My zetec installation into a Robin Hood 2B sounds far too noisy. I have a track day booked in Nov so need to address the exhaust noise before then.

I don't really want to spend a lot but I want it as quiet as I can reasonably get it without effecting performance if possible.

I especially don't mind if the silencer is big or ugly.

Should I just buy the fattest and longest cheapo silencer I can from eBay or will that not do the job?

Is it just the exhaust? What about induction, that can raise the db level a lot!

can't resist - turn off the engine

Has the silencer ever been repacked? If not that's a starting point. There are also DB killers that fit up the exhaust - although you'll need someone else to say how well they last on a track day. Can you rotate the exhaust to point down so the road takes some of the noise?

It's been off the road in bits for a couple of years so now its running I won't be turning the engine off at any point soon!

Not thought about induction to be honest, exhaust is definitely loud though, if I can shut that up I'll look at induction if it's still too loud.

Haven't repacked the exhaust so i'll have a look at that. I have 2 silencers, one carbon fibre thing that looks like a bike exhaust and one, equally small, stainless one. Tried them both (not at the same time before anyone asks). Both sound really loud, loud enough for me to know just by listening that they will be too loud for the track day.

Both point down-ish, but I'll try that. Might save another couple of dB

Not keen on the idea of a dB killer tbh. Not sure why, just seems like a bit of a bodge (although the rest of the car is one big bodge so don't know why that's worrying me)

[Edited on 13/9/16 by Skirrow]

On my locost I have 6 inch diameter silencer, 22 inches long, 2 inch diameter in and out and to be honest I'm not sure it would pass on a track day test either. So I thought I would fit a short 45 degree pipe on the end with a second silencer which would go over the rear wheel arch and make a bracket to attach it to the roll-bar. Should do the trick and be easy to fit and remove after the track day.

Cheers, that's not a bad idea at all considering I already have the 2 silencers!

Cheapest and very effective if you can do it is a second silencer and better if it comes out the back for drive by as people spend a lot of money on large repackable silencers on there cars .

Saw a neat track day solution. 2 silencers side by side.. into 1, 180 bend at the end and then the next silencer facing forward. Exit at the front. Maybe that is an option as you have 2 cans.

Hth

Cheers, I'll see what bits of tubing I have and see what I can come up with

I found a great effect by putting a very small expansion chamber in front of the silencer. Made from an old custom chrome 5inch dia silencer but cut and rewelded to be about 10 inches long.
[img]
Description [/img]

Dusty,
Any idea how much the heat wrap helps with dB reduction?

Heat wrap on the exhaust will increase noise, not decrease it. It causes the gas to hold heat for longer so it's got more energy when it reaches the end of the pipe.


[Edited on 21/9/16 by The Black Flash]

I did somewhere a lot of research into exhausts and found the calculation for the expansion chamber.

New computer, 2 babies and a house move mean i've got no chance of finding it but i got it from googling ..... so it should be there.

If i recall its something like the size of two cylinders uncompressed volume * magic number + the inside leg measurement & ideally wants to be at the point in the exhaust you want secondary reflections to maximise HP .... or you could just fit something and see what happens the idea is the gasses suddenly slow down as the expand to fill the volume. Slower gasses = less noise.

Procomp did make a comment a long time ago about their exhausts that Stainless / Ali was louder than Stainless / Ali based on their experience.
(i also lost a lot of memory when the babies turned up due to sleep deprivation and neither the sleep or memory have returned)