Engine/Transmission (1994 - 1998) Things to do for best MPG???

[Bart]

I'd like to get the best fuel economy out of my rig (see signature). I know the best way is to slow down and I have, 65 mph is about tops for me. I excellerate slowly and coast to stops as much as possible.

Last trip to Oregon I got 12 to 14 with a 10. 5' cab-over camper, dressed out at about 3K pounds. I've often wondered about a timing change. Would that increase MPG? Should I go back to the oem fuel pump plate? I run a stock paper air filter because of the Cummins warning about the K&N I took off. I don't want to sacrafice the engine. Any ideas would be appreciated. I do most of my own work, and can time the spit outta a gasser by this diesel timing is another breed.

 

[RJPotts]

Advancing your timing will increase fuel economy, depending on how much. I'm sure someone will chime in with their findings.

You said paper air filter... is that in the OEM filter box???

If so, take that off and get a BHAF or something similar. That will increase MPG.

I didn't see in your sig if you had exhaust. 4" exhaust will also inc. MPG a bit.



There are quite a few things that you can do. Someone please recommend more ideas.



-R. J.

 

[pwerwagn]

I have a 98 12V 5-speed. I did some adjusting on the afc, I have a #100 plate, a 3" exhaust with a walker muff, and a Scotty intake/uni filter. I average 21-21. 5 with a combination of in town and highway driving. the main thing I have found, is keep your foot out of it. I try to stay below 6 pounds of boost as much as possible, and never lug it.

--Jeff

 

[Bart]

The only things done to the 12v'r is the new exhaust springs (60#) for the exhaust brake, and fuel pump plate. The turbo went out a couple years ago and I had it rebuild to stock. Exhaust is OEM (except for exhaust brake), so is the air filter box. I always try to keep my foot outta in. I know that is where the fuel goes in the toilet. As my rig is orginally from Canada it doesn't have an egr device, I removed the cat. I NEVER lug my baby, when towing/hauling camper and speed deteriates to around 55 and 1400rs I take it out of o. d. and settle in at 50 and 2K to 2100 r's. Exhaust temps are way too high leaving it in overdrive at that speed while towing/hauling. I'm beginning to wonder if the muffler (oem) could be part of the problem. When I lost the turbo a lot of oil went down the exhaust pipe. Could that have screwed the Muffler?

 

[Shell 96]

oil in a fiberglass/insulated type muffler will only burn out the insulation, but original mufflers tend to be quite restrictive.

 

[Bart]

I think I see a new muffler in my future



Any recommendations of the best to get? What about the Flowmaster. I know they make gasser muffler but are diesel mufflers different?

 

[Neibe]

Straight Pipe you won't be sorry!

 

[Bart]

The only experience I've had with a straight pipe must have be one day I was passing a Dodge the was towing heavy and he sounded two Peterbuilts pulling hard off the line. I don't think Iwant that kind of noise.

What about you pwrwagon with 20s mpg you must have something goin' for you.

 

[Cooker]

What plate do you have?



What gears do you have?



When you installed your plate did you slide the AFC all the way forward? If so sliding it back some will result in better MPG's.

 

[Bart]

I'm not sure now what plate was put in. I'm sure the plate was pushed forward though, if I reinstalled the oem plate would that give more MPG?

The installation instructions for the fuel plate say TST Power kit. Mean anything?

I spent most of this evening in the TDR magazine and a company named DPP out of Nashville seems to have the best prices. The wife's gonna spit but with the stainless 4" exhaust, AFE (pro guard 7) stage II air filter, and Banks split ram intake I could eat up a 2K bill in a hurry. She didn't *itch at the 800 for the exhaust brake, or 900+ for the new brake system. She did studder at the $5500 auto transmission though :--) I'm just glad I can install all of this "stuff" myself.

Well, anyway do you think putting the oem fuel plate back in help with the mpg? I'd rather have that than the h. p.

