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Author: Subject: trackday BEC exhaust noise again
andyfiggy2002

posted on 17/8/17 at 11:09 AM Reply With Quote
trackday BEC exhaust noise again

I have had 2 ureka moments recently & wondered if any of these ideas would work for trackday exhaust noise reduction on a BEC. At the mo I have a 4" silencer on the left hand side of car that is the straight through type with perforated tube /fibreglass wadding & a 50mm diameter detachable 90 degree bend outlet pipe, I also have a few metres of 60mm diameter stainless steel flexible flue piping knocking around.

plan A, have 2 silencers by removing my detachable 90 degree bend & fit the flue pipe from the end of the existing silencer going under the car up to another similar 4" silencer in the boot section with an outlet flue from this additional silencer exiting under the rear bodywork?

Plan B, considering the scruiteneer usually has one noise meter & all BEC exhausts seem to exit either right or left of car, could i divide the outlet into 2 so you have a 'Y' or 'T' piece coming off the existing silencer end with the other outlet exiting the other side of car via some flue piping?

would any of these ideas reduce the exhaust noise without affecting performance?

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ian locostzx9rc2

posted on 17/8/17 at 12:41 PM Reply With Quote
Lots of people run a pipe from side silencer by the inside of the wheel then an extra silencer in the boot area just make sure you have good heat shields near the fuel tank and areas near fibreglass panels

[Edited on 17/8/17 by ian locostzx9rc2]

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rodgling

posted on 17/8/17 at 01:01 PM Reply With Quote
As above, Plan A took me from ~105 to 95 dB.
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andyfiggy2002

posted on 17/8/17 at 04:36 PM Reply With Quote
I take it both you guys are running bike engines in your cars?
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ian locostzx9rc2

posted on 17/8/17 at 05:51 PM Reply With Quote
No I've not got a kitcar anymore but a few of my friends have and did this . Only my 100e now
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CosKev3

posted on 17/8/17 at 07:14 PM Reply With Quote
Your first idea is how Caterham have the exhaust running on there 620r iirc.

Ground clearance is the only issue you might encounter?

Why not just fit a bigger silencer instead of the 4 inch one?

I had a Westfield silencer which is just over 5 inch iirc on my car with R1 engine and open foam filter and this passed noise easily at Oulton Park and Anglesey

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rodgling

posted on 17/8/17 at 09:32 PM Reply With Quote
quote:
Originally posted by andyfiggy2002
I take it both you guys are running bike engines in your cars?


No, E36 M3. It's loud if I remove the rear exhaust can.

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blue2cv

posted on 18/8/17 at 07:31 AM Reply With Quote
Back in the 70's when i was racing moto x bikes, a favourite mod was to aim exhaust to the ground works good on dirt for muffling noise, tarmac however maybe not, worth a go cost nothing but time to try
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andyfiggy2002

posted on 18/8/17 at 09:37 AM Reply With Quote
Ok thanks for info, i plan to blitz all the uk tracks & I believe some of them are very strict on noise, most people with a 12K screaming engine either end up with a dustbin bolted to the side, fit DB eaters which stifle performance or are just resigned to the fact they can't do certain tracks. I just want something like a rear additional silencer or an additional outlet the other side to disperse the noise so that I can take them off if I want a blat on the public roads. All I was wondering is there a catch to these simple methods that no one seems to have discussed on here?
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HowardB

posted on 18/8/17 at 10:08 AM Reply With Quote
Fairly certain that someone will have mentioned it already - intake noise on a BEC can be loud, so a good airbox, and even a long cold air feed duct will help. On exhaust there is at least one person on here that has a second exhaust that is bolted on for track days, fitted with a U bend on one end it bolts to the side of the standard can and then has the outlet pointing down at the front.

Fit if required,. cheaper than a black flag

HTH





Howard

Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)

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CosKev3

posted on 18/8/17 at 01:28 PM Reply With Quote
quote:
Originally posted by andyfiggy2002
Ok thanks for info, i plan to blitz all the uk tracks & I believe some of them are very strict on noise, most people with a 12K screaming engine either end up with a dustbin bolted to the side, fit DB eaters which stifle performance or are just resigned to the fact they can't do certain tracks. I just want something like a rear additional silencer or an additional outlet the other side to disperse the noise so that I can take them off if I want a blat on the public roads. All I was wondering is there a catch to these simple methods that no one seems to have discussed on here?


You really are over complicating the job!

Get a bigger silencer made to fit onto your link pipe/end of manifold and just fit it for track days,simple.......

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andyfiggy2002

posted on 18/8/17 at 09:56 PM Reply With Quote
so as ive already got an airbox fitted i simply fit a bigger silencer & it's easy peasy getting my BEC through Goodwood, Combe, Donington & Bedford on static & drive-by?
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CosKev3

posted on 18/8/17 at 10:32 PM Reply With Quote
Plenty of BEC''s do yeah!

Go to a track day and how many BEC'S have anything fitted like you are thinking of making?

Mine passed Oulton Park and Anglesey with ease as above with a Westfield silencer

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andyfiggy2002

posted on 19/8/17 at 08:46 PM Reply With Quote
these trackdays you did at anglesey & oulton in your turbo BEC, were they 105db limit per chance?
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CosKev3

posted on 19/8/17 at 09:10 PM Reply With Quote
It wasn't turbocharged at the time,just standard R1.

Don't think Oulton is 105db tbh,mine registered 96db whatever

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andyfiggy2002

posted on 21/8/17 at 10:00 AM Reply With Quote
quote:
Originally posted by CosKev3
Your first idea is how Caterham have the exhaust running on there 620r iirc.

