Crosswind Posted June 3, 2014 Share Posted June 3, 2014 I'm shortly going to start putting together a 'Wot 4 Extreme'. I'm going to use a DA50R with a Ripmax GT50/DA50 exhaust. The club I fly at has a 82db noise limit. I'm aware that a large contribution to noise from petrol engines is from air being drawn into the carburettor, and a way of reducing this is to draw air from inside the fuselage. As the DA50R has a rear mounted carburettor I'd like to try this. My question is how do I go about this? Do I need to make a tube which loosely covers the carburettor mouth and then goes into the fuselage. Or does it need to be more complex? Does the carburettor effectively need to be sealed in the tube with just the end in the fuselage open, allowing air to be drawn in. if anybody has any advice I'd be grateful, particularly if you've got some photos of a similar installation in a model! Crosswind Edited By Crosswind on 03/06/2014 17:26:37 Quote Link to comment Share on other sites More sharing options...
cymaz Posted June 3, 2014 Share Posted June 3, 2014 If I remember right the DA50r has a rear mounted carb. So the cowl should cover most of the noise. You might need to try a after market muffler other than the Ripmax if you have no joy with that one. Or you could cut the Ripmax one open and add more baffles- that might be the cheaper option. Here ?? Edited By cymaz on 03/06/2014 18:46:22 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 3, 2014 Share Posted June 3, 2014 Yes I think its prop selection and one of the quieter canisters to look at John Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 3, 2014 Share Posted June 3, 2014 I would suggest that the carburettor inlet noise is not a significant contributor to to the total. The exhaust and prop are by far the largest source. Probably more significant is to ensure cool fresh air is drawn into the carb rather than air that has been heated by the engine, unless of course you are flying on a cold damp day in which carb icing, particularly at part throttle, can be an issue! Quote Link to comment Share on other sites More sharing options...
Attilio Rausse Posted June 3, 2014 Share Posted June 3, 2014 Be sure to protect the inlet with something like a nylon stocking, we don't want foreign objects drawn into the engine, you can get a trumpet which fits onto the inlet and fit the stocking over the trumpet. Til Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 4, 2014 Share Posted June 4, 2014 Hi Crosswind . Yes the inlet make up a lot of the noise from a petrol engine . The rear induction are easier to quieten the the port induction type . If you intend to fit a cowling or part cowling then the following may be of interest . While fitting a DA 50 to my mustang I was worried that the stand off mounts were too short an that the close proximity of the fire wall would affect carburation . I overcame this by cutting a large hole in the firewall using a Hole cutter saw in a drill . I then used the plug removed as a former to roll some 1/64 ply strips approx 2in wide around its edge a couple of times . Using some thick cyano to laminate the ply . This formed a sort of drum that was then glued into the hole. This effectively set the firewall back into the fus where the cab would have been . This removes any chance of forien objects being sucked from the fus or fuel spilling into the fus . It also made the induction very quiet once the cowling is fitted without moving the engine too far forward . Sorry if the pic is not clear but its the best one I could find from the build. I also made an in cowl silencer pics in link. It hasn't flown yet ( well overdue ) but tests on the ground are very quiet compared to usual large petrol powered models Edited By Engine Doctor on 04/06/2014 11:48:04 Edited By Engine Doctor on 04/06/2014 11:49:30 Quote Link to comment Share on other sites More sharing options...
Ultymate Posted June 4, 2014 Share Posted June 4, 2014 You can buy purpose made air cleaners that will considerably reduce intake noise, I think IAD sell them but this may entail modifying your firewall. I'm not sure how good that silencer you intend using is in my experience the best silencers come from K&S, MTW or JMB but none of these are cheap. Three bladed props make a significant noise reduction also but again do not come cheap Quote Link to comment Share on other sites More sharing options...
Rich too Posted June 4, 2014 Share Posted June 4, 2014 The carb on my DLE 20 just butts up against the firewall with an appropriate sized hole cut to allow air into the intake directly from the fuse - I did this after researching on the net - you can't hear the intake, just the exhaust, and runs great. Rich ps no air filter Edited By Rich2 on 04/06/2014 13:51:10 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.