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?
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]
As above, Plan A took me from ~105 to 95 dB.
I take it both you guys are running bike engines in your cars?
No I've not got a kitcar anymore but a few of my friends have and did this . Only my 100e now
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 
quote:
Originally posted by andyfiggy2002
I take it both you guys are running bike engines in your cars?
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
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?
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
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?
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?
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
these trackdays you did at anglesey & oulton in your turbo BEC, were they 105db limit per chance?
It wasn't turbocharged at the time,just standard R1.
Don't think Oulton is 105db tbh,mine registered 96db whatever
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
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]
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
quote:
Originally posted by Andy B
I dont think 5 inch Westy silencer will cut it to be honest.
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 🙂
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]
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 🙂
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 🙂
Andy, i'll PM you instead
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...
Doesn't a 1400 rev to 10k & a 900 to 12k? So I think you have the advantage when it's comes to screaming motorbike engines considering the noise tests done at 3/4 max revs on strictist tracks? Or is it 2/3? anyway i would love to fit a dustbin but as Ive only 21" of space would need a bloody fat dustbin & then im gonna hit ground clearance issues. I guess could chop my headers down so instead of 4 into 2 into 1 maybe try 4 into 1 to allow more length (ohh err missus) on silencer or as ive mentioned just have my 4" with additional one connected in-line in rear boot space. I mean your boggy standard road car has 2 silencers or technically a resonator & silencer, maybe some one could enlighten me to the diff between a resonator & a silencer?
Try a stock exhaust, I have one from a GSXR for my R1 4xv works really well as has 3 internal chambers to help reduce pulse.
http://drriders.com/topic8341-10.html
Phil
I was going to use a chambered R1 can until AB told me under hard track day use it would increase engine temps because of it's more restrictive nature
I agree with AB. However it's similar to putting more boxes on, you will restrict flow causing heat build up. I guess it's about finding the balance between cost, decreased performance and heat build up and noise.
I posted this thread as a discussion point & maybe I come out with some wacky ideas but thats how the design of an F1 car evolves, thinking
outside the box.
So why are ALL exhaust tailpipes round directing the noise into a small spot, what if you diffused the sound by fitting a fishtail tail pipe similar
to the old vintage motorbikes rotated so it was directed under the car at say 45 degrees down so it bounces off the road surface first, the noise
would be thrown backwards with the airflow, possibly need some heat shield initially to protect underside of car. Isnt it the same theory that when
you water the garden with a hose pipe the nossle can be adjusted to either throw out the water in a long thin stream or diffused outwards where it
travels half the distance but over a wider area??? I mean where would mr scruitneer direct his noise meter?
[Edited on 24/8/17 by andyfiggy2002]
My 893cc Megablade is fitted with the AB performance composite airbox along with a repackable 6" can. I too was worried about passing the static
noise test on my first track day at Oulton, prior to the day I took it to Oulton whilst there was another track day on and asked the marshalls to
noise test it for me, this gave me the time to make modifications if necessary. However, I needn't have worried because it passed easily - if I
remember correctly it read high 90's on the static and never triggered any of the drive by noise monitors :-)...I've attached some
photo's of the set up below:
Ok I think we've got oulton & anglesey covered........ what about stricter tracks like bedford, donington, goodwood, thruxton or combe in a 12000 rpm BEC & what are these tested at 3/4 or 2/3??