912ULS Exhaust Spring Tension

Hi Karl,

I do ALOT of Flight Designs from all over the US. FD didn't do a great job in tensioning the springs. They had little to no tension. Usually a millimeter or a fingernail thickness gap between coils works fine. That said there are different springs on different planes. They need to have some tension and not be just sitting there doing nothing. You can bend the loops where springs connect on the exhaust pipe to to help widen your spring gap. It's easy and just takes a minute or so to do. Also make sure your springs are safety wired so they can't fall off on a runway, taxiway or over some homes. Don't forget to apply high temp silicone on them to help reduce vibration wear. Do not fill the inside of the spring with the silicone like Vans does. Do not take the safety wire and wrap (circle around the exhaust pipe) it around the middle of the springs and the exhaust pipe. Don't over tension the safety wire. It isn't there to hold the muffler and exhaust pipe together under tension. It's there for the springs.

Thanks Roger!

This is a UK model but it sounds like FD did just as poor a job over here too.

I was curious if I could bend the loops, whats the best way to do this, squeeze with pliers?

Lock wire and RTV already in place exactly as described.

Vise grips or some strong pliers can bend them upward some so you can set the spring tension where you want it. If that doesn't work for you then a metal rod that can go up into the loop so you can lift upwards and just tweak it upward a bit.

Upwards? Are you suggesting I bend the bottom loop attached to the silencer rather than the top loop attached to the downpipe?

Sorry for the misunderstanding. You could bend the top loop upward which is usually the easiest or bend the bottom loop downward, but the bottom loop at times doesn't have much room to work. You're just trying to widen the gap between the two loops just a tad. It doesn't take much. I usually bend the top loop up just a tad. It has worked just fine for 24 years.