BMW Rallying Forum

We have replaced the system from the end of the tunnel back, mainly due to the weight of the rear box which nearly killed me when I took it off.
I was always suspicious that it was too loud, so we did a test at home with a few trees around and got 101. We expected it to be lower in true open field conditionsm, but just in case I knocked up a couple of inserts.
At Noise test for a track day at Castle combe we got 102 with the inserts in, but they don't use open field conditions, and in fact there are tall tress and a brick scrutineering shed that they do noise test in front of. Second go I just pulled forward further and we got 100. People listening to us circulate said we were one of the quietest cars on track.
At the Fatal Bert at the weekend we got 99.5, although apparently the noise test lady holds the microphone behind the exhaust, not at 45. But again there were cars making plenty more noise than us, and in fact on the video you can hardly hear our car.
So, is there a trick I am missing about keeping noise down for noise test (I did pick up the bit about having the clutch bite to make the engine work a little). The exhaust does sound raspy.

find the sweet spot in the rev range there will be a rev it gos quite (ish)

Disconnect the rev counter and then at noise test don't rev it as hard ...... works every time !!!!!!!!

Cheers Dave aka Daishag Rallying 07805835655

Daishag wrote:Disconnect the rev counter and then at noise test don't rev it as hard ...... works every time !!!!!!!!

Cheers Dave aka Daishag Rallying 07805835655

I did have similar thought, since the Tacho is driven from the ECU, then a little recalibration....

Noise limits are to protect our sport, and enable us to re-visit venues with no strife.
Fit a bigger silencer and have one less thing to worry about.
MSA must love reading threads like this

is-si,

I completely agree we need to protect our sport,and I have fitted larger silencers, note I mention my car is very quite, and I mean very. Most other cars make more noise on stage, it is just that it comes out loud at noise test. I discussed it today with someone and we thought that since the ECU is not mapped at no load & 4500, it may be possible to reduce the noise by editing the map in that area.

Here's a couple of pics of my exhaust, custom made by my good friend Cliff Evans who owns the Hockley Built F2000 spec compact.





Must say i havent had any problem with noise as yet with her and have been commented twice that she is actually very quiet and yes my rev counter does work and is correct, sorry for my last comment it was meant as banter

Cheers Dave aka Daishag Rallying 07805835655

do you use any heat shields dai?

That's the sort of setup I have, except mine is in two pipes all the way. It the standard system to back of the tunnel, then pipe to the rear and two boxes, one per pipe.

There is a clip of us having a moment here http://www.madvideo.co.uk/page220.htm. Can anyone actually hear it run ?

I will see if we can fit a longer one in place of the standard item at the back of the tunnel, bit tight for width though. Failing that we will add another between this box and the back box.

If it gets any quiter on stage though I'll have to add whistles to the wings so that people can here us