Exhaust pics

[peter m]

Here are some pics of my S2 exhaust when I re-built it.

The exhaust was opened up and the loose bits removed. I made a baffle plate up from perforated steel sheet, but I only had enough for half of the rear box. You can see where the original was fixed in at the sides. I replaced the restrictor baffle at the junction of the front and back boxes. The baffle plate was fixed in and glass loft insulation lightly packed on top before the lid was replaced.
The welds were painted over to stop them corroding. Note that my down pipes are were welded to the main exhaust by a previous owner so I had to spring the manifolds to drop the system off. The boxes are empty except the baffling shown.














>>> Edited by peter m on Monday 16th August 14:05

[z_chromozone]

Nice job

Z

[kentishS2]

Hi Pete, good timing as this is a job I'm about to do and it looks like we have the same exhaust system.

I'm possibly going to leave my box totally empty, is it likely that it will be too noisy and fail the MOT?
Any idea if it will sound hollow and strange, or just loud and roarty?

Loud and roarty is fine with me.

[kentishS2]

Am I correct in assuming that the front oval section has no baffles, it's just a common oval section and the only baffles are in the long rectangular rear box?

[bridgdav]

You might be better off talking to the chaps at ACT or Peninsula...

They supply the exhausts and would probably be able to tell about back pressure and baffling... Wildfire had reduced bores on his straight thro' to provide enough back pressure...IIRC

Dave

[kentishS2]

bridgdav said:

You might be better off talking to the chaps at ACT or Peninsula... They supply the exhausts and would probably be able to tell about back pressure and baffling... Wildfire had reduced bores on his straight thro' to provide enough back pressure...IIRC Dave

Thanks Dave, yes they are the boys who know although I feel a bit uncomfortable just picking their brains.

Fells a bit cheeky to ask a load of questions and not buy anything.

[WildfireS3]

bridgdav said:

You might be better off talking to the chaps at ACT or Peninsula... They supply the exhausts and would probably be able to tell about back pressure and baffling... Wildfire had reduced bores on his straight thro' to provide enough back pressure...IIRC Dave

Yep, you are correct Dave, if you leave out the baffles in the standard exhaust, you will not have enough back pressure in the system and then you will lose power. I have had the perforated pipes that run through the main silencers made smaller, (done by JP), to get the back pressure back.

If you are having your exhaust repaired, I'd have the baffles put back in.

[kentishS2]

Perhaps I'll go for a perforated tube that has a smaller bore than the inlet and outlet sizes of the box and then fill around this sparingly with silencer wadding.

However, in theory you should have back pressure in most circumstances as the 3 exhaust outlets at the manifold equate to a much larger area capable of handling a larger volume of exhaust gases than the twin oval section they go into and also the rear exiting pipes. I think it would only make a difference if the internal diameter of the entire system was the same or larger than the area of the manifolds. Perhaps the engine likes a lot more backpressure than I guesstimate?

As an ex-hydraulics engineer this would be true but that's where you look to reduce all backpressure to avoid higher pressure on pipework and pumps to eliminate any system pressure failure.

[peter m]

I think that the front oval section used to have a 2 into 1 section then a long single perforated tube running to the back box. I assume that there would have been wadding either side. I have deduced this from the few pieces of broken tube I retrieved out of it.(I could be wrong). Anyway, mine is completely empty.

There is a full width metal plate in the front of the square box, that is at 45deg and goes from the the top of the holes from oval box down to within about 10mm of the bottom. This restricts the gas flow and would provide some back pressure. I did fit this bit.

After the job was done, it sounded a lot quieter than I was used to, but now either I have got used to it or some of the wadding has blown out as it lets rip with you rev it

[ukbob]

Cheers for the pics pete Austec said the sports pipes they are fitting tomorrow will sound much better without tampering with the exhaust.

I called them today to enquire about removing the baffles or putting straight through pipes in when they fit the new exhaust, and Mike talked me out of it.

Anyone know if the V8S standard exhaust comes with baffles or not, and a straight through pipe, or not. Im guessing baffles are fitted as standard, and wondering if I'll regret keeping the baffles in the new pipes I want loud but if baffles somehow make the great resonance and exhaust note, maybe its best to keep them in the sports pipes. Anyone got any thoughts on the matter?

>> Edited by ukbob on Tuesday 17th August 12:07

[peter m]

My exhaust now has booming resonance at about 2700rpm, approx 65mph. This is loud, good for tunnels, but I try to keep out of it generally when going down the motorway.
I did not plan this, it just happened.

[KentishS2]

peter m said:

My exhaust now has booming resonance at about 2700rpm, approx 65mph. This is loud, good for tunnels, but I try to keep out of it generally when going down the motorway. I did not plan this, it just happened.

Yep, same with mine and it has a sort of whining resonance at slightly lower revs which is annoying. I've decided to leave it alone save for trying to increase ground clearance and seal the downpipes. I'll see how it sound once sealed properly. I think my baffles are shot away now, if it sounds rough I'll probably replace rather than mess around with the old one. This is mainly because what I thought are empty pipes at the front also have a baffle and getting that apart and re-welded won't be worth the hassle and is likely to cost as much as a new one.

[gefopsman]

I split my old exhaust box, as I had a loose baffle which sounded horrible. I found that everything in the box was alright so my problem is in the oval section.

I have just got hold of a second hand Stainless S1 exhaust which has no oval section. Just twin pipes all the way to and from the silencer.

It sounds deaper than the original when still but is noticably quieter inside when on the move. I am not sure if this is due to the rounded top of the box giving greater clearance from the body.

At least it now doesn't vibrate against the handbrake as it did at times before.

I may open the oval on the old one just to see what goes inside. I will post the outcome but it is unlikely to be for a while as I am still one legged!!

G

[full-thrust]

My S2 exhaust sounds terrible now, probably the baffles are shot. I may replace the front silencer section with a pair of pipes and retain just the rear rectangular box.

[UKbob]

full-thrust said:

My S2 exhaust sounds terrible now, probably the baffles are shot.

How does it sound?

Do baffles help create resonance? The baffles in the backbox are the only bit from the manifolds down to the tailpipes that are not straight pipe, right? Or mabe that oval bit does something to the exhaust note?