Hello

I am looking forward to let a workshop do some welding on my exhaust on the weekends. The question came up if I know what material the orignal exhaust is. Anybody know?

That way we get a clean weld which will not rust in the future.

Thank you a lot. I will post pictures of the inside of the silencers afterwards if anyone is curious. :-)

Cheers

 

From my understanding Borla was the original provider, so they should be stainless.

 

For the curious among us, as announced the cut open resonators.
I welded a sheet around the open pores of the inner pipe, curious about how it affects the sound.
Curious enough, it did not change the sound at idle at all. Only on full throttle it is ever so slightly louder (or it might even be a placebo-effect).
It seems that the pores of the pipe have a big effect on the sound, even if they are closed with the sheet around it.

Anyone knows why manufacturers choose to put all the wool in it?

 

Steel wool, fiberglass, etc is added for sound purposes. It helps get rid of the high pitched, annoying, raspy sound and makes it a deeper sound. It has no influence, good or bad, on performance.
Some like the sound with it, others seem to like it without.
Fiberglass matting rapped around the perforated baffle is more commonly used than that mess of steel wool and does a better job of deadening that cheap metallic sound.
Personally, I prefer a deeper rumble.
If you do a google search for exhaust wrap, you'll get an idea of the different types used.

 

I understood the functional principle of the resonator, but was expecting a bigger effect with the holes covered.

I am also looking for a bit of a deeper rumble and would love to archive something like this but slightly quieter:

Does anybody know what type of construction the rear mufflers are? Are they Helmholtz-Resonators, Quarter Wave Resonators, chambered or a combination of them?

 

I made a quick sketch in CAD to explain what I have changed. (with close to no effect on the sound level or characteristics)
Anybody with experience in exhaust tuning? I expect that the holes dimples on the inside of the exhaust as it is now, have a similiar effect as the surface of a golfball, and thus still have some
aerodynamic effect on the exhaust pulses which in turn mutes the sound despite the lack of wool.

 

That perforated baffle can have an influence on performance. Maybe not so much in this case because there's an over abundance of mufflers as it is but those holes can diffuse the sound waves so they're not all returning at the same time making it easier for the next outbound wave to pick up the return waves and carry them back out rather than reaching the combustion chamber and causing reversion. As you may or may not know, these Soundwave do a 180 as soon as hit the end of the tail pipes.
Again, probably not an issue here with the cams in these cars. I assume they have little to no overlap. Overlap is the the amount of time that both the intake and exhaust valves are open at the same time. It can huge in making power as the exhaust from some of the cylinders aid in pulling the intake charge into the others which really helps cylinder fill. Cylinder fill is the name of the game when it comes to making power.
BUT, if the exhaust and cams don't play well with each other, that overlap can kill a build and cause reversion which will cause big dips in torque mainly at lower rpms.
With all the other restrictions here it doesn't surprise me what you did doesn't have a huge effect tho it might at certain rpms.
I'm all to familair with exhaust tuning and cams with my Harley where I'm running some S&S cams with 42° of overlap.
The cams in these cars are probably like -5°. Yes, these cams are also EPA compliant. Cams with overlap are not. Another power killer.
It's why they don't have that lumpy idle associated with race cams that those of us performance minded look for.
The exhaust on my Harley have 3" diameter mufflers that have 2" perforated baffles just like those attached to each headpipe and that's it.
The stock mufflers you couldn't see thru, we're huge restrictions, and one of them had a cat in it. Now they put a cat in the headpipes and the first thing everyone does is either pound them out or buy different head pipes without them.

 

Here's Greverrr's, post #39... https://www.jaguarforums.com/forum/x...-159191/page2/

 

That sounds pretty good. Not tinny. Be better with a good set of performance cams tho. Does anyone even make aftermarket cams for these engines?

 

No, I was reading a thread where someone was supposed to get something done to the duration's. But I never saw it implemented. Grinding cams isn't too expensive, knowing what to grind is important.

Here's one on an attempt by Buckhead Imports in Atlanta...note post #2 by Avos...then you'll see how this post drags out...gotta love money bundle bonfires.

 

Sound-wise there is no modification needed on the cams to get a growling exhaust note.

I made a quick clip of how the XJR sounds with a stock system minus the silencers.
Modification is illustrated in the video.



Now the tricky request, anybody has an idea on how to silence this exact noise-signature without loosing its character?

 

No but the right cams with overlap help with cylinder fill and sound wise gives it that lumpy idle characteristic of muscle cars.
Have you thought about eliminating that front muffler, replacing it with an X pipe and leaving the 2 behind the rear axle or replacing them with thrush mufflers of some sort? Maybe magnaflows? This what I'm doing after I'm done with my breather mods but I'm also eliminating the cats. I'll start just leaving the 2 stock ones behind the axle. Replacing them with something else possibly.

