Dynamic mode automatically turns on loud mode. You have the turn the loud button off again if you want the valves closed while all the other dynamic features are turned on.

 

And if your car is like mine, you'll notice a difference if you turn the exhaust switch on, listen a while, and then select dynamic mode.

 

Sorry for the late response, I was traveling. Interesting information. Thank you for the detailed response.

On my 15 XF, I'm not an R or RS (I like my tan interior better lol) my bypass valve on the muffler is pressure activated, there are no electronics to the muffler at all. Maybe that's the difference in exhaust for the R and RS models? Don't know.

Back in the 90's my cousin was autocrossing and road racing a 91 5 liter GT Mustang. It started off mild, then it went to ridiculous to the point the factory computer couldn't run the car if it was below 50 degrees... But, during that time it went from NA to a whipple supercharger which to this day I hold a great amount of respect for. Always worked, and never gave any trouble. Maybe it wasn't the best for drag racing, but for street driveability, it was unbeatable. When it started out with factory 'hammer dent' headers (you old Ford guys will know what those are) and moved to JBA shorty headers, with a flowmaster cat back exhaust. Changed the sound of it, ran a little better, but it wasn't until the 'offroad' H pipe was installed that things really changed performance wise. It didn't get louder, it just got faster. It was a 2.5 inch pipe system. We ported the exhaust side of the heads too. Some point later, the JBA's came off and I'm pretty sure he went with MAC long tube headers and short H pipe, and at that point went to Trickflow aluminum heads. Car was transmission destroying monster at this point... and the computer couldn't handle the car from a cold start below 50F ambient. Somewhere around transmission #3 and getting marriage #2 (biggest mistake of his life) he sold the car.

I ended up with that H pipe on my 351 Capri with MAC shorty conversion headers and Walker Dynomax mufflers, my whole system was 2.5 inch, and I was NA. Honestly sounded really good. It wouldn't crackle or anything, but you knew something abnormal was about to happen when you nailed it at a light.

Where was I going with this? Oh... yeah, car's performance was severely limited in sound and performance with the factory cats in place. What really strikes me as odd is these cars have basicaly 2.25 inch pipe, which is the same diameter as the mustang had 30 years ago, with 225 HP... now we're trying to shove 500 through it? I think it's a tad undersized, as I said before the 5.5 liter E63 is running over 2.5 inch.

 

Apples and Oranges. You are comparing 30 yo naturally aspirated engines with supercharged engines.

 

You obviously missed the part about the supercharger...

"But, during that time it went from NA to a whipple supercharger which to this day I hold a great amount of respect for."

 

Even if he was talking about a 30-year old NA monster a motor (which it was Whipple charged), what difference does it make?

 

And you were presumably pumping out a lot more than 225hp with that SC. When I was running a NA 331 CI Roush engine in GT-1, it was pumping out 600+ hp and, yes, it had pipes on it you could crawl through. Not needed with SC. Needed much more with Turbo engines.

 

Um.... it's the same displacement, and it was running 10-12 psi of boost.... so it's moving the same amount of gas volume as our engines today.

Point being, it appreciated breathing easier with better headers (than stock) and larger pipes. It was never dyno'd but I'd bet it was making similar power to our 5 liter supercharged engines. Back in the mid 90's that was rather impressive for fuel injection.

I flatly reject that a decent exhaust is only required for a turbo charged engine.

 

I started an email conversation with VAP, asking them about the exhaust. They say they measured the stock tubing on a V8 at 2 3/8". I measured 2.2" which gets me about 2 1/5". So, I need to measure more, once I get the car on my lift. Apparently, the diameters are different in various places.

The good news is: VAP uses 2.5" tubing for their exhaust. He didn't say OD or ID. I would "prefer" ID, but sometimes fittings come standard in 2.5" OD sizing. Easier to work with.

"The OEM tubing is 60mm OD or 2 3/8", for the main tubing with smaller diameter for the unions. It's smaller than some similar output vehicles but we have no issues making 660BHP & 630ft/lbs through those sizes. We did review making a larger diameter system from manifold back, but the majority of the market is just looking for downpipes or for an axle back that's OEM interchangeable. I'm not sure that it would necessarily yield any more power. "

so I am asking him if they have every actually dyno'd the exhaust. Interchangeability was their goal.

well, sometime, I do plan on farting around with this. Not sure when. Plenty of irons in the fire.

I just bought a Dragy. Have not used it yet. Need to do some base runs to establish how to launch and get good times.

my mods will go in this order:

wheels first. Just ordered some VS01 VS Forged wheels. I'll Dragy before and after.
Then exhaust, for curiosity's sake. See if there's anything there. I'll Dragy before and after, but it will include the lighter wheels.
Then, finally, ECU. Warranty from Jag is over in October 2020, but it would void the ability to get aftermarket warranty on my basically-new 2016. I'll Dragy before and after, but will include wheels and exhaust.

 

OK my video's camera work sucks! but the measurement info is accurate. I will create another one next time the car is on my lift and try harder to get the camera on the subject.
Also, as I get close to the muffler I keep saying the "exhaust pipe" over and over, I mean the exhaust muffler. Talking about the skinny tubing going into the V-8s muffler.


P.S. not so sure I am going to wait on the ECU tuning.... we shall see.

