Ok, ive got a 97 xj with a airaid intake, TBS, and dynomax cat back right now and am looking fow more power. I already ordered the Clifford header, maganaflow cat, summit cut out, tranny cooler, and bid on some lebaron vents off ebay. ANYWAYS, My question is, where should i mount the cut out, im thinking before the cat. Its a bolt on type so i can open it up and close it whenever, and it will be closed 99% of the time. I just got it cause it was 30 bucks and i want to have something no one else has. But some people have said mount it behind the cat. Dr. Dyno, what are your thoughts as well as what kind of power increases should i get wil the exhaust system im setting up. I will be running 2.5" pipe until it hits the muffler then back to 2.25". ANyones thoughts would be appreciated.
Exhaust set up
- Thread starter JoJo97XJ
- Start date
j99xj
NAXJA Forum User
- Location
- Colorado Springs, CO, USA
I'd say mount the cut out as close to the header as possible. Shorter exhaust systems give a better top end punch. Be sure to direct the exhaust outlet away from any underbody components that might not want superheated gas blown on them.
But if your just looking for better all around performance, all your other mods will serve you well. I'm also running a dynomax super turbo 2.25" system with a 2.5" head pipe and the engine really takes off above 2000 rpm. Below 2000 rpm it feels about like stock or only slightly more torque than stock.
But honestly, I wouldn't waste my money/time on a cutout unless you are building a dedicated race Jeep. You should see a gain (I have no idea how much, but Dr. Dyno should know) on a 4.0 but cutouts really deliever the goods on big v8's with long duration camshafts.
But if your just looking for better all around performance, all your other mods will serve you well. I'm also running a dynomax super turbo 2.25" system with a 2.5" head pipe and the engine really takes off above 2000 rpm. Below 2000 rpm it feels about like stock or only slightly more torque than stock.
But honestly, I wouldn't waste my money/time on a cutout unless you are building a dedicated race Jeep. You should see a gain (I have no idea how much, but Dr. Dyno should know) on a 4.0 but cutouts really deliever the goods on big v8's with long duration camshafts.
Dr. Dyno
NAXJA Forum User
- Location
- Al Ain, UAE
The stock exhaust system is very restrictive so the 4.0 responds well to mods in this area. It responds even better when you've already added a free-flow intake, bored 62mm TB spacer, and bored 62mm TB to improve airflow on the intake side of the engine.
If you add a decent header with a 2.5" outlet, 2.5" headpipe, 2.5" high-flow cat, and 2.5" cat-back, you should gain ~20hp so it's definitely worth doing. Even a 2.25" cat-back would be OK with the front part of the exhaust 2.5" but if you decide to port the head, add a performance cam, or build a stroker, you'll need a cat-back that's at least 2.5".
I'm not a fan of cutouts on a street-driven vehicle so unless you plan to do some offroad racing and rev the cojones out of the engine, don't bother with the cutout.
If you add a decent header with a 2.5" outlet, 2.5" headpipe, 2.5" high-flow cat, and 2.5" cat-back, you should gain ~20hp so it's definitely worth doing. Even a 2.25" cat-back would be OK with the front part of the exhaust 2.5" but if you decide to port the head, add a performance cam, or build a stroker, you'll need a cat-back that's at least 2.5".
I'm not a fan of cutouts on a street-driven vehicle so unless you plan to do some offroad racing and rev the cojones out of the engine, don't bother with the cutout.
streetpirate
NAXJA Forum User
- Location
- Oregon City, OR
I've got my Mr. Gasket cutout mounted between the crossmember and the cat.
just pull the cord, drop it into 2nd, and listen to the sweet sweet music.
just pull the cord, drop it into 2nd, and listen to the sweet sweet music.
Yea, the more i think, the less i want to do the cut out, but its still a thought, anyways, I called like 5 machine shops around my area and no one will bore a TB so i might do it myself and my TBS to 60mm. (i dont want to have to mess with the butterfly at 62mm). Also, Dr. Dyno, when i install the header i think im gunna smooth out the exhaust ports, have you done this? is it a good idea? will i see any gains?
Dr. Dyno
NAXJA Forum User
- Location
- Al Ain, UAE
I did a lot more than just smooth out the exhaust ports. I did a full port job on the whole head and yes, it's a good idea. Read these pages to find out more:
http://www.jeep4.0performance.4mg.com/head.html
http://www.angelfire.com/my/fan/prep.html
http://www.jeep4.0performance.4mg.com/head.html
http://www.angelfire.com/my/fan/prep.html
tealcherokee
NAXJA Forum User
- Location
- CT
Joe i have a spare TB ill bore to 60mm for ya for $40, if youll send me your old one once its swapped
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