96blackxj

im looking to tune my jeep to get better gas mileage and i also am going to be switching to e85 its about a dollar cheaper ... i have been tuning cars since 2007 but i dont know what works in jeeps...

i called aem to ask about their fic and they recommend me the fic8... that things is expensive

anyone have any ideas... if all else fails ill end up using the apexi afc.. but the aem fic is a pretty nice unit being that i can fully tune the map with my laptop and have more adjustments

scottmphoto

I don't have a clue what most of what it is that you're talking about but one thing for sure... DON'T use E85. The XJ is not designed for it. I run ethanol free whenever I can (even though it is more expensive). I get better gas mileage and I don't have to worry about the insides of the engine being eaten up by any corrosives that the ethanol garbage creates.

mr white

e85 has 30% less energy content, theoretically, you'd need to burn 30% more to go the same distance. Is it 30% cheaper than straight gas in your area? Here it's only like 75 cents cheaper which is like 20% cheaper than straight gas. You also have to modify your fuel system components in order to run e85. So you factor in that and your $500 piggy back system and it's not cheaper than gas. If you are doing it to save money, you might check into propane.

andrewmp6

What gas mileage are you getting now?Its a 4x4 they will never get good gas mileage the weight and drag on the engine is why.To run e85 you have to change out all the rubber fuel lines for ones rated for e85,And run bigger injectors and tune it for e85.In a low compression engine won't fully burn so you will lose some gas mileage 5 to 10 mpg in most cases.As far as a piggy back system its going to be a waste of money on a jeep.The real only way to pick up any mileage is maintenance and driving habits.Some people on here break in the low 20s mpg with stock xjs anything higher then that won't happen.

mr white

I got about 25 stock with the 5spd.

96blackxj

wow... soo much mis information about e85 in this thread ... i ran e85 in my h22 hatch for 7 months until i sold it i put it back on pump gas... i was using the stock honda rubber fuel lines with zero problems its not corrosive to the inside of the engine either.....

back on topic

i filled up sunday night cost me 60 something to fill up 16.5 gallons... i have only been driving to work and back all freeway driving at 65mph..

i drive about 30 miles each way to and from work so about 60 miles a day... ive gone about 240 miles and its empty again i just wanna do something to get better gas mileage im sure if i tune that part throttle i can gain some mpg i havent put on my wideband to see where the afr is at yet will be doing that this weekend

hankthetank

wow...you need to do some reading. it doesn't matter what you ran in your honda lol
start here

BKohs

E85 is mostly ethanol so you are correct when you say it's not corrosive, it's a nuetral substance, but there are a ton of materials that disolve in it, such as rubber and many different plastics. Also it's less efficient. As stated before it's about 30% less efficient. E85 was not put out there to get better MPG's it was amrketed as cleaner burning than e10 or fuels that have no ethanol, but that gets thrown out the window when you think about the fact that you have to burn a lot more to go long distances. Yes you can get a little more power out of it, but it burns much quicker. In the end E85 is just a money making scheme.

salad

Last guy I saw doing this built himself a turbocharger and new fuel system. Cheaper than high-octane rating gasoline and he was able o meet emissions targets very easily. I wouldn't waste the money on trying to tune a stock 4.0 let along screw it up by running E85. Certainly not ethanol made from corn, nobody wins with that ****.

hankthetank

one word, hydrophilic.

mr white

While your rubber lines didn't degrade in 7mo they might have had you kept it up for a year or two...

96blackxj

im not trying to convert to e85 for better gas mileage i know it needs 25-30 percent more fuel to burn the same air fuel ratio as pump gas... like i was saying i am a tuner and have been tuning cars since 2007 i have tuned dozens of cars on e85 they love that stuff...

i was going to convert to e85 for the cheaper gas and get a little more performance by advancing the timing i still have to figure out why im only getting 15mpg all freeway driving at 65mph i know jeeps arent supposed to get any kind of magical great gas mileage lol but atleast 20 would be nice i would be happy going 300 miles per fill up

mr white

E85 itself doesn't have more "power", but you can run higher compression or boost with it because its higher octane.

hankthetank

that won't happen...look here

salad

That's the thing. The Jeep 4.0L isn't a tuneable engine by those same standards. It's a tractor engine with roots in the 60s. It's already tweaked to the max and was discontinued because the factory couldn't tune it any further and still meet emissions standards.

If you want to make changes to the 4.0L computer you need to actually modify the engine first. Cams, stroke it, bore it, forced induction, etc. Stock parameters give no wiggle room except for high-flow exhaust and intake... and the still PCM does a great job of keeping things running.