Hey everyone! I hope I'm posting this in the right place. I'm a diesel newbie and just bought my 05 CTD (see sig) Thanksgiving 2010 weekend. I LOVE this truck! I've been trying to do a TON of reading and research before I ask questions so hopefully I don't annoy anyone with repeated crap.

Anyway, My goal is increased mileage 1st and performance 2nd. I have no plans to put big $ into transmission, turbos, etc, etc (though it would be nice). I'm looking to get a little more out of what I have and still make it last.

I have a list of things I want to do. The 2 major ones are programmer/gauges (probably Edge Attitude CTS), and tires (315/70/17's). Once tax money comes in, I'll be able to do one OR the other. My truck is basically stock w/ 4.10's and I really feel them on the highway with stock 265/70/17's turning ~2300 RPM @ 75 mph.

So I guess my question is...should I go for the programmer/gauges, or go for the tires first? Which do you think will be more beneficial for mileage as it's going to be quite a while before I can spend the $ on the other item? The truck doesn't need tires, but I recognize that 315s' will drop my RPM's by almost 10%, and lower RPM's meaning less fuel used. On the other hand, the increase the programmer will give me should help me pick up some MPG's (if I keep my foot out of it) and let me monitor the motor.

I'm really torn, and your opinion is appreciated!!! HELP?!?!

Thanks in advance!

 

Good questions. First, the tires you mention will net you about zero mileage gain. The reduction in rpms (good thing) will be offset by weight and rolling resistance of the rubber. A better option IMO is 285/70/17. A decent compromise. the 4.10's are hurting you more than anything. These trucks seem to get best fuel economy when the tach is between 1750-1950 rpms when empty.
Smarty jr has been the programmer of choice for the best combo of mileage/performance but would require separate gauges. Edge programming has, historically speaking, run hotter in egts without any real mpg benefit. This is not from my personal experience, but just from others here and elsewhere sharing their experience; so from a strictly "I can only do one thing and my goal is better mpg" standpoint, I would do the tires I mentioned above. you should get gauges regardless.

Good luck with your new truck!

 

My thought on the 315's was that with my truck having 4.10's, it'll drop my effective gear ratio down to ~3.73, which it shouldn't have a problem with on the bottom end.

Everything I've seen on the programmer basically said that Smarty is #1 and Edge is a close #2. The thing I like about the Edge on a stock motor & trans is that it will de-fuel when it sees high EGT's or trans slip, hopefully averting damage...dunno

 

I would install a tuner first. You'll see immediate and noticable increases in mileage and (more importantly) drivability. The truck will just run better and feel better.

On a stock truck, save some money and get the Smarty Jr. It has fewer settings, and that's fine. Unless you're racing or using a dyno, all the fine adjustments will just get you lost.

I use a Bully Dog Outlook moniter for gauges. I bought it used for a good price. Easy to install, doesn't take up much room, accurate enough for day to day use on a stock truck.

As said above, taller tires will increase mileage by decreasing rpm's. But you're also increasing rolling mass and unsprung weight. Not sure how that will balance out.

The type of tire makes a huge differance. A lot of people will increase the tire diameter. But they also increase the width and use a more agressive tread. Those two things alone tend to decrease mileage, regardless of tire size.

You live in MD, where you get some snow. You want at least some tread for those few days a year. But you don't want an AT tire unless you plan on off roading a lot. So pick a skinny tire with a gentle tread. Especially with a dually. Four fat tires in the back create a tobaggan effect in the snow.

A tuner and gauges will run you about $500-600. New tires will be $900-1,200. Give or take.

 

As I think about this more, I am leaning towards the tuner first. It doesn't need tires and I'd feel stupid spending money to replace good tires. When I do, It'll most likely be Bridgestone Deuler AT Revo's. I've had 2 sets on our 00 Cherokee Sport and I absolutely love them! Great traction, quiet, & they wear like iron.

I'm also now leaning back towards the Smarty JR & gauges. I'll probably start with boost and EGT, then add trans temp and fuel pressure later as I can scrounge more money. Looks like I can get the Smarty and 1st 2 gauges for ~$800. Anyone have experience with used programmers? As long as they have been set back to stock and are 'unlocked', there shouldn't be an issue...correct?

 

Another tire size you can look at is 285 75 17... its a 34" tire thats not much wider then stock. And Smarty jr all the way! Its been an excellent product for me.

 

id get the tuner first.

 

I convinced the comptroller to release the funds for the Smarty Jr. Almost had a used one for $375 this weekend buy it sold a few days ago.

As for my tires (eventually) I want to get the effective gear ratio as low (numerically) as I can, so I'm pretty sold on going with 315's. They are ~9% taller than my current 265's, and the 285's are only ~3% taller.

 

As said above, taller tires will increase mileage by decreasing rpm's. But you're also increasing rolling mass and unsprung weight. Not sure how that will balance out.


Slower to get up to speed and brakes are less effective. Both of those hurt FE. Plus, more tread squirm under power and in turns. Sidewall "roll" when you don't want it. Not good for longest tire life, so also hurts overall economy (longest life & best performance at relative lowest cost).

Some commercial haulers might make it work, but few of those with our trucks are going to keep the records and analyze the results. The big truck industry -- and who knows more about tires -- doesn't recommend tire size changes for "economy". Truck spec and economy are worked out at the very beginning. Tire size and rear gearing have a fairly direct relationship.

The only reports I see of 100K-plus tire life (and I'm one of them) are with MICHELIN LTX A/S in the stock sizing. It helps that this is a Low Rolling Resistance tire (LRR, or, "Green") by design, but to change the stock size would change parameters the tire depends on to achieve that rating.

As MICHELIN also recommends (as I recall) that tires be removed from service after seven years, one could make the case for similar high-quality snow or off-road tires/wheels to exchange out as necessary over that seven years to maximize performance.

A Green Highway Rib tire should be high on the list for FE. MICHELIN on the sidewall for longest life. The LTX A/S for the best of both. I'll likely buy the second set of replacement tires at 250k miles.

.

 

For someone that knows next to nothing about the smarty jr.... (being the 'best' bang for you buck) how would i go about using it? Would i need to take it to an installer and have them 'tune' the truck for me?

 

Using it really is pretty simple. You plug it into the OBDII port, and follow the directions on the screen. Takes about 15-20 minutes. There's an instruction book that tells you what the differant settings do, and how to use the PoD. Just about the easiest upgrade you can do.

 

Hmmmm, good to know... I'm going to be putting new tires on here soon as well and it would be nice to be able and get the speedo/odometer back on after going with a bigger tire (while tuning the truck for better hp/mpg as well).

 

One things a lot of folks seem to ignore is the primary Dodge CTD weak area. Front suspension. Shocks, SS, Ball joints, sway bar links, steering linkage, front axle u-joints, front drive shaft u-joints, track bar bushings and hub bearings. None of this stuff lasts long because of collective design issues.

Why do we need to spin that front axle all the time? Getting at those axle u-joints takes you all the way into the rest of this stuff. I figure I've used my 4WD capability less than 5000 miles in 80k. Maybe only 2000 miles.

So, for less than $4k, I can make the front invincible with Dynatrac free spin hubs, Maxx sway bar links, PSC steering brace, Dynatrac ball joints, Bilstein shocks, a Radflo SS, and a track bar by someone who knows how to build one.

Then the truck might be as maintenance free as the engine is.

 

Smarty jr.

You don't need gauges. The truck didn't come with them, and the Smarty isn't going to do anything but make all your numbers better anyway. I have gauges and have monitored my jr. for 100,000 miles. Believe me, you don't need gauges to run the jr. They are nice, but not necessary.