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Old 05-23-2013, 07:06 PM
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Stock SRT8 exhaust vs OBX (on a 5.7L)

So I currently have a 2006 Grand Cherokee Overland with a 5.7L HEMI. I have a few mods such as an OME 3" lift, AEV wheels, AFE intake, Diablo Intune, etc.

While changing the oil and spark plugs today I noticed that my passenger side exhaust manifold heat shield was loose. I came to find that somehow one of the rear manifold bolts had sheared off right at the head, leaving a stud in the block and the rest of the stud/bolt and two nuts on the heat shield. I've contemplated upgrading to the stock SRT8 manifolds or even the OBX headers in the past, now even more reason. I'd like to keep my spare so I'll either dump it right at the rear axle after the muffler or somehow get both tailpipes out of the muffler exiting at the stock passenger side location.

I know a few guys have swapped the SRT8 exhaust onto their 5.7L's and even a few OBX header swap have been done. The OBX header swap seems more straightforward as apparently it clears everything with no modding except for the EGR notch.

My main question is, how much would I possible gain going to SRT8 exhaust? What kind of gains going to OBX LT's?

Would I need a custom (mail-order) tune?
How are the OBX cats? Will I throw codes?

Unfortunately I have to keep this on a tight budget. I know OBX is cheap Chinese stuff and I've learned from my years of modding to 'Do it once and do it right' but, honestly the truck is only my daily-driver, now has 105k miles on it and I'd like to get back into an LSX car in the near future (had to sell my last car to buy my house).
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Old 05-24-2013, 05:26 AM
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Re: Stock SRT8 exhaust vs OBX (on a 5.7L)

I was actually quite surprised at the quality of the OBX headers. I was very happy with them.
The cats will throw codes so the best thing to do like I did and order them without and replace the resonators they have instead with the high flow Kooks ones.
Kooks GREEN Catalytic Converter, 3 [GE-90140]

The dyno results I saw from those removing the stock SRT exhaust and fitting the OBX was around the 20-25 hp extra. You would see a greater gain coming from the stock 5.7 due to a much more restrictive setup.
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Old 05-24-2013, 09:02 AM
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Re: Stock SRT8 exhaust vs OBX (on a 5.7L)

Quote:
Originally Posted by Gojeep View Post
I was actually quite surprised at the quality of the OBX headers. I was very happy with them.
The cats will throw codes so the best thing to do like I did and order them without and replace the resonators they have instead with the high flow Kooks ones.
Kooks GREEN Catalytic Converter, 3 [GE-90140]

The dyno results I saw from those removing the stock SRT exhaust and fitting the OBX was around the 20-25 hp extra. You would see a greater gain coming from the stock 5.7 due to a much more restrictive setup.
That's what I've been hearing about OBX, I remember when they first came around to the LS1 cars back in the day. They always got decent reviews.

Those are the exact Kooks Cats I was looking at so as not to have to deal with CEL issues, expensive though!

Coming from the LSX world those are quite some gains for LT's alone. Not bad at all
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Old 05-25-2013, 05:08 AM
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Re: Stock SRT8 exhaust vs OBX (on a 5.7L)

The gain would include the high flow cats and bigger mid tubes as well.
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