Bedford - Noise limit query

[aporschefan]

Would any cars with this exhaust running with open valves be allowed on the circuit?

 

[944 man]

None!

 

[aporschefan]

ok. That's pretty straight forward.

I've not been a on a track day before so am curious to know how the noise is measured at the start of the day and as the day progresses.

Presumably at the start of the day they ask you to rev to n k revs for n seconds and decide? And during the day there are 1 or more points on the circuit where they measure the sound?

 

[944 man]

Yes, the static test is usually a variation on the MSA test and the drive-by will be a lower limit. The drive-by is usually only a problem for turbocharged cars (which have passed the static test without issue).

 

[Highwayman]

Here's the offical line from MSV:

All vehicles participating in track days at Bedford Autodrome must conform to MSV's static noise test limit of 101dB(A). Noise checks to establish adherence to this limit will be conducted in accordance with current measuring methods as defined by the MSA. Essentially this means that the test will be carried out with the meter 0.5m from the car exhaust at a 45 degree angle with the car at ¾ maximum revs.

In addition to the static test mentioned above, vehicles must also comply with our drive-by noise limits. The noise emissions from any vehicle must not exceed 87.5dB(A) measured 20m from the car, which shall be accelerating maximally at over 60mph. Drive-by levels are monitored using noise meters located at several locations around the Bedford Autodrome complex.

If the results of the monitoring show that a particular vehicle is exceeding the drive-by limit of 87.5dB(A), then MSV staff will inform the participant and their vehicle will not be permitted to take further part in the event until the participant has addressed the noise levels generated by the vehicle to bring them within acceptable limits. Further participation in the track day may be precluded if acceptable drive-by limits cannot be achieved at the first drive-by test following the addition of extra silencing.

Phil

 

[Diver944]

When I had my 3.2L Turbo with standard 2.5" but decatted exhaust it passed the 101db static test with ease. It was 89db IIRC

However out on track the induction noise from the cone filter and ball bearing turbo triggered the driveby measurements and I was black flagged. Bedford is very tight on noise and I believe the driveby sensors are actually linked to the local council so there is no escaping and they will lose their trackday permission if it is continually abused so you will get black flagged if you are too noisy.

A standard 944 will have no problems whatsoever. Those equipped with 3" exhausts and a proper silencer will also have no problem, but if you have a larger exhaust than that or no silencers you may run in to problems [&:]

 

[944 man]

It pays to locate the on-track microphones and back off a little as you pass them.

 

[JamesO]

ORIGINAL: Diver944

When I had my 3.2L Turbo with standard 2.5" but decatted exhaust it passed the 101db static test with ease. It was 89db IIRC

However out on track the induction noise from the cone filter and ball bearing turbo triggered the driveby measurements and I was black flagged. Bedford is very tight on noise and I believe the driveby sensors are actually linked to the local council so there is no escaping and they will lose their trackday permission if it is continually abused so you will get black flagged if you are too noisy.

A standard 944 will have no problems whatsoever. Those equipped with 3" exhausts and a proper silencer will also have no problem, but if you have a larger exhaust than that or no silencers you may run in to problems [&:]

This concerns me a bit as I have no AFM, just a short length of alloy pipe with the cone filter behind the headlamp. So induction noise is quite high. Hopefully the standard turbocharger will keep the noise down enough.

My highly scientific tests with an Iphone on a bucket and a tape measure produced 88 db with a hollowed out cat and standard exhaust.

Might have to look at boxing off the filter a bit.

 

[blaine54]

If your marginal on noise I'd recommend short shifting coming out of the 1st few corners at Bedford [] .

The drive by sound meter is in these corners, but as long as you're not using full revs and you've passed the static you should be ok. I've always got through with my GT3 and that varies between 101 and 103 db on the static. Mr sound man always seems pretty reasonable, but if he says your on the edge of the static limit keep those revs low near the sound meter and have a great day

 

[Diver944]

ORIGINAL: JamesO

This concerns me a bit as I have no AFM, just a short length of alloy pipe with the cone filter behind the headlamp. So induction noise is quite high.

You should be fine James, the ball bearing turbo had it's own particular high pitched noise.

http://www.youtube.com/watch?v=vBJSzkWtn-c

There are plenty of 944T's with no AFM and a cone filter that get by the noise sensors without problems. I'm looking forward to seeing your 3.0L in the flesh [8D]

 

[944Turbo]

Love that vid!

I got black flagged at Donnington but I was changing gear at the gantry and there was a small explosion in my tail pipe, short shifting cured it.

Tony

 

[JamesO]

ORIGINAL: Diver944

ORIGINAL: JamesO

This concerns me a bit as I have no AFM, just a short length of alloy pipe with the cone filter behind the headlamp. So induction noise is quite high.

You should be fine James, the ball bearing turbo had it's own particular high pitched noise.

http://www.youtube.com/watch?v=vBJSzkWtn-c

There are plenty of 944T's with no AFM and a cone filter that get by the noise sensors without problems. I'm looking forward to seeing your 3.0L in the flesh [8D]

You may be disappointed, its a bit of a rough old girl.