Hi all!

As we all know, our beloved V8s in these cars are heavily sound castrated. Of course one way due to the amount of silencers and resonators that have been used, secondly due to the firing order...

I want more sound. If I can't change the firing order, I'll change something else The exhaust. But this is where I need some help: what would bring the most benefits?

First of all, I have the tiny 3.2l V8. Don't need the bigger ones. This is my daily driver. For more I have the 5.3l V12 in my XJ-S. So, I would like a little more sound. Something that lets you know, that a V8 is rumbling under the hood/bonnet, but then not too loud nor drones.

What would be cleverest to do?

Remove the silencers BEHIND the rear axle?
Remove the silencers IN FRONT of the rear axle?
Replace the "front silencer" behind the cats with an X-pipe?
Combine a few things?

At the same time, what is in that "front silencer"? Is it just a balance pipe or a resonantor? Is it actually even baffled?

Like said, I'd like a nice rumble, something enough to enjoy but not enough to get on my nerves. Nothing overly expensive (as said, daily driver... anything cheap and cheerful would do me ) so no Mina Gallery or so...

What would you suggest?

Cheers people!

Damien

 

Less exhaust = more sound and flow.
Rip off all mufflers and just pipe it. A bigger pipe will produce better sound too. I would at least tear out the giant middle muffler, that both pupes run into.

My truck is a v6 with no muffler, quad cats, and 3" exhaust that stops right at back of cab. Its loud and people tell me they like it haha. And my friends v6 truck has a 5" home made exhaust that sets off car alarms. 😄

 

I've seen a picture of the centre muffler from an XK, and it's an H pipe that you can see through. No guarantees that the XJ is exactly the same, but if you do end up taking that out, a couple of pics to show what's inside would be much appreciated.

In saying that, if it is an H pipe then it's not likely to be that restrictive. From all of the other threads about exhausts, most people seem to be happiest after removing both small resonators from in front of the rear axle, and leaving the rest.

You can also look at high flow cats, but this can cause other issues (O2 sensors), and it's really not cheap.
Plenty of discussions about those too.

 

I have the 4.0L and removed the rear mufflers right under the rear bumper before the wheel arches. its incredibly easy to do and took 30 minutes to get both out with some heating with a heat gun and a deep socket to crack the clamp bolt. once the clamp is loose its just a matter of wiggling and done. then just straight pipe the rear out and you're done. not too loud but just enough punch

 

Can you post a video/sound clip?

 

My upgrade was born from repairs. I had both rear mufflers rotted out, blown out but the piping was OK. I bought some resonators, tips and a bit of pipe and welded this up. Sound change noticeable at high idle and when you stand on it but thats really it. No nasty sounds, no muscle car horridness.

 

I don't want to take over the thread, but...

I was looking at the Mina Gallery exhaust muffler delete. It's rather pricey, but I was curious if someone could make the same thing themselves?

 

That's pretty much what I did above, except added a resonator. The whole setup was ~$100

 

What I'd wonder, especially for supercharged XJRs where some engineered back pressure may be beneficial, is if any of these modifications have been validated on a dyno to increase or decrease HP/torque.

That sort of data consolidated in a single thread may help many decide on what modifications make sense, along with aesthetics and sound.

.

 

I highly doubt that the mechanical forced indiction will profit from more/less back pressure. If it had turbos, less back pressure is better...

 

Well, it does.... exhaust scavenging, capacity, velocity, sometimes termed "backpressure" .... even heat retention (all more or less), can have an effect on SC engines, as well as all other induction types for various reasons. The entire exhaust "system" should ideally be designed for the optimal performance the engineer is targeting, this includes cam design, headers, catalysts, silencers, diameter and length of pipe. And changing one part can make some, perhaps even significant, difference.

And IMHO, it is unlikely that a "shade tree" mechanic or a small vendor is going to discover a lot of "free" HP/torque that the engineers of a major auto manufacturers weren't able to design with all other requirements being considered. Now, if one throws out requirements for emissions, noise, vibration, heat, durability.... then there could indeed be some "power" left on the table, but there is often a trade off somewhere.

