Brands track day black flagged for noise

[r300chris]

Hi all, suggestions re how to reduce car noise levels, R500 D with Raceco exhaust, no cat, failed by 3db on drive by unsure exactly where on track. Had to reduce revs to around 7000 from then on and use decibel slayer.

The exhaust was repacked before event, car has external noisier exterior airbox.  Engine red lines at 8500 rpm.

what is best suggestion re fitting either internal track air box, although caterham are out of stock and they are expensive.

another option is to try the extra exhaust fitted to most of the R300 D racecars, which consists of a bolt on extra silencer  (supposedly fitted due to Sadev gearbox causing loud pops when shifting) these cars have about 175 bhp so don’t know if the extra exhaust will allow free flow of exhaust gas for circa 260bhp ?

Chris

 

[rj]

First you need to find out if it's the induction or the exhaust that causes the problem.

I have a 200+ BHP K-series with the R500 track day silencer and a bernard s airbox in which I have a layer of foam behind a mesh (to avoid the induction to eat it) - the layer of foam reduces the induction noise around 4dB (!)

The car is so quiet that I have been flagged in as they wanted to know how I had got it that quiet.

[r300chris]

Bit of a catch 22 situation, unless I get one or the other upgrades, I currently have standard foam Pipercross silencer under carbon airbox

[rj]

A carbon airbox is not as "dead" as a GRP ditto.

You could line it with foam like this:

https://www.ebay.co.uk/itm/Silent-Coat-Car-Door-Speaker-Sound-Proof-Deadening-Material-Mat-kit-Starter-kit/272984153608?hash=item3f8f1f9e08:g:vK8AAOSwdu9aqSJC

- I have something similar in my GRP airbox opposite the air horns. This was what reduced the induction noise 4dB.

Mind you that my airbox is the obsolete item with 100mm inlet, which means that it's noisier than the current item.

Given that yours is a carbon airbox I would probably also put on some strips of this:

https://www.ebay.co.uk/itm/Silent-Coat-2mm-x-4-Sheets-Car-Door-Speaker-Sound-Proof-Deadening-Material-Mat/263021651697?hash=item3d3d4fe6f1:g:rVoAAOSwe1xaqSFt

Be aware that the glue will give up at some point. I can confirm that it is not pleasant when the throttle won't return at the end of the long straight because one of the TBs has been eating foam. For the very same reason I have a piece of stainless mesh folded to hold everything in place. Like this albeit 25x25 mm:

https://www.ebay.co.uk/itm/Stainless-Steel-304-Woven-Mesh-4-Mesh-1-25mm-Wire-1m-x-1-22m/322860473523?epid=10008504043&hash=item4b2bfbdcb3:g:Hx8AAOSwNkJZ-zLj

- I probably have all the materials, problem is that I am in Denmark... I guess the mesh is the hardest to obtain locally; if you want to go that route I can of course send you a piece. Sending heavier things like the deadening material cost silly money compared to the value of the goods. Of course, if you at some point are near Copenhagen, I can meet up with you...

(Ian(SM25T) - when are you in Denmark next?)

As I am about to change the clutch and others (after "just" 15k track miles) of my car I will be in the garage a bit for the next days, which means that I can take pictures if the above does not make sense.

 

[SM25T]

Hej Regin. No plans at the moment ... But a return visit in the 7 is long overdue.

[rj]

Hej Ian.

Kattens også. Det havde ellers været let.

(Bugger. It would have been easy).

 

 

[Shortshift]

Chris

As per our exchanges on the other thread, I don't seem to have noise problems yet my car is the same as yours - external cf intake with Pipercross foam filter underneath, and Raceco can (in fact, mine is slightly shorter than the R500 box that Mike usually supplies, so if anything I'd expect it to be a bit noisier than a 'standard' Raceco).  I have not repacked it since buying it, during which time it has done around 3000 miles, a fair bit of it on track.

Sorry I can't help beyond confirming that!