 

[Cooker]

Without knowing what plate you have it is hard to say if the OEM plate will yield more MPG's. I do know that moving the AFC housing back will yield an increase in MPG's. Depending on how far back you can tolerate it will determine you MPG increase.



I would not spend your money on the Banks Twin Ram intake especially in search of MPG's. I'm sure it will only disappoint you.



To save a little money while experimenting for better MPG's you could try a BHAF over the AFE. $50 vs. $200. In the long run the reusable aspect of the AFE will pay for itself over the BHAF's but personally I am not a big fan of oily air filters.



As far the the exhaust, if you only have a plate and are not planning on more fueling mods I would dump the CAT and OEM muffler and install a flow through muffler and give that a shot. 4" has a nicer tone IMHO and but on a truck with a mild plate as it's only fueling mod, I don't think one needs to spend the money on a full 4" system. If your OEM system is in need of replacement anyway 4" would be the way to go.



How much wrenching do you want to do or what do you feel comfortable with. A good CAM will help noticably with MPG's.



Also a little more open turbo will help to. A 14cm WG exhuast housing on your stock turbo will probably help a noticable amount as well.

 

[sstockton]

On my 12valve that I just sold, I had a custom plate, which didn't effect fuel economy too much, an intake and four inch exhaust, which got me from 18 up to about 20mpg. And then I honestly noticed a big difference putting in injectors. My best mpg was about 23 cruising at 65, but I consistently got 19mpg going 75-80, and towing about 10k with o/d off going 45-55 up the Northern california coast (twistiest highway in the country I might add) I got 16. 5. I've also noticed a big jump in fuel economy increase putting injectors into 24valves.



I believe the theory behind this is that the better injectors atomize the fuel more efficently and they will only deliver as much fuel as the pump gives them. So keeping your foot out of it, should make it quite a bit better. Maybe it was just my truck, and I'm sure I'll get some people that disagree with me. But I found that my fuel economy went up with the injectors. And I had my foot in it quite a bit. I don't know really if this will comprimise engine life, but monitor your gauges and you should be fine.



Good luck.

Sean.

 

[Bart]

I'm going to contact to company I bought the plate from to see if I can get the plate #.

Only for the sake of discussion. I talked with Banks and they said that the twin ram cleared up the problem of the two rear cylinders not getting as much air as the front four because of the position of the intake runner. Your thoughts on that statement. I have 3. 54 gears in my 3500. I drive it very conservatively. No hard starts or stops if I can help the stops. A friend said that (in riding in my rig the first time) he felt the truck was kinda slugish off the line. I told him maybe it was because I don't push the skinny peddle don't very had. Maybe it's the oem muffler.

After some sleep, it's quarter to 4 in the morning right now, I seem to rememeber the fuel plate being a #11. Does that make sense?

And one other thing, correct me if I'm wrong, but doesn't smoke mean unburnt fuel? I've had friend's following me and they say that they can tell every time I shift gears because of the change in smoke. I guess I should follow it some time instead of driving it. It's just that no one drives my Dodge. Wife has only drivin' it twice. Mainly, because of the transmission and the way I shift it with the shift lever. I have the torque converter setup to lock up at 18 mph and if I don't shift it it will go straight from first to four at 18 mph and there's a lot of metal parts in there that don't like that!!!

I do a lot of wrenching so a cam change isn't scarey. That's a thought.

I'm planning on a lot more trips to the Bend Oregon area (I just bought 3 acres up there and I'd like to get the best MPG that I can.

Keep the thoughts coming. I appreciate them.

 

[pwerwagn]

Bart, Im running a Walker 3" muffler, no cat. Stock pipe. It sounds good, no drone, and EGT's are, well, not crazy I guess.

I also have the Scotty II/UNI filter. It helped mileage a miniscule amount, but it was noticeable every time I filled up (I check mileage and log it every fill up).

Im running 3. 55's, and 305-70-16's. Not the ideal tire for mileage. But my mileage didnt drop at all going from 265's-285's-305's.

