Nissan Titan XD Discussion

[aardvarcus]

The new Nissan Titan XD has been released for a while now with the new Cummins 5.0L Turbo Diesel, but it hasn’t really made the splash that many expected. Part of the reason is that it doesn’t seem to get the MPG many expected, and most reports on the internet are indicating anywhere from 16-20 MPG. While not that bad, this MPG isn’t really all that good and not the 25+ many expected.

Here are some things I noted about the truck relevant to MPG:

Engine-From an engine standpoint, it is hard to argue that the 5.0l Cummins is fairly technologically advanced, but along with the new technology comes the baggage of the newest emissions requirements. I am sure there are some MPG being left on the table to reduce emissions, the most apparent of which is when the vehicle goes into regeneration of the exhaust.

Transmission- No manual transmission is offered, instead you get an Aisin 6 speed automatic with the diesel. This unit is heavy duty, with a double overdrive topping out at a ratio of 0.634 : 1. For an automatic, this isn't that bad.

Axles- The differentials are fairly heavy duty. The rear is an AAM semi-floating unit with six lugs. Gear Ratios available are 3.916 and 3.357, and it appears Diesel versions default to the first and gas versions default to the latter.

CD-I haven’t been able to find a solid drag coefficient for the new Titan XD, other than the ambiguous “10% less” than the previous model. The previous Titan was credited cd=.44, which at 10% less would imply the Titan XD is cd = 0.396 or roughly cd = 0.4 since I assume the significant digits of “10% less” are one at the best.

Area- Using the base model “S” 4x4, the published width of the truck is 79.5” and Height of 78”. Using the 80% rule, that puts area around 34.5 ft^2, for a cd*A of roughly cdA = 13.6.

Weight- This thing is heavy! Curb weight varies between 6700 and 7500lbs, with a base model 4x4 right around 7,000 lbs. GVWR is just under 9000. That weight is right up there with my 2001 2500HD with the 8.1l big block Allison 4x4. This unit is basically a commercial chassis built with commercial parts, resulting in one heavy truck.

Here are some ideas I had of how a Titan XD owner could improve their MPG up to where it “should be.”

Aerodynamic bedcover. The area of the truck is huge, and with no easy way to pare that back, attacking the not so great cd number would be the first step to getting this thing to respectable MPG numbers. See attached AST-II overlay for ideas.

Underbody smoothing. Other than the bed, the only other part of the truck yearning for aero attention is the underbody. The rest of the truck seems fairly well designed aerodynamically. Watch out for the huge exhaust system though, as you don’t want to trap any heat especially when the exhaust starts to regenerate.

Differential Gear swap- If you have reduced the aero drag, you may want to swap the differential gears if you started off with the diesel standard 3.916 down to the gas standard 3.357. These three items together would really help highway driving.

Weight reduction- I don’t know exactly from where you would lose it, but the huge curb weight would be a boon to any stop and go city driving.

Stick Shift- This would be the hardest thing suggested, but swapping in a handshaker would allow for much better control and driving style of the vehicle. A ZF6 or similar would be a good choice, and obviously lots of computer programming and custom fitting would have to go along with it.

Thoughts or ideas?

[vskid3]

Originally Posted by aardvarcus

Weight- This thing is heavy! Curb weight varies between 6700 and 7500lbs, with a base model 4x4 right around 7,000 lbs. GVWR is just under 9000. That weight is right up there with my 2001 2500HD with the 8.1l big block Allison 4x4. This unit is basically a commercial chassis built with commercial parts, resulting in one heavy truck.

Isn't that even heavier than your 2500HD? Seems like a lot of heft for not a lot of haul.

[bandit86]

Cummins engine, Aisin transmission, and AAM axles? This thing is a doge ram in drag! Without the towing capacity.

[Hersbird]

Tfltruck did a side by side gas vs diesel onntye HD and the gas did really well, so close the diesel didn't seem worth the extra.
Empty the diesel did 19.5, the gas 17.0.
Towing 7000 pounds the diesel did 10.7, the gas 9.6.
Best case in 100,000 miles that's a $700 savings on a $5000 option.
I also have heard they are in the repair bay more then the gas

https://m.youtube.com/watch?v=cPD5C8V9_6Y

[cRiPpLe_rOoStEr]

Originally Posted by aardvarcus

Engine-From an engine standpoint, it is hard to argue that the 5.0l Cummins is fairly technologically advanced, but along with the new technology comes the baggage of the newest emissions requirements. I am sure there are some MPG being left on the table to reduce emissions, the most apparent of which is when the vehicle goes into regeneration of the exhaust.