 

So this is what I get from your measurements.
The systems max volume is limited to the smallest diameter you measured.
However they are adjusting the speed or velocities of the exhaust by necking down then expanding out like a nozzle or orifice.
I would think that this is done to get a larger pressure drop into the expansion chamber (muffler) to get a certain attenuation or note. The same affect you saw with changing the length of the pipes.
Since the designers can’t really shorten or lengthen the system do to the car layout they have to resort to tuning the sound with velocity like a wind instrument.
If you enlarge just the smallest sections you would increase volume which would reduce back pressure but you would also change the velocity at the pressure drop and thus change the pitch of the note.
In my mind it’s similar to a pipe organ, the same volume is fed to the different pipes but as the diameter and length are changed so is the pitch. The larger the diameter the lower the note.
Of course I could be completely wrong but it seems logical to me.

 

Are you a trained musician? I am. I went to music school before doing tech for a living, and yes, I am 99% sure you and I are right, and also, on the same page. I always use the pipe-organ analogy or the wind instrument analogy when trying to explain my tuning approach. The skinnier tubing also acts like ... from the stereo and electronics world... like a high pass filter, filtering out bass. To me, the F-type R exhaust sounds like a normal V8 thru a megaphone: a high-pass filter you can hold in your hand. (and split people's eardrums with:-). The larger tubing for the valved exit side acts like a horn, making it louder on exit.

So now, we get back to my original comment as I watched the car roll off the trailer: "ahhh so THAT'S how they do it"....

So, assuming we are not wrong, that is the sound aspect of it.

Now, I need to find some time to fart around with the performance aspect of it. We all can guarantee if I went larger with pipe and straight out the back it would get louder, and probably bass-ier. Would one gain some power for "free", so to speak? Not sure. Dragy would need to tell us, since I am not going to go in for several expensive and time-consuming dyno runs to determine if there's a performance gain.

 

Yup, sound differences will be easy to quantify, performance will be much more difficult if not impossible.
I would guess that reducing back pressure will yield some gain but it may be so small that it’s not noticeable.
A guy I know has actuated cut outs on his mustang that dump the exhaust half way between the cats and the mufflers, it makes the car incredibly loud but he doesn’t see any significant increases in performance.

 

Is that Mustang forced induction, or naturally aspirated? NA I truly wouldn't expect much other than sound, as he's probably pretty well maxed out already. Forced induction, that's a different animal. I would also note that the cats are most likely the largest pressure drop in the entire system... that problem only gets worse with forced induction.

 

Thank you VERY much for taking the time to do this! I do truly appreciate it. I am amazed how much they fiddled with the plumbing on that car, particularly since that's mandrel bent. Maybe between elements it isn't too hard to swap major sizes, but even still, that's interesting.

This also would follow the theory of why my 5.5 liter turbo E63 has a lower exhaust note, it has larger piping at roughly 2.75 inches pretty much the whole length.

Again, thank you for taking the time to take the micrometer out and do some exploration!

 

oh, gawsh! sure, man! Glad you found this one useful. I have all sorts of questionably useful semi-tech videos. like this one where I play a set of factory M6 headers, like a huge flute.


if you can't play the same note on your expensive aftermarket stainless headers, then, hate to say it, they aint equal length.

I have the M6 up in the air and will make a similar exhaust diameter video for it. BMW does the same thing: huge and I mean HUGE tubing from the precuts to the main cats, then necks down to basically 2.5" ID tubing. So, the idea of necking the exhaust diameter down, after letting it flow from the heads to the middle of the car, or so, is not new. It cuts down on NVH and does not mess with performance all that much.

 

first off was that "Yup" a confirmation that you are a musician? :-)

I am going to try to find some time with Dragy. Bought one, have not taken it out of the box for two weeks. Try to record the barometer and humidity and temp, as well.

Let's get some baseline runs on my car. Come up with an average of those runs. Then we can use science to see if there's anything to be gained.

Not sure if I can really wait till I have 1 to 2 man-weeks of "hobby-time" to spend on opening up the exhaust, even for a crude straight pipe out, to get an idea if it makes a difference. Kind of want to get the VAP stage 3 stuff going, soon. :-P


BTW: anyone have a good video for how to launch? Whether I should or should not use traction control,. etc? I can't find anything helpful.

 

Sorry for the confusing response, no musical training or background. I used to be into high end audio and still am somewhat but unfortunately between hereditary tenitus and abusing my ears for decades I have lost a lot of my high frequencies.

As to the mustang with the cutouts, it is naturally aspirated but I assumed that NA would benefit more than SC simply because it must breathe naturally instead of forced induction. Am I wrong on this ?

I also bought the Draggy several weeks ago and have yet to make any runs. It is reported to be very accurate so getting a couple base line runs should give you a reference point.

I am looking forward to seeing what you come up with.

Lastly, you pointed out a brace between the cats and the X pipe and commented that it might be a chamber. If it is a chamber that would be very strange and I think would somewhat negate the X pipe. Is there anyway to figure out if it is a chamber ?

 

sorry to hear about your tinnitus. I had it severely for awhile, seemed related to weaning myself off good old type-one antihistamines--once I was completely off, and settled in, it gradually disappeared.. Not sure if that is a factor for you?

meanwhile, how will I tell what that brace/chamber is? good question. I was thinking about that earlier. I am pretty sure I can remove that section and just look down it with a powerful flashlight and see, or stick a wire with a hook, in there, and probe.

 

It is what it is, my grandfather, father and uncle all had it.

It would be convenient to be able to visually check that section of the piping, fingers crossed that works 🤞