 

You are right about the cams but in this application there is not a big benefit as it is not cost efficient at all. There are as far as I know no "Off-the-shelf"-upgrade camshafts for the XJR X308.
There will always be the option of a custom-grind and welding but that requires a lot of knowhow from the manufacturer -> costs time&money.

So the quickest and most cost-efficient way would be a exhaust setup based on the stock one. Thats why I asked about the type of muffler used in the stock rear-muffler.
If there is a way on enhancing their silencing effect it would perfect while maintaining the classic look.




(By the way, I have some experience with 285° Cams on a first-gen Exige (Rover K-Series 1.8L) which gave it a nice lumpy sound, so I understand your argument really well.)

 

You're right about the cost of custom grinding them. That's why I asked if there were aftermarket cams available. It's too bad there isn't. A cam swap would be a quick, simple, cost effective upgrade on these 308s.

I've heard sound clips of the exhaust as I described leaving just the rear 2 cans and it has a nice low rumble, not as loud and without the gurgling on decel with yours. At least not as pronounced if that makes sense.

 

The thing with the AJ27 is there have been many efforts to get more HP out of them...hot rod them shall we say. But, those who have thrown money and time at it have basically determined that Jaguar got most all it could out of this motor. They've modified the ramps, port matched what little was left to do and such. Thus there really wasn't a market for cams. Avos, Count Iblis, XJR-99, Sean B and a few others are those you may want to see what efforts they posted...for example...https://www.jaguarforums.com/forum/xj-xj8-xjr-x308-27/x308-xjr-knackered-rear-diff-59936/

Paramount and CarID used to have an X308 exhaust setup, but it appears to be no more. But here's a later model which may give some ideas.

 

In post #10 Stu has a vid on his exhaust work... https://www.jaguarforums.com/forum/x...needed-177300/

Then in #11 Daim has a detail drawing of his.

Then down at #17 Vector has cutouts on his, which I'd like to go that route. Vector is no longer on site, he hit a deer and sold off.

 

It's not even so much about getting more hp out of it as much as getting more peak torque. More hp means losing low end and maybe even midrange torque. I'd like to gain peak torque. Even at the expense of a few ponies up top Where is max hp? Like 6000rpm? I'd like more power around 3000 to 4000rpm.
This is something only accomplished with cams.
I'll gain some power across the board with the COI, exhaust, and that breather mod I'm working on to keep a good vacuum under load. You'd be surprised at how much hp is freed up when the pistons and crank aren't working against any drag from crankcase pressure and aerated oil. Not to mention a cleaner engine and no octane loss. Some engines as much as 30 to 40 hp. Boosted of course. That's why race car engines run mechanical pumps. I'm going run an electric one and a dual port catch can that automatically chooses the best vacuum source at any given load keeping it at 16inHg at all times.
I'm probably looking at 10 to 15ish total but that's a pretty good bump on an NA engine. But it's not the only reason I'm doing it. Just overall better engine health is my main motivation.
Sorry for the hijack.

 

Next thing I am going to try, is to make the perforated baffle half the length, my thinking process behind that thought is, that if a straight pipe is too just a bit too loud and my solution with the welded sheet around the overall length is too quiet,
50/50 of straight pipe and welded sheet around the perforated baffle might be just it.

Another interesting fact I stumbled upon: The end muffler of the x300 got higher throughput. That might be another solution to my problem.

 

I'm going to throw this out there as far as exhaust tuning is concerned. It's a black art that most exhaust manufacturers lack. Sound sells and most manufacturers are only concerned with sound, not performance. It takes a lot of testing to perfect an exhaust that performs well and contrary to popular belief, has nothing to do with back pressure. Back pressure is bad. Period. Unfortunately it's a byproduct of using baffles to lower sound decibles that also change the length of pipe that the sound waves have to travel before reaching the end at which time these sound waves do a 180.
It's all about the timing of these return waves and/or keeping them from reaching the combustion chamber again causing reversion. Reversion is when these returningnsound waves push the intake charge back up out of the carb or throttle body. You'll see the cloud of vapor at certain lower rpms. It kills low end torque. Exhaust and cams are closely intertwined when it comes to performance.
Wide open headers are great for race engines that run high rpm but suck at low end torque. But not because they're wide open with no back pressure. That's a myth. It's because they're short. That's why you see some headers on performance engines that loop making them longer and of equal length for each cylinder.
I understand you're looking for a certain sound but you also mentioned exhaust tuning and you could inadvertently kill low end torque in your quest for sound. Power off the line.
Again, not so much of a problem with reversion when cams have no overlap. But cams with overlap and a good performing exhaust makes for a huge bump in power.
That's why we have 2 cylinder Harleys with performance cams/exhaust doing close to 200hp now days. I've taken my 103ci from stock 67hp to close to 110hp with nothing but cams and the right exhaust. Over 100ft.lbs. of torque off the line peaking at close to 120ft.lbs. by 4000rpm. Haven't even touched the heads yet and that's where the biggest jump comes. Quite the rush on 2 wheels!
Imagine what could be done with these 8 cylinders if only cams were available.