Has anyone installed high flow CAT converters on their Jaguar? For the later models does the ECU balk at those? Would there be significant difference between buying them from a company specifically selling Jag parts or generic high flow CATs at significant savings?
The OEM CATs seem the most restrictive aspect of the exhaust system. While CAT-back setups certainly could add 15 or maybe up to 20 horsepower (maybe a bit more with an ECU tuning after), the CATs would seem the greatest horsepower robber. (Obviously we can't just remove them for the master overseer ECU).

Thoughts on the topic? Anyone heard of anyone putting those on their Jaguar? Which year and model if so?

 

BTW, when did the UK start requiring CATs?

 

Speak to http://www.eapj.com, they have one that is produced by larini. Have this one from EAPJ on my car and although I am not sure what it brings in hp, I do like the extra sound with my otherwise stock exhaust.

 

I have just been thinking about this very topic. My 2003 Jag XJR 4.0 is out of warranty and I wanted to toy with it a bit.

Paramount Performance has racing cats(200 cell) available, pricey, but with 25bhp added.

 

Thanks for the link.
Do you remember the pipe diameter (2.5 or 3.o)?

 

I just communicated with them over those. They informed me that their's only work with the ECU IF you also buy their Milltek exhaust setup too. Those a 2.5 inch pipes that go over the rear axle and you have order it with or without a forward resonator. So it's just over $1800UK delivered - or about $3200 US for both the CATs and exhaust.

 

True with the paramounts ones and fitting, didn't know there’s needed also an ECU adjustment.
Obviously the EAPJ/Larini one is working on my car with a stock ECU/exhaust, but I can't remember the dia, probably a tad bigger then stock as they usually also fit this cat with bigger exhausts.

 

Well that just sucks! What is the point of that? you can get a full cat back Borla exhaust and gain 20hp for $1000.

Well thanks, cause now that made my choice a lot easier. Its Borla or Magnaflow exhaust, ECU and looks like I'll port and rebuild my supercharger.

 

So your running stock exhaust. I though you also went with the exhaust system and was wondering pipe diameter.

 

Avos just posted that the ones he got from the company he indentified works with his stock exhaust. I suppose you could add those and then put in a couple of electric cutoffs (cheap on eBay) after forward mufflers but before your rear mufflers for both worlds of OEM quiet and here-I-come roar (though still somewhat muffled) plus the freer flow of the more open CATs and lesser restricted exhaust.

 

Yeah, but the prices are starting to get up there. 1900 pounds is a lot of cash for an exhaust system when you can get 5hp less for $1000. That money is better spent on other upgrades.

 

I never believe manufacturers or merchants claims on horsepower. Old motorheads can remember when cam companies would claim you could get over 100 horsepower in a V8 merely by putting in their $99 camshaft. Even showing a dyno number on a video can be very misleading. Warm up a motor when it's warm out with any OEM equipment on it - then do it again when the motor isn't hot, the hood is up and with cool air outside and it'll show 10 or even 20+ horsepower gain - just for the cooler intake (denser) air. Don't go crazy on the water/alcohol output or go over 50% alcohol.

A good "roar" or "loud" CAT back under the axle exhaust MIGHT give you up to 20 horsepower more. A big maybe. If it has front and rear mufflers it's probably more around 12-15 horsepower. Better flowing CATs MIGHT give you 20 horsepower more. Probablly more like 15. A good exhaust and open CATS might give you 30-35 horsepower more. For $50 more they can add a generic X-pipe where the forward muffler was. That adds torque, but muddles the exhaust (it changes the "pulse" rates and I think negatively in terms of sound). Under the axle pipes flow better. Over the axle pipes can give some cars a nice exhaust "rap" when motor braking. (Don't know about Jags).

Where you'll see some real benefits on an exhaust swap would be then if your ECU was remapped to take advantage of it. (Remapping/working an ECU is NOT cheap!) I figure an ALL OUT effort would be the mega-costly headers, freer flowing CATs and a big diameter under the axle exhaust with free flowing (loud) single mufflers. MAYBE with ECU work that could give you 50 horsepower on an XKR, MAYBE 35 on an XK8.

For economy, just have a muffler shop put in straight pipes instead of the front mufflers and stick something like Borla racing mufflers (ebay) on the back. You'd be out about $400 tops, it would look the same, sound as good, they could use your tips so no appearance lose and it'd probably toss 10 horsepower your way - and probably within 2 horsepower of what a $1000 setup would do. It's not like anyone every looks under your car to see the brand of exhaust pipes and mufflers. An exhaust sytem is only about "you."

