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Topic: I need to help trying to improve my mpg

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I need to help trying to improve my mpg

I have a 98 Jeep cherokee two door with a 5.5 re lift and 305/70r 16 tires on it, with a magnaflow hiflo cat super 40 muff and a edge 63mm tb and programer, fipk intake just did a tune up not to long ago and a low temp  thermastat.
Heres the list of what I was thinking to do to get better mpgs
1. Header (Manifold is cracked so I m thinking mpg are getting hindered and better flow is always better)
2. 99+ intake (better flow i find equal better mpgs)
3. E3 spark plugs (have read alot of good reviews about them and I think its worth a shot)
4. Fire Wire kit ( better spark= better combustion= i think equals better mpgs some how I forget lol)
5. going either 19lb (four holed) or 24lb (four holed) injectors for better atomzation of fuel just dont know what size cause smaller could have a better  affect on mpgs let me know what ya think)
6. I heard good things about a adjustable map senor think its worth it.
7. Trying to smooth out the underneath to smooth air distubance with 5.5 lift haha any suggestions on what and where to do it
8. I was thinking of gearing since I run stock but thats alot more investment than all of that put together and I only do lite offroading right now since its my dd lol
9. Possibly cutting inside engine bay to get colder air (right under fipk make little scoop to push cold air into bay and than cap off fipk so its a cold air boxish
10. Is anything else you guys can suggestion


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You can do all you want to the motor but until you swap in the correct set of gears in your axle in my opinion your just throwing your money away...

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Well in reference to that Lead Not Follow whats the cheapest way I can get gears for my car, I heard something about swapping in 8.8s from ford explorers. Do they have front and rear axle swaps? Also I just wondering if anyone had an opion on my injector theory? Should I just go 24lbs. As is right now I get around 247 to a tank I want to try to get 300 to a tank thats around 2.5 increase which I think is capable.

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The only way to really see an increase MPG is to do the gear swap. You could do the 8.8 swap,but what rear do you have now? Chry 8.25/D35. The 8.8 swap seems to cost more than just changing gear sets. I am also running 33s on my 99xj and have done all but the injectors on the engine. I still only get 250 miles on a tank. Personally I will be changing to 4.56 gear sets, to get it back to as close to stock MPGs a possiable.

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99 sport.
rust bucket, DD, 3 car seats
04 wj (w/3 car seats too)
DD duty for the lady  

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What type of gas milage are you getting???

This is one of the things that you did not have on your list that is out there:  LINK

I know that I recently put an entire new exhaust on.  All the way from Flow Daddy Headers to straight pipe down to flow master.  I will say that the XJ runs better and gets up a little faster, but I didn't notice much MPG increase if any when doing this.  I don't regret doing it because the XJ sounds AWESOME and does run better, so it was worth it to me just having it run smoother and easier.

That thing that I linked up there, I don't know anyone running this.  So I cannot say one way or another if it works.  I almost bought one but then didn't because I don't drive my XJ enough to justify it.  $200 for 1-2mpg increase (I think is what they claim, maybe 3mpg) would take a while to pay for itself if the XJ is not driven on regular basis.



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Also something to think of, what all do you carry in your XJ?  If you are hauling tools and other junk, take that out.  You will notice a difference in gas milage just by taking un necissary things things out and dropping the weight of the XJ.

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Diesel power mag tested the fitch thing and reported benefits... I'm thinking of trying out the motorcycle one (grumpy you should too) and posting results. The MC version is a LOT less dough.

As for the tornado things, clamp on magnets, and probably other things, they're junk.  I saw no mpg improvement from a magnet thing I found for almost free somewhere.

You could swap a Cummins 4BT into it.smile

-- Edited by ChevelleSSLS6 on Saturday 14th of November 2009 12:39:03 AM

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I have a throtle body spacer, K&N filter and running royale purple in everthing, im getting 2 more mile to the gallon, and i have not re geared. but i want to some day, im only running on 32'' inch tires to with a 4.5 inch lift

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1999  XJ  SPORT,  4.5'' LIFT,  32'' X 11.50''  TIRE'S



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well I get around 15 city and 17 highwayish... I was thinking of running royal purple in everything but if you got only 2mpg out of all that idk than. But I want to get it regeared when I have the money too. Out here in nj they charge around 800 per axle that normal? That fitch fuel catalyst seems interesting. I ll let you know how things go header is on the way and I should be getting a 2000 intake soon too, I want to do injectors at same time any suggestions on size? I would love diesel especially cummings but that requires $$.

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4bt is about the biggest I think would fit in a XJ without MAJOR major mods. It would need major mods regardless...  a couple months ago in diesel power someone swapped a diesel out of a Jeep Liberty into a XJ.biggrin

4bt= 4cyl b series turbocharged, found in all sorts of stuff, most popular application is frito-lay trucks with a TH-400 behind it.

