Metmknice

Have a good local exhaust shop, with a mandrel bender, make a downpipe with a flex joint and your cat-back system. Shouldn't be anymore than 200, unless you are replacing the cat as well.

BlueRidgeMark

terzdesign

I went ahead and ordered these parts from Perf. curve. Everything is 2.5" since I'm starting to join the school of thought that bigger is better! lol. I will go to a shop and have a new downpipe made when I get the old one off. The only thing left is to figure out where to put the 6" flex pipe on that downpipe.

cat link
muffler/tailpipe link
flex pipe link

Can I just weld the entire system together from the downpipe back? Are there drawbacks to that?

mr white

I had my flex pipe out in in the straight section between the bend coming down and the bend going to the cat underneath the bell housing.

5-90

Be careful with that thinking - as I said, there is very much a point of diminishing returns with exhaust, and you will rapidly pass that point and get to where you're actually causing yourself more trouble than you're trying to correct!

(Those kids putting 4" exhaust on Hondas? They do that because they see turbo people doing it - so it must be good, right? Thing is, turbocharger impellers in the exhaust stream change the rules when it comes to cylinder evacuation, and putting a 4" exhaust on a naturally-aspirated - or even a supercharged - engine will actually be MORE restrictive, not less, for reasons previously given. Be careful you don't end up shooting yourself in the foot - 2.5" ID exhaust is borderline for a stocker...)

XJlimitedx99

With that 2.5" pipe you can justify building a stroker!

terzdesign

I will not be putting any 4" pipe on my xj. After reading up on the subject quite exhaustively, there have been many recommendations to moving up to 2.5". It was easier finding parts that were 2.5" also. In addition, Performance Curve recommended these parts

salad

Of course they recommend it, they're selling it!

terzdesign

haha, Yea I thought about that too. I figure though if they have a muffler and tailpipe kit specifically for an xj AND others on this forum have recommended them... well, it can't be all that bad. The prices were reasonable as well. They gave me 10% off for being a member of the forum.

5-90

Ask to see their math, or to fully explain their reasoning. If they can't do that, go elsewhere.

(The 4" pipe was more an example - coupled with the fact that these silly kids put 4" pipe on something that has less than half of the displacement of our engines, and wouldn't need 4" plumbing even if it DID have a turbocharger on it, well ...)

salad

Not quite on the mark there 5-90... they only put 4" pipe for the couple of inches

mr white

Even if 2.25id is the optimum size for the stock 4l you're splitting hairs over minsicule HP gained vs 2.5id or even 3in. Also to be fair the generally agreed upon standard for Turbo honduh exhaust size is 3in.

mr white

Even if 2.25id is the optimum size for the stock 4l you're splitting hairs over minsicule HP gained vs 2.5id or even 3in. Also to be fair the generally agreed upon standard for Turbo honduh exhaust size is 3in.

5-90

For our engines? Yeah.

For some riced-out BS import? Anything over 30mm or so is probably stupid big. If you balance it to run 2,000-2,500 past redline, then MAYBE 35mm would be useful, I'd have to check.

But, I have actually SEEN Hondas up on the lift with 4" tube all the way back (!) no turbo, and they wonder why their performance is suffering (this was in automotive class. They hadn't gotten into theory yet...)

I figure this is the same mentality that compels them to mount a 5" Monster Tach - with functioning shift lamp! - when they've got a JATCO transaxle...

salad

[QUOTE="5-90;2773560"]
But, I have actually SEEN Hondas up on the lift with 4" tube all the way back (!) no turbo, and they wonder why their performance is suffering (this was in automotive class. They hadn't gotten into theory yet...)/QUOTE]

:| I see.