Best performance mods?

I'm just about finished with the budget boost and now will be looking into making some HP. What really works on the 4.0 motor ? I was thinking maybe a catback system. Right now its 100% stock and i'll looking for more towing power. BTW, this site is GREAT!

without knowing the year of your XJ. A catback system, Rusty's or Gibson are great systems. A header, Borla, Thorly. A throttle body spacer, a K&N filter or FIPK open style system. Hi-Flow cat if you XJ is older than 96 (OBDII). Have the throttle body bored out.
I would also looking into a Mean Green Starter, and Optima Battery, and a hi-flow thermostat housing/stat from Turbo City. Help cool it down some.

I would look into gearing, that is going to give the biggest performance gain especially for towing. Figure out what rear axle you have to see if it's worth regearing, if not find a D44 or Ford 8.8 (you can find them geared to 4.10). Determine what tire size you plan to run for at least two years and figure out a good ratio to match it.

mike(nj) said:

I'm just about finished with the budget boost and now will be looking into making some HP. What really works on the 4.0 motor ? I was thinking maybe a catback system. Right now its 100% stock and i'll looking for more towing power. BTW, this site is GREAT!

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Be careful what you ask for or you may get it. "Power" or "horsepower" is what you get at 5,000 RPM, and that's not what you want or need for off-road (except maybe mud bogging or dune blasting), or for towing. What you're looking for is torque. As Kejtar said, especially if you are running oversize tires, you need to re-gear. Beyond that, a lot of mods like high flow cats, open air intake tubes and such don't really do much to increase torque in the low to mid-range where you'll be operating. A good RV cam is a better solution.

i agree torque is more important than HP i added Jet stage 1 power control module, K&N FIPK, Flowmaster Delta 2 muffler,
Performance distributors firepower kit, Autolite platinum plugs to my 4.0 and can't really tell any more pulling power. quicker in 1/4 mile.

Definitely learn from those of us who have spent money on the sex appeal of performance parts. I have spent probably more than 400 dollars on getting more air into and out of my engine with a stinless steel borla header and an exhaust with a high flow cat.
The only useable power inrease I have is on the highway, and thats only when passing.
Apparently, the stock exhaust flows pretty well. There is one point of major restriction at the crook of the downpipe though. I suggest getting a shop to chop that section out and put in a piece of uncrimped bent tubing. Buy a K&N flat filter for the airbox and call it a day.

Re: Re: Best performance mods?

Eagle said:

Be careful what you ask for or you may get it. "Power" or "horsepower" is what you get at 5,000 RPM, and that's not what you want or need for off-road (except maybe mud bogging or dune blasting), or for towing. What you're looking for is torque. As Kejtar said, especially if you are running oversize tires, you need to re-gear. Beyond that, a lot of mods like high flow cats, open air intake tubes and such don't really do much to increase torque in the low to mid-range where you'll be operating. A good RV cam is a better solution.

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What did Kejtar say?

i think he said 500 hp @ 5800rpm good but 500 ft lb @ 1500rpm much better.

Re: Re: Re: Best performance mods?

XJCHUCK72 said:

What did Kejtar say?

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OOOPS!

That's the problem with sharing avatars. I saw that Polish chicken and thought it was Kevlar posting. My apologies.

You guys are right, I need mostly torque. Maybe i'll start with just the K&N and go from there. BTW, my jeep is a '95 country. Thanks

I know this has been debated time and time again but I would get an aftermarket air tube and element instaed of wasting money on a K@N for the stock box.I have tried both and by far getting rid of the stock box is the best. Acouple of years ago one of the rags put a xj on the dyno and tried diffrent mods. the in box fillter didn't even make 1hp more where a cat back made about 7 and a set of good wires made 3hp. Boreing out you TB is a great mod and can be done very cheap and produces great driveabilty power.

stock box

the stock box can flow very well if you take the restrictor out of it!!
(at lease mine had one doubled the flow):bunny:

I have done nothing in terms of lifting my vehicle and have spent all my $$$$'s on performance items for my XJ ('96 2dr, 2wd= very light). Here's a list of the things i can think of that I have done:

Flowmaster w/ dual exhaust set up
Yukon K&N fcone filter
Jet Stage II Chip
Jacobs Pro Street Ignition
Throttle Body Spacer
Mobile 1 Fully Synthetic

And my latest addition is a NOS nitrous kit that I am about a quarter of the way through installing. Each of these mods have added both hp and torque sometimes one more than the other. I have been very pleased with the results and don't know of too many XJ's out there that have that ammount of hp & torque.

If you do all these things and you're still not satisfied then you can always add on the stroker kit and even a supercharger if you really want to get more power. My next addition is going to be a Dana 44 rear end and some wide tires (perhaps Mickey Thompson's) for the rear so I can get all this power delivered to the road.

Good luck man!

Jamie

Have you thought about a traction bar? Also, BTLfed, please do a writeup or at least post the install and a couple of run/dyno pics whan youre done with the N20.

Lucas,

I'll be sure to do that, it's probably going to be a month or so until I have the NOS kit totally installed because there are several custom modifications that I am doing, including bottle mounting, guages, and switches. I am also trying to figure out Zex's new Nitrous delivery system that injects at the base of the cone filter rather than at the actual intake tube. I should have some pictures soon, as I have done some of the installation already.

-Jamie