6bt= 6cyl b series turbocharged... aka "dodge" diesel. Also found in construction equipment and all sorts of crap dating wayyy back.

-- Edited by ChevelleSSLS6 on Monday 7th of December 2009 11:43:18 PM

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1996 XJ "Snowball"- 3.5" lift, bunch of little mods.  I hate pegleg rear axles!
1974 AMC Javelin "Jade Grenade"- 360v8, 4sp, green inside and out. Underfunded Project.
2009 Kawsaki Vulan 900 "Rocket III"- Summer DD

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I know that some people put Mustang injectors on.  I think that they take a whole 5.0 fuel rail but don't know that for sure.  They clame to get better MPG with it, but I don't know anyone personaly that has done it.

You should get better MPG with the '00 intake

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5.0 fuel rail... 4 injectors... 4.0 inline6- 6 injectors. They may work for the four cylinder Jeeps though. I think someone is mistaken speaking of using the rail on a 6.

I think the injectors do swap. I almost got a set off a c4c mountaineer with the 4.6.

-- Edited by ChevelleSSLS6 on Monday 14th of December 2009 01:03:54 PM

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My Fleet
1996 XJ "Snowball"- 3.5" lift, bunch of little mods.  I hate pegleg rear axles!
1974 AMC Javelin "Jade Grenade"- 360v8, 4sp, green inside and out. Underfunded Project.
2009 Kawsaki Vulan 900 "Rocket III"- Summer DD

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I was reading a build on a commanche with a 4.0 in it and they said that they put 5.0 fuel rail on.  I will check up on this and report back.

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Ok, did my homework and this is what I found.  You do not put a new fuel rail on, just the injectors.  Which injectors you ask?  Ask and you shall recieve:

The following is a list of the injectors used on the 4.0L since 1987 along with their rated static flow:

Model Year, ...Part #, ......Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, ...Dark Tan, ...39psi, .................18.6lb/hr
'91-'93, ........33007127, ...Brown, .......39psi, .................21.0lb/hr
'94-'95, ........53030343, ...Tan, ...........39psi, .................21.0lb/hr
'96-'99, ........53030778, ...Grey, .........49psi, .................23.2lb/hr
'99-'01, ........04854181, ...Blue tip, .....49psi, .................22.5lb/hr

The injector flow rate varies as the square root of the pressure drop across the injector. The stock '91-'95 4.0 injectors
are rated at 22lb/hr @ 43psi fuel
pressure, so at 39psi they flow ( sq. rt.(39/43) x 22.0 = 21.0 ).

For stock/modified 4.0 engines or stroker build-ups the following injectors
can be installed. The flow rates are:

Ford Motorsport 19.0lb/hr @ 39psi (Part no. FMS-M9593-C302)
Ford Motorsport 24.0lb/hr @ 39psi (Part no. FMS-M9593-A302)
Ford Motorsport 30.0lb/hr @ 39psi (Part no. FMS-M9593-B302)
Chevy LT1 24.0lb/hr @ 43.5psi (Part no. 17124248)
Chevy LT4 28.0lb/hr @ 43.5psi (Part no. 17124251)
'98 Chevy LS1 25.2lb/hr @ 58.0psi (Part no. 12533952)
'99-'00 Chevy LS1 26.2lb/hr @ 58.0psi (Part no. 12456154)
'01-'02 Chevy LS1/LS6 28.6lb/hr @ 58.0psi (Part no. 12482704)
Accel 19lb/hr @ 43.5psi (ACC-150819)
Accel 24lb/hr @ 43.5psi (ACC-150824)
Accel 26lb/hr @ 43.5psi (ACC-150826)
Accel 30lb/hr @ 43.5psi (ACC-150830)

The '95 Jeep 5.2 ZJ/Dodge 5.9 injectors
(Part no. 53030262) are rated to flow 24.6lb/hr at 39psi.

The selection of injector size will depend on the estimated horsepower output, brake specific fuel
consumption BSFC (assume 0.5), no. of cylinders, and the injector duty cycle (assume 80% or 0.8). The formula is:

Injector size (lb/hr) = (horsepower x 0.5)/(no.of cylinders x 0.8)




So look to the list at the top and buy accordingly to what year XJ you have.  I will say that injectors are expensive new $250-500 depending on what type you buy and where you get them.  The going rate at junk yards seem to be $30.  So go to a junk yard and buy them then clean them up and throw them on the XJ. 

The 19lb Ford (Bosch) Orange-top Injectors  were used in 3.8 L and up engines including the E350 Vans.

The overall opinions of this upgrade varey.  The older XJ's noticed both performance and MPG improvements.  The newer XJ's 97+ notice not much performance but did notice better MPG.  No one said how much for sure, but did notice improvements, so if I had to guess 1-3 mpg. I am sure that I can find more info if I look.  Let me know what you think.  Hope that it helps



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http://www.greatlakesxj.com/tech/injectors.html

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