Thruxton 90db Static Limit

[moorsd123]

Booked a track day at Thruxton and noticed their noise limit is really low (90db static).

I have a R400D with rear exit exhaust so should be quieter than the usual side exit, but I can't find any definitive answer on whether this will still likely be quiet enough?

Does anyone have any experience with running their 7's at Thruxton or know the sort of db levels an R400D with rear exhaust puts out?

 

[Roger Ford]

I think it's unlikely.

I know people have managed to get standard Sigma engined cars through, but only by being a little creative over the rev limit of their cars and the noise testers being reasonably lenient (in contrast to those at Castle Combe, for example).

Not sure if a rear-exit R400 is noisier or quieter than a Sigma. Induction noise might also be an issue, though at least that's going to be some way from the noise meter - probably more of an issue for drive-by testing.

[ScottR400D]

I've just spoken with a mate who's a member on here, has a new 420/210 with rear exhaust. He does a lot of TDs and tells me he's seeing readings about 90. 

He's doing Thruxton this week so we'll find out how it goes! 

[aerobod - near CYYC]

Depending on noise measurement parameters (specifically measurement distance), I can see the 420R being close to the limit.

I'm currently having problems meeting the recently enforced local track noise limits with a standard side exit exhaust (Rocky Mountain Motorsports track), they have about 20 noise measurement stations on both sides of the track, leaving no acceleration area without coverage, with weighted dBA measurements at 15 metres of 95dB max. On the left side my R400D is currently hitting 93dB, but it is hitting 100dB on the right side. They also require GPS flagging systems in-car, so they have no doubt which cars are producing the specific noise levels in a busy session and exactly what the noise profile is of the car due to correlation of GPS position with measurement values.

I'm not sure whether I can get below 95dB with my SuperTrapp noise suppressor (will find out on the next event on 25 Aug), but I'm not sure whether a standard Caterham rear exit system is good enough, either.

[ScottR400D]

I would think it would be hard to get much below 98 with a side exhaust. Mine is usually around that but the limit is 105 so well in. 

[aerobod - near CYYC]

I'm hoping I can average out the left and right noise measurements a bit (as well as about 3dB reduction overall, as measured at previous autocross events) as the noise suppressor directs the exit flow radially from the exhaust tip, as opposed to out to the right, but will see if I can avoid plug fouling due to the increased back pressure at max revs likely richening the mixture.

[moorsd123]

Well I've just tested it using a phone app, which I tested for accuracy at work (I work in the Audio industry)...but appreciate this is still only indicative.

0.5m at 45 degrees at 5800rpm is coming out between 87-88db, so close but near enough that it's worth giving it a go at Thruxton tomorrow....fingers crossed!!

[ScottR400D]

I've never been asked to rev my car that high. Asked what limit is I say 7200, they ask me to go to 5 -5500, I go to around 4800/5000 and get my ticket.......

You are pressing the clutch pedal aren't you? 

[moorsd123]

Passed without a problem 88db (he only asked me to rev to 4500rpm!)...reckon they were exercising some discretion though as there were a few other cars that sounded a lot louder that still got through.

Having said that an Aston V8 got black flagged for being too loud once on track!