MSII v3 - step 50 (hall/optical vs. VR/coil)

[richiea]

I am have built an MSII v3 for use in a 1990 Audi 200 5-cylinder turbo. The distributor does not have mechanical advance but does not have a 5 windows hall sensor.

I will be installing the MS2 for fuel only to start, then once its tuned, I will tune it with ignition. When upgrading to ignition, I will change from the stock distributor to another model distributor with a built in hall sensor. I therefore chose step 50-A (Hall/optical input circuit). I consequently SKIPPED step 50-B and 51.

I chose this since the instructions state: This input circuit is also used if you want to trigger off the negative side of the coil, since the points control the negative side of the coil's primary circuit. However, you can only trigger off the coil's negative terminal if you are NOT trying to control ignition timing

My question is that can I actually use the hall/optical with a negative coil tap for fuel only and then once I want ignition control, just swap the signal for an actual hall sensor output?

Just want to make sure before I close up the case, cause from what I understand, I am all set with only performing the circuit for the hall/optical sensor along with the appropriate jumpers from 52.

THANKS!!!!!

[Bernard Fife]

richiea,

If you use the Hall input, there are a few components you leave out that you should install if you are using the coil negative terminal.

So when switching from the coil negative terminal to a Hall input, you need to remove those components. There's more in the manual about this.

Lance.

[richiea]

richiea,

If you use the Hall input, there are a few components you leave out that you should install if you are using the coil negative terminal.

So when switching from the coil negative terminal to a Hall input, you need to remove those components. There's more in the manual about this.

Lance.

Ok I don't quite understand what you mean.

From what I read, then end of step 50-a says you can even use the hall input circuit for a negative terminal coil signal as long as you're not using MSII for ignition control. I interpret that as if you can use step 50a, jumper it for 50a, and skip 50b and 51.

I've read that part over 10 times now and still am seeing it the same way. Sorry to be ignorant here but what am I missing?

[Bernard Fife]

richiea,

Step 50a. is for Hall/optical sensor, etc. (i.e., a digital signal).

Step 50b. is for the coil negative terminal triggering.

This is if you are reading from here: http://www.megasquirt.info/ms2/V3assemble.htm#input (if you are reading from somwhere else, then you are using an old version of the manual, and should use the current one in the link above.)

Lance.

[richiea]

OK. Thanks! I will then complete 50b and 51, and jumper accordingly according to step 52. Last questions:

STEP 50-a-v: If you have a Hall sensor or optical sensor, do not install D1, put a jumper in its place.

I assume if I want to be able to go from a hall sensor to negative coil trigger, I have to install D1 and jumper it when I want to use the hall sensor?

STEP 50-a-vi: For most installations, diode D2 is not needed. Do not install D2, install a jumper in its place

That then contradicts STEP 51-b-iv: In the place of D2, install a 22V or 24V Zener diode {1N4748ADICT-ND}, in the reverse of the indicted orientation (i.e., put the band at the other end rather than that indicated on the silk screen).

Also something odd I noticed, both STEP 51-b-vii and viii state to install the components "if you are using negative side of coil to trigger". Is it just me or is that redundant since the entire STEP 51-b is intended for using negative side coil?



To sum up:

D1 = install diode for negative coil tap and jumper for hall sensor
D2 = install Zener diode in reverse of indicated orientation for negative coil tap and jumper for hall sensor
C12,C13 = install for either circuit, but is mainly needed for negative coil tap
proceed installing everything in step 51

Then ultimately you can select input trigger type by jumpers as stated in step 52 and by adjusting D1 and D2 accordingly.

Thanks for all the help!!!!

[Bernard Fife]

That then contradicts STEP 51-b-iv:

richiea,

No it doesn't. I think you are reading this wrong. If you are going to use a Hall sensor, etc., you need to follow the steps in 50a.

If you are going to use the coil negative terminal, you need to follow the steps in 50b.

So you do either 50a or 50b, not both.

There is no "contradiction", the installed components are different, and are meant to be different.

Don't forget about C30 as well.

Lance.

[richiea]

Ok, did I mentioned I am MEGAconfused????

Step 51 states

As we noted in step 50, there are two input circuits for the tach signal. One takes the square wave input from a hall sensor, optical sensor, or points.
In most cases, you should install both circuits, and make the selection between them with jumpers.

Now I'm told I can't install both. If that's true, I am lost as to what step 51 and especially 52 are for?

Ok seeing as I can't seem to express myself or properly understand the instructions nomatter how many times I read them I think maybe it'd be easier to start over.

Here is what I want:

PHASE 1: I want the megasquirt to run with a negative coil tap trigger for a tach signal to get my car up and running using megasquirt for FUEL ONLY and using the stock ECU for ignition control. I am in fact told from others that used megasquirt with the same car that I can just feed off the stock wiring harness for the tach signal to feed megasquirt. I assume since the car has no hall sensor that this is similar to the negative coil trigger. I believe for this setup, I would need the coil negative terminal circuit, but maybe I am wrong.

How do I assemble megasquirt for PHASE 1?

PHASE 2: I will then want megasquirt to run both IGNITION AND FUEL. Since my car AS IS does not have a hall sensor, I will install a distributor with a hall sensor. I will then remove the stock ECU and need a new trigger source, therefore I believe I will need the Hall/optical input circuit for this, but maybe I am wrong.

How do I assemble megasquirt for PHASE 2?

[Bernard Fife]

richiea,

Yes, you sound confused.

There are two input circuits, the Hall and VR.

The Hall circuit can be built two ways - for a digital signal such as a Hall sensor or optical sensor (step 50.a.) or for a coil negative terminal (50.b.). these are the same circuit, but different components.

The VR circuit is install in step 51, if desired.

In you case, you need to start by installing the components as directed in step 50.b. for the coil negative terminal. Then later, when you want to configure it for a Hall sensor, you need to change it to conform to step 50.a.

Lance.

[richiea]

Lance, you're the man.

Thanks for clearing that up. I really appreciate your patience!!!

[Bernard Fife]

richiea,

No problem, I will clear up the manual. I think we had different definitions of "circuit", versus the configuration of a particular circuit changing.

It's always good to bring these things up, it helps the manual to improve, and helps others to avoid confusion.

Lance.