If you want to tinker, put on a cheap water/alcohol injection setup (probably cost you less than $300.) This would help prevent your "denotation detector" retarding timing plus cool down the intake air - therefore adding some free horsepower.

And/or you could put on a little wet NOS setup (MUST be wet), but it'd be a bad idea to go much past 50 (maybe 75 tops) horsepower. Go too high and you can melt your motor. Don't have a wet system and you will melt it. Little wet NOS on Ebay if you watch for probably around $500.

So with the home-done exhaust mods, water/alky injection and NOS you'd be up around +65 horsepower or so on the NOS button, and probably 20 or so without it - for just over $1K if you do the under hood tinkering. After than it starts getting expensive quick!

Put on a K&N air filter - 3 horsepower. (That's not much, but it's the cheapest horsepower per dollar you can get - other than leaving the spare tire and jack home, plus have 1/2 rather than full tanks of gas - lose 100+ pounds - that's free. A can of octane booster on a hot day could help too in the sense of the denotation detector allowing a tad more advance).

My 2 cents worth.

 

Dfwx...

I like your ideas.

I was thinking about the x-pipe in the front muffler, straight pipe the middle mufflers and Magnaflows for the rear. Do you think I'll have an issue with loss of backpressure?

Also, I've been having trouble with the Mina cold air intake with K&N filters. It keeps giving my XJR error codes after a week or so of driving. I take it off and all is normal.

About the water/alcohol injection... do you have any links for any? And do you think I should get an upgraded intercooler instead for more daily driving?

 

Your exhaust idea sounds good. I look at the prices they want for pre-made exhausts and go "wow, they sure add a lot for that word Jaguar in the part identification." An exhaust system is an exhaust system. They aren't brand or model specific at all. Just the bends are.

The BIG restriction in the OEM exhaust is a TERRIBLE crimp in the over the axle pipes. If you looked at it you'd see what I mean. They did NOT use a mandrel bender (WHY?) and it bends extremely narrow radius - so the pipe digs DEEP into the pipe clearly rstricting flow.

Don't hold me to much what I write. No, I do not think back pressure an issue at all. But our cars have a particularly evil and inconsistent master brain ECU.

The ECU system is wacko, who knows why it doesn't like your Mina intake? I'm skeptical of the cold air intakes and just did an K&N filter swap out. If I do go with a cold air intake I'll probably try to make it myself to make sure it is a "cold air" intake rather than sucking motor heat.
An upgraded intercooler (actually I think they call it a pre-intercooler radiator?) would be no maintance worry free.

I personally prefer AquaMist, but most people use Snow. Snow costs less. I think AquaMist more refined. Snow probably easier to install. Both systems are on eBay. You'd probably get more performance (slightly) out of a water/alcohol injection system but do you REALLY want to be filling it all the time?

 

No, I dont want to fill the water/alcohol system. So i'm going to go for the intercooler since i have a upgrade upper supercharger pulley here. I was considering porting and rebuilding the supercharger but i'm getting conflicting views on what kind of hp it would gain if at all.

Also, I am going to get the Magnaflow x-pipe(http://www.autoanything.com/exhausts...A2672A0A0.aspx) and a pair of Magnaflow rear
mufflers while I delete the middle mufflers. $4-500 and i'm done, get some nice sound and probably some increased HP.

All said and done, I want to be right around 450 hp. With an ECU, pulleys,intercooler, K&N drop in filter, and exhaust i should be close to that figure.

 

This is mine from behind the factory cats.....all custom 2.5 pipe, x pipe and magnaflow mufflers w 3" tips....

http://www.youtube.com/watch?v=XbtINxEVtlQ

 

How does it sound inside the cabin at 50-70 mph? Did you see an improvement in performance?

 

Yea, more tq def.....hp prob so....When I smash the pedal it kicks out a bit and takes off....gets through the rpms quicker....also have the upper pulley and the mina cold air....

Inside the car is very quiet while driving normal......smash the pedal it and it about the same as the blower whine inside the car.....outside it has a very nice growl to it.....nothing crazy loud like a mustang or anything

 

Great, thanks! Exactly the feedback I was looking for.

 

maybe this week I will do a video from in the car....