15MPG on average on my stock jeep.

My commute is 14 miles one way to work. 7 miles being in stop& go traffic.

On a recent 600 mile trip. I averaged 19-20mpg. Keeping speeds of 70-80mph..Usually sticking to 70mph tho.

 

I just spoke with http://www.mrinjector.us/ Bill.. I bought Filters and O rings for my stock units and for some used injectors Boche 784's that are on the way.. He told me for this style Intake spray pattern is not critical if not relevant at all. Thats why Jeep kept using these injectors that shoot gas like a water gun. Spray pattern is critical in OTHER applications but not on the 4 liter because, according to Bill, this style intake will put gas in a READY mode for use during driving and that gas can SIT inside the motor/ head/ cylynder until its used.. So spray patter is meaningless.. Somehting like this he told me.. Im no motor genius.. These guys have all the rebuild parts for the stock injectors. Anyway, I now have in my possession the fords stated here, I have 2 sets of stock injectors that will be refurbished to new, and I have a set of 784's that Im rebuilding with new rings, filters and caps, I will also be ordering the c4b's. When I am done I will have mileage specs on ALL 4 sets of injectors.. I will run two tanks out on each style to see what gas mileage I get.. When im done the results will be exacting.. Right now im lucky to get 15mpg with these fords Im running as stated in this thread. By the time Im done I will have spend hundreds of dollars to rebuild and buy injectors.. So much so i will begin to sell them off.. I even bought a Jewlry cleaner to clean the tips. lol.. All in the persuit of better gas mileage.. Im starting to spend so much on injectors that I wont make it up on gas..

 

Please explain why my engine does not shut off with the throttle closed when I am coasting in neutral or the clutch in. Does the ECU know that I am in neutral so it keeps it running?

I have studied the ECU code and tuned (as in wrote the fuel map) for my FI Chevelle. Yes the pulse width of the injectors goes down when you let off the gas to decelerate, but it does not go to zero (shut off). If it did, this would stop the engine just as quickly as turning off the ignition.

To TheJerm: Please edit your last post or explain how you maintain speed in 5th, gain speed in 4th and loose speed in 3rd going down the same hill. Seems like you have your throttle cable wrapped around your shifter.

 

The DFCO feature started in the early to mid 90's, pretty standard by time OBD2 came about. I dont know what EFI system your using in your chevelle but i'm assuming is the tune port from the cheby trucks which is a primitive system. Its not that they shut off injectors completely but mostly, using less fuel then idle cause you have the momentum of the vehicle spinning the engine over.

4th is 1:1 and it probably the worse gear for engine braking, 3rd is ideal for anything faster than 35. I dont understand why but i accept that and just use it

 

Well I get 15-22 depending on how I drive and what I haul. its a 2000 xj 4.0 I6 4x4 all black in and out, the only mods i have are lights, sound, and exhaust.

 

I am running fords xr3e injectors getting 15 mpg or less no matter how I drive.. lame.. I just orderd the 63mm throttle body and high flow air intake that im going to drill and fabricate a ram air hole on the hood into the stock air box lol.. open and closing teh hood wont be an issue as i will use and adapter and rubber boot for snug fit. Im then going to seal off teh box under the hood!!

 

@ the people saying no fuel is used during engine braking.

Listen to your exhaust while you're doing this. Notice the exhaust still has a note to it. This means your engine is still running and spraying fuel.

Better yet, if you have the means to, then hook up a diagnostic scanner while doing this. Notice the Injector pulse width.

Saying you stop using fuel while engine braking is just wrong.

I'll be more than happy to make a video showing this if needed

 

Ya that's what I thought. Engine shouldn't be off at any time while moving, I consider "no gas going into the cylinders" as OFF. Imagine this "smart technology" when you start decelerating, your engine cuts off the fuel, you have manual steering, brakes, and you'll be decelerating alright!! Anyone ever heard of an "idle air control motor" Guess what Jerm? It still lets air through when your throttle is closed, no matter your rpm's. it just gives a lot less (idle worth) that's why you slow down. not because it's off. YOU try turning your jeep off (a.k.a- DFCO) while your coasting down a hill on the highway. I shouldn't say that... I can just imagine the news now... Cherokee Forum will be closed forever!!

 

Well i guess i word it wrong, It uses alot less fuel than idling like when you coast down a hill cause the motor doesnt need the extra fuel. This whole thing came about by notop46 saying down shifting and using the engine brake uses more fuel than coasting in neutral, cause higher RPM = more fuel when its really more throttle and rpms = more fuel

When i do engine brake, i cant hear my exhaust, i hear road noise, my ****ty trans bearings and the motor spinning over. Not an exhaust note or my exhaust leak from a slighly cracked exhaust manifold.

Even if you do turn off your engine all together while its in gear, only manual trans here, the momentum of the vehicle will still turn over the engine at high enough speeds, which spins the ps pump giving you power steering and creates vacuum for the power brakes. Ive ran out of gas once when my gauge was messed up coming down I40 into knoxville at around 80-85mpg and i was wondering what was that bucking and why i was slowing down even tho i was giving it more gas. Then i pressed in clutch and the motor was dead and i lost ps, still had some brakes. If none of this was true then tell me how you push start a manual? going 4mph does have the energy to spin the motor but 65+ doesnt?


If you take anything from this, all in all, engine braking is a great way to control you vehicle whether it be on hills to control your speed or to slow down for a light so you dont have to stop. The fuel advantage is just a perk

 

I share a different opinion. If your engine is spinning more revolutions, it should be drawing in more air even with the throttle shut. Why would the manufacturer choose to put in less fuel when the engine is spinnning faster and using more air?

Back to my original posts: I do my best not to stop my vehicle for red lights. I start coasting early and try and preserve as much momentum as possible for when the light turns green. If I know I will have to stop, I shut it off and coast/brake to a stop. The trans is in gear, and my foot on the clutch in case I need to restart for PS or PB.

 

I usually run 15 city-18city. 20-26 hwy due to wind and what not. 95 xj sport. Stock highth though I'm running a slightly taller tire. Cold air intake and oversized exhaust mani. I drive pretty reasonable most of the time. I also took my head off and polished the valve ports. Better compression just Incase you didn't know. If your interested on how I did this without Raleigh it to a shop I'll be glad to tell you. Just ask. Happy trails

 

I'm running a '96 XJ Sport 4x4 4.0L Automatic. I have a few mods on it that have altered my MPG's so I'll list them.

Flowmaster 40 Dual Exhaust Setup= + MPG
Jeep Mopar Roof Rack= - MPG
Zone Offroad 3 Inch Lift= - MPG
31x10.5x15 BF Goodrich All Terrains = - MPG
KC Hilites (fogs, bumper mounted lights, and roof rack lights, running the 26 series and the 57 series) = - MPG
2 12in Rockford Fosgate P1s with MTX Audio amp = -MPG
Lead foot = -MPG

As of right now I'm getting a solid 15-16 city. I coast into red lights like most XJ owners lol

 

89 xj 38inch tires 410 gears 5speed 13inch shoe i get a full tank untill its empty then fill it again

 

That's pretty decent gas mileage. Tell me about the increased compression. Did you mill the head while you had it off? What's "Raleigh it to a shop" mean?

 

Engine brake. Same reason they install jake brakes on semi's, its to better control your vehicle on hills or steep grades