.:I need mods for creating more torque:.

[JaysXJ]

Okay, what mods can you do to a Renix 4.0 to create more torque. I'm not worried about horsepower, just more torque. Mines a lightly modified trail rig only. I would just like to create more torque. Thanks.

 

[ren]

Start with a MANDREL bent exhaust, because the stock sytle is full of kinks and these points can get as small as 1.75" compared to the straight sections of pipe that are 2.25" in diameter. A good header will also help, since the factory design is restrictive by nature. Other than these mods, I do believe that you have to go inside the motor to make more tq/power. Try looking up "strokers" for cam recomendations, and other mods. Dr. Dyno has a recipe for a high torque motor that he calls the "rockcrawler" and I believe it makes around 300 ft/lbs. I am going to build one as soon as I get some of the small parts. HTH Ren

 

[old_man]

I hate to say it but opening up the exhaust in most cases has the effect of lowering the low end torque. Most mods help the HP at high rpms. A different cam or building a stroker are the two most best ways to get more low rpm torque from a motor. Secondly, gears..gears...gears

 

[Pete M]

gears..gears...gears

hands-down, it's simply the best mod you can do.
Jeep on!
--Pete

 

[rockwerks]

Secondly, gears..gears...gears

X20!!!!!!!!!! if you have a manual trans switch to an auto (torque multiplication)

change out TC gearing to 4:1 or add a KluneV for massive gearing....but the best way to keep it drivable, reliable, and comfortable is gearing of one sort or another.

 

[Dr. Dyno]

I hate to say it but opening up the exhaust in most cases has the effect of lowering the low end torque.

In most cases that would be true but in the case of the Jeep 4.0, making the exhaust pipe diameter 2.25" along the whole length would reduce pumping losses and enhance torque across the whole rpm range.
A Borla header with its own 2.25" mandrel-bent downpipe, 2.25" high-flow cat, and a 2.25" high-flow muffler would do very nicely.
You can also install a bored Renix TB (XJ Armor) and make your own K&N FIPK-like intake. These mods will also enhance torque across the rpm range.
The ultimate would be a stroker so when your 4.0 gets tired and is in need of a rebuild, a stroker rebuild would be worth considering.

 

[JJacobs]

I disagree. Every time I've made mods to the exhaust on a 4.0 it has decreased the torque off idle. More torque at a higher rpm, yes, but less at idle.

I'm pretty sure this is also what Tom was referring to.

 

[Dr. Dyno]

I disagree. Every time I've made mods to the exhaust on a 4.0 it has decreased the torque off idle. More torque at a higher rpm, yes, but less at idle.

It depends on how you modify the exhaust. If you go to 2.50" piping or shorten the exhaust by installing a cut out, that would be true.
If you have a 5-speed XJ you would notice a loss of off-idle torque if there was any but I doubt you'd notice any difference if you have an auto. because the torque converter would still be slipping.
In my experience a pipe size of 2.25" is OK for a 4.0. I've already been down that route a long time ago with my Borla header and 2.25" Flowmaster with stock tailpipe. I actually gained torque at low revs, and I have a 5-speed so I could certainly notice it especially in 5th gear.
For the intake, a 60mm TB is sufficient for a 4.0. You don't gain anything by going to a 62mm unit.

 

[8Mud]

I ran the mud pits for a decade or more. A blanket approach to more torque is cubes or gears. Trying to stay in class, kept the cubes down some for us. Gears changed with every track, so we tuned for torque and swapped tires (between 31's and 33's, with 4.11 gears). The axle clearance is only an 1 1/2 difference. 36" tires were just too heavy to get and keep spinning well, with 4.0 cubes. Fine tuning the motor to a specific application, you can tweak the exhaust, the intake, the fuel and the timing/ ignition, generally speaking.
You have to figure out where you want the torque and tune to that target.
Where do you need the torque? Crawling, being able to gas it over a rock? Low to mid to get up a hill? Or pushing mud?
We had a whole lot of things to tune for, while pushing a ton of mud along with us. The thickness of the mud, getting the tires to turn over at the start and not getting caught between gears and out of the torque envelope near the end.
A good place to tune for torque is the flange between the cross over and the cat. if you've removed the cat. try a 1 13/16" re-stricter ( a piece of sheet metal with a 1 13/16" hole in the middle). This will bring the torque down the band a bit (actually closer to stock, with no cat), but may cost you some top end. Cheap and by my experience will move the usable torque, 200 RPM´s lower in the power band.
Tuning for torque, is mostly trial and error, the only way to get more across the entire band is cubes. If your willing to sacrifice top end, then gears. If you run a track or a regular route, you can tweak and tune some for that specific track.