Paul,
My situation [flex plate failure] was exacerbated by a lengthy period of tuning
issues. Turns out it needed diodes on each of the fuel injectors. There was
also a problem with the Renesis style CAS, which I later had converted
back to the stock CAS. I'm sure the rough running engine didn't help
the gearbox any.
Mark
The RX8 style trigger wheel with one CAS is difficult to handle in
software over a wide RPM range. It is easier to use two CAS's 180 degrees
out. The RX8 software must discriminate between 3 different wave shapes. It
takes a very fast processor and maybe an EFI specialised computer chip to
do that. Or missing pulse hardware.
Which CAS system did you revert too? The 2nd gen or 3rd gen?
Tell me more about the diodes on the fuel injectors.
FET's usually have them built in.
Paul Lamar
Paul,
I reverted back to the 2nd gen CAS... the one that came with the engine.
My EC-2 was initially set up for the 2nd gen CAS, but I decided to change
to the newer Renesis "crank mount" style. Tracy had to "convert" my EC-2
to work with that system. After over a year of trying to tune it, I
finally had it changed back. It was an improvement, but there were still
tuning problems. It wasn't until after Tracy told me about the 3-rotor
applications needing diodes in the injector circuits (very near the
injectors) was the problem fixed. I don't think the diodes are needed on
the 2-rotor engines, or with the new EC-3 controllers.
Mark
That version has two mag sensors. One for the RPM and one for 22 degrees BTC. That is
much easier to deal with in software. I have an early EFI and I will take a look at
the FET's and see if they are the kind with the built in diodes.
Paul Lamar
Timers are used in EFI CPU's to interpret the data coming in from the CAS.
A little background on CPU timers.
Obviously one of the primary uses of timers is to measure time. Duh :)
When a timer is used to measure time it is also called an "interval timer" since it
is measuring the time of the interval between two events.
It will increment by 1 every machine cycle or 921,583 times per second in a CPU.
8000 RPM is only 133 revolutions per second.
In a 2nd gen CAS there are 24 teeth on the lower wheel but it rotates at half engine
speed. That means there are 12 pulses coming out of the lower mag pickup in one rev
of the engine.
Times 133 and we get a frequency of 1596 PPS. That means the timer in the CPU can
easily determine the length of time for one of those teeth to go by the lower mag
pickup. The resolution of the measurement is 921,583/1596 or one part in 577.
More than enough resolution for RPM and we are checking the RPM 12 times per engine
revolution.
The drawback to this method is the processor is being interrupted 1596 times a
second. That is once every 625 usecs. It takes about 2 usecs to complete a asm
instruction so we must get everything that needs to be done in about 300
instructions. Does not leave a lot of time to send engine parameters to the
instrument panel display tablet or cell phone.
Now having said all that I am not sure any given EFI program works in that fashion.
There are other ways of doing it.
Paul Lamar
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