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1st Gen Ram Tech'93 & older Rams: This section is for TECHNICAL discussions only, that involve 1993 Rams and older. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.
I have a 1988 Dodge Ram 1/2 ton 4X4 with a 318 TBI. What mods can be done to improve MPG. It runs great but only gets about 9 MPG in town and barely 11 on the highway and is somewhat anemic compared to my 85 van with carb and 318. I am considering headers with duals and some sort of free flow air intake system. I have heard of some sort of spacer or riser for the throttle body, what about that? What other mods can I do to help and what if any components can or should be removed without affecting the computer system drastically. This is for a (1988) model. Also would going back to carb be a good option to help with MPG and maybe more power? My old 85 dodge van with carb gets 14 MPG on the highway. I realize the 4X4 cost some in mileage but feel their is room for some improvement. Also it does not have overdrive and that probably hurts me on the highway. Can any tranny mods be done resonably? Thanks.
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1988 dakota 4X4 TBI 3.9 Liter manual 108,000 miles
Honestly I'm not familiar much with the TBI systems and how they respond to modifying stuff. I trust that you've done a tune up recently? Check plugs, wires, cap, rotor, etc. How old is the O2 sensor? Are the cats getting plugged up?
I'd start there first.
Then any time you can remove restrictions it'll improve the efficiency of the motor, so a better flowing filter, 1 5/8" into 2 1/2" collector headers with a Y into a single 3" with a non-restrictive muffler with high flow cats.
Fuel injection is nice for the cold mornings, but if you don't mind warming it up a bit first, and you don't have to deal with emissions, go ahead and swap it back to a carb setup. It's much cheaper and easier to make power with a carb than dinking around with a computer.
Working with the TBI system isn't as difficult as some think. I have the same truck/engine/drivetrain as yours. I installed Flowmaster full length headers with 2.5" couplers. 2.5" exhaust pipes from front to back with a pair of Flow Master high flow muffs (no cats). I moved the O2 sensor to the coupler on the pass side collector. Don't forget to plug the air pump holes in the heads, just below the exhaust ports!She sounds good and breaths a lot easier over the stock single 1.75" exhaust. The thing to watch when selecting headers is the clearance between the front runner and the vacc actuator on your front drivers side axel. I repacked my leaf springs for a 2" lift and that solved that problem.(and YES, you do have to re & re your starter to install the headers). I used an oversized K&N filter and built a ram air system. I moved my rad overflow bottle and punched a 4" hole through the front wall just behind the grill and beside the rad. It turned out pretty good and feeds the engine fresh cold air. Don't forget to put bug screen over the inlet. You have to disconnect the fuel tank vent line. If it's left venting into the air cleaner you'll end up pressurizing the tank. The /88 318's where over kill on the antipollution kling-on's. I tore ALL that crap off. The EGR was replaced with a flat plate and sealed with (O2 safe!) silicon sealer. I did the same with the 3 port plate on the front of the TBI. The 318's are hard on stock timing chains, replace your stock set with double roller chain set! Power tune your timing, stick with the same octane fuel and keep advancing the timing untill she starts to ping, then back it off a little. Tranny - Mine shifted like mush. I installed a B&M shift kit, she shifts harder and feels more positive. Instramentation - I installed a vacc gauge and tack to keep an eye on things. The vacc gauge shows you how far you've got your foot into it. These are just a few things I've done. I want to install a high rise intake man and while I'm at it, go with a new cam. Comp cam's has a nice "RV" cam but I'm not dropping $250 for one. After some research, I discovered that the stock cam out of a /93 318 will fit the /88 and is pretty close to an RV cam. Pick up a Hayn's book for your truck and keep notes in it. It's a bible with all the testing and building tips. After all this who-haw, I've tripled my gas mileage. I do a lot of long dis hwy running. When I first got mine, it sucked up 1/2 a tank, one way. Now she sips a 1/4 tank round trip!!! Hope this helps, oh, and don't forget, after every mod, no matter how small, reset your ECM!
Yes, start with your fuel injection system (o2, injectors, etc) and then make sure the engine is running good if you havn't worked on it in awhile (ie: plugs, wires, air filter, oil filter)
Upgrades can help give you more power and sometimes increase MPG. Any kind of upgraded intake would help as well as exhaust. Headers will give you a difference as well as some dual piping.
Manual locking hubs too. Hopefully you're lucky enough to have something with tires that aren't too huge. Big tires kill your mpg. Do the obvious and check your psi too. What kind of gearing you got?
There's also other ideas like aerodynamics. A bed cover is said to increase mpg. I also heard that taking the tailgate off does not help you and makes it worse. Weight reduction ... but that doesn't make too big of a difference with a truck this heavy. Just be happy with what you get. My IROC Camaro had a 350 in it and got about the same mpg yet the car is half the weight.