Getting some more power out of my 98

[Ba-Riedo]

So right now I have a 98 XJ with a 4.0 and aw4, the engine is all stock and so is the exhaust except for a flowmaster 40 series muffler. I would like to get a little more power out of my 4.0 without spending a ton of money. I have 35's and 4.56 gears and am getting between 12-14 mpg, I want to improve this also.:tear:

First I was thinking a cold air intake, but my jeep sees the trails about every other weekend:

I don't want to be killing filters everytime I go out because it gets a little dusty, I try to stay away from deep mud though.

Another thing I was thinking was a new exhaust since my header is cracked. I'm not sure if I should go for a cheapy like something off ebay or try for a more expensive one. I will be putting in a flex joint to keep from cracking the new one, and also having the entire exhaust redone. I like the sound of the flowmaster but I have heard they are restrictive, what's the word on these? I think if I am going to redo the exhaust at a shop a new cat would be in order to, any suggestions on these?

What other performance modifications can I do? I have heard of a 99+ intake, but late models are hard to find at the junkyards near me. Will better plugs and wires make a difference that is noticeable?

Thanks,

-Alex

 

[wolfpackjeeper]

99+ intake
small bore and hone on TB say 60mm or so, unless you want to buy a bigger one
try y or long tube exhaust manifold. Pacesetter and APN are cheaper than most
high flow cat
good muffler, junk the flowmaster and go with a super turbo style with better flow.
new downpipe

keep your airbox, it does not do you any good to go to a cone style filter.

 

[BlueCuda]

The flowmaster will be fine, IMO if your running a cat its the largest restriction anyways so most any non stock muffler will do.

If its tune up time get some good plugs and wires. I was surprised that Taylor makes a 8mm spiral core spark plug wire sets for the 4.0. I just put a kit on my jeep the other day and it fit great and they make good wires. Best part was it was about $35 AND it fixed an issue I have been having.

I think a good tune up combined with the better exhaust and fixing your manifold will help things quite a bit.

 

[98 jeepjeep]

Bored 63MM TB and a 99+ intake with Ford 19lb Stick injectors. (have a set for sale)

 

[BlueCuda]

IIRC the ford 19lb injectors are smaller than the OEM ones on the 97+ XJs.

 

[98 jeepjeep]

the are smaller only in the LB rating they are proven to work well.

 

[Johnnie Walker]

IIRC the ford 19lb injectors are smaller than the OEM ones on the 97+ XJs.

Slightly lower pressure, but they have 5 holes and spray better to atomize the mixture better, than the stock single pin.

 

[98 jeepjeep]

Slightly lower pressure, but they have 5 holes and spray better to atomize the mixture better, than the stock single pin.

4

 

[BIgDaddyChia]

are the injectors plug and play?

 

[Talyn]

Slightly lower pressure, but they have 5 holes and spray better to atomize the mixture better, than the stock single pin.

They aren't lower pressure, but lower flow.

 

[98 jeepjeep]

are the injectors plug and play?

they are but..........there are 2 different style plugs. square style commonly Orange color and white which uses the rounded plug. My 98 jeep uses the orange square style.

 

[yossarian19]

The throttle bodies are going to provide a few horsepower at wide open throttle but otherwise, it's just allowing more air in for a given travel on the gas pedal IE just push the pedal further and get the same effect all the way up to WOT
99 Intake is nice but you already said you might have trouble getting your hands on one
If your manifold is cracked, replace it with an APN header and throw a flex joint in there somewhere.
New down tube is helpful, go with 2.25 or 2.5 but make sure they get it snug to the engine or your driveshaft may hit it on stuff
If you get it dusty.. yeah.. avoid the K&N
Otherwise... check out this link:http://www.angelfire.com/my/fan/
You probably want to go stroker or re-gear. 4.56 is pretty shallow for 35s... you want closer to 5.13 if you could get it. On stock axles you could manage 4.88 and I think that would help you a lot with power AND MPG.
Just adding tricks & toys externally isn't going to get you far on a 4.0 - its an ancient engine just about wrung out from the factory. You'd have to raise compression or stroke or both to get a ton more out of it. Or add forced induction, of course.

Gears are probably your best bet.

 

[Ba-Riedo]

Ok, thanks guys.

-Alex

 

[Frankensteineken]

I'm gonna have to agree that the bolt ons really don't cut it. Slowly but surely I have "upgraded" most of the parts that are supposedly performance, and haven't noticed any real gain from any of them. I did cat back, a APN header, new down pipe, changed the intake, bored throttle body and probably something else. Unless you are replacing broken parts I really wouldn't recommend any of it. I will most likely upgrade the injectors next, since I will be replacing them anyways.

I'm at the point where I realize what someone else in this thread said; the engine is close to being maxed out as it is and there's not much you can do with out strokin and pokin or supercharging it. When (if) mine ever wears out, I will probably go the stroker route.

 

[XJEEPER]

I'm turning 285's (33x11.50) with 4:88s in my 2000 with an AW4 and they are perfect for both road and trail. Driven daily, my mileage is 17f/15c.
5:13's will give you the most bang for your buck......I know, you want cheap.

 

[ert01]

What vehicles do the ford injectors come out of?

 

[98 jeepjeep]

I'm turning 285's (33x11.50) with 4:88s in my 2000 with an AW4 and they are perfect for both road and trail. Driven daily, my mileage is 17f/15c.
5:13's will give you the most bang for your buck......I know, you want cheap.

what is your highway speed/RPM.

 

[Bricktop]

I know I'm a newb here But, I've been around Mustangs for 15 yrs and The Corral.com for 10. The 19# injectors can be found in any Mustang,Crown Vic, F150 with the 5.0 VERY common injector. Basicly if it's a ford with a 302, it's got 19's.

 

[BlueCuda]

Unless its a Cobra, then its got 24s. Would be a tough junkyard find though.

 

[projectTK]

or just get smaller tires ?:jester:

I get avg of 15mph with my 89xj 87sb350 31's and 355 gears