Guys,

I currently have my V3 MegaSquirt running just fine on my FC using an '85 distributor for ignition. I want to change over to have the MS controlling ignition using the CAS.

I've read the FAQ, and it focuses mostly on the method using a second conditioner - I don't trust myself with such delicate soldering, and also don't necessarily want the hassle either! Can someone explain to me what exactly is involved in a) removing the two teeth from the CAS, and b) what the resultant wiring looks like? I am using DIY Autotune's harness currently - do I need to still run wires from the board itself or is everything contained in the DB37?

Primarily, where does G+ (input) go without the Second LM conditioner?



Additionally, using LS1 coils (which have only a signal and a ground), what are the other 2 ignition outputs (IGt-T and IGf-T) used for on the trailing coil? Are they even needed?



Thanks in advance, next step is a Haltech if I can't get this going!

 

IGf-T isn't used by the MS

IGt-T is the trailing timing signal, you also have to drive the coil-select signal on the stock trailing coils.

I don't think anyone has ever tried wiring using ls1 coils like you intend to do though.

Wiring for the missing tooth method is fairly easy. Just cut 2 opposing teeth out of the Ne wheel on the CAS, and then wire Ne+ to pin 24 on the MS, and Ne- to ground on the MS, making sure you have VROUTINV wired to TSEL internally on the MS.

Ken

 

What is the VROUTINV and TSEL? Sorry, I didn't build my MS (bought it prebuilt) so am clueless on that part!

I'm guessing from what you are saying that I should stick to using the stock coils?

 

That would be my recommendation. The stock coils provide a very strong spark.

VROUTINV and TSEL are jumper locations on the board. You'll have to open up the MS and make sure that the internal jumpers are all correct before you try to start up the engine...

Also, there are other modifications necessary to the MS internally in order to run a rotary engine, which are detailed in the FAQ. You will have to do many of those as well.

So either way you're going to have to get out your soldering iron most likely.

 

I'll help you out with getting your coils to work.

I got my Bosch Ford Falcon Coils working on my car. Just took a tad of testing.

If you want a primer.

First with non FC RX-7 Coils you need.

Ignition Modules
Coils

Assuming your coils are single post, and have just a +ve and a negative on the back.

The Ignition module shares the +ve wire. The Ignition module controls the negative wire on the coil to control charging and discharging.

You drive the ignition coil by putting the megasquirt spark output (comes from the LED/pullup resistor section, you'll know what I'm talking about when you read the FAQ), and the -ve input on the module is just a grounding point on the car, preferably close to the ground your megasquirt is using.

You select FD trailing mode, this way the megasquirt drives, the first led (closest to the serial port,[the one you plug into your laptop]), exactly the same way it drives the signal in FC mode.

But specifying FD mode changes the way the other 2 leds operate.

The next LED does the coil select signal in FC mode, which means its just a 0-5V toggle. It goes high when the dual post stock FC coil is meant to send spark to the front rotor(trailing), and gets pulled to ground (0V) when the FC is meant to send spark to the rear rotor(trailing).

In FD mode the signal for the 2 different rotors are driven in a similar but different fashion to how the leading coil is driven for both methods.

The signal on each LED only contains the timing information (in terms of how the Ignition module is driven), for one rotors trailing plug.

As Maui has told me earlier there is no garantee that the VB921 chips will work in FC or FD mode with output inverted selected in the software options.

So your best bet is to either use stock FC coils, or do something similar to what I do, ie using Bosch BIM024 or some other *dumb* ignition module. Just whatever you can get rather cheaply.

 

Also If you want to try another thing different, I have an idea for using 2 FC trailing coils.

You would drive Both Coil Select inputs on both trailing coils off the 1 LED15 output, and then drive each coil signal off the other 2 LED's. Just assuming here, but it would probably work fine. You will end up with a single spark instead of wasted spark leading. mauitaibxr has posted earlier that the FC coils produce a very strong trailing spark.

 

For cutting opposing teeth, this is what I did.

Pull cover off the CAS.

Turn engine to 5ATDC (-5BTDC), ie where the First timing mark is on a factory pulley.
Allign CAS in centre of adjustment, then rotate it slightly counterclockwise, push CAS into engine without holding the wheel steady.

Pay particular attention to how pushing the CAS into the drive teeth, turns CAS, it will turn 2 more teeth, and end up in dead centre of adjustment again. This is exactly what you want. The tooth, current on or closest to the Ne sensor is the 5ATDC tooth now, if you do this.

Count back one tooth(in counter clockwise direction), if that tooth was -5ATDC, now you are on 25BTDC, count back another, now you are on 55BTDC, count back one more tooth. This is the tooth to cut.

Mark to tooth to chop with black Nikko pen (permanent marker, bearing blue, nail polish/ whiteout you guys might call that liquid paper). Remove that tooth, and the one completely opposite to it.

You will need to strip down the CAS to remove the 2 teeth.

Get a punch/nail and hammer on the pin holding the gear on the bottom of the CAS off. Remove the 4 screws holding the sensors inside the CAS body. remove the sensors and be very gentle with them. Take the one that was for the 2 tooth wheel and store it in a safe place (good working backup incase you fudge up the other one).

Remove the other 2 screws holding the shaft/bearing assembly in, push shaft out, then remove the teeth. Reassemble in reverse. leaving out 2 tooth vr sensor.

I'll explain the trigger settings for you.

Because the missing tooth is on the 85BTDC, the tooth count is reset here. The next tooth passes the sensor, and the MS adds 1 to the reset tooth count.

you can see you are on 55BTDC when this happens. The trigger settings are usually 1 3 7 9 for missing tooth setup on 12-1 wheel.

So the ignition timing starts, and the ECU just does a delay to retard the timing back to where you want it.

As the engine keeps turning the 2nd tooth passes the Ne VR sensor, count=2.

Turns more, 3rd tooth passes the VR sensor. count=3.

Because you setup the timing to use crank based timing, tooth 3 passing the VR sensor tells the ECU to fire here for cranking timing, you see this will result in a cranking spark advance of -5BTDC or 5ATDC.

As soon as the engine rpm gets above the cranking rpm value the timing changes over to using the 1st tooth trigger and the appropriate delays.

The teeth 7 and 9 are just the same as teeth 1 and 3 only 6 teeth away, ie 6x30degrees = 180degrees out of phase. Which is exactly how much the front and rear rotors are!

Hopefully that makes a bit more sense for you!

 

Thanks guys for all the help. I actually decided to buy the V2 error* daughterboard from Glen's Garage and brave the installation (actually looks pretty easy). I wanted some of the additional functions on the board anyway.

Thanks for the help, I will report back soon!