Ground clearance is the only issue you might encounter?

Why not just fit a bigger silencer instead of the 4 inch one?

I had a Westfield silencer which is just over 5 inch iirc on my car with R1 engine and open foam filter and this passed noise easily at Oulton Park and Anglesey


Considering all the posts about people struggling to get noise down for trackdays you will have to excuse my sceptism, can anyone else confirm I just simply bolt on a 5" westfield silencer & it will be easy peasy getting my BEC down to 96db?

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ian locostzx9rc2

posted on 21/8/17 at 02:28 PM Reply With Quote
Simple answer is no all bike installs vary intake mechanical and exhaust noise but fitting 2 silencers should sort the issue and a few intake mods as said .maybe worth getting a db meter so you can see the improvements as you sort the issue .

[Edited on 21/8/17 by ian locostzx9rc2]

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Andy B

posted on 21/8/17 at 02:39 PM Reply With Quote
We are running 6 inch stainless steel silencers on the CBR1000rr 08 on engined Arions, we use acoustafil ZX blanket packing and can do all of the tracks ok with the exception of Bedford - weve given up with the idea of going there the limits are so tight.
DB killers are a real bad idea for high revving BECs - forget performance loss take a look at the rise in cylinder head temparatures.
I dont think 5 inch Westy silencer will cut it to be honest.
Problem is that the noise reduction falls off exponentially with increase in diameter - 4 inch to 5 inch makes a big difference, 5 inch to 6 inch less but worth having, 7 inch less and 8 inch getting debatable as worthwhile.
We tried baffled type silencer as opposed to straight through absorbtion type abd sent head temp sky rocketing before melting the aluminium can.
Biggest issue would appear to be knobs buying houses near racetracks that have been there forever and then complaining about noise
Would have thought the answer would be to get a trackday car and use the facility on the doorstep really.
Look on the plus side soon we will all be driving sanitised electric vehicles and the problem will die - along with the fun and passion - deep joy

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CosKev3

posted on 21/8/17 at 05:11 PM Reply With Quote
quote:
Originally posted by Andy B

I dont think 5 inch Westy silencer will cut it to be honest.



Yeah I lied and made it all up

Unless of course it was all a dream...........

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Andy B

posted on 21/8/17 at 05:31 PM Reply With Quote
My mistake
based on the fact that over the last few months we have replaced standard 5 inch silencers on 3 Megablades, a Zetec and 2 mega busas all of which had failed noise test at Snetterton, Brands and Oulton respectively. Even running with the 6 inch silencers we are close to the levels and have to stay on top of repacking. Lots of the noise meters have been replaced with newer and more accurate kit with many now linked to local council monitoring sites and a lot of the leeway has gone now. With limits set to drop again my thoughts were more about future proofing than specific examples.
I am sure you didn't lie or dream it but circumstances are changing and we are having to react in a regular basis to get these cars compliant.
Doing BECs on a day to day basis as a living and spending most weekends at the tracks my observations were based purely on what we are seeing happening out there currently and not meant to cause offence
I'll get my coat &#128578;

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andyfiggy2002

posted on 21/8/17 at 05:42 PM Reply With Quote
Hi andy, guru of all things BEC. So putting intake noise to one side if I were to fit two 4" acoustafil ZX blanketed cans in line will that equate to an 8" thereby halving the noise from the outlet at the rear of the car?

Similarly if I have 2 outlets, one either side of the car from a single can am I again halving the sound that a static or driveby noise meter would pick up?

I'm just thinking outside the box as an alternative to the traditional bolting a dustbin to the side of your car




[Edited on 21/8/17 by andyfiggy2002]

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Andy B

posted on 21/8/17 at 06:06 PM Reply With Quote
Hi Andy
Done a lot with the BECs over the years but still learning every day so don't have all the answers.
My gut thoughts are that two cans in line will not halve the noise but will serve to bring it down - how much I couldn't say as I haven't tried it but I will rig something up to see when I do the next system.
The 4 inch silencers are just not up to it nowadays there is just so little space for the sound deadening wadding.
I do know that the 6 inch will do the job saving a lot of hassle and can be made so that if you just wanted to slip it on for trackdays and then revert for road use it could happen.
You need to be careful splitting to two independent silencers serving two cylinders, the bike engines do like a little back pressure - we have seen this on the later CBR engines - move from a two inch tertiary to a 21/4 inch and you see a good gain in Performance but go to 21/2 inch and you lose a lot of torque and some power - the gsxr engines at very sensitive to this and we don't go bigger than 2 inch exit on these
You can also lose some of the scavenging effect when you separate cylinders in this way
My choice - 6 inch repackable acoustafilled silencer with slip on and spring retainer - job done &#128578;

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CosKev3

posted on 22/8/17 at 07:09 AM Reply With Quote
LOL he's told you his choice!

Surprise surprise he's said fit a bigger silencer..........

quote:
Originally posted by Andy B
My choice - 6 inch repackable acoustafilled silencer with slip on and spring retainer - job done &#128578;

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andyfiggy2002

posted on 22/8/17 at 02:02 PM Reply With Quote
Andy, i'll PM you instead
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chutley

posted on 22/8/17 at 07:02 PM Reply With Quote
I have a 28" x 7" 'dustbin exhaust' on my car. Heavy no doubt, but brings a zx1400R bike engine down to 98db. With my custom airbox keeping induction down, not had any problems with noise. However, have yet to try Bedford...
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