Exhaust under or out the side?

[norma]

Having had my zetec on the road for 7 years now, the standard (read sh*te) exhaust (aka noise generator and power consumer) has had enough.
It runs under the car and has had so many knocks, its now about 1.5" dia at the point at the back of the seat where it goes up at 30 degrees towards the silencer.
Anyway - its alwayd been noisy and always been down on power - now running 200bhp spec Zetec and mapped at 185
Went to Oulton Park today for a track day and failed the 105db noise test at 5000rpm (3/4 max revs) so the nice man said "drop it to 4500" which i did and it came out at 105db!
Anyway - I then failed drive by noise test and was black flagged.
Legged it to Demon Thieves and got a db reducer pipe - fitted and tested for afternoon session - still 105db (sounded exactly the same!)
Anyway, they let me out and "looked (or rather listened) the other way" until 4.30pm when they'd had enough and dragged me in again (shame really - I was really on it).
So I've decided I must sort it this winter - I don't really want to put the pipe through the sill as I prefer the look of a standard sill and exhaust out the back.
So no my feeling is, get a 3" exhaust pipe, flatten it to 40mm (so its oval) this will give me the same open area as a 2.5" system (which is what I need for 200bhp).
This would overcome my exhaust scraping moments - and hopefully a new manifold + system might/should bring down my volume too!
So my idea is, new 4 branch manifold, mated to 3" pipe that is then 'ovalised' for its journey under the car, where it goes up towards the fixed axle, go back to 2.5" for silencer and tail pipe.
Of course by putting the exhaust underneath again - I am not able to lower the car any (which would be nice really).
Just wondered what you guys have done - suppose I'm hoping that one of you has had a Eureka! moment that they would share with me

cheers fellas

[Pete&Matt]

i have seen some photos of someone who ran the pipe through the sill, up around the rear arch, then out the back, this way its not slung under the car. I like the sill silencer myself!

[jefferybond]

i have seen some photos of someone who ran the pipe through the sill, up around the rear arch, then out the back, this way its not slung under the car. I like the sill silencer myself!

I run mine like that, both sides because it's a V8. I've got 4" diameter silencers (2" bore pipe) which fit inside the standard sills with about 1/2" to spare, and then the pipe goes up and over the rear wheels, inside the rear wheel arches. I've got no holes drilled in the sills either, apart from being open front and back, but I did stick silver reflective fibreglass matting inside the sills. The silencers are quite long, so are still pretty effective, despite only having a 1" think layer of wadding around the perforated pipe.

Overheating the sills has never been an issue, in fact the front wings get warmer than the sills.

Jeff

[stylussprinter]

If you have 200bhp in theory , you wont get it unless your manifold has equal lengths of between 28 - 32 inches and 1 7/8 primaries diameter(with a 2lt zetec). Also you can't get the power from a 2lt zetec / low enough db's ,unless the silencer is minimum 6 inches diameter(7 is better ) and as long as space will allow for down the side exit. (my point being you'll never get the power and meet the db's with an underbody exhaust cos there's no room for what's required ) Plus of course the car wont handle the power , if you get it , being so high off the ground .. Keeping it in sill is also not on cos you do need the 6 inch diameter so you'll have to expose it and let it protrude somewhat to avoid fire risks plus get your power and meet db's.
Have a repackable and use basalt not e glass or rockwool . That alone is worth 2 to 8 db's . Mine went from 105db's at 4500 rpm (lying about it's max rev's) to 98db's after upping power from 200 to 225 bhp . Fitting an airbox/pipe/cone filter plus repacking my 6 inch silencer with basalt . My manifold joins into a 2.75 inch collecter and silencer through pipe , then exits at 3 inches.
Check out the primary diameter , I might have forgotten the precise measurement. This info came from Paul Dunnell .
Finally , get the chassis closer to the floor and she'll fly

[Werner Van Loock]

i have seen some photos of someone who ran the pipe through the sill, up around the rear arch, then out the back, this way its not slung under the car. I like the sill silencer myself!

I run mine like that, both sides because it's a V8. I've got 4" diameter silencers (2" bore pipe) which fit inside the standard sills with about 1/2" to spare, and then the pipe goes up and over the rear wheels, inside the rear wheel arches. I've got no holes drilled in the sills either, apart from being open front and back, but I did stick silver reflective fibreglass matting inside the sills. The silencers are quite long, so are still pretty effective, despite only having a 1" think layer of wadding around the perforated pipe.

Overheating the sills has never been an issue, in fact the front wings get warmer than the sills.

Jeff

Jeff, can you at some point make pictures of this? I have to run my exhaust that way as side exhausts are not allowed in Belgium.

