Still refining the exact numbers but here is the basic cause.
The diode clamp on the injector drivers (in EC2) serves 3 purposes.
It limits the inductive flyback voltage to protect the driver transistor.
It recovers some of the energy used to open the injector thus reducing the
current consumption of the system. It eliminates arcing at the A/B
injector switching relay that can cause noise problems with the processor
chips.
Unknown to me until recently, it also significantly increases the closing
time of the injector after the driver pulse ends. I thought the delay
would be negligible. The actual delay depends on several factors but may
be as much as 5 ms (!) Ed will know what a big deal this is. The
factors that go into this and how much it is magnified by the diode clamp is
still under investigation.
The good news is that there is a very simple fix. (Note, Do NOT go
out and remove the diode clamps! That isn't the fix!
----- Original Message -----
Sent: Friday, March 09, 2007 7:13
AM
Subject: [FlyRotary] Re: The truth??? /
Injector flow rate mystery solved
I certainly don't know, Rusty. Like I said
the only thing that Tracy and I could conclude was that Mazda was under-rating
their injectors - I wondered whether it might have something to do with
the way an engine is taxed in Japan.
In any case, Tracy is clearly ignoring our pleas
for more information - poor guy is undoubtedly working furiously getting
orders completed before Sun & Fun. But, he really shouldn't tease
like that {:>)
Yes, I understand what you mean about measured
flow rates - I suspect there is something subtle about this matter.
Perhaps the current profile used to open the injectors plays some role in this
as Tracy indicated he was working on a Fix. Perhaps a two stage or
progressive flow rate profile - opens and provides normal flow for typical
automobile usage but, when wide open (like ours are at cruise) perhaps the
flow rate is more. Who knows - Tracy Crook that's who.
Ed
----- Original Message -----
Sent: Friday, March 09, 2007 12:19
AM
Subject: [FlyRotary] Re: The truth??? /
Injector flow rate mystery solved
Tracy and I have been discussing this
injector flow rate anomaly for years -
For some reason, I was certain that the Mazda
injectors flowed more than they were rated for, but after sifting through
some old logs, that's not true for all Mazda injectors. I sent 4
slightly used 550's to RC Engineering, and they tested them at 547,
549, 551, and 551. If that ain't 550, I don't know what is
:-)
I guess I'm baffled now. Does Mazda operate
them at 5 volts or something, rather than 12V? That would slow down
the response time.
Hey the HKS is a good little engine in my
opinion - not as good as a light weight rotary (which we don't have yet -
Richard! get a move on {:>)), but it'll get you flying again.
Thanks for the comments. It can't hurt much to try
it, because I've already got people who want to buy it if it doesn't work
out. Still, it's as much trouble to install as the rotary, so it
really comes down to a weight issue, and perhaps whether I'll ever get my
redrive from Autoflight...
Rusty