From my third-world perspective, I'd rather get the overseas-bound ISF3.8 instead of the ISV5.0 fitted to the Titan. I know it might seem an apples-to-oranges comparison, since the ISF3.8 is a 4-cylinder and relies on an OHV valvetrain. Once again, the perception of the amount of cylinders as a premium feature seems to affect the fuel-efficiency.

Stick Shift- This would be the hardest thing suggested, but swapping in a handshaker would allow for much better control and driving style of the vehicle. A ZF6 or similar would be a good choice, and obviously lots of computer programming and custom fitting would have to go along with it.

Even a ZF5 might be enought, BTW there are some forward-control Volkswagen trucks made in Brazil and Mexico fitted with the ZF5 behind the Cummins ISF3.8 engine.

[aardvarcus]

Some good points made by all.

Vskid,
It may be a bit heavier than my 2500HD. The Curb Weight and Gross Weight are within spitting distance of 3/4 and 1 tons of a couple generations back. I think Nissan just went really conservative on the tow/haul ratings, but for as much as this thing weighs they could have at least fit a fully floating rear axle in there.

I think in their quest for between ½ and ¾ ton they skirted the line in the wrong direction a few times. I would take a bit lighter frame and heavier axle, like the heavy half’s or light three quarters of yesteryear.

Bandit,
It is definitely trying to imitate the ¾ tons. I don’t know that conventional half ton transmissions and axles would have held up to the Cummins low end torque though. I think that is the crux of what drove the weight so high.

Hersbird,
If you did all highway driving based on 19.5 and 17 you could see up to a 750 gallon savings at 100k miles, but you are right the 10%-15% improvement still isn’t the sweeping improvement that was expected for such an expensive option.

Cripple Rooster,
Yeah, for the truck to really compete in the half ton segment the inline four diesels make more sense, especially to reduce the strain on down the powertrain and hopefully therefore the weight of the overall vehicle.

Any “truck” transmission with a granny low first with a decent overdrive would pair nicely with this engine. The engine appears to have a standard SAE bellhousing with an adapter ring to mate to the Aisin, so with the help of readily available SAE adapters you could bolt up pretty much any transmission you wanted, so long as you could make the computer not freak out. This would probably shave off a decent amount of weight right there.

[Hersbird]

Oh yeah, I forgot to multiply the 700 times the price, although here again the diesel is over 10% above regular. So say $1500 savings on a $5000 option.

[cRiPpLe_rOoStEr]

Originally Posted by aardvarcus

Yeah, for the truck to really compete in the half ton segment the inline four diesels make more sense, especially to reduce the strain on down the powertrain and hopefully therefore the weight of the overall vehicle.

I wouldn't really mention the ISF3.8 as a featherweight, but sure its weight penalty is reduced. Anyway, the main advantage would be the lower cost not just of manufacturing but also to overhaul the engine when the time comes.

[slowmover]

Published shipping weight on my 2WD SRW truck was 6,860-lbs. Engine is 5.9L straight six at 305HP/555TQ. Four door Quadcab with manual transmission. 3.73 gears with limited slip on 163" wheelbase. Michelin LTX M/S tires lowest pressure per Dodge is 50-psi all around. Now at 55-psi [80-psi max]. Tow rating is 12k conventional.

The day I bought it I took it to the T/A truckstop near Sanger, TX to put it on the CAT Scale. With Leer topper, MOPAR bedliner, full fuel [35-gls], and 200# driver it was almost dead-on 7,400-lbs. Same condition but with tools and usual gear it is within 40-lbs at all corners at 7,940-lbs. Roughly 1k remaining cargo capacity (taken up by travel trailer tongue weight).

This is essentially an HPCR turbodiesel that is emissions-exempt (software is OEM; low NOX). The latest Dodge with DEF tuning is about the same on MPG (maybe not as high).

At 58-mph/1,725-rpm at above weight or near 9k maximum, MPG doesn't fall below 24-mpg on low altitude, level terrain. Highs of 27. The range in city is from about 17 (extended idling in high heat + traffic) to 25 (cool weather, no idling and greatest distance on freeway system in off hours).

It's important to note that my numbers are among the highest for this era. A 4WD with non-highway tires and automatic might see 20-mpg as highest. Most are 16-18 at 65-mph. Owners are generally not FE minded.

I offer as a comparison, and look forward to what the V8 can do in similar circumstances with a conscientious driver.

That last part is the least likely. MPG desire by most is to make no changes by the driver. Just a magic device or expensive drivetrain.

That said, I'd imagine someone will be able to give us a comp of 60-mph on cruise control on similar terrain and climate for over 100-miles.

Percentage changes for different conditions can be deduced if that test is forthcoming.

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