[jefferybond]

Jeff, can you at some point make pictures of this? I have to run my exhaust that way as side exhausts are not allowed in Belgium.

Hi Werner,

I haven't got any photos showing under the wheel arch or sill to hand at the moment, but here is one showing the tail pipes exiting at the back (taken at the Llandow track day! You could have had a good look then if you'd known!). If I get a chance, I'll take a back wheel off and take some more pics.

Jeff

[Werner Van Loock]

The other guy with the blue V8 also has this way I think, he's got oval tailpipes.

[hearbear]

oval tubing and bends http://www.webster-race-engineering.co.uk/burns.htm

[jefferybond]

The other guy with the blue V8 also has this way I think, he's got oval tailpipes.

Nah, they were side exits with mesh covering holes in the sills. This is Mark's V8:

Cheers,
Jeff

[jefferybond]

If you have 200bhp in theory , you wont get it unless your manifold has equal lengths of between 28 - 32 inches and 1 7/8 primaries diameter(with a 2lt zetec). Also you can't get the power from a 2lt zetec / low enough db's ,unless the silencer is minimum 6 inches diameter(7 is better ) and as long as space will allow for down the side exit. (my point being you'll never get the power and meet the db's with an underbody exhaust cos there's no room for what's required )

Yeah I agree with all the above. I think it's easier on a V8 because you have two silencers, and each one only has to deal with about 100bhp's worth, so you can get away with smaller pipes.

Jeff

[stylussprinter]

i have seen some photos of someone who ran the pipe through the sill, up around the rear arch, then out the back, this way its not slung under the car. I like the sill silencer myself!

I run mine like that, both sides because it's a V8. I've got 4" diameter silencers (2" bore pipe) which fit inside the standard sills with about 1/2" to spare, and then the pipe goes up and over the rear wheels, inside the rear wheel arches. I've got no holes drilled in the sills either, apart from being open front and back, but I did stick silver reflective fibreglass matting inside the sills. The silencers are quite long, so are still pretty effective, despite only having a 1" think layer of wadding around the perforated pipe.

Overheating the sills has never been an issue, in fact the front wings get warmer than the sills.

Jeff

Jeff, can you at some point make pictures of this? I have to run my exhaust that way as side exhausts are not allowed in Belgium.

Werner , if you look at cars for sale you'll see that the green car I sold had it's exhaust from sill to rear exit over the wheel in a piece of flexy.Photo of rustproofing the rear left seat pan shows it.

[norma]

If you have 200bhp in theory , you wont get it unless your manifold has equal lengths of between 28 - 32 inches and 1 7/8 primaries diameter(with a 2lt zetec). Also you can't get the power from a 2lt zetec / low enough db's ,unless the silencer is minimum 6 inches diameter(7 is better ) and as long as space will allow for down the side exit. (my point being you'll never get the power and meet the db's with an underbody exhaust cos there's no room for what's required ) Plus of course the car wont handle the power , if you get it , being so high off the ground .. Keeping it in sill is also not on cos you do need the 6 inch diameter so you'll have to expose it and let it protrude somewhat to avoid fire risks plus get your power and meet db's.
Have a repackable and use basalt not e glass or rockwool . That alone is worth 2 to 8 db's . Mine went from 105db's at 4500 rpm (lying about it's max rev's) to 98db's after upping power from 200 to 225 bhp . Fitting an airbox/pipe/cone filter plus repacking my 6 inch silencer with basalt . My manifold joins into a 2.75 inch collecter and silencer through pipe , then exits at 3 inches.
Check out the primary diameter , I might have forgotten the precise measurement. This info came from Paul Dunnell .
Finally , get the chassis closer to the floor and she'll fly

Cheers for the help - through the sill it is then - Tim did quote me for a thro' sill 6" system+manifold. Guess I'll give him a bell when he's better....

[norma]

No reply from Tim - can anyone recommend a good fabricator for new manifold and sill system as described by stylussprinter?
cheers
Alex

[stylussprinter]

No reply from Tim - can anyone recommend a good fabricator for new manifold and sill system as described by stylussprinter?
cheers
Alex

Depends where you live EXHAUSTS BY DESIGN did mine using the measurements I gave him . £600 plus silencer. He's near BUCKINGHAM . BTB are excellent near DAVENTRY.

[norma]

Depends where you live EXHAUSTS BY DESIGN did mine using the measurements I gave him . £600 plus silencer. He's near BUCKINGHAM . BTB are excellent near DAVENTRY.

Too far - I'm North and West a bit! (Chester). I'll do some asking about - there's a rally prep garage not far from me, they must know someone......