VR signal input > RPM > Direct Coil Control

[Chrisso]

Hi all,

I have an MS2 v3 on v.2.888a code. It's set up for VR input and Direct coil control.

What I'd like to know is if the MS2 would see, and show in datalogs, an RPM signal if the Direct Coil Control components (step 65) aren't installed?

So, my idiotic mistake was I missed installing the components at step 65 and have tried to crank the engine a couple of times. The dials & datalogs didn't show any RPM. I don't get over to work on my car often, so i'm trying to figure out if these missing components would also explain the no RPM condition or is there something else I need to look at.

I have a v2.1 stim and that appears to work just fine. I have a spare dissy with me, so how would I patch this into the stim instead of the RPM pot?

My set-up is:
Toyota ESA dissy - 24 tooth signal wheel, missing 2 opposing teeth. Running a 4 cylinder 4age engine.
#52 I've jumpered VRIN - TACHSELECT & TSEL - VROUT
#65 I've jumpered IGBTIN - JS10 & IGBTOUT - IGN

My settings are:
Decoder wheel 12-1, skip 6
Input Capture - Rising edge [the dissy signal is falling edge]
Crank Trigger - Trigger rise
Coil Charge - Standard
Spark Output - Going High (inverted)

Regards,
Chris

[Matt Cramer]

The input and output side are separate, so if you are getting a good RPM input it will show up even if the output circuit is missing. Note that your wheel decoder settings will not work on a V2.1 Stim.

[Chrisso]

Thanks Matt. That confirms that my lack of RPM in the car is something else and not caused by the formerly missing output components. The stim works fine and shows RPM when the ignition settings are decoder wheel=0. Does this indicates the input circuits are fine and my problem is with the signal from the dissy?

What I would like to do is bypass the stims RPM pot and wire in the output from my spare dissy. Any suggestions on where I should connect it to the stim?

Thanks,
Chris

[Matt Cramer]

You could remove SW2 and R4, then feed it in through the non grounded end of R4.

[Chrisso]

Thanks Matt. I'll give that a go. I found a thread with a post by Al which steps through testing the input circuit, so I'll dig that up also once I've got this set up. I assume that moving SW2 so that it's open is the same effect as removing it.

EDIT *******************

Okay, so I removed SW2, and tested continuity between pin 24 and the two ends of R4 (which I've removed). I've found that the end that shows continuity is powered, ~8-10v, while the other end is showing <2mV. My non-electrical brain would say I need to connect to the end showing continuity, but the VR doesn't require power?! This is only the case when the Stim is connected to the MS. Just powering the stim and testing voltage at those points results in to <2mV readings.

I'm going to go back and check each step of the VR input circuit again incase I've stuffed it up.

I've also noticed some really odd fluctuations in the dials while I'm not changing any of the inputs. I've attached a datalog that shows the irregularities. I noticed this earlier in the week, but didn't pay much attention to it.

Thanks in advance for your help,

Chris

[Matt Cramer]

Do you have a pull up resistor installed in your ignition input circuit? If so, you'll need to remove it.

[Chrisso]

No pull up resistor in the input circuit. I worked my way through the inputs and realised that D1 is unpopulated. If I've read the manual correcly this should be jumpered for my application and the diode is only required for triggering off the negative terminal or points. I'll jumper this and try again. In your opinion, would not having a jumper in D1 cause the voltage issue?

THanks,
Chris

[Matt Cramer]

D1 is not used with the VR input. I would first try reversing the polarity on the VR sensor as sometimes you can have it wired backwards and the MS won't "see" the missing tooth correctly when you do.

[Chrisso]

I've been playing with it a little over the christmas break and after speaking with a few people I've got a list of questions.

1. is there any documentation showing expected voltage and wave forms for the input circuits?

2. what is the minimum amount of voltage/amperage that the MS will recognise?

3. when I'm trying to test this using the stim with the dissy wired to it should I ground the dissy using the sensor ground db37 pin #19?

4. related to the above, on the car should the dissy be grounded through one of the earth wires coming from the MS?

Thanks,
Chris

[Matt Cramer]

This link will partially answer the questions about the VR input:

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

The distributor will need to be grounded to a signal return on the MS.

[Chrisso]

Hi, I've been away from this for a while and just getting back to it. I think my grounding is incorrect as I've got the shield for the signal wire terminating at DB37 pin #2. In going over the external wiring diagram again it would seem that this is where the VR '-'ve should be. Is the ground for pin #2 any different to the other grounds? The reason I ask is because when I run the dissy with the drill and have megatune running, it cuts out when I start the drill/distributor and ground the VR signal on the heatsink.

[Matt Cramer]

All ground pins (1,2, and 7 through 19) are the same.

[Chrisso]

So, any initial thoughts on why grounding the -ve from the VR sensor would cause a reset?

[Chrisso]

I thought I'd post and say "Thanks Matt" for answering my inane questions. I've managed to solve my problem, but working back over the board in detail has been beneficial. So, my problem was that the earth and signal leads were connected incorrectly even though I thought I'd checked these innumerable times and switched the capture edge settings in Megatune back and forth to account for having them connected in reverse.

Along the way I found that connecting the dissy signal into the stim I got a cleaner signal by soldering straight to the DB37 (on the stim) pin #24. I'm in the process of re-wiring my loom and pigtail as I must have been on drugs when I did it the first time (same applies for building the MS) so I should have it back in the car next week and hopefully started for the first time in 14 months.

Thanks again,
Chris

[dr.occa]

i hope this is still on topic.

i'm working with a turbo 4AGZE setup. i'm using the VAST distributor (4 tooth). megasquirt II v3.0 board.

the unit was pre-assembled. a jumper is installed on D1 and all the recommended jumpers on the bottom of the board were all already completed. i asked this on MR2OC as well but how do i proceed w/ the pull-up 1k .25w resistor modification w/ a jumper in place of the D1 diode?

also, what would be the correct "Advanced Ignition Options" settings for the 4 tooth distributor? thanks in advance.

[Chrisso]

DIY autotune have a write up on their website for setting up a VAST 4age