What exhaust noise have you got away with??

I'm just about to rebuild the exhauast on my shitroen axgt. What kind of noise have you guys got away with "longterm".

I'm planning to weld up a straight through pipe, with just a single rear silencer ... of the "performance" flavour.

I'm trying to reduce backpressure on my engine ... its got a large overlap camshaft and it doesn't like much backpressure at low revs.

Obviously there are noise limits, but just how loud can i go.

My mate owns a tvr ..... very noisy, echos round the houses,etc. The local plod drive transits ... very noisy engines, also echo round the houses (seriously). So, my mate hasn't been pulled, plod haven't pulled themselves, so how will i fare??

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FEo2 Welder
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FEo2 Welder raved thus:

:: I'm just about to rebuild the exhauast on my shitroen axgt. :: What kind of noise have you guys got away with "longterm". :: :: I'm planning to weld up a straight through pipe, with just a single :: rear silencer ... of the "performance" flavour. :: :: I'm trying to reduce backpressure on my engine ... its got a :: large overlap camshaft and it doesn't like much backpressure :: at low revs. :: :: Obviously there are noise limits, but just how loud can i go. :: :: My mate owns a tvr ..... very noisy, echos round the houses,etc. :: The local plod drive transits ... very noisy engines, also echo round :: the houses (seriously). :: So, my mate hasn't been pulled, plod haven't pulled themselves, so :: how will i fare??

I made an exhaust for my mk3 Escort which was just a straight through rallycross 'silencer' from the local proper motorsport shop, a bit of straight exhaust pipe, a (I think) 45 degree bend, a shorter box of the same type as above and then an exit out from under the car. It exited just in front of the nearside rear wheel. It was noisy as f*ck but the only time I got pulled was after the rear silencer was torn off after an incident with a manhole cover entering a garage forecourt.

I got a vehicle defect notice and all I did was fix the exhaust (it had come apart at one of the welds - ahem) and take it to the local MOT station. It was just as loud as before and they signed the form no problem. However, this was 1990 when as long as you weren't pissed you could get away with pretty much anything where I lived; 80mph on the 40 mph ringroad springs to mind.

The car was running twin 40 DHLA's at the time and with the short exhaust and lack of restriction would spit flames if you downshifted and backed off the throttle, which I obviously did all the time when slowing for traffic lights, junctions etc.

Blew the engine in that car racing a Manta. The Manta left the road and spun into a sign a few yards further on. Those were the days... I don't do such things nowadays; I'm all respectable.

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¤¤¤ Abo ¤¤¤

The description above now applies to my system. The manifold bores were wider than the head bores, but the old exhaust was the same as the manifold .... the new exhaust is wider than the manifold now. One other thing you omitted to mention ... if the exhaust gas flows into a wide bore, it slows down whilst filling the void .... therefore it stays in the pipe longer, has more time to cool, and becomes more dense and "sticky" .... increasing system pressure.

Initial 0-100mph tests do show an improvement over previous attempts, with all things being the same as before (1 occupant - 1/2 tank fuel - 1 run into head wind and 1 into back wind, then work out the average). The main thing is, its a gastight system (unlike the factory spec. system i removed).

0-100mph, 18 seconds from a 1.4 litre car (actually 104mph allowing for the true reading of my gps unit). 23 seconds in my 3 litre beemer.

-- (Scum Mail Bouncer In use). (Remove the two "n" from email address to reply directly).

Regards..... Steve.

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FEo2 Welder

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