Big Brother Posted April 4, 2002 Share Posted April 4, 2002 Can anybody tell me how loud a 1700cc Supersprint with a 4 into 1 exhaust will/should be. I am thinking of doing an airfield day soon but the venues noise level is 103dB - 0.5M @ 3/4 max rpm I had the car checked about 6 months ago just for fun. I ended up with 108dB! however this was at around 5000rpm and up against the wall of a pub so probably not very accurate wink.gif Alternatively has any one local got access to a meter and can spare a few mins? I am in Yateley Hampshire ADVthanksANCE Steve www.Se7en-Up.co.uk id=green> Link to comment Share on other sites More sharing options...
Graham Perry Posted April 5, 2002 Share Posted April 5, 2002 Steve, You are going to be borderline. My car has been tested more times than I care to remember and it is a different level every time. It is usually between 101 and 108 DB and averages about 104. It amazes me how inconsistent these measurements can be. Tell them your car maxes at 6000 and they will only measure it at 4500, but even then you may be close to the limit. Link to comment Share on other sites More sharing options...
Silver 21 Posted April 5, 2002 Share Posted April 5, 2002 Steve I competed with my 1700cc Xflow with a 4 into 1 exhaust at Loton Park at the weekend and it tested at 103dB so I think you should be OK, that was at 4000rpm, Hope this helps Graham cool.gif1700 Live Axle X/Flow, got the engine upgrade now all I've got to do is try & beat the rest of the guys up the hill!!!!!id=red> cool.gif Link to comment Share on other sites More sharing options...
DohNut Posted April 5, 2002 Share Posted April 5, 2002 The size / age of your silencer will have a big impact, I have a very old 4" silencer which measured 110db+ (120db?) on a drive by at goodwood last year but the meter was placed where I was hitting max revs in first gear. I need to get a new 6"+ silencer but I am just trying to get my head around the price. Link to comment Share on other sites More sharing options...
rgrigsby Posted April 5, 2002 Share Posted April 5, 2002 With a brand new 4-1 Caterham silencer with the car warmed up I managed 98dB at Kemble last year but that was probably a bit lucky. Other times I've pretty much always been between 101-105dB. It does very much depend on how much packing there is left in the exhaust, unless it's reasonably new I would guess there won't be much left. Definetly say you have a 6000rpm rev limit though! The measurements tend to vary a lot due to a combination of differening weather/air pressure, differently calibrated sound meters, exactly where the sound meter is held in relation to the exhaust and also where the car is tested in terms of nearby walls/buildings etc. Basically unless you test a car on the same sound meter in exactly the same place with exactly the same air pressure/weather you will almost definetly get a different result. Cheers Rob G www.SpeedySeven.com Edited by - rgrigsby on 5 Apr 2002 09:56:08 Link to comment Share on other sites More sharing options...
Drumster Posted April 5, 2002 Share Posted April 5, 2002 My supersprint, with 4 into 1 exhaust and an 8 year old 5" Caterham silencer registered 110db a year ago, so I changed to a Techcraft 6" repackable silencer with the immediate effect of reducing noise to 97db. Its now beginning to creep up again and is probably around 105db. Time to change the packing I think. Chris Alston Se7ening - it's all miles and smile.gifsmile.gifsmile.gif 1800 Supersprint - Loud and Proud teeth.gif ...well it only sounds fast officer blush.gif Link to comment Share on other sites More sharing options...
Big Brother Posted April 5, 2002 Author Share Posted April 5, 2002 I was informed today by an acoustic engineer that there is a level of inacuracy built into all noise meters of around +/- 3dB Apparently this is to allow for reflective irregularities???? Not sure if it would work on a scrutineer though wink.gif Steve www.Se7en-Up.co.uk id=green> Link to comment Share on other sites More sharing options...
JonnyS Posted July 26, 2002 Share Posted July 26, 2002 Hello I just found this thread and read it with interest. I'm also concerned about my noise levels as I am going to Bassingbourn airfield soon. The last time i went to Castle Combe I miserably failed the noise test at 102db (4500rpm). I have been thinking about getting a Techcraft 6" repackable silencer (as my current 4:1 one is not packable) but I have been advised by my friends at RatRace that this might not make any difference. Has anyone else found this? I would therefore be wasting my money. 2 more questions: where is a good place to buy a Techcraft silencer - Merlin? And what about driving shoes? Anywhere in NW London? Jonny Link to comment Share on other sites More sharing options...
rgrigsby Posted July 26, 2002 Share Posted July 26, 2002 Jonny you could try speaking to The 7 workshop. Chris there sells quite a few Techcraft silencers with pretty good success at reducing noise levels. It does also depend on the engine tune/health to a certain extent as well... Cheers Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
AMMO Posted July 26, 2002 Share Posted July 26, 2002 My Supersprint measured 109 dBA with a 5" stainless silencer. This went down to 103 dBA with a quiet type 6.25" silencer. The same two silencers on a 2 litre Zetec measured 104 and 98dBA. This was measured on concrete at 0.5 metres at 45 degrees at 5,000 rpm. Sound level doubles every 3 dB so 6 dB less is actually quite a lot. AMMO Link to comment Share on other sites More sharing options...
Jam Mad Posted July 26, 2002 Share Posted July 26, 2002 some airfield days don't actually check you, but they have to advertise it. it depends on the company. you can also, when asked the question " what are you maximum revs ? " tell a white lie... it will make a small difference, but it might be important. my x flow is noisy, but at 105db days i haven't had a problem. first was an airfield day at elvington, second was at brands. from the x flows that i've seen, the techcraft silencers seem to do an amazing job. cheers, j Link to comment Share on other sites More sharing options...
Taran Las Posted July 26, 2002 Share Posted July 26, 2002 I have a Techcraft 6" silencer. Although I've never had the noise measured when I fitted the Techraft there was a considerable reduction in noise. This was confirmed by my neighbours! Philip. D. Owen Membership No. 3976 Link to comment Share on other sites More sharing options...
Big Brother Posted July 26, 2002 Author Share Posted July 26, 2002 As already mentioned, try speaking to The 7 workshop. They sell an exclusive version of Techcraft silencers called the "Goodwood". Steve www.Se7en-Up.co.uk Link to comment Share on other sites More sharing options...
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