JKOwners Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
288 Posts
Discussion Starter #1
2015 JKUR with all the "normal" trimmings... 40's, tons, coilovers, etc., etc.

Hated every minute of it with the 3.6l buzz box even after trying a number of performance tweaks from transmission tuning, engine tuning, basic bolt-ons, but stopping short of a blower. Don't get me wrong, on the trail I had no complaints but if I had to drive it to the trail, forget about it.

10k miles on the odometer and I was done with the stock drive train. Body came off and in went a crate LS3, 6L80E, and 241 using MoTech's swap. I didn't think the smile would ever leave my face and I was extremely thrilled to drive the Jeep both to and on the trail.

Of course I cant leave anything alone and the pursuit for more began after turning 8k miles on the LS.

First call was to John at Overland Performance for a new tune. Robbie, in his (well respected) pursuit for OEM like achievement, certainly leaves some ponies on the table. John, after just a few tune changes, had the LS driving/shifting exactly how I wanted it. As I told him, the tune "fit me like a well crafted suit".
 

·
Registered
Joined
·
288 Posts
Discussion Starter #2
We pick up 6 months after John's tune went in. I started the Jeep up to head to CO for some wheeling and I heard a catalytic converter rattling.... pissed!

After looking around at options and getting ready to pull the trigger on something similar to @Dkjeep and go full stainless 3" with some bullet cats, I saw a post from @Dkjeep regarding the Kooks headers which were getting ready to be released.

So yes, a rattling cat turned into an order for a set of 1 7/8" stainless long tubes, catted 3" y-pipe, and a 3" cat back order from Kooks.

 

·
Registered
Joined
·
288 Posts
Discussion Starter #3
The journey to getting what amounts to a custom set of headers and full exhaust was one the I expected to take a bit of time but in this case from order to fulfillment was just over 8 weeks (slightly better than Dynatrac :grin2: ).

The wait was well worth it however as through my discussions with the Kooks team, I knew they were working to perfect this system. The initial offering was more of a mid-length design and they had not released a cat back.

The new iteration is (or very near) a true long tube design with careful consideration for the JK's tight clearances around suspension, drive shafts, fuel tank, etc.

Beautiful craftsmanship...







 

·
Registered
Joined
·
288 Posts
Discussion Starter #4
Ok, lets talk install...

Taking my time, I completed the install over the course of a day and a half or roughly 10 hours, working from the ground.

A few hours to strip everything down up and through the manifolds, trans cross member, plugs, wires, etc. Most disassembly and reassembly steps were easily completed through the fender access with the exception of cylinder 1 which was accessible from the top (with a lot of foul language).

Driver side header went in with only a couple of minor clearance issues. One of the A/C hard lines coming out of the compressor was too close for comfort and was easily hand bent out of the way. The other clearance issue was specific to MoTech's engine mount design which required removing 3/4" x 1" of material on the rear of the mount cradle.

Driver side installed -









Drive shaft clearance looks tight but a full suspension cycle shows no worries with a 1350 Adams shaft

 

·
Registered
Joined
·
288 Posts
Discussion Starter #5
Passenger side was a much tighter fit and after many attempts to sneak the header in I caved and raised the body. I only needed to loosen the body mounts and raise the body about 2.5" to gain the needed clearance between the starter and/or floor hump in order to get the header in.









 

·
Registered
Joined
·
288 Posts
Discussion Starter #6
Header install was completed using a set of Stage8 locking header bolts and the OE MLS gaskets. If you intend to reuse these gaskets be sure to be careful when removing the stock manifolds not to drop, smash, or bend them.

You'll likely notice that I leveraged a number of different DEI heat shield products including their 8" plug boots, 12x12" peel and stick, as well as their Velcro split wire/hose wrap.

All hoses/wires running near the headers were wrapped and exposed floor pans were covered. I also wrapped the bulkhead connectors on the passenger firewall to prevent the heat from making the plastic brittle over time.

Some might ask why I didn't wrap the headers, simple, it will void Kooks warranty.

The final step in ensuring things keep their cool was to modify the inner fender liners to allow more crossflow both at the front end as well as at the rear opening. Yes, I could ditch them but I have never cared for the look of or the open cavities at the rear wheel opening.
 

·
Registered
Joined
·
288 Posts
Discussion Starter #7
I would certainly like to say the remainder of the install was a straight forward bolt-on but we all know that is never the case.

The y-pipe, being a ball&socket design requires very close alignment of both the ball and socket for a leak free fit.

I found the Kooks y-pipe to be close but requiring prying/pushing and the use of some well positioned ratchet straps in order to bring it into the correct position.

There was some interference with the cross-over from passenger hitting the trans mount. This was temporarily resolved by cutting a small section of the mount itself, removing some of the rubber, and positioning the trans as far towards the driver side as reasonable. I also found that I had to cut the mount plate (the one which bolts to the trans crossmember) on the passenger side by roughly 3/8" from front to back in order to clear.

All of the O2 sensors (both on the headers and y-pipe) are extremely well positioned and offered no clearance issues. Each of these can easily be replaced without removal of any other components.













 

·
Registered
Joined
·
288 Posts
Discussion Starter #8
Finally... the "easy" part :grin2:

The cat back was certainly straight forward and as with the front half very well fitting. I'm running King 2.5" rear shocks and had no clearance issues. I am also running RK's rear arms and am stretched 1" from stock with the sway bar pushed back 1" as well, no clearance issues there either.

I did find that I was not happy with the way the tailpipe was angled given the position of the two hangers. A little heat and an angle finder helped move those hangers into a position that I liked. The tailpipe is now tucked up high out of the way of rocks, not close enough to damage the bumper, and near straight down from a gas exit perspective.











 

·
Registered
Joined
·
288 Posts
Discussion Starter #9 (Edited)
The results....

Sound -

I'll start off by saying if you want to be an ass hole with this setup you certainly can be. It is loud if you get into the skinny pedal but sounds great, somewhere in between Borla and Magnaflow but definitely a straight through sound.

I'll try to get a clip posted in the near future.

At cruising speeds between 55-85 there is no drone and the Jeep is fairly quiet, easily being able to have a normal Jeep conversation.

Power -

The engine revs noticeably easier, it is very apparent (despite what I have read) that the stock manifolds are a restriction and leave much room for improvement.

The torque below 4,000 RPM seems to have picked up across the board and reaching the upper end of the RPM range happens in the blink of an eye.

The dyno will soon tell, after some tuning, what the real results (by the numbers) actually are here. I was told by Kooks that the test mule picked up 31 HP w/o tune adjustments but as we all know those are peak numbers.

And for anyone wondering... I no longer have a rattling cat :grin2:
 

·
Premium Member
Joined
·
4,087 Posts
Great write up and pictures. Thanks for taking the time.

Just going by the pictures, they look like they might fit my hacked up junk. I have the LS moved back 4", so the dvr side rear primary is just rearward of the plane of the firewall. Those Kooks look like that primary might go forward enough to clear.

Very interesting.

Sounds like those Kooks actually work. The shorty type headers, I don't think are really much better than manifolds.
 

·
Registered
Joined
·
1,020 Posts
That's a sharp setup no doubt. If I ever had to get back into mine or remove it for any particular reason I might pick up those headers and cut on my existing exhaust to make it work. I'm just not motivated enough to dig into what I already have and drop that much more coin on exhaust right now when its working fine.
 
1 - 14 of 14 Posts
Top