LoT - Donington & Oulton - 28-29 Oct 2019

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robin
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by robin » Thu Aug 29, 2019 8:42 pm

Yes, the static limit for OP is published at 104 or 105dBA (cannot remember which) and is measured in the standard 500mm from exhaust tip at 45 degree angle, high revs (2/3 or 3/4 of rev limit). You'll pretty much always pass this so long as you raise the revs smoothly and wait for the thumbs up before closing the throttle.

The drive by limit of 92dBA is directly related to the above, but obviously you'll be at full throttle. Baz was OK in the GT3-something-something-something-very-very-loud at OP last year. The only car I would think might fail is Doug's powder blue Exige :-)


Donnie don't have a static limit for quiet days I think - they just rely on the 98dBA drive by, which quite a lot of people failed, especially Baz :-) I think you can treat their drive by like a static limit - the microphone must be right next to the track (and of course the engine is under load rather than in neutral, so a lot more power being generated = a lot more exhaust gas = a lot more noise).

Fit a standard back box or prepare for dissppointment :-)
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robin
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by robin » Fri Aug 30, 2019 7:51 am

BTW, after some quick sums, I reckon that the Oulton Park drive by sensors are approx 2m from the track; inverse square law says that power drops in proportion to the square of the increase in distance - so going from 0.5 to 2m is 4x the distance, so power level will be 1/16th. 1/16th is almost exactly -12dB:

1/16 = 0.0625
10 log10(0.0625) = -12.04 ... let's call it -12.

So if the static test is 104dBA at 0.5m then -12dB gives you 92dBA at 2m.

Of course actually the meter could be nearer or further away but then the result adjusted by subtracting or adding some dB offset to compensate - physics is physics after all :-)


And that is what I think Donnie are doing - I think their 98dBA limit is meant to be equivalent to a 98dBA static test - i.e. it's the equivalent of 98dBA at 0.5m. The actual mic distance from the track will be more than 0.5m, but they'll just add back the right number of dB to compensate for that (and maybe they use multiple mics in each location to account for the car taking different lines and different exhaust positioning).

The problem with working out whether or not you'll pass it is that it's very hard to measure with the engine under load (without a rolling road). If you had a friend with a sound meter you could attempt a full throttle fly by on a quiet road and try to line it up so you're near full RPM as you pass them (might take a few calibration runs to get your eye in :-)). The meter would need to be on fast averaging and probably have some peak hold mode to capture the loudest point. Then if you position yourself 2m from the line that the exhaust will take and then make sure your peak is less than 98-12 = 86dBA. Make sure the sound meter is on dBA (A is normalised to account for human perception of noise; without an A weighting you'll over read).



Of course no need for the complex experiment if you fail the static 98dBA test ;-)
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hendeg
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by hendeg » Fri Aug 30, 2019 7:58 am

If I was fine at Zolder then surely I’ll be ok at Donnie.
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by campbell » Fri Aug 30, 2019 12:19 pm

I think what you are trying to say, Robin, is that the simplest thing is to fit a std box. So clearly that’s the one thing I’m not going to do

Not least because I just removed the crazy Lotus supplied Stage 3 and invested in the 2bular QP in good faith

But thanks for all the Fisics cos we can use the data as benchmarks when I get scrutineered at Knockhill tomorrow
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by Clarkie » Fri Aug 30, 2019 9:42 pm

Wow thanks Robin, couldn’t hear what you had written🤣 sorry that’s flippant, you are knowledgable & articulate as always.
Recognise noise is likely to be increasingly an issue particularly with electric/hybrid power trains on the horizon
It would be good to have the car tested and noise levels agreed ahead of any track day but then that would be open to abuse as the silencer could be changed in the interim.
Understand if I fit a standard back box it’s not good for the engine.......
3eleven must run same exhaust silencer?
I’ll get it checked between now and then, if too loud I’ll swap to a 2bular QP for next year

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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by campbell » Fri Aug 30, 2019 10:30 pm

Clarkie.

11.45 tomorrow, Sat 31 Aug, at Scrutineering Shed, KH. Be there.

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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by Clarkie » Sat Aug 31, 2019 7:39 am

campbell wrote:
Fri Aug 30, 2019 10:30 pm
Clarkie.

11.45 tomorrow, Sat 31 Aug, at Scrutineering Shed, KH. Be there.

Image
Thanks for organising i’ll be there👍

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robin
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by robin » Sat Aug 31, 2019 10:40 am

We should start a noise thread - i.e. car/track/noise test/level so that we can see which engine/exhaust combos are likely to pass/fail any given track.
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hendeg
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by hendeg » Sat Aug 31, 2019 12:54 pm

That would be good. Even just a list of the failures would be a good place to start.
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by campbell » Sat Aug 31, 2019 1:38 pm

Here you go...

viewtopic.php?t=44528
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by greyrigg » Sat Aug 31, 2019 3:48 pm

My car was okay at Castle Combe which according to the list is 100db static and 94db drive by so should be fine. I have a Komotec db killer just in case, knocks 3db off.

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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by C7Steve » Mon Sep 02, 2019 10:36 am

Is there fuel on site at Donnington and Oulton Park or will I need to take a fuel can with me?


Steve.

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Mike Scib
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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by Mike Scib » Mon Sep 02, 2019 1:45 pm

Fuel available at both tracks Steve.
C7Steve wrote:Is there fuel on site at Donnington and Oulton Park or will I need to take a fuel can with me?


Steve.


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alicrozier wrote:As Robin said, need to be comfortable and confident to push right up to the limit - sometimes you only find the limit by going beyond it...
(that's why I think Mike will do fine, that and his lack of imagination). :roll: :lol:

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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by C7Steve » Mon Sep 02, 2019 2:25 pm

Mike Scib wrote:
Mon Sep 02, 2019 1:45 pm
Fuel available at both tracks Steve.
Thanks Mike. :thumbsup


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Re: LoT - Donington & Oulton - 28-29 Oct 2019

Post by campbell » Sun Oct 06, 2019 10:25 pm

Travel planning time.

What are people’s plans for Sunday 27th then, for outward to Donnie / East Midlands airport hotel?

Range of starting points I imagine! - but shall we team up somewhere?
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