06/05/2005 12:12:11 Paul Rigg [color=black]Hi all,[/color] [color=black] [/color] [color=black]My wife had a great time at the Donnington Beginners evening in my MGF Trophy race car. Only problem was that the combined ITG air filter and MG Sport & Racing Exhaust system recorded nearly 100dB on Donnington's drive-by noise meter! (The limit was 98dB) Even stuffing both of my socks into the air intake didn't limit the car's breathing enough to reduce the noise by the required 2dB. So please be careful if you decide to modify your exhaust, you may end up seeing black! (flags that is).[/color] [color=black] [/color] [color=black]Cheers[/color] [color=black]Paul[/color]

06/05/2005 13:06:11 d.breen crikey i bet my v6 zs was over an all then ,its got induction and then sport manifolds ,motorsport cat and twin exits an all ,,,how did you find out it was to loud.

06/05/2005 13:24:03 Tim You can rent a sound meter from book-a-track for £9.00. See my post in the General section 'noise meter'

06/05/2005 14:21:26 Dave Hi Paul, I'm glad your wife enjoyed the evening :) About the 100dB - is it a full spec cup car with direct to head throttle bodies? These will add considerably to the noise. A combination of just air filter and exhaust shouldn't be a problem. 100dB is pretty loud! So, you have the honour of having one of the very few MGoT black flags do you ;) - at least for non-embarrassing reasons! I hope you didn't lose too much track time over it - did you resolve it or not?

06/05/2005 14:46:22 d.breen oh right didnt realize yours was a race car paul ,,mine should be well quiet enough then ,,hope so cause im at c.combe next tuesday with xpf lot and they have noise limit as well.

06/05/2005 14:56:34 Dave [QUOTE=d.breen]oh right didnt realize yours was a race car paul ,,mine should be well quiet enough then ,,hope so cause im at c.combe next tuesday with xpf lot and they have noise limit as well.[/QUOTE]Hi Dave, Castle Combe is also 98dB, but does a static noise check (at 3/4 revs). However, you should be OK - plenty of other ZS180s have passed it with no problem. :)

06/05/2005 16:07:09 d.breen you sure its 98 at combe only it says its 100db on xpf thread,,,hope it is for a bit of a margin.So they do the test at 4000rpm and at 45 degrees to the zorst but what do they when testing twin exits,,ie one each side of car,,do they test em independantly or put it in between em?.

06/05/2005 16:20:33 Dave [QUOTE=d.breen]you sure its 98 at combe only it says its 100db on xpf thread,,,hope it is for a bit of a margin.So they do the test at 4000rpm and at 45 degrees to the zorst but what do they when testing twin exits,,ie one each side of car,,do they test em independantly or put it in between em?.[/QUOTE]Apologies Dave - just checked the MGoT details from last year. "[font=Arial][font=Verdana][size=2][color=#000000]100 dB(a) measured at 45° from the exhaust at 0.5m and 4500 rpm (static test)"[/color][/size][/font][/font] [font=Arial][size=2][/size][/font] [font=Arial][font=Verdana][size=2]I seem to remember them just measuring at one tailpipe, but I can't be sure.[/size][/font][/font]

10/05/2005 09:07:46 Paul Rigg [color=black][/color] [color=black]Hi Dave,[/color] [color=black]Hope I haven't scared anyone away by mentioning noise levels! A lot of the cars on track had modified road exhausts and none of these seem to have been too noisy. I took a decision not to use my road car for track days but bought an ex-race car instead, my thinking was that it would be completely fit for the purpose of flying round racing circuits and removed the risk of damage/wear and tear to my road car. The down side is that the exhaust fitted was designed by MG Sport and Racing primarily just for racing and is very loud! [/color] [color=black]As well as track days, I’ve also competed in a couple of races in the car where it has to pass a static test 105dB at 0.5 metres & 45 degrees from the exhaust pipe at ¾ maximum revs. I’ve not had any problems passing this test, although I don’t know the actual readings taken. [/color] [color=black]Now for the maths… The dB measurement is a logarithmic scale and relative to a known value. Basically, if one noise is twice as loud as another, it will always be 3dB higher when measured in dB’s. Also, every time you double the distance you move away from a noise it will sound half as loud, i.e. 3dB less. Hence, 105dB at 0.5 metres = 102dB @ 1 metre = 99dB @ 2 metres = 96dB @ 4 metres etc. So by my calculations I assumed that if I passed a 105dB test at 0.5 metres, I would be somewhere around 96 dB at 4 metres away from the car, (i.e. across the other side of the track from the drive by sensor) and below the 98dB limit. Where the calculations fall down is in the difference between a static test and a drive by test. When the engine is under load then obviously the exhaust is louder then if the engine is being revved with the car in neutral! [/color] [color=black]Thanks to Tim for pointing out that it’s possible to rent a sound meter. That would be really useful for confirming a noise level on a static test, although I’m thinking of how I would explain to a policeman what I was doing if he caught me performing a drive by noise test at 90 MPH![/color] [color=black]To save any further red faces and black flags, I’ve just bought a standard VVC back box very cheap from eBay. I’ll use the MG Sport & Racing box for the competitive events and the standard exhaust for the more refined track days! See you all at Bedford. :) [/color] [QUOTE=Dave]Hi Paul, I'm glad your wife enjoyed the evening :) About the 100dB - is it a full spec cup car with direct to head throttle bodies? These will add considerably to the noise. A combination of just air filter and exhaust shouldn't be a problem. 100dB is pretty loud! So, you have the honour of having one of the very few MGoT black flags do you ;) - at least for non-embarrassing reasons! I hope you didn't lose too much track time over it - did you resolve it or not?[/QUOTE]

10/05/2005 16:26:31 Shawn Moore mine was the white midget, I was really concerned about my noise level, although it turned out to be ok. The problem is that the car is so small, my ear is only a couple of feet from the exhaust. Did it sound loud from the pit wall, or did it just have the general racket of an old car?

10/05/2005 17:17:31 Ralph [b]10 year celebration of the F[/b] BTW and completely off topic.... Paul, I believe that your car is the ex-B&G racer and that it was one of the press release cars. As you are no doubt aware there is a meeting later in the year to celebrate 10 years of the F. What are the last 4 digits of the VIN number of your car?

11/05/2005 08:14:37 Paul Rigg [color=black]Hi Ralph,[/color] [color=black]You’re completely correct about the cars history. I intend taking the car to Gaydon in October for the celebrations. It's chassis 81.[/color] [color=black] [/color] [color=black]Cheers[/color] [color=black]Paul[/color] [QUOTE=Ralph]BTW and completely off topic.... Paul, I believe that your car is the ex-B&G racer and that it was one of the press release cars. As you are no doubt aware there is a meeting later in the year to celebrate 10 years of the F. What are the last 4 digits of the VIN number of your car?[/QUOTE]