ConnorW06 Posted February 24, 2017 Share Posted February 24, 2017 Evening all, I've tried looking online and can't seem to find any solid info on dB levels of the aftermarket exhaust systems for our Zeds. I was looking into track days recently and understand all tracks come with noise limits, and wondered if anyone had ever got a proper read out of the dB level at the required distance / RPM for their car that a track would test at? (Either on track or off). Most of the tracks I've been looking at have around a 105dB limit, and I have no idea whether the Motordyne TDX2 exhaust and ART pipes I'm running would exceed this? I know it's one of the louder systems for the Zeds, but has anyone else ever had their exhaust tested? And if so, what was the dB? Or, if you have been to a track with a rather loud exhaust, do they even check? Apologies for all the questions, I'm eager to here anyone's story if they've tracked their Zed before! Many thanks. Quote Link to comment Share on other sites More sharing options...
Ekona Posted February 24, 2017 Share Posted February 24, 2017 You'll get a load of people now tell you what dB they tested at. Truth it, it's all nonsense as most results will vary day to day and TDO to TDO. It shouldn't, but it does. Get yourself across to Snet when MSV are running a day, they'll test you static for free and then you'll have a rough baseline. Most people now fall foul of driveby noise though, which is impossible to guess: I've seen a Viper be borderline static but clear driveby, and a quiet R32 smash the driveby on the same day at Bedford! That said, if the ART pipes are test pipes then it's likely you'll fail. Most decats are too loud. Also, given the NIMBY attitude towards motor racing these days, we have a responsibility to make our cars as quiet as possible to not give them any more ammo IMHO. 1 Quote Link to comment Share on other sites More sharing options...
shaun350z Posted February 24, 2017 Share Posted February 24, 2017 I don't know what the Motordyne with decats dB reading would be but I think the Ark Grip and Motordyne exhausts (no decats) are around the same dB (I could be wrong though) and Tarmac Sports states that the Ark Grip exhaust is around 88dB at 3000 revs... https://www.tarmacsportz.co.uk/nissan-350z-2003-08-3-5l-ark-grip-true-dual-exhaust-system-burnt-tip.html 1 Quote Link to comment Share on other sites More sharing options...
shaun350z Posted February 24, 2017 Share Posted February 24, 2017 Quick google and I found this on the US forum (post no.6) 114db with ART test pipes at 1m distance at WOT http://my350z.com/forum/intake-exhaust/533556-decibel-level-of-motordyne-tdx-v2.html Quote Link to comment Share on other sites More sharing options...
Ekona Posted February 24, 2017 Share Posted February 24, 2017 Exhaust tests are 4875rpm at 0.5m, so will give massively different results. 1 Quote Link to comment Share on other sites More sharing options...
Jetpilot Posted February 25, 2017 Share Posted February 25, 2017 (edited) Ekona is on the money, most exhausts on their own "should" pass static and drive bys (of course there are exceptions), add hfcs and you will be 50 50 at the quieter days, add decats (even silenced) and you will really struggle. My personal choice would be, a pair of hfc coupled with an exhaust with decent silencers, i.e Milltek, Fujitsubo, Nismo. I have mentioned before its actually a real bug bear of mine that there is no standard testing that we can all adhere to, I dont agree that we should make out cars as quiet as possible just to please the nimby's, that is not to say I think we should be able to run our cars as loud as we want, but being in or watching a 350z (as an example) wafting by with barely a noise removes part of the whole experience of enjoying the cars, you only have to look at one of the biggest complaint of the new f1 cars, lack of noise. Sorry to waffle but to answer your questions, you will not be allowed on any track without being tested, there will also be drive by tests, fail either and you will not be allowed on track and no money back. I dont think you will pass with your current set up. If you like your current set up, just bolt up a std system and book a day, see if you like it. Edited February 25, 2017 by Jetpilot 2 Quote Link to comment Share on other sites More sharing options...
Ekona Posted February 25, 2017 Share Posted February 25, 2017 I wish they got rid of the driveby test, then like you say at least we could standardise the static tests. If possible with your exhaust setup, personally I would grab a cheap OEM backbox and chuck that on for the day. No issues with noise then, plus it shuts the NIMBYs up. Quote Link to comment Share on other sites More sharing options...
BobbyZ Posted February 25, 2017 Share Posted February 25, 2017 (edited) TDX2 is a true dual, so not possible to stick a OEM back box on without the mid- and y-pipe as well. Edited February 25, 2017 by BobbyZ 1 Quote Link to comment Share on other sites More sharing options...
