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Decibel Slayer - Best Option?
Stuart15 - 30/5/18 at 08:12 PM

Evening all,

I've got an upcoming track day at Combe in my new Fury and am somewhat concerned about noise restrictions. I'm tempted to preemptively buy a silencer of some kind. Ideally it is very easy to remove and install without modification to the exhaust.

This Decibel Slayer seems widely promoted, is this my best bet?

https://www.demon-tweeks.co.uk/motorsport/universal-exhaust-silencers/decibel-slayer-bolt-on-exhaust-noise-decibel-reducer-insert

Thanks,

Stuart

[Edited on 30/5/18 by Stuart15]

[Edited on 30/5/18 by Stuart15]

jeffw - 30/5/18 at 09:07 PM

Merlin Motorsport are on site

https://www.merlinmotorsport.co.uk/s/exhausts/merlin-racing-silencers-and-mufflers/merlin-racing-muffler

Andyouteast - 30/5/18 at 10:29 PM

I'm interested in these too. Do these actually do the job without killing power, I spoke to an exhaust builder who was quite critical of them for the amount of power they drained. Having said that, I was black flagged at Donington last month for being too noisy. If they really do help, I'd get one just in case.

cliftyhanger - 31/5/18 at 06:29 AM

All the DB killers do is reduce the exhaust size at the outlet, and increase back pressure. I have seen somebody get some strips if metal, so it partially covered the outlet, and made into a U shape so they was attached with a jubilee clip. Add enough until it passes.
Best bet is to fit a quieter exhaust, or repack the existing one which may help. I am over the "louder=better" thing, and find a quiet, but hopefully efficient system is plain better. Stops one looking/sounding a cock when driving around too.

Stuart15 - 31/5/18 at 06:47 AM

Thankfully the exhaust isn't too obnoxious! I'm not too worried about a reduction in power, after all I'd rather drive with less power than not at all! Might take a trip to merlin at the weekend and see what they recommend. Thank you all.

russbost - 31/5/18 at 07:04 AM

Alternatively you could go to Ollie at Furore Products & save yourself a fortune

Link to dB killer

He also stocks exhaust packing which is basically identical to Acoustafil but about half the price. Re how well they work & power loss etc, providing you have adequate space prior to the exhaust exit for the gases to expand into then adding a dB killer at the END of the exhaust will barely affect power, but can make several dB difference in terms of noise output, I've had 2 in series in separate sections of exhaust with straight thro' box in between with no significant loss of power

Irony - 31/5/18 at 08:10 AM

quote:
Originally posted by russbost
Alternatively you could go to Ollie at Furore Products & save yourself a fortune

Link to dB killer

He also stocks exhaust packing which is basically identical to Acoustafil but about half the price. Re how well they work & power loss etc, providing you have adequate space prior to the exhaust exit for the gases to expand into then adding a dB killer at the END of the exhaust will barely affect power, but can make several dB difference in terms of noise output, I've had 2 in series in separate sections of exhaust with straight thro' box in between with no significant loss of power




I actually bought these exact DB killers from Furore for my IVA. I had to cut them so they fit into the exhaust and bend round a corner. Easy to fit however as long as the diameters match. My Rover V8 passed at a whisper quiet 91db. They were a tight fit so rather than screwing them in I just hammered them in. As I was pulling away from the IVA centre and giving it some beans the bloody thing 'coughed' one out and sent it pinging across the car park. IVA man just laughed.

I suspect they won't kill power enough for the common man to notice - unless you are a world class driver.

See this link for what restrictions in the exhausts do to power loss.

Rinky Dink Link

russbost - 31/5/18 at 08:43 AM

Having just watched that video clip, I have to say that I'm slightly shocked that the larger restrictions they made to the headers make so little difference, but overall the result is as I would have expected - just somewhat exaggerated.

The clever thing about the dB killers is that they don't just restrict they also send a reflection back down the pipe to re-expand wherever there is space, you'll get different results on different exhausts, some more noise reduction & some less, but they most certainly do work, with no noticeable power loss

Irony - 31/5/18 at 09:25 AM

The Engine Masters Series on youtube is pretty good. Not sure all of the videos are relevant to people on Locostbuilders but still good info. It is rare to see actual exact comparisons of upgrades rather than peoples 'gut' feelings which are normally inaccurate. The shows about DIY head porting and air filter comparisons I think are very relevant to LCB.

Surprised you haven't watched them Russ.

swanny - 31/5/18 at 01:29 PM

Irony: have you got a pic of the modifications you had to make to yours?

paul

Irony - 31/5/18 at 09:21 PM

No, sadly I haven't. Building an extension at the moment so stuff is in storage.

I essentially cut a slots along one side and bent them around in a curve. You can see in my archives that my exhausts are bent at the tips

swanny - 1/6/18 at 08:14 AM

great thanks. Mine are bent too. Will get a couple of them and have a go!

car looks great BTW

adithorp - 1/6/18 at 09:11 AM

Do you have a circuit local enough to call in when there's a track day on. They'll usually noise test your car for you (even if not booked on that day) and then you'd know whether you have an issue or not. Drive by limits are more difficult to know without actually taking part.

mark chandler - 1/6/18 at 05:35 PM

Interesting post this one, DB killers do that to power so I have been looking at alternatives.

First thing point it to the ground so I have purchased a mandrel U bend to chop into a band to point at the ground, I have twin pipes.

I am also looking at making a spiral baffle where you have a tube with blades to spin the outside exhaust gases so hopefully very little restriction, have a Google.