rwalbourn Posted March 12, 2001 Share Posted March 12, 2001 i need to get 1.6SS down to 98db. currently 102 db with a 4:1 with a 5" silencer. anyone have readings for a 6" or 7" box? Link to comment Share on other sites More sharing options...
Rob Walker Posted March 12, 2001 Share Posted March 12, 2001 I am currently running a 6 " box on my 1.6ss it measured 94dba at 4500rpm at castle combe. Link to comment Share on other sites More sharing options...
rwalbourn Posted March 12, 2001 Author Share Posted March 12, 2001 Rob thanks for that. are u running a standard caterham exhaust? Richard Link to comment Share on other sites More sharing options...
Rob Walker Posted March 13, 2001 Share Posted March 13, 2001 Yes I am running the Caterham 4:1 competition primaries and the Caterham six inch box which is also the vauxhall race box. I must state that it was only necessary for me to replace my 5 inch box when I converted my 1.6 to VHPD spec last year. Now my car is back to 1.6ss spec the 6inch box has reduced noise down to 94dba @ 4500 rpm and gives a nice deep note . 102dba sounds very high for a 1.6ss even with a five inch box, either the packing is burnt away or the measuring equipment may need calibration. I would expect around 97dba @ 4500, bear in mind that 3dba is the half power point as the scale is exponential so at 97dba is twice as noisy as 94dba. Edited by - Rob walker on 13 Mar 2001 19:26:28 Link to comment Share on other sites More sharing options...
rwalbourn Posted March 13, 2001 Author Share Posted March 13, 2001 Rob test was at goodwood. it is of course possible packing is shot. exhaust is 4 years old but has only done 4000 miles. they did however test at 5200rpm, apparently 3/4 rpm is what is required now. u reckon 6" box will be ok. why did u bin VHPD spec? Richard Link to comment Share on other sites More sharing options...
Delberts Wallet Posted March 13, 2001 Share Posted March 13, 2001 Re-packing of exhaustquestion.gifblush.gif Wahoo...The nights are drawing out and the clocks change in a couple of weeks cool.gif Link to comment Share on other sites More sharing options...
EFA Posted March 13, 2001 Share Posted March 13, 2001 Yes, Any of the Caterham silencers will be shagged after 4000 miles. When running CCC we cust open a couple of low mileage examples and were astonished at how quickly the packing had burn't away. BTW The vauxhall race and JPE only use a 5" silencer. If you have a 6 incher its not (unless very recent) a Caterham item. They do however make a 7" silencer for the SLR A good quality repackable is the best way forward. When repacking, wrap the baffle in stainles stell wool wired on with stainless welding wire first. This makes the rest of the packing far more durable. Arnie Webb The Fat Bloke blush.gif in a Slow Old Vauxhall wink.gif Link to comment Share on other sites More sharing options...
Delberts Wallet Posted March 13, 2001 Share Posted March 13, 2001 Hmmm....my cars done 20,000 and reg in Mar 99. What do you reckon. Its a 5" standard 4-1 with 5 inch silencer. Wahoo...The nights are drawing out and the clocks change in a couple of weeks cool.gif Link to comment Share on other sites More sharing options...
rwalbourn Posted March 14, 2001 Author Share Posted March 14, 2001 arnie: thanx 4 that, am now talking to techcraft. u reckon well packed 6" will get below 98db. i was surprised that even if packing blown the reading was 102db. seemed v high 2 me. i dont drive it hard, honest!! Link to comment Share on other sites More sharing options...
Andrew Russell Posted March 14, 2001 Share Posted March 14, 2001 FWIW I spoke with Caterham yesterday about a new silencer box to replace my burnt out 5" box. I was told that there is a 6" silencer now available to fit the Vauxhall 21/4" side exit race 4 into 1 manifold. I also had a very interesting chat with Chris Wheeler at the 7 Workshop about Techcraft units which are not cheap but available in a variety of diameters. Andrew Link to comment Share on other sites More sharing options...
rwalbourn Posted March 14, 2001 Author Share Posted March 14, 2001 Andrew i run a k series, but have chated to techcraft and caterham too. general view seems to be that a caterham unit will only last 5 mins, whereas clearly the techcraft is repackable. But yes they r expensive. Link to comment Share on other sites More sharing options...
