flyrotary@lancaironline.net Mailing List Archive

Hi Bill,

Well, when you have two conditions that must be met (rpm and Manifold pressure), it pretty easy to control rpm – but manifold pressure starts out at ambient (29.92”HG) during initial start attempt, then once it fires and the engine spins faster, it drops the manifold pressure down to be low 13 “Hg (Hopefully). Then and only then is the lower bin pointer based on RPM, at least that is the way I read it. Now, that raises the question that if you do not have manifold pressure below 13” Hg what decides which bin gets pointed to. Apparently not RPM as both conditions have not been met, that would leave me to believe that the point will based solely on manifold pressure. So the EM2 may show the operating point on the MCT as different from what you would expect based on RPM.

I think Joe and I saw that when we worked to fire up his 20G 3 rotor a few days ago.

Yes, my personal experience with 8 years on the EC2 is that you normally idle on the primary injectors only. You can test this by being at idle and turn off the secondary injectors – nothing happens. Turn the secondary injectors back on and turn off the primary injectors and the engine continues to run just fine. But, that could be caused by the cold start doing its thing and I think that is what Bob is stating. That both primary and secondary injectors are firing below staging – he may be correct, but that is not my understanding.

Bob and Steve do make a good point, however, its not required that you necessarily understand what is going on inside the “black box” only that you know how to control its out put. My personal opinion is that if you wire your EC2 according to Tracy’s instructions, you will have no problem and cold start and injector switches will work as advertised by Tracy.

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Bradburry
Sent: Monday, July 06, 2009 2:40 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Potential Low range MCT (MAP) Problem on EC3/Ec2

Ed,

That was mentioned before by someone (Tracy?). They said that is why the addresses above and below 31 that have the same manifold pressure should be the same or very close. The EC-2 could begin to “hunt” moving back and forth between the upper and lower addresses and if they were not close to the same, there would be a problem.

Also, reading both Steven and Bob on the injector disable… I don’t think either of them is correct. I think Tracy said or implied that if you shut down the primaries, the EC-2 would turn on the secondaries, period. Not to do this would mean that you would be a fool to try it if you were staging because the engine would shut down. You also do not have to turn on the cold start switch because that is done automatically when you flip the disable switch. If you are staging, the cold start switch should have no effect because you are just looking for 2 injectors. If you have different size injectors, you would have to mess with the mixture. Above staging, the cold start would be effective, but you would still have to mess with the mixture if you have different size injectors.

I sounds like Steven is actually doing this with his engine and reporting what happens. If that is true, then theory be dammed, we are staring at facts unless he used a different wiring scheme.

When will Tracy be back to tell us what really should happen. You cant make proper decisions about operating the engine if you don’t know what it is supposed to do under certain circumstances.

Bill B

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Monday, July 06, 2009 10:25 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Potential Low range MCT (MAP) Problem on EC3/Ec2

I happened to be reading the EC3 operating manual – doesn’t everyone do this for pleasure reading{:>)? When I came across something that may explain something that Joe and I observed (and may have played a role in the hard to start problem we initially encountered (after the CAS wiring problem was fixed)

Joe has the later version of the EC2 where the lower rpm operating of the fuel MAP (or more correctly the MCT - Map Correction Table), where the common assumption/understanding is that the operating point below 2300 rpm is based solely on rpm. Turn’s out that assumption is not quite correct per this extract from the EC3 manual.

EC3 Mixture Correction Table addressing is illustrated on the following page. Note that below 2300 rpm and 13” manifold pressure (absolute), the MCT address is a function of rpm as opposed to manifold pressure. If you have an EM2 engine monitor to display the data, you can use a copy of this chart to record your table data after the engine is tuned

Not that there are two conditions that must be met before the EC3/EC2 uses only rpm to determine the lower operating point. The engine rpm must be below 2300 AND the manifold pressure must be below 13” Hg. So that implies that if you are operating at 2000 rpm, but your manifold pressure is at 13.5 or 14 or higher then the EC2 is using the manifold pressure to determine the operating point and not the rpm.

So lets say you are trying to start your engine – rpm < 2300 but manifold pressure > 13. Therefore the MCT pointer may be pointing to the bin corresponding to a manifold pressure that is close to ambient (29.92” Hg). That is also the point for WOT throttle (Lots of fuel). So its safe to say that on the first turn of the prop that is where your Ec3/2 is at. The instance the engine fires, the manifold pressure immediately begins to drop – how fast it drops will depend in part on what throttle setting you have. If you throttle is closed, the manifold pressure will almost immediately drop to low values (presumably below 13” hg) and all is well. If however, your throttle is set at ¼ or more open, then the manifold pressure is not as likely to drop below 13” hg. If this is the case, then the operating point is going to be based on manifold pressure which may be considerably above 13” Hg. That point in turn may be overly rich for idle conditions and your engine fails to sustain operation do to excess fuel and floods.

Tracy, of course, may have algorithms to deal with this, but based solely on the comments in the manual – looks like this could happen. Particularly in the early stages, before you get the MCT tuned.

Thought I would pass this on – my older EC2 only uses manifold pressure across the entire range.