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sqpilot@earthlink wrote:
----- Original Message -----
From: "Mike Robert" <pmrobert@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, June 04, 2004 6:38 AM
Subject: [FlyRotary] Re: Turbo boost limits in the EC2
John Slade wrote:
Cutting fuel till the MAP comes down is the only workable solution I can
see.
Yes, I tend to agree. Tracy - are you listening? Does this make sense to
you?
Anyone else care to comment? I'd really like to get something built into
the
EC2....soon.
Regards,
John
Again, - I'm speaking auto use - you have to be very careful using fuel
cut in a boosted rotary, all it takes is a couple of hard knocks
instigated by a transient lean condition to break apex seals. There's
plenty of fuel coating the inside of the manifold, etc., to do this even
if you shut the injectors completely off. It's a very short phenemenon
but it is there. Another thing - hard fuel cuts are scary in a car, I
would imagine the soiled underwear factor is quite a bit higher while
flying when you hit cut. I use hard fuel cut as a rev limiter in my NA
and it STILL gets my attention. That said, I believe Tracy's ECU manages
spark as well as fuel. Random spark cut and/or massive retard may be the
way to cut your boost in those temporary situations.
-Mike
Hi, Mike....my concern is that if you cut spark, and still have fuel going
into the engine, you may end up with a flooded engine, or worse yet, a
terrific backfire due to the excessive fuel build-up then reintroducing
spark. I used to take my 1960 Ford, coast down a large hill with the
ignition off (standard transmission in gear), then turn the key back on, and
scare everyone with the loud backfire. Did that until I blew my muffler
right down the seam one day. Got too expensive for a 16 year-old (expensive
firecrackers). Just another consideration. Paul Conner, MicroTech ECU with
fuel cut boost limiter.
Good point, Paul. I do know that some aftermarket ECUs do the random spark cut thing as a soft rev limit. I have no experience myself with that scheme other than getting grounded for a month after doing the key off/coast/key on/kablam thing with my father's 1972(?) Torino, blowing most of the exhaust system apart. :-) I'm wondering if a closed exhaust (cat, restrictive muffler, etc) is necessary for the exhaust backfire scenario? The hard fuel cut may be the least worst method of emergent excess boost management now that I think about it some more. I would think that the lean transients could be minimized if not eliminated by injector placement. In the irons, as stock, is a great place to address the lean transient thing. I have a 20" intake tract on my car with the injectors at the TB - there's enough wall wetting in that system to run the engine for a good 2-3 seconds after I kill the FI electronics. The stock / near port placement of injectors would not/ does not do this AFAIK.
-Mike
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