flyrotary@lancaironline.net Mailing List Archive

Brian,

If you still have the smaller injectors as primaries, you may want to also force the system to use the larger secondaries when doing the test Ed suggests. However, when the injectors reach the point when they are open full time, this does not cause a large sudden mixture change or engine rougness. I have installed primary injectors as small as 22 lb on my engine stand and cannot induce roughness up to 30 inches MAP. The mixture will go lean when the fuel requirement exceeds the injector flow rate, but the engine still runs smoothly. Increasing MAP further results in the power gradually dropping off to the point where the engine goes from running smoothly at reduced power to where it just quits. If you have a tachometer driven by the primary injector signal, the tachometer reading will go unstable and eventually go to zero if the injector goes static (on full time).

If you look at the startup sequence page on the website www.rotarycopilot.com you can see the signals that can be recovered from the CAS, injector, and ignition systems. If you can move the connector to the EC2 away from the EC2 box by about 1 inch, you can insert the adapter that I used to capture those signals and no wiring changes would be required. I can send you the adapter and the laptop computer that captures the signals along with instructions on how to record the data. I would not recommend doing this in flight unless the connectors can be secured. So if the roughness cannot be induced on the ground, this may not be of much help.

I also had a situation where the external tachometer malfunctioned when connected to the primary injector signal, but worked properly when the trailing coils were disabled, and worked properly when the trailing coils were enabled and no input signal was connected to the tach at all. I also had problems with a homemade microprocessor based instrument that measures RPM, injector pulse width and fuel flow. Replacing the spark plug wires with Magnecor 10 mm wires cured these problems. The old wires were Bosch high temperature silicone wires which visually appeared to be in good condition. This is just an interesting and frustrating problem that I had and it may have nothing to do with what you are experiencing.

Steve Boese

From: Rotary motors in aircraft [flyrotary@lancaironline.net] On Behalf Of Ed Anderson [eanderson@carolina.rr.com]
Sent: Tuesday, June 21, 2011 6:44 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Check This Try This was : [FlyRotary] This has got to stop

Agree, Brian, something is amiss (no pun intended).

One question I have - is your prop 88(Dia) x 74 (pitch) or more likely 74 (dia) x 88 (pitch)? - conventionally the diameter is mentioned first.

CHECK THIS

One thing you may want to check. While it doesn't have any bearing on your rough running it may on your static rpm. Two folks I know have had Catto props made for the rotary - in both cases the chord of the prop was way too much and over loaded the engine and surpressed rpm and power.

Measure your cord across the broadest point in the blade. The Props which cause folks problems measure around 8" - whereas my 74 x 88 Performance Prop chord measured 5 1/2". Sam Hodges, Rv-7A with Renesis, had worked months trying to get his static rpm above 5000 including making several intakes. When we put my prop on his engine, it immediately got 6000 + static rpm - it was the prop all along. So measure that chord.

The reason for the emphasis on the prop, is that with that set up and a prop the size of mine - you should be turning 6000 rpm static (at least). All of this referenced to sea level air density.

Another aspect, what type of air/fuel ratio indications are you getting while the engine is stumbling? Is 18" Hg near your staging point?

- there is the possibility that something is happening after you stage - for example if your primary injectors were OK, then the engine would run smoothly - until the engine went to all four injectors - then if is there was a problem with one of you secondary injectors you could get rough running.

Then as you suggest, it could be an ignition problem. As you know several folks have had ignition misfiring problems using the Renesis type pulley timing mechanism - particularly at the higher rpm -apparently alignment is very critical - I can not recall if you are using the CAS or the Pulley type.

TRY THIS

It is either your fuel or your ignition - try to eliminate one or the other - using an oscilloscope can help in that type of trouble shooting, but if you don’t have access or experience in using one - well, need I say more. I would try to determine if it is fuel related first - because I think that could be the easiest to work with.

Here is what you can try - if you turn off power to your secondary injectors, then when you go through the staging point only the primary injectors will be firing. Two 450 cc/min or larger primary injectors can easily get an engine up to 6000 rpm (provided you are not over propped). So if you engine runs smoothly all the way up past 5300 rpm on primary injectors alone, then I would strongly suspect something in the secondary circuitry (injectors, intermittent connection, etc). So take the secondary injectors out of play by turning off their power. While I have had no problem staying airborne on two injectors, I don't suggest you try flying with two - just do this test on the ground.

IF running on just the primary you get to 5300 rpm and the engine starts to miss or run rough, then I think we can eliminate the secondary injector circuit as the problem and perhaps concentrate on the ignition.

That's all I can think of to suggest at the moment

Good luck Brian

From: bktrub@aol.com

Sent: Tuesday, June 21, 2011 12:19 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] This has got to stop

I'm going to ground my airplane until I get to the bottom of this. I can tune it on the ground and it will run just fine all the way from idle to full throttle. I get about 5300 rpm at full throttle at 29 in hg. MP. I have 12 hours in the air so far but can't get past this issue. Other than this, the plane is an absolute joy.

When I get off the ground, when I go through around 5400 RPM, I start to get stumbling and engine roughness. At this RPM I am about 18 inches MP. Just below this point, I am making about 50% power and the engine will run smoothly.

I went to another airport and had a lot of roughness on takeoff, but I am used to it and so continued on my way to my home airport. When I got back I found out that someone at the other airport wanted to report me to FSDO because he thought my engine was going to blow up, but he didn't get my tail number.

So, I thought I had it sorted out before I flew today, but it's back to the drawing board. I've tried both leaning and enriching the mixture at all throttle settings, but to no avail. At and above 5400 rpm I start getting all sorts of roughness so I think that it has to be an ignition issue. My injector wiring is separated from my coil wiring, but could I be getting inductance between the different coil wiring?

I have a 93 13 BREW normally aspirated, 2.85 RWS redrive, EM2, EC2, 88x 74 CAtto Prop. This is getting to be really frustrating. It's got to be something simple that I'm overlooking. I don't know anyone with an ocilliscope, and have never used one.

Brian Trubee