bad mpg what to do?

Progressive shifting is great when you want to save MPG. You normally can get up to speed almost as fast as revving it out with a lot less fuel. The problem is sometimes you need a little more rpm on an up grade or sharp turn to make a clean shift because you will loose more rpm on the shift. At TMC you can rev the motors a bit higher then 1400 rpms if you need to going up hill and such.

With an s60 motor, there is a progresive shifting option in the ecm. If turned on, no matter what the motor wont give you any more rpm. Once it gets to the shift point, no mater what, you cant get any more out of it. This hurts on hills were you might need a little more, and the time youneed to pull out real fast into traffic. (although prog shifting is almost as fast. By enablint his though, it keeps drivers from going nuts reving out the moter all the time.

 

I don't care what you do to your truck, 74,000 lbs GVW at 70 to 72 mph is going to get you crappy fuel economy. You want to get 8 mpg??? SLOW DOWN.

 

Itds not about climbing hills. Your peek torque is much lower then 2200 (unless yo have an old mechanical) The problem is up shifting going up a hill. You loose so much speed so fast during the shift, you need to accommodate for a larger rpm drop on the shift. If you drop to low, your under the peek for the motor when you get in the next gear and thus need to dowshift lol. Now 1700 should be enough for almost all situations, depending on motor. Some detroits are limited even lower. I never get over 1700 on steep upgrades. 1200-1700 is the peek range on my s60. Norm i rev to 1500 and shift which drops the rpms by 200 and thus 1300. In small grades ill drop 300 rpms and be right at 1200. On steep grades i might drop more, but rarely rev above 1600. Now I have a 13 speed which helps, but even on a 10 you shouldnt need over 1700 rpm very often.

 

Progressive shifting in a nut shell: Your in 8th climbing a hill or merging on an on ramp, THEN, you hit 1,600 RPM and it forces you to up shift around 35 MPH. You up shift, now you have no power and you're lugging the motor and losing speed which causes you to down shift. Example two, I'm in 10th gear doing 65 MPH and going down hill, then, as I hit the bottom it goes up hill very steep. I down shift into 9th gear and mash the throttle, I go from 65 to 54 MPH and there is NO THROTTLE response until I hit 54 MPH. Once I hit 54 MPH, it slowly boosts and adds power. So slow, in fact that I'm only doing 48 MPH by the time I get the power band going. If progressive shifting was disabled, I would have down shifted, mashed the throttle and would have done A LOT better up that hill. When I drove for CRooked'E for a short time, they wouldn't go over 1,600-1,700 RPM. The trucks were absolutely gut less, this was with an empty trailer struggling to merge onto the on ramp.

If you want to save fuel, you will KNOW when to shift. I want full control and to be able to pick where I want the engine to rev. The engine may have peak torque at 1,500, but if you can down shift and pull at 1,800 - 2,100, the Series 60 likes to pull at a higher RPM. This isn't happening with progressive shifting on. You want the engine to have momentum, maximum horse power and maximum boost. TO get that, you want the max RPM when climbing a hill. This is ESPECIALLY true at higher speeds, such as 50 MPH +. If you're doing 35 MPH, I'm sure you can climb decent at 1,500 RPM. But, for steep hills, drop a gear, maybe two and get that momentum going. The goal is to get up the hill as FAST as possible, knowing that the slower you go the faster the speed you will lose. Second, as soon as you stop climbing that hill the sooner you stop burning so much fuel. Compare taking 90 seconds to climb a hill doing 35 MPH, or 30 seconds climbing that same hill doing 55 MPH at 1,800 RPM like a freight train.

I don't know any other shops. Diesel Doctor is a quick, low cost solution. Talk to him, he can recommend a shop and look and see what is out of whack. He may be able to fix it, he may not. Rather than waste any money, I'd just call him and find out when he is available. At 4.25 MPG, you're losing hundreds of dollars a day. You keep throwing money out the stack.

It depends on the truck that you're driving. On this ISX with the 10 speed, the ratios are pretty close, it takes me a second or less to down shift if my RPM's are low enough from speed falling. I just ease the throttle off to break torque, tap throttle quickly and shove it in. Takes less than a second if done right. But, its kinda help less when you have 400 HP and your speed continues to drop. Imagine 400 HP and your foot to the floor. Then, imagine this, imagine 400 HP and only give it half to 3/4 throttle. If you have 500 HP and you put your foot to the floor, that 400 HP just turned into 500 HP. The power is there in these engines, the OP is set at 455 HP or less, and that is part of the problem. I've driven one of these 455 DPF S60, they don't feel anything like 455 HP at all. They just don't have the response.

 

One question... did you get the overhead done?

 

Everyone says "Get the over head, change your air filter, check your fuel filters." These are good things, but it is an electronic or emissions related issue, even if it does not set a check engine light. The OP could change all these, and I can gaurantee he will have low power and poor fuel economy. If this was a non-EGR engine, then these would be good things to start from. Or, maybe I'm not as optimistic as you guys? Doubtful. DieselDoc is a $300.00 solution.

 

how do you know its electronic or emissions? I dont think we (i) was saying it cant be electronic or emissions, but start with the cheap stuff, then work your way to the more expensive stuff. It would suck to install a new dpf and still have the problem. But what do i know, i just spent 12 in maintenance on my truck loll.

 

Don't haul cheap freight and this won't be an issue.