How free flowing should the XJ exhaust be?

sad to see thread die....

Cliff Notes:

What is the bes exhaust? Consensus is free flowing is good. Contention on if cats are worth keeping or trashing. Small issue made about size of exhaust tubing, but it was between 2.25 and 2.5. Large debate on worth of using dual exhaust, pretty much one guy vs all.

chime in, keep the 14 page thread going to 15...
 
I would not run a remote turbo on anything that is going to be wheeled. It does not have the air speed past it to help in cooling it down, longer oil lines and hoter engine oil. There is also alot of turbo lag on the remote systems which would require you to rev the engine alot higher and slip the torque converter/clutch before you have the power to climb over that rock or stump. If I was going to mount a turbo I would use the stock header/manifold because of the small volume and shorter turbo lag. The manifold would need to be strengenthed with some thicker walled tube welded to it. Ceramic coat it and build a heat shield between the manifold and the intake manifold. I would try to have some type of innercooler. Either a vacuume pump or a manual master cylinder for the brakes. And some type of aftermarket engie computer, probably the F.A.S.T. I would run a turbo that is almost too small for it so it would spool up faster.

~Alex
 
kinda what I was thinking, a T3 hooked up to a slightly small compressor should work well with the existing powerband. Since I am already lifted, and planning on going higher, I was kinda looking at "massaging" some clearance room into the fenderwell.
 
My brother bought a t3 or a t3/t4 hybrid for his xj, but he didn't get a chance to install it before he was shipped overseas, so it's waiting for him when he gets back(I didn't want to add another variable to my first engine rebuild).
 
gradon said:
My brother bought a t3 or a t3/t4 hybrid for his xj, but he didn't get a chance to install it before he was shipped overseas, so it's waiting for him when he gets back(I didn't want to add another variable to my first engine rebuild).
Click to expand...

And that. my friends, is how free flowing the XJ exhaust should be.
 
alex22 said:
I would not run a remote turbo on anything that is going to be wheeled. It does not have the air speed past it to help in cooling it down, longer oil lines and hoter engine oil. There is also alot of turbo lag on the remote systems which would require you to rev the engine alot higher and slip the torque converter/clutch before you have the power to climb over that rock or stump. If I was going to mount a turbo I would use the stock header/manifold because of the small volume and shorter turbo lag. The manifold would need to be strengenthed with some thicker walled tube welded to it. Ceramic coat it and build a heat shield between the manifold and the intake manifold. I would try to have some type of innercooler. Either a vacuume pump or a manual master cylinder for the brakes. And some type of aftermarket engie computer, probably the F.A.S.T. I would run a turbo that is almost too small for it so it would spool up faster.

~Alex
Click to expand...

Since when are turbos designed to be air cooled? Every turbo out there is oil cooled, with or without coolant. And actually turbo lag is not affected much at all in a remote mounted system. This is because 90% of the turbo's work is caused by exhaust velocity and pressure, which does not change much at all over the length of the system.

Key notes:
- I've made a TIG welded sch40 stainless log turbo manifold for the 4.0 as a test peice. The manifold would have only allowed a small T3 due to UCA, and engine mount constraints. Some people here will remember the pics.
- my remote mount kit will be intercooled by the use of a methonal injection system. A simple 3 gallon tank will last almost 2 tanks of gas. I will be trying to get a custom front mount bar/plate IC design worked out, but I'm worried about it interfering with an oil cooler/a/c core/radiator.
- you don't need a vaccum pump. a turbo will have nothing to do with limiting vaccum. I do reccomend good brakes however.
- The fast unit is great (although I prefer Motec), but it's a little more ECU than needed for a mild Jeep build. I beleive the Splitsecond FTC1 with some 400cc injectors, and some tuning time is really all you need. I will be running this setup on my 99.


wolfpackjeeperkinda what I was thinking, a T3 hooked up to a slightly small compressor should work well with the existing powerband. Since I am already lifted, and planning on going higher, I was kinda looking at "massaging" some clearance room into the fenderwell.
Click to expand...

Thats exactly what's wrong with the 505 kit. The main factor in any turbo's ability to spool, is the A/R of the turbine and the physical size of the turbine wheel. This is why a T3/T4 is the perfect turbo. You will have the same (or better) spool, but the larger compressor will flow more air and you'll produce more power at less boost. More power at less boost is always safer due to lower intake air temps.
 
BBeach said:
Does anyone have a cross sectional view of a high flow cat vs a stock cat?
Click to expand...

They honestly just have larger honey comb structures (bigger holes) and typically only have 1 element where as most factory cat's have 2-3 elements.

I actually have a 2.5" high flow catco cat if your interested.
 
So basically a constant honeycomb or are there any major obstructions in there? I was thinking that maybe the honeycombs could actually straighten out the air in there making it less turbulent. That's just a shot in the dark though. ;)
 
Bryson said:
They honestly just have larger honey comb structures (bigger holes) and typically only have 1 element where as most factory cat's have 2-3 elements.

I actually have a 2.5" high flow catco cat if your interested.
Click to expand...
How much were you looking for? Anyone have a part number for one? Preferably with an O2 bung already in it? Anything special needed for cali emissions package? I saw on autozone.com that there's one for cali only.
 
Did we cover the part about a smaller diameter cat back being better for low end torque because it will have a higher velocity with less exhaust flow through it? It will have less top end due to too high of a velocity and some wacky reverberations and such inside due to the hihg velocity.
I'm going to go with for my stroker. I want low end torque.

~Alex
 
alex22 said:
Did we cover the part about a smaller diameter cat back being better for low end torque because it will have a higher velocity with less exhaust flow through it? It will have less top end due to too high of a velocity and some wacky reverberations and such inside due to the hihg velocity.
I'm going to go with for my stroker. I want low end torque.

~Alex
Click to expand...

Yup, we did. :rolleyes:
 
ok. I started thinkin about it while i was drivin around today.

~Alex
 
Let me ask, do any manufacturers make a dual outlet header for the 4.0?
Answer: Yes. Who? Clifford Performance, see below
===============================================
Fittment: All 1987-2005 Jeeps 242 cid (4.0L). Includes smog fittings. Description: This is a shorty street rod header which includes the header gasket and street hookup kit. Average gains on a stock engine are 18-22% when bolting on this header. By seperating the heat created by the engine in to two collectors, we can increase the life of the engine and make more power with exhaust scavenging. Want to use a single exhaust? Use our universal Y Pipe (09-240) to single out the exhaust to bolt to your stock exhaust system.
===============================================
Do any manufacturers make a bolt on dual exhaust system for the 4.0 in an XJ? I don't have an answer here, help me out. Not planning on doing any of this, just curious, and please don't flog me.
 
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