As promised a much better-looking F-Type R stock exhaust measurement video. Sorry for the previous one.

You Tube

Now, is it that uncommon to make a performance car exhaust that gets smaller towards the end? No. For comparison and contrast, here's the same measurements of my V10 BMW M6. Stock 500hp motor has a supercharger kit on it that produces 650hp. Now, that said, BMW only goes down from 3" OD to around 2.6" OD Tubing, unlike Jag's 2.4" OD tubing that necks down to 2.1" right before the muffler.

You Tube

 

Great videos man. Having your musical background have you ever thought about trying different length tubes within a pipe? It’s difficult for me to describe but think of taking a 4 inch ID pipe that let’s say 16 inches long and then stuffing it with a bunch of half inch tubing with varying lengths, say from 14 inches to 6 inches.
I have always wondered if this would create a jet like sound at high RPM’s ?
As long as the total ID of the combined tubing was the same or greater than the smallest ID in the rest of the system, it should not add any restrictions.

 

Interesting. Compared to the stock F-type R sound, what about it do you want to sound jet-engine like? More screaming harmonics? A complete change of the engine's character?

I know what you mean, and with my limited experiments in this area, I think it would not do "the thing you want". There's guys on this forum with degrees in fluid mechanics which could explain the flow implications (its a lot like the way the cells in a catalytic converter work), and maybe some physics majors who could tell us why a honeycomb of smaller tubes within a bigger tube would not change the pitch or emphasize any cool overtones, even if they were different lengths.

What you might want to try to see if you can emphasize some overtones using an acoustic high pass filter.

https://commons.wikimedia.org/wiki/F...imp_hpass1.jpg

We cannot add a pitch to or change the pitch of our "instrument" which is the engine. The pitches the engine creates by going up and down in RPM "are" the notes/pitch it's playing. What we can do is emphasize some harmonics we like or help attenuate certain aspects of its primary note that we do NOT like--or unwanted harmonics,, so we hear other harmonics or less harmonics and more primary note. In a lot of ways, it's more analogous to electronics. High pass, band pass, low pass filters and band-stop filters (Helmholtz resonators)

These are acoustic filter examples, but most people in electronics would recognize immediately what they would do if they were applied to an electronic audio signal. You can't change its pitch with these filters, but you could emphasize certain harmonics.

https://en.wikibooks.org/wiki/Acoust...Implementation

I played with trying to do a high-pass filter on the V10 M6. I did not have much luck, I also did not have endless time. You have to get lucky and tap the high pass filter at just the right length/point in the tube at just the right pitch (RPM) to happen to grab the harmonic you like and emphasize it. If the harmonic is a short enough wave you might be able to get it at just about any point in the exhaust pipe, but then, you have to select the correct diameter, and the length of the high-pass filter as well. I gave up.

On the M6, I was going for higher overtones. I decided to treat the muffler chamber I was playing with more like a mouth and nasal cavity. Sounds crazy, but in my mind, I thought I would-- and did have--way better luck controlling the exhaust sound, since I have to do things intuitively, and don't have a super computer calculating all these tubings sizes and high pass filter points for me. I wanted to do all the shaping within an enclosed box, where I had "some" control over the shape and size of the orifices, the direction of them, and which way they faced, and could imagine intuitively what a mouth would do (I also sing). Think of a Tuvan Throat singer. He sings one note, but changes the shape of his tongue and mouth inside his head to pull out those crazy harmonics. The best simple example is this woman's demo video. She is signing one note, but emphasizing many different harmonics. She demos it at 27 seconds. You don't have to watch the whole thing to get the point.


my ham-fisted notion was to do this. I have never shared this video with anyone yet, (yikes) I consider it to be a work in progress and only interesting because the "mouth and nasal cavity" thing I was trying to do, totally worked. The problem is, I still was not into the sound the M6 made.

...But it would probably apply nicely to a V8, especially one like this with a good amount of harmonics to play with.

here's the theory of the experiment. Bear with me, the interesting thing happens at 50 seconds or so.


Here's a video with three separate adjustments to the mufflers internals. The two tubes either shoved way into the mufflers, or pulled out, or turned away from each other, and also, with longer organ-pipes (tubes) attached to the end. This is really REALLY cheesy, in that it's all held together with clamps and the buzzy rattly sound you hear is, indeed, loose clamped pipes rattling around inside each other. But its just to test a theoroid.


Will it flow? probably not real well. Will it kill HP? Probably.
Well... the idea of this was to create a way to shape the sound for street-driving and then maybe have a Y-shaped diverter valve to dump a larger pipe with no muff, if you wanted to go racing. You could drive normally with a tailored sound, and go wide open when necessary. (btw: none of these setups was at all quiet:-)

Here's the stock M6 exhaust before ANY mods. Not saying I improved anything, necessarily.

