This looks like a real simple way of using megasquirts on rotaries and you have
redundancy. The engine will run on one rotor. It solves a lot of problems using just
one Megasquirt on a rotary.
I has the advantage of using a notebook computer with a USB connector to tune and
save injector tables to share with other people merely by emailing them.
Megatune is very sophisticated and easy to use tuning software that runs on a notebook.
IMHO this is a great idea.
Paul Lamar
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Using MegaSquirt ‘out of the .box’
www.not2fast.com/megasquirt/doc/rotary_injection.doc
MegaSquirt introduction.
The MegaSquirt was design by Bruce Bowling and Al Grippo to be a simple and cheap
batch fire fuel injection system. Been around for years.
There are 2 injector driver outputs on the MegaSquirt, running off the PWM channels
of the MCU. This allows both saturated and peak and hold injectors to be used on the
same hardware: very clever. This allows 2 different injection events to occur in
parallel, which suits our purposes very nicely.
Specific needs of Rotary engines.
The rotary engine, due to the rotor layout has a few key differences with a
reciprocating engine. Many of these work in our favor. And remember, the otto cycle
is the otto cycle:
There are 2 rotors, spaced 180° apart. EFI.
Build 2 MegaSquirts.
Fit a pair of hall effect sensors one at 22 degrees BTDC and one 180° later (top and
bottom) Hook one MegaSquirt to the top sensor and one to the bottom.
Burn in injector staging code if required.
Ignition.
The ignition pulse on 1 rotor corresponds to 22° BTDC on the inlet cycle of the other
rotor, give or take the amount of advance being used. Very handy.
Use 2 MSD capacitor discharge units per rotor. One per plug. This is what the racers
do and is it very simple and straight forward. Each Hall Effect sensor fires two MSD
units 22 degree BTDC.
Injection.
Around 220-280° is available for injection. In a reciprocating engine, you
can ‘puddle’ fuel on the inlet port to increase the injection time. In a rotary there
is little time for this before the next inlet cycle starts. This forces relatively
large injectors to be used, with staged injection being a
useful method of getting high max flow rates and a good dynamic range. For example,
at 8000 RPM 1 revolution is 7.5ms, giving around 6ms for injection.
In terms of injector strategies there are a couple in general use
The best for our use here is 2 injectors in each runner.
The code mods are very simple, if needed at all
You get the full 6 ms for injection at high RPM
2 MegaSquirts are needed so adding a full $100 to the costs
Tuning will be a little more tricky as you have to set each parameter twice
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