Low-impedance injectors require some form of current limiting. MegaSquirt can run low-impedance injectors with resistors and feed them a +12V supply directly or MegaSquirt can use Pulse Width Modulation (PWM) to limit the current and perform peak-and-hold without using any resistors.

The easiest method (the way I run it) is to use the resistor box and disable the MegaSquirt's PWM injector current limiting (by setting PWM% to 100%, and time threshold to 25.4msec). This way you don't have to deal with correctly configuring the PWM parameters.

Definetly read up on MegaSquirt's site about injectors: http://www.megamanua...manual/minj.htm

The resistor box is wired up the same way it is with the Honda ECU: +12V into the resistor box, 4 wires out of the resistor box to the 4 injectors, and 4 wires from the injectors to the ECU to which the ECU supplies ground to open the injector.

Cool.


I've been assuming you have something like a 4G SI distributor with 3 VR sensors, an ingitor, and a coil crammed inside. But you mention wanting to switch to electronic advance so, I assume you have a vaccum advance distributor.

Those have an external coil, no? Are you familiar with the VR sensors inside your distributor? Does is have a 4 spoke TDC VR sensor? That is key to signalling the MS when each piston is at TDC.

Be sure to read this on connecting the MSD 6a with MegaSquirt: http://www.megamanua...m/ms2/msd6a.htm

Looks like you'll still need to use the high current ignition driver. Your setup will be a little different from what I've outlined at http://buddyabaddon.spaces.live.com. The information there is more of a plug-and-play setup for MegaSquirt with Honda OBD0 cars.

By using the MSD ignition, you are essentially replacing the Honda ignitor unit. This means that instead of connecting wire D36 from your MS to the Honda ignitor in the distributor, you will connect it to the advance control signal (white wire) of the MSD unit. You won't use the VR sensor inputs on the MSD unit. Instead, you will still have the Honda TDC VR sensor in the distributor signal the MS which in turn, sends out a square wave signal to the MSD box (via the white wire) using the high current ignition driver. The one thing I was curious on was what value to use for the pull-up resistor for the MS high current ignition driver, they make no mention on the MSD page. So, I checked the MS forums: http://www.msefi.com...ic.php?p=148197. Looks like the MSD can handle floating ground inputs, so no pull-up resistor is needed with the high current ignition driver.

Also, what are you using for a coil?? Do you have an MSD coil or are you planning on using the Honda coil in the distributor?

If you plan to use the Honda coil, definately read the section on page 21: http://www.msdigniti...ies/6series.pdf
You're going to have to wire the MSD up to the coil in the distributor.

Man Honda crams a bunch of crap in their distributors

Let us know how it goes. I've wanted to try the MegaSquirt with MSD ignition at one point, looks like you beat me to it.