Ignition settings for cb750 4 cyl wasted spark 2 tach inputs

Post by **grippo** » Wed Feb 20, 2008 11:10 am

You are changing too many things at once - I can't keep up. You changed to VR1. OK now we need to resolve the shield problem. Some units had the shield correct and others didn't. I believe Lance has put in the manual what you need to do to determine this and how to fix it. So I would do this first. Then repeat the run with trigger offset = -320 and 2nd channel offset =0 and let's look at the spare 4, 5 variables. This tells me what the computer is seeing. If it's not correct, it's not going to work and there is no sense trying different variables.

If the offsets are wrong, either because of input timing or because of the settings, then they won't necessarily affect both channels equally. For example if the setup causes you to fire too late, the code will cut it off (spark) early and if you make it even later, or earlier but still past the cutoff time, then you won't see any change. That is the only answer I can give you as far as why the spark outputs are not consistent.

Bernard Fife · Post by **Bernard Fife** » Wed Feb 20, 2008 11:26 am

The info Al refers to is here: http://www.microsquirt.info/dualspark.htm which I have re-written and expanded substantially in the past several days.

Al hasn't reviewed it yet (I am still tweaking things before asking for his comment), but it should be close and expalin a lot of the dual spark stuff better.

Lance.

750essess · Post by **750essess** » Wed Feb 20, 2008 11:34 am

I am going to go over the new instructions, and see if I missed anything stupid. I will post new logs tomorrow.

750essess · Post by **750essess** » Thu Feb 21, 2008 5:14 am

Confirmed that the shield is the input on VR1 and center conductor is ground.
Ran the log with -320 offset , 0 odd ang , rising edge and calculated as requested. Channel 1 was off, it was greater than 90 degrees off (as far as my light will go). Channel 2 fired a t TDC.

Post by **grippo** » Thu Feb 21, 2008 9:35 am

The shield is supposed to be ground, so it looks like you have a unit with the VR1 having reversed wires. This could explain what is going on here since it is the 1st channel that is coming out wrong. I have placed Bruce's post on this and how to fix it below.

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From Bruce's post:

OK - you and "Old Guy" appear to have harnesses with an error. As pointed out, the shield should be on VR- and the center conductor should be on VR+ terminal.

I have the harnesses made up by a contract manufacturer. On the first go-around, the harnesses were made up proper w.r.t. shield and center conductor. However, the second batch made up appears to have the two reversed. It took us awhile for figure this out. We test each and every MicroSquirt to make sure it operates. But the harness is just a visual, and with the heat shrink on the connector end it is hard to see.

If you want, I can fix the harness for you (email me offline at bbowling@earthlink.net). You can also easily fix the connector yourself, it takes 3 minutes to do. All you have to do is pull off the red clip on the harness connector, this will expose all of the pins. Next, find the two pins for the coax shield and center conductor and *gently* wiggle them while gently pushing the terminal - it will dislodge and push back. then switch the locations and push back in till it clicks in place. Then reinstall the red clip (line up all of the terminals).

750essess · Post by **750essess** » Thu Feb 21, 2008 10:23 am

I will fix the harness and try again

750essess · Post by **750essess** » Fri Feb 22, 2008 6:42 am

Alright, went through the directions completely, everything ok. swapped the Vr pins so center conductor is signal and shield is ground, no difference. Installed my old Dyna S unit, which is designed to drive the coils directly, so I know the trigger outputs can't be offset or anything. No change with these sensors either. Unless you have any other ideas, I am abandoning using the microsquirt for ignition and using the dyna box to drive the coils and to trigger the FI. On a side note I set it to dual cam sensor inputs to see what happened and it behaved exactly the same? Does this offer any clues?

Post by **grippo** » Fri Feb 22, 2008 9:55 am

In my experience, getting the tach input to work properly and reliably is the hardest thing there is in engine control. I don't blame you for your decision. The only way to confirm that the problem is that the 2 sensor inputs are offset is to scope them on a 2 channel scope and see whether the peak of the 2nd channel always falls in the center between 2 peaks of the 1st channel or is offset. This should be done not just at the VR inputs, but at the point after the VR circuitry processes the VR signals and sends them direct to the processor. geoffct did this properly and told us exactly where the right place is. This should show that the rising edge of chan 2 always occurs halfway between the rising edges of ch 1 - or not.

What I did in place of the scope was to simply grab a .128 ms clock every time I got a VR interrupt and subtracted the previous clock value and dumped the result into a spare variable that is datalogged. There is some jitter to the process, but its only a few ms at worst, which is not significant during cranking, plus it would be random. The datalogs consistently show numbers of 600 and 900 +/- 10, no others.

750essess · Post by **750essess** » Fri Feb 22, 2008 10:03 am

I think you missed the part about me trying the dyna s setup. This directly replaces the points and drive the coils directly. I hooked this into the inputs of the microsquirt and the outputs are not the same. I still think some setting is not applying to both channels. Another possibility is you vr conditioning before the cpu is messing it up. Remember these are hall effect and make a very clean square wave. How hard would it be to bypass the vr conditioning and go directly to cpu inputs? can the cpu handle 12v square wave in directly?

Post by **grippo** » Fri Feb 22, 2008 1:36 pm

The reason I don't think it is a setting that is messed up is that the time measurements I made have nothing to do with the settings you put in. It just grabs the times of whatever rising edges come into the 2 VR input pins on the processor. But yes the 2 VR processing circuits could be messing things up - but I believe the 2 circuits are the same, so if the 2 inputs are the same we should see only a shift in both channels. But what is possible is that a wrong component got soldered in by mistake, for example, a 50k resistor instead of a 100k resistor in one of the circuits. Unfortunately, you can't bypass the conditioning and you definitely can't appl 12V direct to the cpu. But if you want to send me your unit I can compare it to what I am seeing. (just PM me.) Remember I too have even cleaner square wave signals (from another processor) coming into the VR circuits.