Power advice

  • Cold air intake (flow = go, as @custommuffler would say)
  • Throttle body spacer (stack 2 or more of these for a real power boost)
  • 86-port injectors (basically the more ports the better)

Don't forget the best device ever made. :cool:
tornadoair (2017_11_20 00_38_12 UTC).jpg
Installing the correct gears for your tire size will make the largest difference. The I6 4.0 is only 190 HP, so it's not a hot rod and will never be 'fast'. The only thing it does that is fast, is drink up all your gas.

I did my XJ with 4.88 a couple years back I can't believe how much this costs from then to now.
Don't forget the best device ever made. :cool:
View attachment 530852

Not sure that's legal in Michigan!!
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I ran a Kenne Bell Supercharger on my I6 for years. About 300 ponies and 400 torque at the flywheel. Most reliable mill I’ve ever run.

I'm likely getting around 300hp and 350 lb-ft of torque @7 psi with Banks turbo (flywheel). If my kit was stolen today, I'd likely buy Jezza's turbo kit bc the extra power really makes a difference in drivability & enjoyment. This is my first boosted vehicle and I'm hooked.
You just need the gears. 513 for a Sport is as deep as you can go without changing axles. Yes, 513 for the 42rle and 33’s. You could also get the wranglerfix pcm tune.

I agree…my ability to enjoy the 5.38 gearing and FRP’s tune was held back by the stock shift points. It sounds like Mark has raised them, which I recently learned makes a big difference after bumping mine up quite a bit.
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What's the best thing you've down to add power to the 4.0l? I'm not talking a blown hemi or anything so...

If ever there was a loaded question on this forum this question and what is the best shock would be it! But with that said …for me …I take a put it in the bucket approach… meaning nothing moves the needle in singular modifications but do a few things then yeah. My most noticeable thing probably switching my whole drive train over to Redline synthetic but I also have a manual transmission. Dont think the auto will be as rewarding. Like regearing it’s not adding power just getting what you got to the ground mor’ betta.
Only thing I've done to my 4.0l that increased power was add 40 cubic inches,increase compression,a cam and edelbrock head. It certainly worked but it isn't cost effective.

To make the jeep faster, getting rid of the 3.07 gears was right up there with the stroker
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