Jetpilot Posted February 25, 2017 Share Posted February 25, 2017 I wish they got rid of the driveby test, then like you say at least we could standardise the static tests. I suppose its swings and roundabouts, they made particular mention at Goodwood that if you have active exhaust valves (race/track mode), make sure they are open for the static if you intend to have them open on track, if you keep them closed to pass the static test and then open them when on track, they will not be pleased. I also guess people can fudge their static with bungs, valves, screamer pipes etc etc but then "change" that for when they go out, so obviously louder, i guess drive bys are as important for this reason and very difficult for "us" to test without being at a particular circuit at a particular time. Quote Link to comment Share on other sites More sharing options...
colesl4w Posted February 25, 2017 Share Posted February 25, 2017 I've heard of people in other countries putting on exhaust tips that point the opposite direction of where the drive by mic is hahah. Not sure you'd get away with that in the UK. Quote Link to comment Share on other sites More sharing options...
ConnorW06 Posted February 25, 2017 Author Share Posted February 25, 2017 Evening chaps, thanks for the replies, really appreciate your input. Like BobbyZ mentioned, chucking a standard or aftermarket back box onto my car isn't going to be possible due to the TDX2 being a true dual exhaust, which is why I'd much rather be able to drive there, have some fun on the track, and drive back without (ideally) having to swap half or all of my exhaust over. I understand that HFCs are an option, but reading online there isn't a huge difference, if any, between the noise level of HFCs and the ART pipes. Having never been to a track day it sounds like they're rather particular with regulations, especially noise. It's funny because of all the things you'd imagine could be an issue on the track, tyres that are in bad condition / bald, or the general 'safety' of your car being on a track with other drivers and needing to stop or go around corners fairly close to one another, you'd think noise would be the last thing they would worry about - do they check other parts of your car in these test areas? I know in some cases the locals like to have a moan because of 'noise pollution', but most of the tracks i'm looking at are in the middle of nowhere! Anyhow, don't get me started! I actually managed to get my hands on a Decibel meter today, not the most high-end piece of kit that's on the market, but states its accuracy is within 1.5dB, more than enough for some preliminary testing! Found some quiet, open land, fixed the meter on a tripod, positioned it centrally to my exhausts and placed it 0.5m back from the exhaust at around 1m up from the floor. I've just had a quick read-up online (while typing this) and the microphone is usually placed 0.5m away from the car at a 45 degree angle to the side of the vehicle, so my microphone being in the centre of the car may yield higher dB results? I presumed having 2 exhaust exits they would place the microphone centrally, can anyone confirm this? The results were as follows: Idle - 72dB 2000rpm - 95dB 4000rpm - 105dB 4750rpm (<- as close as I could get to it)- 110dB 6000rpm - 112dB 7000rpm - 114.5dB (shaun350z - That US forum you posted to link to was almost identical to my reading, despite being from 1m away instead of my 0.5 but they were using higher end equipment in a garage, interesting!) Revving like a yobbo in a Mcdonalds carpark - Peak 114.7dB Drive-by from approximately 8 metres away from the car @5000rpm - 85.4dB So taking the information from the Meter as an accurate-ish reading, it appears I would be over the static limit but within the drive-by limit. Ideally the next step would be to get the car measured somewhere that has the proper equipment and see what static results I get. I've had a look online Ekona for anywhere local to me that has the means to do testing similar or the same to that they would do at a track day, but everywhere is quite a drive from my house - typical! But for the mean time it gives us an indication of the noise levels coming from my exhaust. I would love to go to a track day sometime this year, but hate the idea of travelling down, paying for the track day just to be turned away at the door and sent on my way. It's a tricky one, sounds like you chaps have had different experiences with how strict they are and who they let carry on driving on the track! I know the safest option is to get another exhaust fitted if I were to go to the track, but after dropping a wod of cash on this exhaust just to change it over, seems like a huge shame and waste of money! 2 Quote Link to comment Share on other sites More sharing options...
Jetpilot Posted February 25, 2017 Share Posted February 25, 2017 (edited) I've heard of people in other countries putting on exhaust tips that point the opposite direction of where the drive by mic is hahah. Not sure you'd get away with that in the UK. People do it over here, but tracks arent stupid, there are db metres on the inside and outside of the circuit so at some point your exhaust tip is angled directly at the db metre, so sadly not the simple. The best idea is to actually point it directly at the ground. Op, static and drive bys are completley different, my vx at goodwood was 95db static, well within the static test, drive by was spiking the metre at 102db, black flagged and had to spend the rest of the day off throttle past the 3 drive by metres, no fun at all. At 110 you wont pass any static, so you have no choice, an exhaust swap shouldnt take longer than hour, so maybe 35 quid. The noise limits are not set by the tracks or organisers, they are set by the councils for the moaning nimbys. You could simple try a db killer/exhaust bung, wont cost you much to try. Edited February 25, 2017 by Jetpilot Quote Link to comment Share on other sites More sharing options...
Ekona Posted February 25, 2017 Share Posted February 25, 2017 Yup, def need to change exhaust. They'll also measure it from one exhaust pipe not centrally, so potentially even louder. Quote Link to comment Share on other sites More sharing options...
