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Steve, I was looking at the wrong image (the one you sent of the CAS & dwell at cranking speed of ~150 rpm.) . I must have missed this other one when you posted it. I'll take a look at the 1200 rpm dwell behavior again. I never noticed that. Possibly because 1200 is well above cranking speed but below my idle speed of 1600 rpm.
Do you recall the date of your last EC2 update? The low rpm dwell algorithm has changed a few times.
Tracy
On Thu, Nov 26, 2009 at 8:04 PM, Steven W. Boese <SBoese@uwyo.edu> wrote:
First let me echo the wish expressed by Tracy and others that a Happy Thanksgiving be enjoyed by all.
It is a privilege to participate in this list where the messages are always positive in nature.
I am obviously not presenting the data from my EC2's concerning the coil control signals in such a way as to clearly show my concerns. In the labeled image referred to previously, a dwell time of <0.3 ms is shown below the "ignition threshold" (on the left) and above this threshold, a dwell time of 4.3 ms is shown on the right. In the unlabled image, a dwell time of 106 ms is shown below the threshold (on the left) and a dwell time of 4-5 ms is shown on the right. I don't see a dwell signal in the 16 ms neighborhood.
I agree that dwell times longer than longer than 16 ms would have no benefit. This is because the coil modules limit the dwell time to about 8 ms internally and generate a good spark at that time regardless of a coil control signal that is still high. It makes sense for the coil module to do this to limit the internally generated heat.
An image is attached which shows the coil control signals obtained using the EC2's ignition diagnostic function at the top. Shown at the bottom are the CAS signal and #1 rotor leading coil control signal obtained at about 1200 RPM using a mode 8 setting of 8 degrees advanced. The time scales of the top and bottom plots are as close as I could make them. Hopefully, this attachment shows what I am referring to as "short" dwell times which result in very weak sparks.
Finally let me stress that once the engine is started and running, my EC2's have never failed to get me home.
Sent: Thursday, November 26, 2009 2:09 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Ground isn't ground
Good info Steve, guess I didn't remember the coils you were using correctly.
In any case,
Best I could measure on your photo, the EC2 was delivering about 16 ms of dwell which is way more than enough to fully saturate the coils. I would conclude from this that there is nothing to be gained from increasing dwell at cranking speed. For reference, the dwell during coil test is around 5 ms.
Tracy (Happy Thanksgiving Day to all)
On Thu, Nov 26, 2009 at 11:58 AM, Steven W. Boese < SBoese@uwyo.edu<mailto: SBoese@uwyo.edu>> wrote:
If you refer to archive message# 49009 on Nov 8, traces of coil control and CAS signals are there. I have 2 EC2's driving LS1 coils and all 4 controllers show the same behavior. This affects spark intensity and timing only below about 1200 RPM and is only a factor on start up or very low idle. Above the transition at about 1200 PM, dwell time are consistently in the range of 4 to 5 ms regardless of the mode 8 setting or RPM.
Steve Boese
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