Megasquirt Info Thread

[Whizbang]

im still confused on how to run the injectors. since it has two outs, would i have the injectors that are firing at the same time run one rotor at a lower pulse width?

[RotaryProphet]

Originally Posted by Low Impedance

im still confused on how to run the injectors. since it has two outs, would i have the injectors that are firing at the same time run one rotor at a lower pulse width?

That depends on what you're using for your intake & injectors.

The MS default is to pulse both injector drivers at the same time off the same map. On most non-rotary cars (or rotaries using the non-oem intake setup) where all the injectors are the same size, you can set it to alternate the two banks off of the same map.

So for instance, if you were running an IDA throttle body like I was for a while, you would wire both of the outboard injectors to one driver, and both of the inboard injectors to the other, and run them in alternating mode. You can set it up with one driver per rotor, but you lose a hidden benefit. In alternating mode you are basically running the engine off of two injectors, but as the load increases the injectors will start to overlap; one bank is still firing when the next starts. Eventually at 200% (calculated) pulsewidth, both banks are firing all the time. This gives you a very good dynamic range, and makes it easier to idle on big injectors.

Now the tricky part comes in when you have differently sized (staged) injectors, or when you have an intake setup with secondary throttle blades that don't open immediately (sound familiar? Both of these are true in various 13b configurations).

At this point you have to run dual table. Wire the small/primary injectors to one bank, and the large/secondary injectors to the other. Then you have to map out both injector banks individually. One thing to note is that you can't put a zero into a VE table bin to stop the injector from firing at all (under most firmwares; check local listings). Instead, when you want an injector to not fire (ie, secondary injectors before the secondary throttle opens) put a "1" in the VE bin, and it'll put out -almost- no fuel. Close enough to get the job done, at least.