ConnorW06 Posted February 25, 2017 Author Share Posted February 25, 2017 (edited) It's crazy really, Silverstone for example is set in its own complex which the closest place that the sound would intrude on must be 5-10 miles away? Mad to think even they have noise restrictions. Had a look at some dB reducers and bungs online, most of which state a possible (being the key word) reduction of 10dB, which the tracks I'm looking at are 105dB static, so I'm only over by 5dB if the reader I used today is anything to go by. Obviously for ease of use and cost I'd much rather go this route. Anyone use a bung or dB reducer on their Zed with any conclusive results? Edited February 25, 2017 by ConnorW06 Quote Link to comment Share on other sites More sharing options...
Ekona Posted February 25, 2017 Share Posted February 25, 2017 I used them on my K1, many moons ago. Brought me to just under the limit at Woodbridge, but only just. You won't really know until you try. Things like the Supertrapp exhausts work very well, adjustable too, Quote Link to comment Share on other sites More sharing options...
Strudul Posted February 25, 2017 Share Posted February 25, 2017 It's crazy really, Silverstone for example is set in its own complex which the closest place that the sound would intrude on must be 5-10 miles away? Mad to think even they have noise restrictions. You still upset the wildlife Quote Link to comment Share on other sites More sharing options...
Jetpilot Posted February 25, 2017 Share Posted February 25, 2017 Sorry to the bearer of more bad news, dbs dont work on a linear scale, so roughly every 6bd more is twice as loud, so 5db is probably still two times louder or there abouts than the allowed and sound travels a long way, , all depends whats between the circuit and the moaning neighbours, if its wide open space, there is nothing to deaden the noise. Try some bungs though, its a cheap punt and if you do get on a day, it will be worth it, they are great fun Quote Link to comment Share on other sites More sharing options...
Jetpilot Posted February 25, 2017 Share Posted February 25, 2017 Or put std cats back in, that will make a big difference. Quote Link to comment Share on other sites More sharing options...
ConnorW06 Posted February 25, 2017 Author Share Posted February 25, 2017 Sorry to the bearer of more bad news, dbs dont work on a linear scale, so roughly every 6bd more is twice as loud, so 5db is probably still two times louder or there abouts than the allowed and sound travels a long way, , all depends whats between the circuit and the moaning neighbours, if its wide open space, there is nothing to deaden the noise. Try some bungs though, its a cheap punt and if you do get on a day, it will be worth it, they are great fun Just been reading up on how they're tested on track days etc and the readings are taken from a 45 degree angle, rather than standing dead central to the rear of the car. So I think tomorrow I'll get another set of readings and just see how they compare to today's, you'd imagine the readings I took today standing centrally to both exhausts would be higher, as the microphone is being hit equally by either exhaust. I understand sound travels, but logically you would think that the sound would be reduced when the microphone is not directly behind the exhaust. But we'll see! Worst case is that I'll have to look into bungs and see if I can find any good ones that don't require drilling, I've seen a couple that use clamps that simply tighten over the standard exhaust tips. I've been looking at Snetterton track days which have a 105dB static reading, so it may still be within reach with my current set up! Seen a couple of other tracks that are 95-97dB which I know I've got zero chance of getting on! Quote Link to comment Share on other sites More sharing options...
nub Posted February 26, 2017 Share Posted February 26, 2017 If the tdx2 cat back is the same as the shockwave for the 370z then there's no chance of passing. It's one of the loudest combos you can get, just look at it, it only has one singIe straight through silencer the back, plus the two chambers which are great, but dont reduce the decibels dramatically. I recently swapped FI HFCs for motordyne ART pipes on my 370z. I also have a FI cat back which would be a fair bit quieter than shockwave. With the ART pipes added, overall it got slightly louder than the HFC but also reduced certain frequencies and sounded much nicer with the Helmholtz chambers. At WOT motordyne shockwave plus ART Pipes is mental according to the YouTube videos I've seen. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
nissanman312 Posted February 26, 2017 Share Posted February 26, 2017 (edited) I passed at Cadwell..... with invidia /de cats and supercharger So did my pal with same set up on on a 350 maybey the tester was feeling generous Edited February 26, 2017 by nissanman312 Quote Link to comment Share on other sites More sharing options...
TT350 Posted February 26, 2017 Share Posted February 26, 2017 1.21 gigawatts! Quote Link to comment Share on other sites More sharing options...
nub Posted February 26, 2017 Share Posted February 26, 2017 Look at invidia compared to shockwave. It's the straight through back boxes that absorb a lot of sound. Motordyne doesn't have them, and it steps up to 3". Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
nub Posted February 26, 2017 Share Posted February 26, 2017 (edited) Your best option to keep as much power is probably a stock nismo exhaust, or find out which is the quietest after market cat back. I don't intend to track but I'm gonna change my Fast Intentions to ark grip as it should be similar but a bit quieter. Shockwave is my favourite but I just can't go even louder Sent from my iPhone using Tapatalk Edited February 26, 2017 by nub Quote Link to comment Share on other sites More sharing options...
nub Posted February 26, 2017 Share Posted February 26, 2017 (edited) Double post Edited February 26, 2017 by nub Quote Link to comment Share on other sites More sharing options...
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