Richf Posted August 16, 2015 Share Posted August 16, 2015 Bought a pair of decats and added them to my Invidia Gemini on my 370z a/t and I think they are going to be too loud , going to live with it for a while but as the car will need to go on track occasionally I suspect it will fall foul of noise testing . No booming or suchlike on cruise and its fine but when you floor it its rather fruity for sure Unfortunately it does pull so much better above 5k than it did so I'm rather loathed to get rid of them What options do I have ie Berk HFC or suchlike, will they temper the noise without strangling performance? Has anyone gone from decats to hfc? Quote Link to comment Share on other sites More sharing options...
Bodyboarder81 Posted August 16, 2015 Share Posted August 16, 2015 Motordyne art pipes .... Best of both , all the benefits from decats and quieter than hfc . Speak to Torqen . 1 Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted August 16, 2015 Share Posted August 16, 2015 Why don't you do a drive by and static test before you make any changes, or buy a meter. Remember that you can get rear inserts to reduce the DB. Quote Link to comment Share on other sites More sharing options...
nissanman312 Posted August 16, 2015 Share Posted August 16, 2015 Sure gm passed for track with same set up and supercharger Quote Link to comment Share on other sites More sharing options...
GMballistic Posted August 16, 2015 Share Posted August 16, 2015 Sure gm passed for track with same set up and supercharger Yep I had the same set up on my 350 with the supercharger to boot. I did pass the static noise test at Castle Combe and was able to go on track. After I came off the track though I got pulled in for another noise test as I had failed a drive by noise test. Passed the static test again at 4.5K rpm but when I revved it above 5K rpm it was too loud so I was told I wouldn't be allowed on the track again as it was just too loud on the drive by noise test when I went above 5K rpm. Oh and my car with the Invidia Gemini exhaust system & Berks De-Cats registered 92Db @4.5K rpm from 0.5metre which passed the sound regulations but when I came in after being on track I was told I had registered 101Db as I drove by the pit lane so was told it was too loud. They re-checked it and when I revved above 5K rpm it was close on 105/7Db from 0.5metre away. Luckily I only wanted to go on the once. Link: http://www.350z-uk.com/topic/97440-performance-car-action-day-at-castle-combe-video-pics-250415/ Bit of a bummer as it sounded so good on full chat. Berks HFC's are a good option as I had those before with my Invidia, ...definitely quiter. Quote Link to comment Share on other sites More sharing options...
Ekona Posted August 16, 2015 Share Posted August 16, 2015 Track cars should be as quiet as possible, IMHO. No point in creating problems for us all, we're hated by NIMBYs as it is Easiest thing to do is to swap the stock backbox on before track. Easy enough to do yourself at home, or a £20 favour to your mate down the garage. Quote Link to comment Share on other sites More sharing options...
nissanman312 Posted August 16, 2015 Share Posted August 16, 2015 Track cars should be as quiet as possible, IMHO. No point in creating problems for us all, we're hated by NIMBYs as it is Easiest thing to do is to swap the stock backbox on before track. Easy enough to do yourself at home, or a £20 favour to your mate down the garage. that would mess the tune up if supercharged tho surly Quote Link to comment Share on other sites More sharing options...
Richf Posted August 16, 2015 Author Share Posted August 16, 2015 Stock backbboxbox isnt interchangeable with the invidia system , a full exhaust change before going on track wouldnt be one of my favourite ideas Quote Link to comment Share on other sites More sharing options...
GMballistic Posted August 16, 2015 Share Posted August 16, 2015 Stock backbboxbox isnt interchangeable with the invidia system , a full exhaust change before going on track wouldnt be one of my favourite ideas Some tracks will lend you or hire you exhaust bungs to bring the noise level down. I actually witnessed a Skyline owner having to fit them at Castle Combe, ...they looked bonkers on his exhaust as they actually stuck out a fair bit but must have worked as he was on track later. Personally if you think you're going to be doing enough track days that this will be a nuisance to you then I'd go for the Berks HFC's. You'll still get a lovely sound from your exhaust and the noise level will be much lower in comparison to the De-cats. Quote Link to comment Share on other sites More sharing options...
