Our cats are twin units in one housing. The downstream cat is located in an air gap in the middle. I assume he broke up the rear section of the cat with a steel dowel. If the front one I suspect the cat efficiency CEL code would pop up.

 

 

Hope not hijacking but would like a little more info

My XK-R has the Jaguar active exhaust.
If I wish to do any work to it how do for example 3types of Spires exhaust compare

Is the Jag active the same as stage 1 or......what?

 

The exhaust box has a larger I.D. than the stock pipes, as they slip inside of it. My pipes are same I.D. as inside of the rear box.

I gutted after the sensor, pre-sensor would create problems.

 

Thanks, all, for the replies. My takeaways:

On tuning, opinions/experiences seem equally split. For every person who sees gains from a tune,there's someone who can find no difference and probably wouldn't do it again, given the opportunity. Not sure I like those odds. Still thinking about it.

Would still love someone to directly address the issue of a pulley swap as part of a tune, addressing A) why didn't Jaguar install a smaller pulley to begin with, and B) would there be a detrimental effect on the supercharger or engine, and C) does it really help a tune that much?

As to the exhaust, PUN ALERT: I'm EXHAUSTED by the some of the responses regarding you-know-what. (See what I did there?) Long story short, think I'm going to leave my exhaust system as is, for now.

The simplest solution, it would seem, would be to upgrade to a newer XKR with Dynamic Pack- Performance Active Exhaust, leave all that as is, and have a tune done on THAT car. (But I think that includes the non-cooled Sport Seats. Oh well.)

 

Before you throw in the towel.

This car is better than Sophia Loren in her 20's. It hasnt changed despite all the years.
If it took your breath away when you first drove it, you may have become acclimated.
What can be done there?

Towards that end- a tune, pulley, carbon fiber engine cover that no one sees, all work, because its all what matters to you anyway.

What I have got from your posts is how great this car is. You would have clearly jumped ships if there was an alternative, and there isnt.

Dont worry about engine longevity too much, if getting a tune that Jaguar put in the XKRS keeps you in the car for 3 years longer than it would, you have just increased the car's useful life.

One last and significant point. I am forced to see things 20 years out because of what I do, this is one car that is worth investing in the long run. As in its acceptability and utility.

 

Per the blower, all compressors have curves where they are most efficient. The Eaton is a roots style blower, one of the more inefficient designs due to how the lobe crash into one another as they come together. Turbulence nets friction, nets heat. Heat is the bane of all compression. A screw style compressor pushes the air from one end to the other compressing it. A roots just smashes it together from one side to the other. A screw compressor will run much cooler at higher levels of boost and do it with less drive losses.

So to answer the question, the Eaton roots style blower is not efficient at higher drive speeds and the engineers kept it running at an efficient speed where it won't come apart or cost unnecessary load on the engine. As a secondary concern I think they kept the ECU tune tame enough that the engine seldom sees max load. That's why I suggested up stream about monitoring the I/C temps and working to get the ECU to unleash the beast instead of holding it back.

 

Got it. And I think I'm finally up to speed on all this. Sort of.

- I'm happy with the exhaust note as is. No need to tweak that for me.
- I'm not happy with the crispness/cleanness of the kickdown, especially at 40-50 mph where it seems the zf wants to have the engine at about 15-1800 RPM. And in my s=experience the kickdown from there is awful. I've really got to put my foot in it, almost like there's a turbo lag, which I've never liked. (who does?)
- would love a little more low-end crank in general. Above 3000 RPM it is, as others have said, a beast.

So, keep the exhaust. No pulley swap. I'll keep thinking about a tune.

 

I found my 2009 was much crisper and willing to kick down after having to boot it back up from leaving the headlights on during a mega thunder storm, I didn't notice in the lit loading dock over hang I'd pulled under when I bolted inside.

Over time its sluggished back up. I wish instead of "smart" transmissions could just pick the modes ourselves. Rapid taps of the left side paddle would give you what you want though, no? I have a habit of hitting the right side paddle to keep it in gear, letting the engine work at lower RPM without it making the fuss of downshifts. I think this is why it shifts so dead after a few days from the reset.

 

As I look around at exhaust options, I have to say that active exhaust systems are a great invention. The quiet of a cruiser, and the snarl of a hot rod all without changing parts out.

