I just bought a 07 JKU Rubicon with lots of upgrades already done.

A friend also has an 07 JKU (non rubicon) with similar upgrades (lift hight, tires size, etc)

When driving his I noticed it feels like his has more power/torque.

My JK is running 35s, been re-geared to 4.56, has K&N intake, Gibson Headers (gp403s-c) and Rancho exhaust.

His has 35s, stock gears, stock manifold, airaid intake, gibson exhaust.

Both are automatic btw.

Obviously there are lots of variables here.

A few questions are:

Could this combo of intake, headers and exhaust causing my power loss?

Does the JK computer know to adjust the air/fuel ratio for the added headers or does it need to be re-programed?

Does anyone have experience with Rancho exhaust? (I love their products, but Rancho isn't a name synonymous with exhaust to me)


Thanks

 

That's an interesting issue. It seems like you should be pulling more torque than your friend with the setup, though I don't have too much experience with all of that.

Can anyone else chime in?

 

When you 'open up' the exhaust system, you typically gain both HP and torque, however the powerband moves up the RPM band. In every case I have seen, you lose low end torque. Even though you have a higher peak torque and HP readout on a dyno, your butt can feel this as a loss of power since you don't have the power available off the line.

You have to decide where you want the power. Do you want your power off the line or do you want it on the highway?

In theory, the performance products you have, if you go easy on the skinny pedal, should make your motor more efficient and help your gas millage (not by much though as we drive a vehicle with the aerodynamics of a garage door....).

Josh

 

Thanks Infinity. That makes sense and is accurate to what I'm feeling.

Considering the lift, tires and garage door I drive, the milage isn't too bad.

I think I'm going to swap out the muffler though. Mostly because it sounds like my JK is farting.

BTW I'm originally from Nashville. I grew up in Franklin.

 

Mines a 6 spd It's the gears 3.73 will give you a better 0-60 time but less performance off road I have the same if not less 0-60 time going from 3.21 to 4.88 so 3.73 look the best for off the line speed. The larger the number the harder the wheels turn not faster. the 4.88 rip on off road trails but you shift a lot for a daily driver

 

I live in Franklin. Small world I guess!

 

Horray nice to see some jeepers in the franklin area!

 

Update to this.

It turns out that at some point there was a situation that caused the computer to torque lock the Jeep.

I took it to the dealer to have my computer flashed and was told that the computer sensed a dangerous driving condition thus limiting the power.

The bummer is that according to the dealer only they can reset.

$150 later for 15min of work and it's like it have a new Jeep.


Has anyone else experienced this?
Is there a way for the user to clear this?

Thanks

 

Sounds like the computer went out of range of its preset parameters possibly a lean condition caused by all the power adders. When you do that much to a engine it is a requirement to tune the fuel and spark curves to match. I would suggest contacting a couple of programmer vendors and see if they have tunes that will compensate for the extra intake and exhaust flow. Some Manufactures say power adders don't require a tune, but that is only taking the one adding into consideration. You install several and you can get into trouble.