Richie94gts Posted August 16, 2015 Share Posted August 16, 2015 You could try baffles, I actually preferred the sound on my old mr2 turbo. I guess there'd be a Performance impact but not sure how significant that would be? Quote Link to comment Share on other sites More sharing options...
Ekona Posted August 16, 2015 Share Posted August 16, 2015 that would mess the tune up if supercharged tho surly Unlikely by enough to do any damage, unless the tune is borderline anyway (which it shouldn't be). If in any doubt, map with the stock backbox on. I was replying to the OP though, not GM. 1 Quote Link to comment Share on other sites More sharing options...
ukstang Posted August 25, 2015 Share Posted August 25, 2015 Why don't you do a drive by and static test before you make any changes, or buy a meter. Remember that you can get rear inserts to reduce the DB. Hi There Where would you go about purchasing rear inserts, tried searching but found nothing. Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted August 25, 2015 Share Posted August 25, 2015 Why don't you do a drive by and static test before you make any changes, or buy a meter. Remember that you can get rear inserts to reduce the DB. Hi There Where would you go about purchasing rear inserts, tried searching but found nothing. What exhaust and tail pipe design are you running? Quote Link to comment Share on other sites More sharing options...
ukstang Posted August 25, 2015 Share Posted August 25, 2015 Why don't you do a drive by and static test before you make any changes, or buy a meter. Remember that you can get rear inserts to reduce the DB. Hi There Where would you go about purchasing rear inserts, tried searching but found nothing. What exhaust and tail pipe design are you running? Stock for now, trying to weigh up my option if I get something louder. Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted August 25, 2015 Share Posted August 25, 2015 Why don't you do a drive by and static test before you make any changes, or buy a meter. Remember that you can get rear inserts to reduce the DB. Hi There Where would you go about purchasing rear inserts, tried searching but found nothing. What exhaust and tail pipe design are you running? Stock for now, trying to weigh up my option if I get something louder. Bungs come in different shapes and sizes, so no point searching or buying until you have your new exhaust. Quote Link to comment Share on other sites More sharing options...
ZonixX Posted August 25, 2015 Share Posted August 25, 2015 Richf, are you sure, that the exhaust, especially the decats part does ABSOLUTELY perfectly seal? Even a tiniest blow-by throught the gasket will cause a significant amount of noise. 1 Quote Link to comment Share on other sites More sharing options...
Richf Posted October 12, 2015 Author Share Posted October 12, 2015 Just to update Yes everything was well/is well sealed I'm learning to live with it , the extra 35hp gained by fitting them has helped Quote Link to comment Share on other sites More sharing options...
flyboy Posted October 12, 2015 Share Posted October 12, 2015 35Hp From decats? Quote Link to comment Share on other sites More sharing options...
Jonnymonno Posted October 12, 2015 Share Posted October 12, 2015 I've got the Invidia with de cats on my supercharged Zed and its only loud for a while on start up and flat out but superb sound Quote Link to comment Share on other sites More sharing options...
Richf Posted October 13, 2015 Author Share Posted October 13, 2015 35Hp From decats? yes just by fitting the decats it made 19hp but went quite lean, after the map was tweaked by Jez at h-dev it made 35hp , 1 Quote Link to comment Share on other sites More sharing options...
flyboy Posted October 13, 2015 Share Posted October 13, 2015 I have an invidia and hfc's on my 370 and its only loud on cold start. The Takeda long tube CAI makes a great sucky noise too. Quote Link to comment Share on other sites More sharing options...
Kharmon Posted October 22, 2015 Share Posted October 22, 2015 Motordyne art pipes .... Best of both , all the benefits from decats and quieter than hfc . Speak to Torqen . Id say this ^^^^^^ is your best bet for performance whilst keeping the sound down . Im running invidia cbe with berk hfc and its still pretty loud but i love it haha Quote Link to comment Share on other sites More sharing options...
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