So if one takes off one silencer, or increases the tube diameter a fraction of an inch... will catastrophe ensue? .... not likely. But push it too far and remove all perceived "restrictions", silencers, change out to 3" pipe end-to-end with true headers, etc and one may find they end up with a loud and tough sounding car that backfires, lights CELs, gets poor mileage and may even be noticeably down on power. But it may indeed sound cool The only way to know is to test and measure the results as the modifications are individually implemented.

For example, on the X300 side we've had reports from those that put in high-flow exhausts that had a negative performance impact on SC cars, and a former Jaguar engineer that has commented on the challenges with tuning the intake/exhaust for the SC'd cars

Also my experience on the last gen Buick Riviera board (also supercharged) showed similar issues finding the right balance of intake and exhaust tuning to move the power band around to where you want it to be. Just seemingly removing restrictions didn't always produce more power, or power where you wanted it.

And in the motorcycle community, where it is even easier and cheaper to bolt-on aftermarket "high performance" crossovers and silencers, various combinations of free flow exhausts and straight pipes sometimes even produce poorer results as compared to the original "restrictive" stock systems Even simple differences such as an H versus X crossover, and the number of and where placed sometimes made a big difference.

So again, if it were me, I'd be curious on both NA and SC applications what effect certain exhaust modifications had on performance. It might not keep me from experimenting if that data isn't available and I'm just having fun tinkering, but it would be nice to have as part of the decision making process.

In my opinion, it would be a disappointment to go to all the effort/expense of "upgrading" the exhaust and end up with less performance and even perhaps issues with proper engine operation.


BTW, after all of this... I'm not knocking modifications to the exhaust system.

I'm simply saying when possible it would be helpful to understand the actual measured typical performance impact (good or ill) of any modification, as part of the decision making process.

.

 

well said.

 

Exactly. Not worth putting a grand or more into an exhaust for a possible 1 hp gain and possibly problems down the road. I just stick to removing mufflers and sometimes the back few feet of pipe. The exhaust on the xj8 is pretty freaking straight compared to my truck and i would just do a muffler delete.

 

When I did my exhaust, I removed everything from the flex pipes back. Too many resonators, mufflers and that garden hose piping had to go. I went with 2.5" all the way back and stuck a Magnaflow Tru-X muffler right in the middle where the old one was. Wouldnt have it any other way. Then again, I like loud things.

 

Absolutely, in the end it is about your vehicle and what your tastes & goals are

.... for example, on my V11 Guzzi, it has been well documented that keeping the stock "restrictive" airbox on the intake versus individual velocity stacks, and that moving to a 2-into-1 exhaust versus an X crossover and duals produces more HP/torque..... but guess what I have? I have dual velocity stack intakes and twin exhausts because I like the aesthetic, and so I lose a little top end.... and it sounds great


.

 

Okay, did some measuring today and a friend is going to make me a stainless steel X-pipe to replace the crappy "center baffle H-pipe thing". At the same time, the rear silencers/resonators infront of the rear axle will be replaced with piping.

I'm sticking with 2" as that is the factory diameter. I can't go too loud, as the TÜV limits that here. But a little more sound will be great

So, that should be good to go soon I expect October will be the "exhaust month" for me

 

Please get pictures of the internals of the H pipe so we can see if it's actually straight-through

 

If the X-pipe does improve sound, then the "H-pipe" will be cut open and looked into... I doubt it is straight through, as then it would be cheaper to make an H-pipe without the "silencer shape" around it...

 

So, X-pipe has been fabricated:



Stainless steel I guess the rest will be a matter of days

 

With all the modifications that have been done to both XJ8s and XJRs, I would have thought somebody would have cut open the x pipe and the other silencers/resonators, if only to take a look.


After all, it is a lot easier to modify something if you know what you are starting with.