Jareduhhh

Has anyone installed one of these (or similar) right before the cat?

http://www.jegs.com/i/JEGS-Performan...ductId=1287065

If so, did you feel an increase in power?
And how good does it seal when closed? (is it stil loud when closed?)

dfm_13

dont do it, not enough back pressure

dfm_13

stock engines dont like 'open headers'

crbnfibr

thats to maintain street legality

Gorillaxj

I would agree, not worth doing, just loud and screws you with no back pressure.

cherokee90

lol you dont need back pressure as long as you have a some exhaust off the the head your fine. and ive had those on lots of my cars(camaros, firebirds... V8'S), on a xj its just going to give you the option of running open header or quite exhaust.

TheNerd

I couldn't help but notice that "XJ" was off your list of cars that you've put these on...

cherokee90

Thats because while installing an exhaust on a xj i drove it around with an open header... Well lets just say it sounds worse then expected.

Jareduhhh

Would installing it after the cat provide enough back pressure then?

What's the cause of not having enough back pressure?

And yes, I'm installing this so I can maintain a quiet exhaust through town and open it up off roading.

Jareduhhh

Found this, sounds like the guy knows what he's saying.
"When you remove backflow from the exhaust, you do make MORE power, but the open, free flowing exhaust now moves the torque curve/power band up higher in the RPM range.

You might have made 200 ft lbs torque @ 2500 rpm with the cat on. With it removed you might make 210 ft lbs torque but at 3000 RPM. At 2500 rpm now, it may only have 180 ft lbs

So where your engine makes power will change. With a 92 you have an overdrive trans and doing even interstate speeds of 80 mph only puts you at 2600 rpm.

If your never reaching the RPM where the "mods" puts your power gain at, you will NOT gain anything

My 600 HP 355 would be a dog and get wasted by your stock truck if I had to run at the same RPM as you do. My engine makes peak power at 7,000 rpm. It only makes 179 HP at 2500 rpm"

dfm_13

were they stock engines,,,,,,your rings probably didn't like it if they were stock

dfm_13

cause when you open that up, the flowing exhaust is going to take the path of least resistance, so it wont be going through the cat.

CBR III

How many of you guys saying "don't do it, not enough back pressure" have had the exhaust cut before the cat before?

That's the current state of mine (the exhaust rusted off) until I can afford a new setup. I have noticed no loss of power whatsoever, at any rpm.

Also, in case y'all are wondering: it's not too loud except at full throttle and is almost silent cruising at 2000rpm. It doesn't sound too bad and it takes out some of the whiny six cylinder sound you get with some mufflers.

dfm_13

im not talking loss of power at all, im talking about what is best for your engine

Jareduhhh

Why would this affect the rings? I can't see how back pressure would have enough power to affect the rings when the engine is constantly combusting with much much much more pressure than exhaust back pressure.