Rob Walker Posted March 14, 2001 Share Posted March 14, 2001 I think you would be Ok with the six inch box. The seven wont fit and gives too little ground clearance unless you are running a very stiff suspension est up. Why not have a go at making your 5 inch repackable? If the end plates were to be cut like opening up a tin of beans but leaving 10 mm of end plate, the outer sleeve can be slide off. Repack the silencer, slide back the outer sleeve and secure by making two round plates to cover the cut which could be fixed with self tappers or pop rivets. In fact if you know a sheet metal worker he could roll you up a 6 inch sleeve which could be attached in the same way. By the way I didn`t bin the VHPD set up but sold it to a friend pay for my latest monster a 230bhp 1.8k. Link to comment Share on other sites More sharing options...
StewartG Posted March 14, 2001 Share Posted March 14, 2001 Techcraft are good but you'll need to customise a pipe from the primaries into the silencer and make up a bracket to secure the back end. Link to comment Share on other sites More sharing options...
rwalbourn Posted March 14, 2001 Author Share Posted March 14, 2001 Rob: Thanx 4 advice...................u have never seen any of my DIY!!! and i dont know any sheet metal people. Stewart: they will do it 4 u, of course at a price. do u think the repackable is worth it. Link to comment Share on other sites More sharing options...
Andrew Russell Posted March 14, 2001 Share Posted March 14, 2001 Chris Wheeler will fabricate all the necessary pieces to suit the Techcraft box, including a larger bore pipe out of the collector to slow down gas flow and hopefully improve longevity of packing. Andrew Link to comment Share on other sites More sharing options...
Tony Martyr Posted March 14, 2001 Share Posted March 14, 2001 Just fitted a caterham 4:1 exhaust c/w 6 inch exhaust to a 1600k ss with QED/dta TB upgrade. 94/95 dbA taken at 5000 rpm about 1 metre at right angles to the car opposite the tail pipe. This is about the same as the previous standard Cat exhaust it replaced but that unit had done 12000 miles including 10 track days when measured. Subjectively it is quieter as the note seems to have gone deeper. The new TBs have increased the intake noise a lot. I don't have before or after figures but I may just line the underside of the bonnet to take some of the harshness off. Any expereince of this mod? Link to comment Share on other sites More sharing options...
Steve W Posted March 14, 2001 Share Posted March 14, 2001 I have a 7'' Techcraft on my Zetec. Fitted by Chris he can source all the pipes needed. The 6' should fit straight on. I had a new pipe made to fit to the collector for the 7'' to move it out from the bodywork (also to go out to 2 1'2 from 2 1/4). Not cheap or light but a nice bit of kit well made. Link to comment Share on other sites More sharing options...
Gary Furst Posted March 14, 2001 Share Posted March 14, 2001 The test should be to measure at 0.5m and 45Degrees to the tailpipe outlet (in the same plane) at 3/4 maximum revs. A preferred technique for getting through scrutineering used by all/most of the racers is to lie about your maximum revs, as the scrutineers cannot know the details of every car they see. This will obviously only help if your noise level is marginal and you aren't too blatently fibbing! Link to comment Share on other sites More sharing options...
rwalbourn Posted March 15, 2001 Author Share Posted March 15, 2001 Tony: No have not changed TB's but would be interested to know what difference it has made. Gary: Thanx for that will fibb a little. Lets hope no scurtinners hack into this forum! What difference would it make between 0.5 and 1.0 m. Not much I would have thought. Link to comment Share on other sites More sharing options...
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