James

[tomwood]

Hi Chris,

sorry to hear you got black flagged.

im going through the process of quietening mine down at the moment too and have opted for a raceco to help with matters to start with.

Everything I've read in the archives suggests that you're best off going with the track day air box from  Caterham as well though, the one with the K&N style filter that sits on the end under the bonnet. I've no doubt this will hamper performance to some degree compared to your current arrangement which draws air from outside the bonnet but the fact that the induction noise will remain inside the bonnet has got to improve maters. Better to take the edge off the top end performance a little bit but still be able to rev it out surely. Short shifting is just annoying.

id try that first as will be cheaper than swapping out your raceco for the track day silencer from Caterham you're referring to. I also don't particularly like that particular exhaust as I've seen a few of the secondary silencers under the fuel tank hitting the floor at the bottom of the hill around brands hatch.

which raceco can do you have? Is it the 750mm sleeved one? I understand they do a longer one as well, could that also be an option perhaps?

incidentally that air box on the Caterham parts site is unlikely to ever be in stock. I think it's a special order part for those interested in getting hold of one.

Tom

[Shortshift]

Be wary; the underbonnet air intake arrangement has a significant effect on power delivery - not just at the top end but it also introduces a substantial hole in mid-range torque.  I've no doubt that the K&N approach is much quieter from an induction perspective but optimum performance is definitely achieved with the exterior intake used in conjunction with the foam (Pipercross or similar) filter.  Remember that the underbonnet intake is not only devoid of the aerodynamic benefits of the external arrangement (much work was done on this just after the R500D was introduced) but it is also drawing in hot air from around the engine rather than cooler air from outside.

Given that other cars of similar spec (including mine!) seem to work without problems, I'd see what can be done whilst retaining the external intake first...  

James 

[tomwood]

James, am I right in thinking you don't have this style one then?

https://caterhamparts.co.uk/other/4649-track-day-airbox-r500-duratec-2008.html?search_query=Airbox&results=21

i know Caterham used to sell one that they referred to as the 'race type' but I can't seem to find it on the parts site anymore. That one exited the bonnet and simply had a slit around the circumference of the oval that came out of the bonnet. I assume it's that one you've got?

again, question for James. Has yours been remapped at any point? I do wonder if that's worth considering in Chris's case. I suspect that the lovely pops and bangs on the overrun don't help with noise. I wonder if some of this can be dialled out by running a customised map rather than the generic Caterham one?

Tom

 

 

[r300chris]

Hi Rj, thanks for comments, a picture could be useful, of the airbox foam and mesh if that’s not too much trouble 

chris

 

[tomwood]

Ah, I stand corrected, I found it.

James/Chris, are you both using this type of air box then?

https://caterhamparts.co.uk/other/2812-air-filter-cover-race.html?search_query=Carbon+race+intake&results=346

Tom

[r300chris]

Hi Tom, I’m not looking to replace Raceco, but to add another silencer, similar to R620 rear exit, on top as per the cars I saw at brands R300 race cars, it clamps into end of exhaust exit and then sits on top of the raceco, somewhat obstructing the drivers door opening and clamps to the inlet end just after the decay pipe, the exhaust then turns down to the floor.  The current extra exhaust costs about £240 but will need to be modified as Raceco can is longer.  

‘The only query I have is whether it can cope with the extra power of my car re exhaust gas flow.

when I used the decibel slayer, I had a massive hole in torque curve around 4K rpm.

chris

 

[r300chris]

Hi tom yes I’m using the box you just posted, which I believe is a race box, James has the internal airbox with K&N filter

chris

[tomwood]

Ah ok, interesting. Thanks for clarifying.

so in which case we know that in all likelihood, if you were to switch to the other air box arrangement then you'd get the noise down to an acceptable limit but at the expense of some performance. I suppose the big question is, which is likely to reduce performance less, the revised under bonnet air box or an extended exhaust.

ive not seen the exhaust arrangement you've described, sounds novel! I had envisaged that you'd meant extending the pipe work and running an extra (smaller) back box at the rear of the car rather than over the top of the raceco.

