kenair

My Feedback: (10)

At local warbird group of flyers, we have had four Jtec P-51 DLE 55 muffler failures, three were on Top Flite P-51's and one was on a Top Flite P-40. My muffler broke on my TF P-51 DLE 55 after about 20 or so flights, the muffler was a couple of years old but not much service on it, I think the J etc muffler one the P-40 broke after about 12 flights.

I sent my Jtec muffler in to Jtec on August 22 for their review as the number of local failures and those reported on the web seemed high for a $129.99 muffler. I heard nothing back, so today I send an email inquiry. Jtec says the muffler bolts were over tightened and the muffler mishandled.

I've been flying big birds since 1995, and have never seen a rash of muffler failures like these Jtec P-51 mufflers, I wondered if they are getting made offshore, they do not hold up to every weekend flying.

Interesting enough, on the last four flights the DLE 55 would start to die and I would abort the flight and get down immediately, I thought the DLE 55 was too lean even though my spark plug was dark brown, seems like the muffler was leaking hot exhaust gas into the engine compartment and causing the problem.

cheers - ken

Lifer

My Feedback: (1)

Forget about any after the sale service from JTec. I had an issue with them for selling me something listed on their website as "In Stock" and then had to wait for nearly a month for them to build it. I put a stop-pay on my credit card and they raised a fit claiming I committed fraud. They hadn't even shipped the muffler....

Try Slimline or Bisson.

ccostant

My Feedback: (38)

I had the same problem with a two JTEC P-51 mufflers on a DA50 two years ago. I did two things. First I mounted the DA50 standoffs to a 1/4" aluminum plate which was then bolted into the firewall. I did this to eliminate any possible compression of the firewall plywood at the standoffs over time that could lead to excessive engine vibration. Second, and I believe this is the real fix I switched to a slimline muffler with a strap. No more problems. My spinner and propeller were balanced in both cases.

deatonbt

I can't tell in the pictures. Is there a tube that supports the mounting bolt where it goes through the muffler? If there is not a tube, the bolt will crush the muffler over time causing it to distort and loosen; a poor design. If there is a tube, the bolt can't really be over tightened. I have a couple of inexpensive mufflers for gas engines that have a tube supporting the bolt. Either way, the muffler shouldn't fail that quickly at that price.

Brian

ccostant

My Feedback: (38)

The early version of the JTEC muffler did not have a spacer for the mounting bolt. It was added to later version.

radfordc

My Feedback: (14)

A support bracket will help keep failures like this from occurring. http://www.troybuiltmodels.com/ns/learn/pittsbracket/

rossmick

Photo 1-2; DA 60 with additional standoffs installed. Note - DA 60 can not be mounted with individual leg standoffs, must be fully supported as shown (makes it a pain to hook up fuel, throttle and choke).
Photo 3; proposed location of ignition module.
Photo 4; Throttle swivel connection with no standoffs. Also see the standoff profile on the work bench.
Photo 5; Cowl in position with cutout for the engine. Additional cut out will be required when muffler arrives.



Photo 6; 22x12 prop in spinner. Noted that the spinner is not scale, but don't have time to deal with it at this time.
Photo 7-8; show choke extension through cowl. The yellow Ny rod will be painted black. The flexible Ny Rod allows cowl to be mounted. Also the muffler is taped on to see how it works with choke.
Photo 9; Just side view with rudder, canopy, cowl, spinner and prop.




Photo 10-13; Elevator mounted with nylon pinned hinges. Then the outboard and inboard hinges are then pinned with a screw so the elevator can be removed to be recovered. Also the push rod exit ports are enlarged to reduce binding of the push rods. Note the wrinkling that has started since first iron down. Also I used epoxy to glue the stab. but then followed up with Aero Poxy.
Photo 14-15; Rudder is mounted the same as elevator. First photo shows hinges with rudder pulled out to expose them. I had to trim out the area in the elevators and rudder to hold the hinge pin so the controls mount totally tight.


Photos 16-21; Wing with aileron and flap connections. I used threaded rod and swivels on each end. Wing glued and clamped. I installed tubes in wing to hold the servo extensions and did not use the strings, photos of the tubes later.



Photo 22-23; is the initial location of throttle servo, fuel tank, and aileron servos. This could change as the build continues. I did follow the advise to mount the fuel tank close to the CG which I thought was a great idea. As I don't need the air tank I used that area to mount the fuel tank. I had to cut the former out to allow the tank to slide in and there is a heavy piece of foam under the tank. Later I will attach structure and hold down Velcro straps and a stop block at the front of the tank.


Thanks for the information on JTEC. As DA is only 20 miles away I buy the engines direct and know the folks there pretty well. DA highly recommended JTEC so I am quite surprised with the failures as noted. Hopefully, I can come up with some support to keep the muffler from failing.