My new X-pipe exhaust
 

I finally got a new exhaust, this summer, but only now got round to posting some pics.
I will take some video so you can hear how it sounds too.
There are a few issues, they installed the exhaust tips the wrong way round, and more importantly there is annoying drone between 1500rpm and 1900rpm.
So I will have to go back to sort out those issues.
Apart from that, it sounds great, finally the very loud rattling stock cat is gone.

The X-pipe design is my choice, to go before the cats is key, and also to copy the Mr Ott X-pipe or V2 pipe as he calls it. The copy was not completely successful, I think they should have done a smaller angle on exit, and the cross over section should have been a little bit longer.
The cats I bought myself, they are HJS cats.

I modified the rear valance myself, but had to take it to a local spray shop for painting. I'll do a separate thread on that, I should have some pics somewhere.

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477164908

http://forum.a8parts.co.uk/attachmen...1&d=1477165500

Exhaust porn :love:

Thats a most impressively clean floorpan!! :cool:

Have you welded new flanges on the stock downpipes?

That welding is actually sexy. Looks great

That must sound awesome!
(And unlike American's, I don't use that word lightly!)

...Provided it doesn't drone!
And with cats, mufflers and resonators, it's even legal in Oz (provided the 90dB driveby restriction isn't exceeded!)
:thumbsup:

That x-pipe is a real thing of beauty! +++

Thanks guys +++

Yes, those are definitely not stock flanges. Although I didn't do any welding (I can't weld), all the thanks goes to Mike Edwards he made the whole exhaust, amazing welder. He is based near Heathrow.

No more plastic covers in the rear below the boot?

Very nice!! ++++++

I've been considering something very similar myself.

Is an additional heat shield above the X-pipe not needed?

Was it designed/fitted by trial and error or does he have plans and measurements accurate enough to make another without the vehicle present? Assuming he wants to make another, I might be interested in having one made and couriered up to me, if he could be confident of a perfect fit.

Hi Sergey, I had to remove it, it was in the way of the exhaust pipe.

There was no extra heat shield for the original exhaust either, I don't think the X-pipe would generate much more heat than the original exhaust (but I could be wrong).

I don't know, I left the car with him for a few weeks. Probably trial and error if I had to guess. This is his facebook page. I went with him because of loads of good reviews on several sites including Pistonheads.
He has a mandrel bender his exhausts are proper mandrel bends.

https://en-gb.facebook.com/Edwardsmotorsport37/

If anyone else goes for a X before the cats, try to get it made to look like this one. I spoke to one of the designers of this pipe for a Porsche 928 (also a V8) and he says the crucial elements are the wide entry angle of the exhaust from downpipes, the narrow exit angle before the cats, and the size of the crossover and the distance from the header.
He found moving the X just a few inches forward or back lost some of the power gains.

Of course I have no idea if my X is in the right spot as it was not placed based on dyno testing.

http://forum.a8parts.co.uk/attachmen...1&d=1477238697

http://forum.a8parts.co.uk/attachmen...1&d=1477238697

http://rennlist.com/forums/928-forum...pping-now.html

http://rennlist.com/forums/928-forum...sale-sold.html

Excuse my ignorance Goran, if you've posted something on this before - though I did just go back through a lot of your old threads.

Judging by your exhaust pictures, your gearbox looks to be a manual.

As it is UK registered, I'm assuming it's RHD (I know that's not strictly necessary in the UK).
So do you have a conversion thread?

What pedal box was used to add the clutch?
What master cylinder was used to add the reservoir the clutch system etc...??

He bought factory manual LHD from Germany IIRC and imported it.

Yes I gave in and sold my RHD S8 to buy a LHD manual :)
The RHD to manual conversion is not dead yet though, I gave my converted pedal box model, and pedal to fit RHD manual to Mike, the most recent news I heard is that he took it to his machinist who is going to make the custom pedal box. I gave him the master cylinder too, which is just a stock Audi A4 metal master cylinder. The pedal box is just a stock RHD A8 or S8 pedal box. It has plenty of room on the pedal pivot shaft for a Clutch pedal. My design is simply an additional aluminium casting or machined part to bolt or weld onto the stock RHD pedal box so that a factory master cylinder like the A4 cyliner can be used for easy replacement.

Here is the thread with some pictures of the wooden mock up pedal and master cylinder bracket. The pedal would need to be changed a bit to give more room for the foot where the rubber pad is. The stock LHD pedal is an aluminium casting so there is no problem to machine the RHD clutch pedal out of aluminium.

http://forum.a8parts.co.uk/showthrea...=pedal&page=10

Welds look invisible, wow
Unfortunetaly when custom exhaust drones nothing much can be done about it.
It all up to silencers used. To fix this it will be a trail and error with different box sizes.
Been there, spent a lot of money to get it right but in the end went for original boxes at the back and drone was gone with perfect sound too
Cannot post here ha ha as I'm talking AMG

Wasn't there a discussion about adding a Helmholtz resonator to control the drone?

Yes it cures it
i reckon with the OP's such a nice set up would be a sin to modify now.
If I would ever go custom again it would have to be design with resonator before it goes on a car, so is nicely blend in to look like it meant to be there

Spot on HP, that's what I'm planning to do, go back to the guy and ask him to fit Helmohltz resonators to each pipe at the back (starting just in front of the rear silencers and pointing back) and try to angle them so they aren't visible from behind. I did a bit of reading about them and the rpm resonance range vs length, so I'm thinking to ask to have them variable length and jubilee clipped so they can be tweaked. I'm going to guess 31" length for the initial try.

I am guessing its something to do with the resonance of the whole exhaust and its length and shape, and its temperature, because the drone is much less pronounced on cold start, but 5-10mins later when it warms up, in the same 1500-1900rpm range the drone appears.

Those pipes to the rear silencers are already different lengths so may be (more likely are) resonating differently already. Interesting challenge. :respekt: