More torque & top end out of a 99 4.0L

[Howey]

I was wondering if any one had any tips to help me out here? It's a 5 speed and has around 40,000 miles on it.
It has decent torque but the top speed is around 80 to 85.
Any suggestions?

 

[Dr. Dyno]

You can go to my performance website and get some ideas for hopping up your 4.0. If you decide that 4.0 power is still not enough (as I did), you can build a 4.6L stroker and enjoy the extra torque.
____________________________
Dino's "Mean Green Machine"
1992 XJ Laredo 4-dr - 4.6L I6 HO Stroker - 181k miles - AX15, NP231, D35c, D30

263hp@4900/321lbft@3300-3800, 1/4 mile = [email protected], 0-60 = 5.8secs
Websites - Jeep 4.0 Performance, 4.6L Stroker Build-Up, Dino's Jeep Tricks

 

[Howey]

Thanks for the info.

 

[Sarge]

You do realize torque and top end are two different things, right? Torque is off the line power and top end is horse power. Not saying you can't have both tho.

Sarge

 

[Mike@Accurate]

80-85 top end? Something is wrong. You should eventually be able to get to the speed limiter (116mph, usually). Do you have giant tires ? Weigh 5k# ? Barn door on the front end ? Before you start looking for more power, you should try to find the missing power. I could hit the limiter with my '97 TJ 5spd and my '00 XJ auto when they were stock. MIKE

 

[Howey]

I probably need a serious tune up but I appreciate the help with the top speed numbers. Sarge I am aware that they are two different things. I was just trying to find different ways to improve both. Thanks though, I appreciate the help.

Howey

 

[DeftwillP]

Just recently, I finally finished my airtube and ignition which were years in planning. I build a heat sheild and long tube intake along with putting on magnecore wires with my MSD coil and .055 gapped plugs. At first, I didn't notice anything down low. But on the highway, what a different story. I can accelerate from 55 to 70 in a snap. It really improved top-end performance.

 

[Howey]

thanks

 

[Atl XJ]

80-85 top end? Something is wrong. You should eventually be able to get to the speed limiter (116mph, usually). Do you have giant tires ? Weigh 5k# ? Barn door on the front end ? Before you start looking for more power, you should try to find the missing power. I could hit the limiter with my '97 TJ 5spd and my '00 XJ auto when they were stock. MIKE

Yeah, seriously, even when mine was stock it would do do barely touching the gas and easily hit tripple digit speeds.

 

[phaythe]

Yeah, hitting the limiter should be CAKE in that thing...there is definitely a problem if you can't get above 85...run out 3rd gear to 5k...not sure where that puts you in a stock manual...but I can't get to the top of 3rd in my auto...limiter stops me at around 4800...and pisses me off to no end...hehe But that will soon be gone

 

[Howey]

I also haven’t really tried to go over like 90 but like I said I couldn’t get over 85 the last time I tried. Besides a tune up should I do anything else? I just had it in the shop to replace the front drive train and asked if there were any other problems and they said no. I appreciate any and all help.

 

[Dr. Dyno]

Try gutting the cat. A plugged cat is a common reason for Jeeps being sluggish on the highway and reaching lowly speeds even with the pedal mashed to the floor. Unless your Jeep is lifted or has bigger tires, it should reach 110mph with ease. A 5-speed should hit the top speed limiter at about 116mph.

 

[Howey]

I cant cut the cat. They have crazy strick emissoins in anchorage. I'm due soon. Thanks for the tip though.

 

[FUNKYTEE5]

I cant cut the cat. They have crazy strick emissoins in anchorage. I'm due soon. Thanks for the tip though.

Check and see if the thing is plugged

 

[Howey]

How? Do I just disconnect it? And if it is hw would I clean it out or do I have to buy a new one?

 

[FUNKYTEE5]

How? Do I just disconnect it? And if it is hw would I clean it out or do I have to buy a new one?

You could hook a vacuum gauge up to the motor and find out if the exhaust is plugged. Or you could take the cat out and look through it. You should see a honeycomb looking structure with holes all the way through. If you can't see all the way through it then it may be toast. You could also do a noisy uncorked run with the cat out and see if the motor runs any different?

FUNKYTEE5

 

[redyouch]

something is defintetly wrong, my 95 gets to 85 MPH like nothing

 

[scoobyxj]

I would defenitly get a tune up done. Then check that cat. At around 40K it should still look new, but you never know. I can still hit the limiter with 3", 31's, auto, and 3.55 gears then run there for the rest of the day as long as every dip in the road dosn't through me through the roof. You might check the muffler for obstructions too.

 

[c420dragon]

Helloe all,
I am new here but here is my 2 cents. I have a 95 Xj and I can bury the sped. with no problems.

I track tested my stock XJ and ran a 17.4 qtr mile. I then added a Venom 400 Control Module which changed the Shifting (I have an auto) andmisc other things. I also put a high flow cat, Borla exhaust (cat-Back), a 1" Throttle Body spacer and a Home made Ram air kit in. I could def.. fell the difference in the take off and climbed to top end quicker. I have yet to be back to the track to test it. So I don't have another acurite qtr mile figure to give, but I am guessing maybe 17 sec qtr mile.

FYI I just took off the "home made ram air" I was too afraid I was going to suck in water since the entry point was in the bumper. I am going from Street Performance to Off-Road stuff now. A little less speeding

 

[BruteXJ]

....(wiping a tear from my eye)....god bless a 4.0 and a 5 speed. There is nothing quite like driving a blue brick up a mountain, passing Mustangs and Hondas while laughing all the way.

If nothing else is wrong, get a hi-flow filter and a nice muffler. I wouldn't touch anything else on my 4.0 .