Exhaust question..

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Psychobert

Original Poster:

6,316 posts

263 months

Wednesday 7th July 2004
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Popped into my local exhaust place today as it was dangling a bit loose under the car, (one too many bumps at speed) and the chap that fixed it for me made a suggestion about rerouting it..

Basically, on the S there is a cross member right in the way of getting a smooth radius from the downpipe to the pipe running the length of the car. On the off side you could take the pipe above and behind this, but not on the near side. What he thought he could do was join the pipes in the engine bay, have one down pipe through the hole and then split the pipes again into 2 somewhere in the middle of the car.

I ignored the bit where he asked me if I wanted a silencer fitting..

Needs a bit of thought, but it seems it would give me more clearance and it gets rid of a section with horrible bird-shit looking welds on it. Thats not a bad thing, having run my finger inside some of these there are huge globs of weld on the inside of the pipe which can't be helping gas flow.

The bit that confused me, was that he suggested I'd get better performance from the car if I did this. Ok, I know the pipes are squashed and restricted, but he suggested that I'd never balance a V6 engine properly unless the exhaust was merged, (after that I can split it or not, up to me).

I can't see how this would work.. Any ideas?

Having not opened the bonnet he'll not see that this is probably not possible, or at least very difficult, so I'm not going to do it. The performance improvement through merging the pipes bit interested me..

MGBV8

160 posts

263 months

Wednesday 7th July 2004
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HarryW

15,277 posts

276 months

Wednesday 7th July 2004
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Burt have a look at a V8S when you get the chance. The left and right banks are joined at the front of the engine in the Y piece, a single pipe then goes down the near side between the block and the main chassis rail. This then enters the only box and the split re-appears after the box to the tail pipes.
Not sure of the clearance on the V6 and the main chassis rails though or what effect it would have on the performance. You would have to be very careful with the bore sizing too.
If you are getting it as a bespoke job, then you can get single sections that are oval shaped to help either fit between the block/chassis or keep the exisiting arrangement but have the down pipes already flattend but full bore with the oval section. Thus improving the ground clearance.

Harry

Psychobert

Original Poster:

6,316 posts

263 months

Wednesday 7th July 2004
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Thanks.. Link does indeed explain things..

I'd have to look under the bonnet of the V6 and the V8 to compare them, but my gut feeling is that if there is space in a V8, there ought to be in mine. Can't think off the top of my head what the manifold arrangement is though..

The system was bespoke and fitted when I bought the car, but the fitting could have been a tidier job. One section has about 6 welds in as many inches, and from the outside, the welds look a little messy. To give me extra ground clearance the pipes under the corss member have been crushed, but I don't have a clean oval, just a squashed pipe, (made worse by a big dent in it). I need to do something sometime as one of the pipes is less than half of the diameter of the rest of the pipe at this point; can't be good for gas flow.. Bore wise we thought 2 1/2 or 3 inches..

Oh, and a phat chrome bit on each end. Not..

HarryW

15,277 posts

276 months

Wednesday 7th July 2004
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Psychobert said:
..... Bore wise we thought 2 1/2 or 3 inches..

Oh, and a phat chrome bit on each end. Not..

Having had a slighlty modified set up done on mine and having done all the calculations for gas flow/speed etc I can confirm that 2 1/2" is Ok for the V8S so would not be a problem for the V6 IMHO.
To be honest and IMHO, there might even be some benefit from increased gas speed to go for 2 1/4" or even a 2" on the V6 but I'd get that confirmed by someone that knows the engine type first. If it is OK then this will make the job of routing so much easier.

harry

Fatboy

8,084 posts

279 months

Thursday 8th July 2004
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Why not just have 6 straight pipes from the head sticking out the bonnet? Couldn't be much louder

Psychobert

Original Poster:

6,316 posts

263 months

Thursday 8th July 2004
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Good point Grant, thats about the only way I could make it louder..

I thnk some calculations are due. The more I thnk about it, the more 'I reckon we'd do it with 2/12 or 3 inches' seems a bit vague..