87 CRX Tach Signal and Ignition Control

[1gturborex]

I am currently in the process of building my MS 2 with V3 main to run my 87 crx si turbo, which uses mechanical contact points on the distributor for ignition. I have already locked out all advancing mechanisms and I understand that if I am to use the MegaSquirt for ignition control using the (-)tive directly from the coil, then I will need a separate sensor, VR possibly, to have a tach signal input for the V3.

If I were to send the output from the distributor points to the V3 and thus control a MSD 6a using the ignition circuit, would I still need a separate sensor, such as the VR, to obtain a tach signal for the V3? Does using the MSD represent direct ignition control from the V3? Can I avoid installing a VR sensor and trigger wheel if I obtain an MSD 6a? Are there any other ways to use the MegaSquirt for ignition control and still retain my stock distributor?

Thanks

[Matt Cramer]

No reason you can't use points as an input to the MS; see the distributor pick-ups article for how it's done:

http://www.megamanual.com/ms2/pickups.htm

It's at the bottom of the article.

The inputs and outputs are two different components and can be treated completely separately, except in a few cases of OEM ignition systems that are nearly self-contained (HEI, EDIS, etc). So you mix and match different ignition inputs (points distributor, VR distributor, or crank trigger) and outputs (BIP373 for direct coil control, Bosch 124 module, or MSD box).

[1gturborex]

In the manual it states that if you are going to use the wire that would otherwise go to the negative of the coil to use for direct ignition timing, you need to fix a different signal for the tach. Does this mean I need a separate sensor for my tach signal because it has to be fixed?

What I am interpreting from the MS manual is that if I want to use the direct control ignition which triggers off the wire that would go to the negative of the coil, then I will need another sensor for a tach. Is this right? I found out that my distributor uses a reluctor (VR) built in instead of points so that means I have one sensor.

Can I wire both the inputs to the tach and ingntion control circuit from the VR?

[DonTZ125]

If your distributor uses a VR instead of points, that is all the sensor you need for fuel and spark.

Yes, you will need a signal going to your tach, but the MS unit can provide that.

[1gturborex]

ok thank you