i guess the issue you'll have with that is that, although it's £240 for the extra silencer, you'll have to have some custom fabrication work to join the new silencer to the raceco which will probably double the cost and make it more expensive than switching the air box over. Furthermore, I assume you'd have to cut off the rolled edge that's on the end of the raceco exhaust at the moment which might make it look a little odd when you're not running the additional silencer.

its hard to know which is least likely to reduce the performance. I'm inclined to think the additional silencer may be least damaging to performance but that's just a guess.

the 620r runs that extra silencer successfully enough although I guess that's forced induction so we aren't exactly comparing apples with apples I suppose.

what diameter raceco did you end up getting? Is it the 63mm or 70mm inlet?

i wonder what diameter the pipework is on the extra silencer you refer to.

Tom

[elie boone]

R300C, does your exhaust has a domed mesh insert at the end of the internal mesh tube ? this also reduces the noise and costs only 2p, i just don't know exactly by how much the noise is reduced.

[Shortshift]

Tom

Replying to your post #12; yes, that is the external cf intake that I am using (the so-called air filter cover - race), in conjunction with the foam Pipercross filter.  This is the optimum specification for performance (both the cover and the filter) but is also the noisy option.  Some investigative work carried out by an early R500D owner (Martin Phillipson - stand up and take a bow) showed that the combination of the two parts (cover plus filter) is more effective than running with just the foam filter alone.  I understand that this was a learning point for Caterham Cars at the time.  To do with aerodynamics and pressure waves in the vicinity of the near-side front wheel and intake position, I believe.

And you just wouldn't run with just the external cover and no filter, would you...?

Somewhat confusingly, the underbonnet installation is the so-called trackday intake, which is the quieter version but is markedly inferior i terms of torque characteristics as well as top-end power.

James

[Shortshift]

And to correct Chris's post at #13:

Hi tom yes I’m using the box you just posted, which I believe is a race box, James has the internal airbox with K&N filter

chris

Err no; as above I'm using the external intake with the Pipercross foam filter.  So the same set-up as Chris, yet I have no noise problems on trackdays (touch wood, tempting fate and so on!).

James

[tomwood]

Very interesting, thanks James. It seems the plot thickens then.

have you had your car mapped at any point James?

i was thinking I was going to have to go for the under bonnet one on my r400d but given what you've now said I may re-evaluate. One would also imagine mine would be a bit quieter than yours anyway given it doesn't Rev out quite as much as your r500.

Tom

[Shortshift]

No mapping carried out (as yet), Tom - just as it came from CC, except for the bespoke (shortened) Raceco can.  And yes, I guess the 500 does rev a bit higher than your 400.  So there must be something else going on to explain why (touch wood again) I don't have issues whereas others do.

James

[rj]

The picture was taken from where the air filer used to be.

The filter is just a K&N cone.

[SimonR300]

I expect you know about this material which expands when heated.  There is a calculator to work out how much to buy.  I can recommend it.

http://www.textiletechnologies.co.uk/acousta-filr-zt1-exhaust-silencer-packing.html

 

Here is the McMillan racing additional silencer.  Stumbled across it the other day. Posted on 3rd May.

https://en-gb.facebook.com/McMillan-Motorsport-221277681273020/

[r300chris]

Hi tom I’ve been working in the garden all day.

Raceco is 750 mm long, o/d inlet pipe is 63mm.

the extra exhaust has a swaged end that pushes into the Raceco outlet pipe, my outlet Is 61mm i/d so extra exhaust will be something like 58mm i/d so a bit more restrictive.  

 

 

[r300chris]

Ellie, my Raceco just has a straight through perforated pipe going from inlet to outlet, nothing else, so I’m interested in what you mentioned, is it a standard part or added by yourself.

chris

[r300chris]

Hi RJ, thanks for the picture, I now can understand what you mean by damping, I will look at my airbox and see what can be done.

Chris