914 power loss

Hi Anthony,

I think we are starting to experience the same problems with our 914 Cavalon that you have experienced. Did you resolve your issues or are they still ongoing?

Regards     Rob

I had the same problem with my Autogyro Calidus. It has Rotax 912 but with an aftermarket Mitsubishi turbo and a variable pitch prop. Over a few months my takeoff performance was getting worse and worse - to the point were I stopping taking a passenger. Engine was developing max 5700rpm and had full boost pressure but seemed to be gutless. I checked the compression and tappet clearance but nothing obvious found. After not flying for a few weeks I found a large puddle of oil on floor under the engine. The oil was leaking out the air intake filter and the compressor side of the turbo flooded with oil! 

I had the turbo professional serviced, de-greased, seals & bushes changed (even thou no problem was found) and the wastegate operation checked. No issue found with the turbo. After reassemble the takeoff performance was back to normal. To be 100% sure I purchased a digital scale and a wire rope to measure the maximum static thrust. I measured it at 250kg at max power with takeoff pitch. AirMaster say a 914 is expected to produce 240-250kg. (100HP 912 = 215-220kg)

The only thing I can think of was that the oil on the compressor scroll causing the problem. Note a genuine 914 has a 'pressure valve' (ball bearing & spring) on the oil feed line to the turbo to prevent oil flowing into the turbo when the engine is stopped. My aftermarket setup did not have this valve. I've since retrofitted one.

My suggestion would be to check that your compressor is clean. If oil is present check the pressure valve is sealing correctly. Good luck

Rod

Hi Rob

I also have the cavalon , wonderful machine, this power problem though has caused me some grief over the last 12 months that's for sure

as has the raised oil temp that has accompanied the power loss. A LAME did a leak down test 10 months ago and said it was mid range of the rotax specs,but just last week I did a compression test which is sorta similar but not , and I think that is the problem, the numbers came out as

140,138,140 and 85 , so its like running a race wearing one shoe, the bore looked perfect, piston appears ok but the compression rings had

aligned themselves, so I'm assuming that and or lost tension in number 4 is the cause, as for the increased oil temp the mechanic thinks

is a secondary result of the lower compression, being its working harder all the time, and with the resultant reduction in prop pitch all combined

to create three and a half cylinder motor working its guts out to match performance that I was used to.

now this sounds very feasible and im exited to find a probable cause, I will let you know in a weeks time , parts are on order and will be fitted and test run within the week so fingers crossed

in the meantime I would suggest a compression test not just a leak down as they recommend.obviously you can have a low cylinder holding low values and it wouldn't  show anything to be alarmed about , and see what psi you come up with, that's what has happened in my case .I've been chasing my tail because I was told the leak down was in spec 

cheers

Posted on an earlier thread about power loss. Look at the fuel pressure regulator if all else fails, will definitely run lean and very hard to diagnose.