Trackday noise tests

[DeanoRR]

I'm just thinking ahead, but after having to struggle to get my TVR through the different noise tests at trackdays, I wanted to see how many of you manage to get your BEC on track. And also if there is anyone who makes a track focused silencer and airbox to cut down on induction noise. I know this will hurt the performance but if it gets me on track... I cannot believe his fast 50 mph feels in one of these things.

[alfaspecial]

Just for your info and I imagine other circuits have similar policies;
http://www.castlecombecircuit.co.uk/trackdays/cari...
Quote" Noise Restriction
All vehicles must comply to the strict noise limit of 100db(A), which is measured at ½ metre from the exhaust outlet at 4500rpm. All vehicles will be sound checked prior to taking to the circuit, please ensure that your car is in suitable condition for circuit driving and to MOT standard. Cars fitted with slick tyres are only permitted subject to strict monitoring of driving standards. In the event of a car failing the sound check, then the driver will be entitled to a 75% refund. If you are unsure if your car will get through the noise test, then you could always come over to get it noise tested prior to booking a place."


Castle Combe Circuit did offer a silencer for hire although I couldn't see one offered on the website. Give them a ring? Other circuits may do likewise.
Merlin Motorsport @ Castle Combe sell silencers and components eg
http://www.merlinmotorsport.co.uk/EXHAUSTS-Merlin-...
http://www.merlinmotorsport.co.uk/EXHAUSTS-Exhaust...




A few years back I bodged a silencer - my Alfa engined special would have been way over the limit- simply by packing the (large diameter) exhaust tube with loads of loft insulation, held in place by a perforated tube. (similar to Merlin tube above) I passed the noise tests but by the time I actually went out on track most of the insulation had blown out. Performance restored!

[ugg10]

Note that some tracks also have a drive by noise test, was at Silverstone last week and they have track side monitors that are checked by race control, they were very intereasted in a certain caterham. Also some tracks have significantly lower limits, Goodwood is particularly strict IIRC, http://www.trackdays.co.uk/tracks/ gives you a guide as to what the limits for different tracks are.

Hope this helps.

[Stuart Mills]

Donington always amuses me, they have some very sophisticated measuring equipment with several monitor screens in the control tower. I was called up to look at the evidence as my demo Exocet car was called in to question. On the straight at full power it was on the limit. Then a jumbo went over....

[DeanoRR]

I've sprinted at Coombe and Goodwood, I thought they always measured you at 2/3 max rpm, if they test a bike engined car at 4500rpm, that's not much above tickover.

[andygtt]

Stuart Mills said:

Donington always amuses me, they have some very sophisticated measuring equipment with several monitor screens in the control tower. I was called up to look at the evidence as my demo Exocet car was called in to question. On the straight at full power it was on the limit. Then a jumbo went over....

yes but the old couple that bought the bungalow next door a few years back should be able to sit in their garden without listening to your car race around the track.... in fact its such a disgrace the track should be closed and moved somewhere else!

[DeanoRR]

Lol, yes, because you expect piece and quiet when you decide to move next door to a race circuit, just like the people who move to the area around heathrow and complain about the planes.

[Dimski]

I've been repeatedly tested at 99db, on one occasion the chap double checked and told me that he had calibrated his machine that morning. I had no problem at Silverstone, Cadwell, Oulton, Snetterton or Rockingham.

Castle Combe tested me at 107db @ 7k rpm, which was 500rpm lower than I was tested at other circuits. A small discrepancy is understandable, but 8db difference?

My exhaust (fitted by AB performance) is about as quiet as it is going to get without adding serious restrictions, which could take the head temperatures to rather risky territory.

Perhaps a decent air box might help knock another db or so off, but losing 8-10 to get past Combe? I doubt it would be possible.

Basically, I have crossed Coombe, Donnington, Croft and Brands off my list until I have a different car.

[DeanoRR]

I would be very interested to know what db your BEC's have registered. Me thinks Castle Coombe will be the problem as usual.

[Monty Zoomer]

Stuart Mills said:

I was called up to look at the evidence as my demo Exocet car was called in to question. On the straight at full power it was on the limit. Then a jumbo went over....

They've got big, sensitive ears and they faint easily when they get a fright

You need to learn a bit of consideration.

[BusaMK]

The microphone on the donington straight is clearly visible on the pit wall. If you avoid overtaking cars on this straight and stay right short shifting out of the corner you should be fine. The staff are also particularly helpful and will let you back on following a noise infringement if you've added an additional silencer(which isn't difficult to add, especially if it is a straight through bike can with the same bore as your existing exhaust).

This is completely different to bedfords staff attitude- They will not let you back on despite their noise management plan stating that you are allowed back on if you make an exhaust change.

[R1 Indy]

Does anyone have any experience with standard bike silencers?

I've just fitted a 4xv R1 silencer to my 08 4C8 R1 Indy.

At idle And low revs it does sound rather quiet , but as it gets into the higher revs it does still sound very loud.

I will try it first at a track like blyton park with a 105db limit.

But wondering if anyone has any experience in this type of setup and DB levels?

[DeanoRR]

I was thinking along the same lines, having a nice sports can for road fun and a standard R1 can for trackdays. I would of thought that this route would be kinder to the power levels rather than a purpose built track-friendly exhaust. Has anyone noticed a difference with an enclosed airbox rather than the open filter?

[Dimski]

I bought a standard can to replace the stubby which was fitted to my car when I first bought it (and burnt through not long after), but never fitted it as I was advised that the standard cans can be quite restrictive; the back pressure could result in high cylinder head temperatures.

I went for a re-packable silencer (it was an expensive weekend! ) and I think my problem now is more on the induction side of things.

BTW - I think Blyton has a drive by meter, there is no static test IIRC. You should be ok unless the car is really loud.

[andygtt]

the exhaust doesnt NEED to be restrictive to reduce noise.... the biggest noise reduction is length and bends.

What I did on my ultima was to do a 90 deg bend at the rear of the car and go back and do another circuit of the engine bay added 1.5m to the exhaust length and a few sweeping bends... dropped noise 9db over stock whilst having a free flowing exhaust than stock as it was a straight through silencer rather than a z trap.. so win win.

Ok so on a BEC it wont look pretty and will add 10kgs... but it will get you on track without stupidly restrictive end baffles etc.

[Hobzy]

You've got room to experiment in the engine bay - look on Locostbuilders Dean, there was a guy on there who routed his under and twin canned out the back. If you do away with the minimal boot you could move the fuel tank inwards to give room for a rear exit exhaust...

Induction noise will be an issue to I think - there must be modern more lightweight soundproofing to replace the heavy matting that was in there. Anyone any ideas? AndyGTT got any suggestions?