I also have the 99-02 sport conversion bumper. wonder if that helps mileage at all by being more aerodynamic/lighter?

But nonetheless, my biggest gains come from the way its driven.

--Jeff

 

[Bart]

Thanks Jeff (aka Pwrwagon) for the information. Where did you get the muffler from? I think I'm going to be doing this in stages to see what does the best. I've been "keeping my foot outta it" for a long time.

I just got back from Oregon (Bend area) a few weeks ago and with my camper in the bed and driving max of 65 I got 12-14 on two different fill ups. Terrain had something to do with the two different reading. I expected better than that by a bunch.

In reference to the fuel pump plate it's a TST brand and if the company that sold it to me was correct I should have a #8. I'm going to contact the company to see if there's anyway to id the plate.

I had a K&N air filter in the stock box but after reading the Cummins warning I removed it and went back to a paper rig. I'm looking at the AFE filter ( with that pro guard 7) that's between $300 and 500 depending on what kind of box I use. I think I could get the same (AFE) in a stock configuration but don't know if it is restrictive also. Do you know? Please feel free to jump in here at any time Cooker. I value all opinions. I'm looking for a million miles outta this engine and treat it accordingly. So I want the best. I LIKE my 12 v'r and don't want to trade or change. Besides "it's paid off!!"

In reference to your tire sizes I have 235's and they're smaller than yours. As I have a dually I believe that's the biggest tire I can go to. I don't mind being corrected any time you guys have different ideas.

My best mpg was about 23 cruising at 65, but I consistently got 19mpg going 75-80, and towing about 10k with o/d off going 45-55 up the Northern california coast (twistiest highway in the country I might add) I got 16. 5. I've also noticed a big jump in fuel economy increase putting injectors into 24valves





SStocton if I got that kind of mileage I'd think I died and went to Dodge heaven!!! Are you running a 24 v'r? You mentioned that, I don't know if that would affect a mechical diesel or not. What say you?

 

[Joe G.]

Changing the plate will have little or no affect since it is not in play except at or near WOT. Moveing the AFC back will limit fuel during accelleration so that may help. Advanced timing should help. A better muffler will help. A better air cleaner will help. Driving slower will help. Driving easier so you don't need to use your brakes as much or accellerate as much on curvy road will help. I think driving habits have more affect on mileage than anything else.

 

[JGK]

Always drive down hill?



Sorry. Couldn't help it. Everyone else has pretty much covered all the other options.



-Jay

 

[TRCM]

If it's a tst plate, all you have to do is pull the afc housing... the plate will have the number stamped on the top of it.



if it is a tst, you can exchange it for another plate curve for 50 bucks.

 

[sewman]

My 98 12v also gets 23 @ 65 & 18 around town drivin easy. I've owned this truck for over a yr & just changed the oil & put on a walker muffler w/4" tailpipe & lost the cat. around town I don't let the rpm get over 1700 when taking off(stock converter)

Don't forget to check the air in your tires,I noticed an increase in mpg since I put 65 in the front & 55 back,was running,50 & 35

Bob

 

[AMink]

For an exhaust system, I'd suggest one from Rip Rook at Source Automotive. I put a 4" turbo back on mine. It may not be as fancy as stainless, but for where I live, rust is not a huge issue. Also, a BHAF (NAPA part #2790). You can look in my reader's rigs to see how I installed it, but I'm sure there're other ways. I also put a cover on it from Outerwears on. I don't have a part number handy, but if you tell them it's for a BHAF and give them the dimensions of the filter, they'll set you up. Get the water repellent material. Make sure all your intercooler hoses are tight and not leaking so that you get the most out of the air the turbo is pushing. I don't have one, but have heard that a 10 plate and 3000 gsk kit work very well together. If you already have the 60# exhaust springs, you may ask around about a 4000gsk kit. With the mods I've done, I haven't seen a huge growth in mileage, but I get the same or better with MORE POWER! :-laf Next up--new turbo and injectors!