You see the black cup on the bottom pipe of the stock exhaust box?

That was your active exhaust control flap.

 

Yes. But I re-installed stock exhaust Saturday! Hence the pulling of the fuse!

 

Well, after about six months of no fuse 19, I have decided to plug it back in. I am having a pproblem with a lazy downshift in manual mode and I suspect that the Fuse19 was the cause. After putting fuse 19 back in II have noticed much smoother shifting. However, the lazy downshift still comes back after a long drive with a lot of manual downshifting. I think it will just take some time because the TCM has learned the shifting without the active exhaust.

 

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You will have a noticeable decrease in power during full power high rpm
Because your butterflies are closed and savaging is reduced to two pipes opposed to four pipes..... Try re installing fuse 19 and see the difference

 

That doesn't make sense. With fuse 19 removed the car will use all 4 tail pipes all the time. Even with fuse 19 in, the exhaust valve opens above 3750 rpm at full throttle so whether the fuse is in or out the valve should still be open with all four tail pipes in use.

 

Ironically, although the exhaust sounds louder under 3750 rpm without the fuse 19, I think it actually sounds worse. The car's exhaust note seems to have been carefully tuned, and around town it sounds much more musical with the fuse 19 installed. Also, it's probably just psychological but it also seems slightly more torquey at lower RPMs with the fuse installed.

And as I said, manual (and automatic) shifts seem much much smoother with the fuse 19 in place.

 

Well, it turns out it was completely psychological. My shifting woes were actually caused by a bad axle, which has since been replaced. I unplugged Fuse 19 again, and I do think it actually sounds better. At little bit more warbly at low RPMs like a V8 should sound, and there is no range where the exhaust suddenly comes alive--it is a much more gradual increase in volume.

 

An interesting tidbit from the service manual:

The red highlight is mine. The table basically shows that in auto-shift mode (either D or S), the valves stay open up to 1100 RPM, then stay closed until 4000 RPM - unless the throttle is more than 80% open, in which case they reopen at 3750. But as soon as you play with the paddles, they stay open.

 

Interesting... what year is that manual?

 

11-May-2011 - so it covers up to MY11. Sorry, should have specified that, because they may have changed it later.

 

That's exactly why I prefer it pulled. (Plus its still quiet while cruising, which for my taste makes it perfect.)

Glad you got to the bottom of your axle problem, must be a great relief.

 

just pulled #19 from 2014 xkr with performance active exhaust - 2 comments - 1) owners manual says fuse is driver side footwell and this is wrong, it is rear center seat compartment (as many of you have correctly indicated) and 2) the lower rev sound becomes a deeper rumble as opposed to an angry crackle (maybe due to reduction of back pressure) - drove the car for a bit then replaced the fuse because decided i missed the crackle/snap/pop - clearly a matter of preference, but i can confirm the sound does NOT become noticeably louder

 

We have discussed in the past that there are 2 different XKR exhaust systems. Both of which have the butterflies on the rear muffler. As we know the difference is the performance exhaust has the X pipe and the standard XKR active exhaust has a small center silencer. So as we talk about sound I suspect the 2 systems may sound a little different. Maybe we should split this threat into the 2 systems and then compare the sound. I have the performance active (X) system and I can hear the sound change when I first start the car which I attribute to the valve closing. When I get into the go peddle with the top down the system RAPS around 4000 rpm. Now if I hit the DSC(checkered flag button) I hear the system open up and the RAP is all the way up the rpm range. With the button on I also get the crackling and popping on deceleration which I like. It is also more of a drone at low speeds which I don't mind. The good part is that with the system closed and my bride in the car cruising at 50-70 mph it is very quiet in the cabin even with the top down. The best of 2 worlds for me.

 

agree two systems likely sound different - i am always in "s" gear with "dsc" on - for me this provides most aggressive exhaust notes (also on deceleration as you noted) - removing fuse 19 actually made the sound more tame/hollow, at least to my ears - i was hoping to get a more active sound at lower revs, much like the maserati has - it seems to accomplish this, i may need to change out the exhaust, which i am not willing to do for warranty reasons - thanks for the information

 

You can change out the exhaust system with out worrying about the warranty. I put in the Mina system about 9 months ago and have had the ETG tune. My dealer is aware of both changes and has not ever made any comments about the changes.

 

thanks - might consider changes to exhaust if i ever add that engine chip which apparently boosts the hp to 550

 

I have done the same on my 08 XKR and have never turned it off since installation.

 

Why would you need a switch to do this since according to the manual excerpts above "When the transmission is in the manual (sequential shift) mode, the exhaust valves are permanently open.". Couldn't you just stay in manual mode full time? I have not picked up my 08 Portfolio yet so maybe I am missing something.

 

You can, but if you are in drive it goes back to full auto by itself if you haven't changed gears for a while. And if you want to drive in sport, it is a bit heavier on the juice and the changes are a bit lumpier (I think) unless you are giving it the hammer.


personally I don't know that pulling fuse 19 made that much difference, I notice it much more when I do the chequered flag thing, but then the ride gets firmer.

 

The quote is also from the 5.0L workshop manual. The 4.2L workshop manual doesn't mention it, it just says the valves are opened in response to engine speed and throttle angle (they also open when the car is first started).

I took the fuse out on my '07 XKR soon after I got the car so can't confirm either way.