 

Wow, love the adjustable exhaust thinking.
To answer your questions on “Compared to the stock F-type R sound, what about it do you want to sound jet-engine like? More screaming harmonics? A complete change of the engine's character?”.
I like the sounds the stock exhaust makes up to about 4K (I am referring to being in Dynamic mode).
After 4K it seems to just get louder but doesn’t really increase in pitch, I think it might sound better if the pitch increased all the way to redline.
Jet engine sound was probably a bad example, perhaps V10 era F1 is a better description.
These cars already have a dual personality exhaust, perhaps it would be possible to add a third by adding dump valves to a small chamber that cuts the base out like your description of the music crossovers?
I totally get that without some serious science and computing power all of this is hit or miss and that takes a large amount of time and labor, that is why so few venture to try anything other than reduce back pressure by making everything as large as possible.
What changes or improvements would you like to hear from modifications?

 

Also, never thought I could get exposure to music and harmonics theory on a car form, awesome just awesome 😎

 

well. yeah. For me the BMWs have been all about improving the sound. BMW makes the most innovative engines and they sound like turds. Trying to polish them, I guess. And BTW that adjustable muffler was a prototype. The idea was to adjust to taste, take notes of what you did, then remove clamps and weld it all up.

what sound do I want for the Jag? well honestly, I want to see if flow can be improved. HP gained. THEN worry about sound. I honestly would like to see the upper RPMS be a bit less grind and buzz-saw-like. That's relatively easy--resonators. 95% of the performance cans people put on their cars are just resonators--a straight thru pipe that flows real well, and has perforations and fiberglass. The problem with them is, they are a perfect low-pass filter--allowing all and I mean, all bass to come out.

Drone.... (thumbs down)

So, the engine is the engine is the engine. It has what it has for sound and pitch, and the V10 M6 was a great example of that. I wanted it to sound like an LFA, or Porche Carerra GT. I even BOUGHT a used, (creatively cheap--$1300!!!). Carerra GT muffler off a shop, thinking it was a magic black box and had some cool baffling or filtering that made it scream, and hooked it up temporarily.

this video is also unlisted and never before shared.


as you can hear, the pitch is the same, the upper harmonics are a bit more present, but it ain't a Porsche Carerra GT sound. I read an old wiki page that said the BMW motor was a 70 degree V10 like the Porsche and Lexus, which are 68 and 70 degree. It is not. It then was updated to accurately say its a 90 degree V10. Totally different firing angle. Totally different characteristics to the sound of the engine.

 

I think it’s starting to sink in now, regardless of how you change or tune the exhaust, the design of the engine has a base sound characteristic that can be accentuated but you can’t get a V8 to sound like a V12.
I was hoping that the top harmonics could be manipulated to sound more like your last video, I like that non raspy higher pitch but also like the lower RPM growl.

 

You are more likely to get a V12 sound out of a V6. The sound you get out of a V8 will be all Detroit.
Improving flow on the F-Type engines seems to be elusive. At best just a few hp can be gained. Not worth the effort.

 

I agree on the Detroit angle for V8 sound...

>Improving flow on the F-Type engines seems to be elusive. At best just a few hp can be gained. Not worth the effort

you've said this twice, now, yet, there's no dyno proof, one way or another. Why not let me have some fun? And whether its "worth it" is subjective. You could lay down some serious cash for 2/10ths in a 1/4 mile for a TCU tune? is that "worth it"? I'm sure it took a decent amount of effort for VAP to do the research. But, it's just 2/10s over a 1/4 mile. Not even 0-60. .... that said, "I" would buy it.

It's the old "90/10 rule".
10% of the money to get 90% of the HP, and another 90% of the money to get the last 10%. it's hot-rodding man :-). If anything is gained I would expect it to be mainly in the top end. My experience is: 2" pipe is not small enough to harm the performance at lower RPM.

 

If any of you know someone who has installed VAP or other cat replacements, please send them to the classifieds. I have a WTB ad there. I want a set of stock cats for AWD F-type R that I can cut up, for research. (sorry for the cross-post)

 

If you can wait a month or so, I got a set. Waiting for VAP to have their annual Black Friday sale to pick up a set of HFCs. My stock cats are toast.

 

Dang.
Looking for working cats... :-P.
Sorry, I did don't mention that. I plan to actually drive with them. What makes you say they are "toast"? And at what miles did they become toast-like?

