N62588 Phase 1 Flight Testing

[Nev]

My firewall was drumming early on. I added several beads of RTV to adhere it to the airframe. This made an audible difference. Also the lightweight carpets reduced the drumming on the aluminum floor panels.

[TJ_Slice]

I used this product on the face of wall studs when I was building a theater room 15 or 20 years ago. I wonder about marking the tubing locations on the floorboards, and then sticking the tape on the floorboards: https://www.greengluecompany.com/noi...cts/joist-tape

I also plan on doing carpet.

[rodsmith]

I placed 1/16th rubberized cork strips over the tubing before installing the aluminum floor. Can't say how much it helped. I used 5/8th open cell foam on the backside of the firewall and on top of the exhaust tunnel, and the grey insulated blanket material on the inside of the boot cowl. That is the extent of my sound proofing and even at full power I can talk on the radio and hear responses ok. My entire front doors are covered with .100 lexan and skylight is .125 lexan.

[svyolo]

The tunnel and Firewall are definitely going to get something.

[Bissetg]

Hi Brooks, I too had horrendous ambient noise levels. I was running straight exhaust pipes, no muffling. After trying all sorts of things and worrying about not hearing traffic calls I bit the bullet and got MotorSport Solutions to custom build me a 4 into 1 tuned exhaust.

Thats what made the real difference, I could dial back the volume on the radio 25% and still hear it better than before.

Soundproofing and going to Bose ANC headsets all helped but the big win for me was the exhaust.

Good luck, noise is annoying, fatiguing and a safety issue.

[Bcone1381]

Acoustic Noise:

The source of noise on my ears ended up being mitigated by Bose A20 headset without earplugs. I did not immediately identify that the noise overpowered the intercom using the David Clark One-X. The easy way to test this is to unplug the mic and experience quiet. I suppose one might blame my intercom manufacturer for not having a mic gain adjustment.

The Bose A20 with no ear plugs and max engine power is satisfactory. It seemed negatively effected with headset+ear plugs which I don't understand.

Additionally, I tested the noise source by controlling the drumming with a felt covered board then acoustic foam. I pushed it against each window, the floor, the sidewalls, and firewall to stop the drumming while I monitored the noise on an iphone acoustic sound app that measured Hz, and dB. There was no change heard or recorded.

Hot Fuel:

My engine has an issue running smooth when returning home from a flight and it's not cold outside. I experienced it in the traffic pattern and idling on the ground at 60F (15C). It's been diagnosed as hot fuel in the fuel lines (Bendix Fuel Injection system.) The fix is to get better airflow to the fuel pump cooling shroud and change the fuel injection plumbing so fuel lines are shorter. My tight baffling resulting in little extra airflow in the lower cowl may be a contributor also. We need more data after we fix those two items. Vetterman Crossover exhaust also has a lot of hot tubing plumbed in the area. We'll see. This is experimental aviation!

[Nev]

Brooks, regarding the hot fuel, when you notice it in the traffic pattern, is it with the engine at idle or under power ? Mine runs rough at idle on the ground when hot, but runs smooth when I increase to take-off power. In other words I've never noticed an issue inflight. Just a data point for you.

[Bcone1381]

I notice it shortly after I bring the power back to 1800 RPM when the OAT is not cold. I reduce power abeam the runway threshold on downwind. It seems the fuel flow decreases, so the speed the fuel travels through the system slows down and gives it time to cook. My firm data points are a heat soaked fuel pump that was hot to touch, and the Fuel Flow transducer mounted to the firewall that was hot as well. Those are Heak Sinks. One fix moves the transducer into cool air.

I would guess your issue of rough idle on the ground when hot is the same as mine, but not to the degree.