Exhausts - Legal?

satancom · Post by **satancom** » Sat Nov 01, 2008 7:15 pm

I am starting to look at the exhausts on my 1980 Land rover. What is required legally for sound levels etc?

As much as I would love a pair of straight through pipes, I don't think I can get away with it. I have a Y-pipe but may run two seperate systems for ease of routing!

Any advice is welcome

Alley Kat · Post by **Alley Kat** » Sat Nov 01, 2008 10:01 pm

Pretty sure it's been covered before, but without any specific knowledge on decibels or whatever, it seems to be up to the MOT tester. But hopefully someone who knows more definitely will chime in.

Straight-through will just p*ss people off anyway imho, and become a pain to live with too - I've had a V8 with sidewinder straight-throughs and the noise is good for a time, gets wearing soon enough really. All jmho

satancom · Post by **satancom** » Sat Nov 01, 2008 10:18 pm

Im thinking of running a twin system with just a single silencer each, mainly for cost at the moment, although If I can get away with straight throughs until funds allow silencers I may do this.

I need to get this on the road so I can sell my other car, freeing up money to finnish my project properly.. ctach 22 and all that

Cheers

Alley Kat · Post by **Alley Kat** » Sun Nov 02, 2008 12:27 am

Stuff like 'Turbo Mufflers' are pretty cheap if it helps, I got a pair from Real Steel for around £36 exc post, a while back. Plenty of nice bark to those.

RoverP6B · Post by **RoverP6B** » Sun Nov 02, 2008 10:21 am

Twin pipes with no mufflers....seriously loud....even too loud.

The major downside apart from being pulled over by the police for excessive noise is that it will also most likely be inflicted with the dreaded drone

Nothing worse than a drone.

I would be very inclinded to put at least one flow through muffler in each pipe, should you choose to run twins.

I run a single joined in a 'Y' behind the engine with a flow through glass pack and a resonator or cannon as they now seem to be called with a 3" outlet, and it sounds fantastic...really deep (4.6 helps there) and loud but not offensively so.

Ron.

mx5v8 · Post by **mx5v8** » Sun Nov 02, 2008 11:02 am

Don't know if it helps but I've got 4 cherry bombs on my system, I think they were about £25.00 each. Passed it's MOT without comment, has a nice rumble to it and doesn't wear you out on long runs.

ChrisJC · Post by **ChrisJC** » Sun Nov 02, 2008 5:12 pm

Technically you are not allowed to have an entirely 'straight through' system - there must be baffles in it somewhere.

However, my Landie has the Y-piece, then a single 2.5" system with two Jetex straight through silencers. It sounds great at full power, but is pretty quiet normally. No issues with MOT's.

Chris.

Stu E · Post by **Stu E** » Sun Nov 02, 2008 7:50 pm

The limit for kit cars at the SVA is 101 decibels.

satancom · Post by **satancom** » Sat Nov 08, 2008 8:06 pm

Excellent, will have to look at some silencers of some sort then

Cheers

mgbv8 · Post by **mgbv8** » Sat Nov 08, 2008 10:43 pm

I run a 4.6 with 2.5" pipes each side.
I only have one Turbo Muffler each side and my MOT man is happy with it. The Turbo mufflers are about 20 quid each from Real Steel.

satancom · Post by **satancom** » Fri Dec 05, 2008 10:50 am

Ok so being on a bdget I have managed to knock up an exhaust sytem from some scrap pipes

Manifolds and downpipes from a rangerover 3.9.
Running along some flexi to the Rangerover Y-pipe
The y-pipe is 2 1/4" outlet and the next section is 2 1/2" inlet. So I have sleaved the end of the y-pip up to 2 1/2"
This then goes into a silencer and the pipe out of the silencer is around 2"

How much effect will the change of pipe diameters make to the engines running? I know its not ideal changing the bore halfway through but its a temporary thing till I have more money/time/daylight to run a proper custome system!

topcatcustom · Post by **topcatcustom** » Fri Dec 05, 2008 1:00 pm

A 2 1/2 to a 2" step will create a bit more pressure in the large section- not ideal. As to performance I can't really say how much it may sap!

ramon alban · Post by **ramon alban** » Fri Dec 05, 2008 2:29 pm

satancom wrote:How much effect will the change of pipe diameters make to the engines running? I know its not ideal changing the bore halfway through but its a temporary thing till I have more money/time/daylight to run a proper custome system!

I dont think you would be able to put an exact figure on any perceived power loss. But if you calculate the relative cross section of the pipes before and after the constriction one might speculate the loss in power could be inversely proportional to the change in section.

On the other hand, because back pressure can an asset you may even save on losses cause by restricted throughput.

By and large the bigger the exhaust the less the power loss, and the best exhaust of all is wide open to the world but it does upset 'er indoors.

So in your case knowing the science may help you get an answer. In laymans terms you will find some useful guff in the PDF available here.

http://www.vintagemodelairplane.com/pag ... ust01.html