 

It's not fatally clogged or critically damaged, no misfires or knock issues associated with such diagnosis, it just no longer filters emissions effectively within ranges acceptable by the O2 sensors. I had a few threads about my run-in with my P0420/P0430 codes, but I've come to accept my cats simply need to be replaced, after diagnosing practically everything. I'm not exactly certain what the condition of the cats are in, as I haven't physically taken them out for inspection, but there's no rattles that indicate the honeycomb broke into chunks. Currently at 13800+ miles. VAP thinks the stock 600-cell cats are too restrictive and causes heat issues, but I'm not sure if it's just a sales pitch, as there are others that survive for a long time. On top of that, I'm the 2nd owner; not sure what kind of life it had with the 1st owner, but I can tell the guy can't drive for squat, seeing all the curb rashes on the wheels.

 

Great video Thank you for sharing! That sandwhiched OEM cat on the driver side for AWD cars is certainly an issue for heat-soak when at stage 2 and possibly melting/clogging. I don't think there will be any power gains from going bigger OD after the upgraded downpipes. The system flows very well at 650hp and is not a bottleneck.

 

I believe people who are upgrading their ECUs and pulleys are benefitting from gains. There are dyno charts and slips to prove it. Which is why I plan to do ECU, TCU and pulleys, as well. But...since there are no before and after dynos to prove this, and no larger pipe exhausts to dyno with., this statement of yours <The system flows very well at 650hp and is not a bottleneck.> has yet to be proven. I would love to be proven wrong, but I would not agree to that until I see proof.

 

A tuned mid-length Exhaust manifold and 200 cell down-cats will net an additional 4-5 hp On a V6 that has been pullied and tuned (~450hp) but at the expense of yielding a cacophonous raspy over-the-top loud exhaust sound. (Yes, as measured on a dyno).

 

comparing Apples to Hams. totally different engine and also, different max HP capability. but... you "did" get some gains. ;-P

this thread is about the R and SVR V8.

 

I'm curious as well. Most of the V8's I've built to be faster and even the V6's were all 3 inch tubing. There is a smaller diameter mid pipe. I looked at that and wondered if that was to go away or not. Since Stuart at AP didn't recommend it, I figured their tune was with it. So I left it alone. I can't see paying for an $800 tune and a cost of probably another $1000 for a pipe justifiable to get at 700 hp car near where the head gaskets sometimes blow.

 

hmmm, need some clarification, please.

I have not searched on this. are you saying at 700hp people are blowing head gaskets?
If so, how are they getting to 700hp? what else are they doing besides two pulleys and an ECU tune, and probably VAP downpipes?

and which smaller diameter mid-pipe were you talking about? my measurements show the smallest tubing right smack before the muffler itself. 2.1" OD. Not necessarily in the middle.

 

One thing I have not shared with the group I probably should. There's lots of speculation and assumption that since VAP does not offer a bigger exhaust, it's either bad, or not effective. And everyone cites "the VAP headers story".

I did talk with Stuart at length about all this--after I started this thread. When I asked him why there are no larger-tube exhaust systems for sale by them, why there are no dyno charts along with the exhaust systems they do sell, and why anything they make bolts right up to the stock exhaust points, with all the (apparent) restrictions, especially right at the connection points.

eg: https://www.velocityap.com/product/j...g-sound-level/

He said, "that's what people want". Meaning--plug and play with existing components. This appears to be what all aftermarket exhaust companies are offering. Plug and play with the existing components. Not performance gains. We are right back to my original question in this thread. This is NOT an indictment. I am just not interested in getting a "more aggressive sound" with my exhaust. I am mainly interested in whether or not there are performance gains to be had.

Apparently, people did not ask VAP for more HP--which is not a judgement, its just what I gathered when I spoke with him. He cited the "headers story" as well. But he did not cite using those headers with a larger cat back exhaust system--which may, to may not made some difference in the performance of the headers. No one can say without building something and testing it.

I asked why there were no dyno charts for gains from the VAP downpipe/cats he said "because they were not made for that" and explained the heat thing people were running into, on the track, especially. OK, I can buy both explanations.

eg: https://www.velocityap.com/product/j...-and-downpipe/

that said, they do claim gains, but no chart. I remember him saying the gains were not the big selling point, it was the heat relief. I could still imagine buying some, especially if my stock casts died prematurely.

So, he never said "well....we tested larger tube exhaust systems extensively, and found them to be ineffective, or to cause problems". I gave him plenty of chances. So we moved on to talking about the ECU and TCU tunes. Now, people are going to jump all over me, I guess. I am just reporting what we talked about. There was no comprehensive, tested proof that a larger system was tried, and rejected by VAP.

....Unless he forgot to bring it up.