Subject: Using 2 Megasquirts. One per rotor
From: rotaryeng
Date: 7/5/2012, 4:44 PM
To: AAAA Put this in the To box 



 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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I had an idea of using 3 megasquirts that fed a logic box that compares the outputs
and forwards the one that at least 2 ms boxes agree on. Not sure if it's really
feasible since that would induce some lag in the outputs.
Joshua

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SymTech Labs' coolant temperature sensor is a standard GM CLT sensor capable of
interfacing with all MegaSquirt ECU's. It features 3/8" NPT threads and can also be
used as an intake air temperature sensor (IAT/MAT). Each unit is shipped with a 6"
pigtail for easy installation.

Intake Air Temp/Manifold Air Temp

The big question that I have is there seems to be conflicting info. Often they talk
about a MAP sensor but this block diagram does not show it. A Manifold Air Pressure
sensor (MAP) can be used to control the amount of fuel injected just like an O2
sensor. That is what Tracy does.

Any type of feed back from an O2 sensor will not work as 100LL is death to O2 sensors.

The MS flow chart shows a read of the MAP but the schematic shows no connection to a
MAP sensor.

Can anybody help me out on this? Is the sensor on the mother board? Where is it
connected?

BTW The megasquirt has the built in capability to send engine parameters back to the
notebook in real time for use as an EFIS. The notebook software is already available
to display these engine parms in real time. This is a real cheap EFIS.

Paul Lamar



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