do a lot of fabrication of vehicles for special needs.
In my "spare time" I build Wildland fire engines at my house.
I am also a volunteer firefighter and EMT in the rural area I live.
My goals are to help people whenever and wherever I can while learning from you all to assist me in picking the right vehicle for me for retirement. I'm liking DDC powered stuff since I know them inside and out. (Series 60 is a plus.)
Thanks for welcoming me.

Great to have you here with the group! I am sure we will have a ton of questions for you and others. I for one have a Freightliner Columbia with the mbe 4000 435hp. Now if you can get me better mileage like BushPilot I would be a happy camper!

Sam

My pleasure. In all honesty mileage is effected by so many variables, my suggestion is always the same... If you want to play with big trucks then make sure you bring BIG BUCKS!...
Seriously though... What kind of mileage do you get and how heavy are you? I see you have a 2005 Columbia, is your engine maximum engine RPM 2100 or 1800 at no load speed? How many over drive gears in your transmission? What is your RPM at cruising speed? What is your cruising speed? How much idling do you do?
I know; I know; too many questions... I just like to help...

not sure about no load but it get up to 2100 when it shifts, I have a 12 speed ZF/Meritor Smart Shift. I am 42, long tow a Jeep Liberty and we wt in at 34,500 to 800 depending on the water I haul. I cruise at 65 mph and turning 1500. 7.5 mpg, Not much on the idling and running the genset. Ask all you want I am ready.

The peak torque of the engine is down around 1200-1500 RPM. If you can feather foot the throttle see if it will up shift lower than 1600-1700. If not see if you can manually shift sooner to keep the RPM down between that 1200-1500 RPM. Slow and easy still gets you up to speed.
Torque is what pulls you up hills and down the road. RPM is just speed. With those weights I would be surprised if you couldn't get in the 9's pretty easy. Granted wind resistance plays in but Class A flat nosed push a lot more air and I had quite a few of those come through the shop in the 9's and 10's with Series 60.
I will say too for every 5 mph over 55 you are pushing 10 times more wind resistance, so at 65 you are pushing more than 100 times the amount of wind than 55.
Learned that from PACCAR Research in the 1990's. Just sayin...

Bushpilot gets 9 at 70+ and lower rpms than I do. So I guess he has different rear end gear and he is 450 hp. I would think I should get 8+ when I set the cruise at 65 and go 500 to 600 miles down an interstate? And I use the cruise ALL the time.

You correct. I think you should get at least 8 mpg even with your gears. I think it still has to do with shift points. If you can get the transmission to shift sooner and utilize that torque I think you can get better mileage.
The other possibility is getting a recalibration for your engine for more horsepower which could change the ratio of horsepower to RPM. However this needs to be looked at closely. I can't remember the curves on the MBE4000 but I do know on a Series 60 that the torque curves and horsepower was identical between 1200-1500 on all the same size liters of engines. It was different when RPM exceeded 1500 that the bigger horsepower would cause a slower drop in the torque as RPM went up. This gave better hill climbing as well as increased mileage as the only fuel needed was to overcome the friction. So with more torque and RPM and when the load was not increased it was easier to pull it.
The rear end gears could be changed make them taller to help too get your RM of 1500 at 70 or 75 also.
The big question is return of dollars... Rear end change say $3000 per differential versus 1or 2 extra miles per $3.00 gallon of fuel. Is it worth it?

Welcome Chief Mark!

Sam - Ill record the video but I don't recall our coach shifting that high (rpm), iirc I shift around 1300, maybe 1500 tops.

I'd love to be able to identify what ratios are in the trans.

Mark - I consistently see 9.9mpg at 70/72 mph...and I've never seen anything lower than low 8s. ONCE I achieved 13 running backroads (foggy night) between Atlanta & Destin...but I don't think I ever got over 55mph maybe 60 tops.

we are single rear axle similarly weighted to Sam - w/ the MBE4000 (DD13?) and the rear end is a 3.21

https://www.truckconversion.net/attac...bf7b9576cf.jpg

https://www.truckconversion.net/attac...515962cc94.png

Am I correct in assuming all 12speeds have the same gearing?
Ours is an MO-16Z12A-A16...

https://www.truckconversion.net/attac...9446d972cf.png

I think you are spot on with the rear end ratio of 3.21 keeping your RPM down. That engine is more than enough to pull those weights thus giving you good fuel mileage. (I like to agree with the statement "Go Big or Stay Home!")
I would be interested in seeing Sam's specs compared to yours...Apple to Apple.
Funny how one small change can make a huge difference...

