What exhaust would you recommend?
- Thread starter Cidamli7
- Start date
Improving the performance of the 4.0 takes way more effort than changing the exhaust. The easiest way to increase the TJ's performance would be getting a V8.
All you are going to change is the sound. If you want it louder, have at it. Wont be faster though.
Just leave it be.
If you are REALLY interesting in more power you will build a stroker or swap a V8.
Just enjoy the 4.0 for what it is.
What gears and tires to you have now?
If you are REALLY interesting in more power you will build a stroker or swap a V8.
Just enjoy the 4.0 for what it is.
What gears and tires to you have now?
Sorry buddy, but contrary to popular belief you are NOT going to gain any realistic power by replacing your exhaust system. This is a long perpetuated myth that has no basis in reality.
Now, the exception to this would be if you went with a full long tube header system and a tune, such as this one:
https://americanracingheaders.com/collections/jeep/products/jeep-1998-2006-tj-4-0l-long-system
With that setup and a good tune, you could realistically expect to pick-up 20-30 WHP.
But just replacing everything from the cat back, that won't do anything for you other than increase sound in most cases.
Now, the exception to this would be if you went with a full long tube header system and a tune, such as this one:
https://americanracingheaders.com/collections/jeep/products/jeep-1998-2006-tj-4-0l-long-system
With that setup and a good tune, you could realistically expect to pick-up 20-30 WHP.
But just replacing everything from the cat back, that won't do anything for you other than increase sound in most cases.
Jeeps need Torque. Not Horsepower. We rarely rev over 3k, and that is on the highway. 2k or lower on trails. So even if the exhaust could gain HP it wouldn't appear until well over the rpms that a Jeep runs. Sorry.
Speak for yourself. I shift around 3.2k and try to cruise, highway or not, around 3k. These engines love the 3k-3.5k rpm range. Let it live a little.
I would be interested to see a hp/torque curve from a dyno pull of a 4.0 with the ARH headers. We’re assuming where the pickup under the curve occurs, but does anyone know? I suspect it may increase hp (and thus torque) across the board.
MrMark52
TJ Enthusiast
You don't say how many miles you have on yours, but I replaced my complete OEM exhaust on my '03 with 118l or so miles on it - from exhaust manifold to rear bumper- and now have improved pep over what I had. I replaced with a combination of components since OEM is no longer available - I've given a listing of what the components used on another thread.
I also changed all 4 O2 sensors.
And, I recently made certain my engine was running at 210 degrees by using an OBDII bluetooth scan tool. To make a long story short, the 195 degree stat I put in 2 years ago was letting the engine run too cool (again, another thread somewhere on this board will give the details).
All of the above gave improved pep. Mileage improvement is TBD, particularly for the thermostat upgrade (done just this past week).
And I agree with the others (above) - Jeep TJ's are not designed to be passenger cars - they're designed for (at a minimum) back country use.
Edit: And let me make it clear - what I call pep is not to be mistaken to be anothers "improvement in performance" It's all relative to what one's expectations are for performance.
Me, I would like better performance (like my dearly departed '03 Grand Cherokee had) - but that just ain't gonna happen with a TJ.
I also changed all 4 O2 sensors.
And, I recently made certain my engine was running at 210 degrees by using an OBDII bluetooth scan tool. To make a long story short, the 195 degree stat I put in 2 years ago was letting the engine run too cool (again, another thread somewhere on this board will give the details).
All of the above gave improved pep. Mileage improvement is TBD, particularly for the thermostat upgrade (done just this past week).
And I agree with the others (above) - Jeep TJ's are not designed to be passenger cars - they're designed for (at a minimum) back country use.
Edit: And let me make it clear - what I call pep is not to be mistaken to be anothers "improvement in performance" It's all relative to what one's expectations are for performance.
Me, I would like better performance (like my dearly departed '03 Grand Cherokee had) - but that just ain't gonna happen with a TJ.
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Ok you have a 2002 automatic which means you have the 3-speed 32RH automatic. You also have very slightly oversized tires which in and by itself reduces performance since larger tire diameters reduce engine rpms at any given speed.
The question is what is your axle ratio, 3.07 or 3.73? If it's 3.07, that's the reason for poor performance. 3.07 reduces the rpms too and 31" tires further reduce them which combine for reduced performance.
Look at the 9 o'clock position at either differential where you'll find a steel tag bolted on. That steel tag indicates your axle's gear ratio, this one shown below indicates a 3.73 ratio (inside the red circle). Depending on which axle you look at, those tags could say either 3.07 or 3.08 or 3.73 or 3.74. The front and rear axles are .01 different from each other.
If the tag says 3.07 (or 3.08), that produces very poor performance. Your axles can be regeared to a more appropriate axle ratio like 3.73 or 4.10 which will substantially (!) improve performance.
And X2 to the others saying a new exhaust won't make a noticeable improvement in performance. Rarely will that happen and it certainly won't help unless your catalytic converter is plugged/blocked.
I've seen you recommend this a few different places but don't see much discussing on what comes out behind it. What's the recommendation there, if any, that would mate well to this header?
Nothing is going to mate well to this other than a custom exhaust. I’ll have something for you soon as I am going to be installing mine in the coming few weeks, which means a custom exhaust to go with it.
İ cant see it coz i think they were paint it before
i can read only this numbers on my rear
And here is front
Take a wire brush/ wheel or some sandpaper to it and try and clean it up
After some work with Photoshop that does appear to be 3.08 in the axle which would account for the bad performance. I'd clean that extra paint off with some Acetone to make it easier to read to confirm.
