LOL, ya my bad. 70 mph.

At 80 -90 mph I'm getting out of the way!

 

Based on the onboard computer...uh huh...with a Hemi and 3.55's and 4WD.

My best..only checked once..2006 Titan CC 2WD, 55 MPH, 5 speed auto with o/d, 2K on the odometer, a/c off. 2.94-1 rear axle ratio...mileage = 18.7.

 

Bill,

If you note, I indicated that I have checked the on-board computer at every fill-up, and it has consistently been within .3mpg of my actual, hand calculated mileage. Actually, with another fillup today (after logging over 400 miles yesterday, bringing my current total to just under 2100), the on-board computer has been within .287 mpg of actual, hand calculated mileage over the life of the truck to date.

I'd note that my mileage isn't out of the realm of ordinary compared to what other Hemi drivers (with MDS) report. Nor is yours for the Titan, which is not equipped with any form of MDS.

As a sidenote, my 5th gear OD is .67, coupled with the 3.55 gearing for a 2.37:1 final drive ratio. Your 5th gear OD is .834, coupled with 2.94 gearing for a 2.45:1 final drive ratio.

My tire height is about 31.5 inches. Yours are probably (depending on your options 31.5 or 32 inches. At 65, I'm turning 1649rpms. At 65, you're turning 1700 (assumign the same size tires). Even with the lower axle gearing, you're turning more RPMs, as your OD gearing is higher. And you don't have MDS. So scoff all you want, but I think my reports are realistic.

 

I could beleive the possibility of getting 20MPG out of a 4x4 hemi 1500. Heck, I did manage 18mpg once on my superduty 5.4, 4x4 4:10. I was never able to repeat it, but I did it once.

 

Just as a point of interest. All the magazines and companies that compare all the trucks regularly say that the dodge hemi gets the worst mileage of any full size when comparably equipped...

 

And if you read any of those comparisons you will notice that the MDS is not in use (due to the competition not having it and it needs to be "comparably equipped") and more times than not its an AWD. The Dodge Hemi MDS is capable of producing 20 MPH in a 4X4, one of my best friends has one and he says it will get that mileage "with the cruise set on the interstate, but the minute you give it gas its back down to 12-13".

 

titans are geared like that? no wonder they are getting 19mpg...lets not forget the wieght difference between the other brands here..not sure about the larger suv's and such but i know the superdutys outweigh them by quite a few.daimler chryslers MDS fuel saving deal is like having 4 dead cylinders, its a joke. ford builds trucks not fuel effecient grocery getters..

 

The 2.94 gear ratio in a Titan is similar to a 3.73 (I think, could be a 3.55) in an F150, due to the way its transmission is designed...

 

Suzuki,

I'm not sure how you get "it's like having 4 dead cylinders"...the MDS deactivates the fuel injectors, so no fuel is wasted, and closes the intake/exhaust valves to minimize pumping losses. So it's not realy like having 4 dead cylinders...it's more like having a much more fuel efficient 4 cylinder engine.

 

Titan rear axle ratios (Dana 44) 2.94-1 without the tow package, 3.31-1 with.

 

Yah I agree with ya, who wants 345hp and 25 mpg on the highway. I sure don't seeing gas is soooo cheap these days.

I have to agree with you again! Ford does build trucks with 300hp and gets 15 -20 mpg. ( and I'm being generous with the 20 mpg ).

 

The real reason auto manufacturers have gone to cylinder de-activation systems is simple. They have to meet the US Government mandated CAFE standards.

CAFE: Corporate Average Fuel Economy.

Sooner or later, all the manufacturers will have some sort of cylinder de-activation system. Besides DCX, GM also uses a similar system.

When gas reaches 4-5 bucks a gallon, you will thank your lucky stars the truck you are driving has this fuel saving system.

 

I applaud that the manufacturers (well other than ford) are attempting to make the engines more fuel effiencent. I am just not convinced that the savings are all that great with the cylinder deactivation. In my experience it seems to be good for 19 or maybe 20 mpg highway. I get 18 in my extended cab 4x4 06 f150 when driving in the same area. It is an all flat area so I suspect the deactivation should be working as good as it ever will. In hilly regions I don't think there would be any difference at all. I also would be concerned of the durability of this. How much does this add to the cost of each engine. 1, 2 or even 3 mpg is not that great and will not make driving a truck more affordable when gas goes to 4 or 5 dollars a gallon.

Don't get me wrong I am in no way defending fords apparent lack of progress on the mod motor. I just strongly feel that cylinder deactivation is little more than a temporary gimmick. I think the best solution is to put smaller more efficient engines (4.6) or small diesel into a truck the size of the early 80's pick-ups. The increased size of these trucks and on-going horsepower war will prevent anything from getting much over 20mpg with whatever engine is used.

 

My 2007 dodge ram bighorn quad cab 4x4 hemi with 20" wheels and 3.92 gears will consistantly get 20+ mpg on the highway if i keep it under 72 mph. 75-80 mph will drop it down to 18 real fast. The mds is very neat technology and is not noticeable unless if you have a loud aftermarket exhaust and intake system. I will tell you around town the ram will only get 13.5-14.5 mpg. The biggest misconception with the dodges is that all these idiots by a ram hemi thinking they have a race car. They drive em hard and fast and then they complain about the mileage lol!!! I am sure i could turn my truck into a gas sucking pig too but i don't feel the need to put the pedal down all the time.

 

As a possibly useless data point, the Team Lead for GM's DoD system was on record as saying their system wasn't going to be used to increase baseline fuel economy numbers, but was going to preserve existing numbers with a planned increase in functionality elsewhere in the vehicle (i.e. more crap/weight in the truck).

In practice, the system has shown to deactivate almost never; the parameters chosen for deactivation are usually only met on super-flat roads (only found in parts of NE, KS, OK, and TX); at speeds well under the posted speed limit of 70 or 75; and with vehicle weight substantially less than what most vehicles actually scale out at; in short: conditions that exist almost nowhere in most of their vehicles lives. I seem to remember reading that even if speed and weight parameters were met, if there was anything even remotely resembling a hill coming along in intervals of something less than 10 miles, the system never deactivated either. It would seem that the cruise parameters were trying to closely mimic the EPA mileage test, which has been shown to accurately reflect NO real-world driving conditions.

-blaine