I've added some more details (as I discovered / cross referenced the trans model number).

honestly id love to be able to cruise faster (need to have the cruise control reprogramed to something more than 72mph). I'm happy w/ the mpg but wouldn't mind getting my RPM's down a little lower (so I can cruise faster w/out giving up MPGs) -

https://www.truckconversion.net/attac...0271233ae3.jpg

https://www.truckconversion.net/attac...8b3f4f2a32.jpg

I didn't do too well on this one - 8.03 mpg - but was running a little faster than usual.

https://www.truckconversion.net/attac...b14e26e297.jpg

You should be able to have your cruise speed set to maximum vehicle speed with a simple in dealer computer change. There would be a labor fee and possibly a surcharge for computer use but no interaction with recalibration fees should be involved. Old days we did these changes with a hand held "diagnostic reader" but now everything has gone to lap tops and smart phones so the dealer has to recoup some costs for these items so they put surcharges to cover the expense.
Years ago I had to program a Texas Heavy hauler with a road speed limit of 65 mph but he had rear end gears so high (2.something) I had to fool the computer as it wouldn't allow me to put in the actual numbers thinking it couldn't drive. I believe he was capable of 1200 RPM at 89 MPH. pretty sure he had to down shift to get over the cigarette butt on the road though. Never did hear how his idea came out. I did also install a transmission in a local trucker in Oregon that insisted on his choice which put him at 800 RPM at 65. He very rarely ever got into the top two gears in his transmission. After about 6 months we took the transmission out and put his original one back in.

Are you mixing diesel 1 and 2? Am I reading your fuel receipts correctly?

no mixing -
the CHEAP ($1.79 per gallon) fueling station is Buc-ee's in Baytown Texas - really not intended for "trucks" (since they don't offer master/slave pumps like a conventional truck stop).

I fill one side/tank, turn the coach around and fill the other side/tank...
Buc-ee's are HUGE - 100 pumps or more usually (depending on the location).

the receipts show the gallonage / price per tank Left & Right side, and the odometer reveals the miles since filled up.

The best diesel price in town right now is 2.15, was 2.16 a couple of days ago, back in the early fall they were down to like 1.81. Don beats me on price and mpg...... NOT fair! LOL

its a low priority really, I've just been too lazy really - not a real reason to take the coach in so I havent had it reprogramed. I expect when I do it - ill also have the HP turned up if I can.

I'd be curious what your thought might be in turning up the HP on the MBE4000 / DD13?

we don't do too many local trips (which kills the mpg) our coach really likes to stretch its legs....Its a pain in the butt to do a local trip....we kinda run ours like a station wagon...back and forth Houston to Virginia (kids were in college in Virginia and our parents are in Virginia as well)....now its just the wife and I - and work is getting in the way these days.

Sam - that was back the end of September (2016).
That same station, today, is $2.16 for diesel.

Yep, didn't ck the date, your still beating me! LOL

I just noticed on the slips where it states Diesel 1 on the right slip and Diesel 2 on the left strip as well as a different pump number. Either way I wish I could get any fuel for $2.16 I think our regular gasoline is about $2.65 and Diesel is about $2.99 right now.
As far as more horsepower on any engine the biggest concerns are cooling system capability and transmission input abilities. If you only use the HP when you really need it no harm but if you push things the maximum all the time, you will shorten engine life.
I had several loggers (Boy am I dating myself.) that I pumped up their 8V92 Detroit engines with bigger injectors and more RPM. One of them used to run around like a sports car leaving charcoal briquettes out his pipe everywhere and the other guy drove responsibly and guess who needed an overhaul 75,000 miles sooner.

Amen! We have a pair of 6v92 DDECs in our fishing boat that are set up at 635hp each by DD (max hp configuration, to my knowledge). They had to be rebuilt at 1600 and 1750 hours, and we did not run them hard, by boat standards! I think the previous owner had a heavy hand on the throttles.

I too am intrigued by the potential that may be unlocked by exploring the settings on our truck's Series 60, but also a little reluctant given our previous experience with pushing hp.

What year is your 60? Also what model # should look like 6067-XXXX with the XXXX being numbers and letters. This will let me know what your basic model is capable of. Most common from the 1990's were 6067-GK60 but then they moved into LK;MK and HK.