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One of the creative solutions that was offered, had two crank sensors. Two
ECU's. I think he said it was Tec system or something like that. One ECU and
crank sensor is used for normal operation, but it activates a relay if it ever
loses crank sensor. That relay powers second ECU and second crank sensor. The
guy tested it by unplugging sensor and it works. I was impressed. As I told him,
way better than my system.
As I mentioned, this is relatively low frequency failure. But the EFFECT
when it fails is pretty severe (loss of power). The frequency is so low, that
it's unlikely you would experience it in your 600 hours. On top of that, you
have stock wiring, so much lower risk. I know of three out of four where wiring
was the direct cause.
The crank angle sensor is a single point of failure. There is only one,
so it's not redundant even if you have two controllers. However from my
experience driving RX-7s (70 miles round trip to work for the last 10 years)
I've never seen one fail. Haven't seen an ECU fail either. Occassionally one
of my cars wouldn't start, I would unplug and then reseat the crank angle
sensor connector and it would then start. I've only seen this phenomenon on
one car. Probably just needed some contact cleaner.
Generally I think
any problem with the crank angle sensor would mean the engine wouldn't run at
all.
Might be good to have one controller running on the stock crank
angle sensor and a second running from an independent sensor on the e-shaft
front pulley.
You can't have redundancy everywhere. I have one cranks
sensor and one ecu and my engine has never quit running in 600 hours. If you
really want redundancy build a plane like a twin-engine Defiant, that can
truly fly on one engine.
Perry
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I understand that it's totally natural to feel defensive in this
situation. I know you may find this hard to believe, but the goal of the post
is to help others reduce risk. It's not a personal attack. There's no rotary
reference in it anywhere. As far as the readers know it's a piston
engine. But I hope there's at least one person on this list that
sees value of looking at the other causes.
The essence of the post is accurate. Doesn't matter if you are near home
base or not. Ignition failure is very high risk item. An ECU that was better
at self diagnoses would have greatly reduced your risk. On your car, it would
be recognized immediately. Ecu would say "Hey, my cam sensor just went thru
it's normal 50 pulses per revolution with the normal 5 and 8 ms. gaps. But I
didn't get the normal 20 pulses and signal gaps from the crank sensor.
Turn on warning lamp and crank code. Use cam sensor for timing info." You
don't see value in discussing stuff like this? If you guys just used toothed
wheel with pulse gaps, then the ECU could easily self diagnose.
You know what was cool on the other list? Guys came back with
"confessions" of how this parallels a problem they encountered. 2 guys
said, "yeah, I had partial failure, thought it was x, took off only to find it
was y". Then other guys described changes they made to system that totally
eliminated the risk. Some really creative stuff. Then we discussed just how
risky crank sensor really is...we see one ever 1 1/2 to 2 years. Etc. Etc.
Very positive experience that may save someone's life. That's the goal.
Hi Tim,
Isn't it
wonderful how stories get twisted around as they fly from list to list.
Obviously this particular twisted story relates to my recent experience, so
let's dilute the fun a little by adding some truth.
-al wick
Artificial intelligence in
cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on
engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk
assessment, Glass panel design
info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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