 

What Q&C posted in #42 above, and what I own, is the 75, which was where Jaguar introduced the x-pipe exhaust and the higher tune that eventually led to the R-S. According to one of the guys who worked on the 75, the additional HP in the 75 was "partly due to the exhaust, but mostly the mapping".

So, you would get a small HP boost from switching from the standard XKR exhaust to the x-pipe, but probably not enough to really change things. I prefer the more aggressive sound, but that's just a personal taste.

 

Or I could just take a look at this. The ONLY British Racing Green R-S 'vert I've ever seen. Still can't get past that rear spoiler, though...
Pre-Owned 2012 Jaguar XK XKR-S For Sale in Bentonville, AR | Serving Fayetteville, AR, Joplin MO, Fort Smith & Rogers | VIN:SAJWA4JA3CMB48036

 

I'd like to see some A/B dyno testing (stock vs. mod). Most of mods described herein talk about "sound" rather than HP/torque.
Folks seem to like the sound of the 5.0 F Type, so why not simply replicate the F Type sound? First mod might be removal of resonators in exchange for an "X" pipe. Should not cost much at a competent exhaust shop. Want more, then consider the F type rear muffler part T2R17354: MSRP $2437.50 - Gaudin Jaguar sells it for $1462.50.
The F Type muffler "looks" identical to the XKR, but has a different part number. A 2013 XKR muffler is CP24867 at $2765 MSRP/Gaudin $1677.

 

The F-Type has Fuel Management that creates the pop-snap-growl of the exhaust, so it's pretty much Computer Controlled.

 

Cee Jay, I wonder just how "fuel management" works to create additional sound?
I imagine an ultra rich mixture on wide open throttle might leave some unburned fuel to burn/crackle in the exhaust. But, all Jaguars already have a very rich mixture on open loop wide-open throttle.
What is your source for this information?
Thanks.

 

Right here; Jaguar F-TYPE: exotic exhaust notes explained | The Chronicle Herald
... most specifically where it says,
"Justin: What causes that delightful pitter-patter drum-beat from the tailpipes when you lift the throttle at higher RPMs?
Dr. Denne: This is delivered through a combination of the exhaust internal tuning, and fueling calibration."

There are many other sources on the interwebz also, some deal more specifically with the Fuel Management.
What it all means is that you CAN'T merely swap exhaust pieces from an F-Type and get F-Type sound.

 

Umm, have a look at the video of the black XKR I posted earlier in this thread?

 

Yep, a little extra fuel and retarded timing on the over run gives a cackling sound.

 

Dr. Denne's very brief comment that the delightful sound when backing off from high rpm is due to fuel calibration (and exhaust tuning). Assume for this discussion that such"fuel calibration" allows unburnt fuel to enter the exhaust system (and burn) on a closed throttle at high rpm. What else could it be?
Most modern cars have a complete fuel cut off on a closed throttle - when operating in "closed loop". This is an emission requirement.
But on full throttle or high rpm the fuel system transforms into an "open loop" with far richer fuel mixture. Rich mixtures do not fully "burn" the fuel. Perhaps, what Jaguar is doing with the F exhaust is simply deleting the fuel cutoff on a closed throttle in open loop thus allowing some unburnt fuel into the exhaust system.
Generally, aftermarket computer tuners do not modify the closed loop system. This system is directed to provide a 14.7:1 fuel mixture under most conditions - a perfect full burn system. Modifications to the closed loop are not permissible.
Open loop tuning is permissible. Autos make the most power on about a 13:1 fuel mixture, but most oem open loop systems deliver a fuel mixture considerably richer. My XK in open loop at wide open throttle is about 10.5:1. Tuners routinely deliver more power by simply leaning out the open loop mixture. I don't know whether or not our Jaguars do a fuel cut off on a closed throttle in open loop. If so, a tuner could delete the fuel cutoff, but it would then deliver a leaner mixture (more fully burned) to the exhaust and no joyful sound. The ultimate trick for a tuner might be to provide a leaner mixture on full wide open throttle, thus increasing power but with a basic fuel "dump" when throttle is closed. I don't think ignition timing needs "adjustment" as all fuel mixture variables can be easily controlled otherwise.
As for exhaust tuning, we all know about the "x" pipe. Whether or not the internals of the F rear muffler are identical to the XKR remains undiscovered. The F has center exhaust outlets, but that in itself is not a big deal. There is a cut-a-way drawing of the rear muffler in my CD Jaguar Shop manual. Wonder if such exists in a F manual for comparison?

 

Porsche does a similar thing.