Engine/Transmission (1994 - 1998) Ultimate MPG 12V.....

[MrDiesel]

OK so maybe not "the ultimate" b/c I'm starting w/ a QC 4x4... But looks like my 02 may be going to live with some one else, and it would give me a good reason to start working on my 98 12V finally. As stated it's a QC 4X4 and long bed too. It's got a 5-spd and 245K on it. BONE STOCK, even exhaust, pump never touched! I was thinkin since fuel is WAY up there right now, what is every ones suggestions as for the steps I could take to get the best MPG possible out of this truck? Oh ya 3. 5 gears too... I either gotta start wrenchin or sell it!

 

[EKlem]

The three areas to address besides driving style are driveline efficiency, windage, and rolling resistance.

As for the efficiency of the driveline, I would start by putting synthetic fluid everywhere. Also, making the engine breath easier will help so changing intake and exhaust would be good. Pyro and boost gauges could really help you with how to drive the truck. Running good low rolling resistance tires will help too. This generally means a tread with very small cuts, a narrow tire, and high pressure. Also, choosing the diameter will be important since slow speed and stop and go driving favor smaller diameters while highway speeds favor a slightly taller tire.

Windage is hard to address. Doing something to clean up the airflow around all of the little gaps in the body, grill, lights, etc will help. Lowering the truck would help but I don't know whether you want to go that far.

Lowering rolling resistance really comes down to the tires that you choose and the road surfaces that you drive on. Believe it or not, some pavements are much better than others.

I still think that the biggest thing of all is driving style.

 

[McCRam]

Don't forget weight. Remove anything you don't need everyday. I went through my toolbox the other day, and I know I pulled three hundred pounds out of it. Going to take the pressure washer to it this weekend. I found a lot of caked on mud and grease underneath when I was greasing the joints. A lot of gravel sitting inside the frame rails also. I might be able to shave another 100 lbs.

 

[MrDiesel]

Great start... I already planned intake/exhaust mods if I keep it. What about motor mods?

 

[GAmes]

Increase you timing to 15. 5 to 16, that helped my highway mileage, but turbo spoolup in town was slower. To fix that a PDR cam, and it came with an increase in mileage also. Off the lot my duelly weighed 6700. After adding the Rhino liner, fuel tank, hitches, and a full toolbox it weighs close to 8000. For awhile my highway mileage was more than stock, even at that weight. With ULSD it dropped a little, but I just replaced the original injectors with new 215s and will find out next week if it restores any economy.

 

[SRath]

In the August issue of Diesel Power magazine, they took a stock '97 12-valve dually with an automatic that routinely averaged 21 mpg and reached 30. 9 mpg with a total of $9. 26 in "modifications" and changes in driving habits.



Some of the "mods" were a little impractical (like folding in the mirrors), but their efforts and results were admirable and prove alot.



I have always believed Dodge has missed the boat by not fitting a 4-cylinder Cummins into a Durango-sized vehicle. I saw a K5 Blazer with one and the guy claimed nearly 40 mpg with it. That's as good as my 3-cylinder, 70 hp, gas motored Subaru Justy and a heckuva lot more to my liking size-wise!



Unfortunately, there really is a conspiracy going on to negate efforts to improve diesel mpg. OBD III laws that may reduce emmissions a tiny bit per gallon, but lower power so drastically that it requires more gallons to haul the same weight the same number of miles resulting in an overall increase in pollution as well as a decrease in mpg. The same goes for ulsd fuel.



These outrageous fuel prices may be artificially and temporarily good for Wall Street, but they're killing Main Street and the folks who live on AverageJoe Street. It will all implode upon itself soon. The record mortgage foreclosures are just the beginning...



BTW, that same magazine issue has the most awesome and well-done Cummins-into-a-crewcab Chevy conversion I've ever seen. A real Chevy; one with solid axles and an NP205, etc. Absolutely fabulous. Exactly like my old beloved K30 Chevy, except mine is not a dually.

 

[JFaughn]

It maybe a good idea to do some things with the fuel also , putting some BTUs back in , I am putting together an old dual filter dual by pass filter system together to clean use eng oil , I need to find a chemical to neutralize the PH , some of the problems with doing anything with fuel is like SRat mentioned , they seem to be making the trucks/fuel systems in such a way as to keep us from doing this , as an example , instead of making the truck work well with bio diesel , to reduce emissions & imports of oil , the common rail polymerizes the bio , then ULSD , as said above makes us use more fuel , was there any gain ?
We are on our own , with the [ them ] working against us .
Its sooooo dang obvious that they are screwing us , take the internet , we can find all sorts of ideas on fuel , alternatives , engines , tech , some are bogus , but with the cost of fuel , the panic in media about globule warming and many good products & ideas , almost never hit prime time on major media , that tells me that they own it & are sticking it to us .
This was up last yr or 2 , any nothing has happened with it , that I have seen ,


Angel Labs :: Resources
There are many others , this is just to make a point .
I am going to use some cardboard & tape to see for my self , 10 MPGs boost for under $10 , I saw that also .

 

[Forrest Nearing]

realise that things like camshafts etc. will be diminishing returns for a while. takes a good while to recoup the costs just on fuel mileage.



bump the timing, loosen up the AFC a little, slide the plate forward... Wait a second... the AFC gives more pre-boost fuel, how can more fuel give you better mileage!!?!??!? IMPOSSIBLE!!!!



let me 'splain:



these engines are designed to be run under boost. That's why they only have 16:1 compression.



A naturally aspirated diesel usually runs in the 20-22:1 range for compression ratio. If you lowered the compression ratio on a non-turbo diesel to 16:1, torque and fuel mileage would suffer quite a bit!



the turbo boost makes up that compression and then some and allows the engine to "act" as an engine with larger displacement than it really has



before boost comes in, the engine is operating under it's optimal efficiency



anything you can do to help bring boost on quicker (better flowing air intake filter/system, free flowing exhaust, AND loosening up the AFC to bring fuel in sooner) will help



why didn't they set them up like that from the factory?



easy... the EPA! emissions and particulate (soot)



news flash to everyone that says visible smoke is just wasted fuel... not necessarily so! ESPECIALLY on a 12v!



now, I'm not talking about looking like a steam locomotive and blacking out the sun, but a light to moderate gray haze durring pre-boost acceleration will yeield better mpg as you're getting some heat in the engine and you're getting into that efficient turbo boost sooner



now, with all that out of the way...



don't lift it, don't put mud tires on it. I've had good MPG results from the BFG A/T's if you gotta have an offroad tread. I didn't really see a mileage decrease going from 265's to 285's, but I did going from 285's to 315's. The 315's were not E rated. All BFG A/T's



biggest killer is speed... I can't drive slow, so I deal with 17mpg at 85mph

 

[MrDiesel]

Forrest... is this the reason I see so many 12v getting better MPG with some plate mods and/or small injectors? I had already planned on bumping the timing, I've got some more good ideas too. With 245K on the stock injectors, should I be looking at replacing them? With what?

 

[GAmes]

realise that things like camshafts etc. will be diminishing returns for a while. takes a good while to recoup the costs just on fuel mileage.

Say it ain't so:-laf I charted it out once. I believe the result was only 54,000 miles

 

[Forrest Nearing]

Forrest... is this the reason I see so many 12v getting better MPG with some plate mods and/or small injectors? I had already planned on bumping the timing, I've got some more good ideas too. With 245K on the stock injectors, should I be looking at replacing them? With what?

the stock injectors should be fine for now, and yes, moderate mods usually yield a MPG increase. Same on the newer, computer controlled trucks



the best injector I've run to-date for power and mileage were the DDP4's, but I'm sure there are better offerings if all you're looking for is mileage. You could put thin washers on your stockers for a little better burn with the increased timing.

 

[MrDiesel]

the stock injectors should be fine for now, and yes, moderate mods usually yield a MPG increase. Same on the newer, computer controlled trucks



the best injector I've run to-date for power and mileage were the DDP4's, but I'm sure there are better offerings if all you're looking for is mileage. You could put thin washers on your stockers for a little better burn with the increased timing.

Thanks I will keep that in mind... PS did you get my response to your ad? I'd like to see pics. of the truck...

 

[Forrest Nearing]

Say it ain't so:-laf I charted it out once. I believe the result was only 54,000 miles

shoot, that's about a year's worth of driving for me! and if it makes thosse 54,000 miles that much more enjoyable, it sounds like a deal!



don't get me wrong, if I really want something, I buy it. I'm in my truck all the time, so I want to enjoy my time behind the wheel!! Heck, I could probably go from 17mpg to well over 20 if I turtled along in the slow lane at 65mph, but I don't enjoy going 65mph!

 

[GAmes]

shoot, that's about a year's worth of driving for me! and if it makes thosse 54,000 miles that much more enjoyable, it sounds like a deal!

Only about 6 months for me. That was calculated last summer when fuel was$2 something a gallon. Now that it is over $3 the payback would be much faster.

 

[Forrest Nearing]

Only about 6 months for me. That was calculated last summer when fuel was$2 something a gallon. Now that it is over $3 the payback would be much faster.

pretty soon, that camshaft's gonna be giving you a paycheck!

 

[Vaughn MacKenzie]

Only about 6 months for me. That was calculated last summer when fuel was$2 something a gallon. Now that it is over $3 the payback would be much faster.

$3 a gallon, it's just under $4 around here. . . better get that cam!



Forrest compression is 17. 5:1 on the 12V

 

[Forrest Nearing]

I thought they were in the 16's, but I guess that was the 24v engines



amazing that the 12v's will take so much boost at that CR!

 

[JHenry]

I would consider a set of DynaTrac lockout hubs for the front drive axle of your truck. I have a set on my '06. The immediate results were 1 1/2 to 3 mpg. increase. Initial cost is around $1900, but with the yearly miles that are being discussed here, it won't take long to get that out of the way. Plus, less wear and tear on the bearings, u-joints, etc. No, I don't work for them, just satisfied with the product.

 

[Vaughn MacKenzie]

I thought they were in the 16's, but I guess that was the 24v engines



amazing that the 12v's will take so much boost at that CR!

Yeah. . . although the better breathing head of a 24v probably makes up for it a little by allowing more air into the cylinder on each stroke.



I think most 24v motors are 16. 3:1 but the CR motors are 17. 0:1?

 

[CToney]

I would try some dynomite diesel injectors. Their smallest injector will flow more fuel than your 215's and will effectively advance your timing. Better atomization and thus better mpg. Loosening off the afc will help. Before I did that I always had to downshift. The longer you can stay in 5th the better your milage. Check lift pump and overflow valve operation. Don't run ac or defrost(defrost /floor) as the a/c compressor runs sucking hp as well as additional loads on electrical system cause the alt to work harder. Air dam attached to the front bumper may also help.