Help with building your Speeduino, installing it, getting it to run etc.
By kettlekev
#48365
Plugs are good.

So starting at the beginning to trace the noise, I am starting with HT leads and plug caps. The coils I have should be OK with resistor caps, that will help reduce the noise. I checked tonight and I have copper core HT leads so I will swap them out for higher performance carbon based ones with more screening.

I've got some ferrite coils coming for the power and LT/Trigger feeds so by next weekend should have the optimum answer.

I have looked at the cct diagram for the speeduino I have and there are only a few analog inputs spare so hopefully they have pullups? and I have resistor grounded CLT and IAT which were probably working as aerials.

Thanks for all the pointers guys.
By LAV1000
#48367
kettlekev wrote: Sun Feb 14, 2021 11:02 am ignmod2.PNG

Standard setup. Speeduino feeds primary via the FET driver

and here's the trigger detail.

igntrig1.PNG

Its definitely noise crashing the CPU somehow. If I just run it on the starter motor (no coils power) the mega stays up and the serial comms is solid and I can grab logs. With the coils firing all that gets intermittent and there is noise on the speeduiino 5v rail.
Maybe a translation issue.
Can you post a foto on how you did connect the ignition coils ?
By JHolland
#48368
Are you 100% sure that your spark isn't breaking down? if that happens and your ignition driver is gate clamped then that will cause the gate to rise to something like 14V which will back feed into your ignition driver circuit. You should have adequate de-coupling near the driver to absorb the charge.
#48371
Guys,

Thanks for all the help.

Taking a step back and forgetting about finding a cure and concentrating on a cause, it turns out to be as simple as non-resistive spark plug caps and copper cored leads. My bike has both and combined with older coils all in a small space, is just too noisy.

A quick start today without trying to log but using a timing light showed no sync losses and that is only replacing caps for ones with resistors (5k ohm). I've got new resistive core leads and ferrites for the power coming this week so will do a full log run then.

In the final build will tidy up the cable lengths and improve the screening again but pending a final log, it all looks good so far! :D

Next step is to look at coil/spark dwell. I know speeduino does some adjustments with revs/voltage and I know where to set it up. I have running set to 3ms right now which seems pretty standard but would like to optomise it but dont know where to start with a 2 stroke setup with higher current 3 ohm coils?
User avatar
By PSIG
#48373
kettlekev wrote: Mon Feb 15, 2021 6:00 pmNext step is to look at coil/spark dwell. I know speeduino does some adjustments with revs/voltage and I know where to set it up. I have running set to 3ms right now which seems pretty standard but would like to optomise it but dont know where to start with a 2 stroke setup with higher current 3 ohm coils?
Start here, and it links to a post with a calc program. With a $10 LCR meter (induction,capacitance,resistance), you can calculate coil dwell, and repeat for various voltages. Note exceptions are for coils with internal diodes or certain blocking drivers, where the LCR meter cannot read. You can simply test for primary and secondary resistance with a multi-meter in both polarities. If that works, the LCR meter should work.
Last edited by PSIG on Tue Feb 16, 2021 9:47 pm, edited 1 time in total.
By kettlekev
#48387
PSIG,

Thanks. Great calculator!

I've been looking at 3 ohm Vs 4 ohm coils, lots of arguments/conversations but nothing to make me believe I should switch from 3 ohm unless I have power (alternator capacity )issues.

Did a log run to day as a last noise check and I still have some sync loss above 3500 rpm which is expected due to only changing plug caps thus far. Will finish the mods are report back after I have fitted the high compression heads.

Thanks again......

Kev
By JHolland
#48401
An LCR meter won't be very accurate because they don't have the drive capacity to create any magnetic flux in the former. What you really need to do is measure the rise time of the current waveform and then calculate the inductance from the time constant. If you do use an LCR meter then try a 100 Ohm resistor in series with the coil - often those meters just don't have enough drive current work at all with a low-z coil.
As a general rule lower resistance coils have more energy because the energy in the coil is proportional to the square of the current.
By kettlekev
#48417
I tried a test today with the basic meter and populated the program PSIG linked me to earlier (below).
(579.71 KiB) Downloaded 184 times
Attached are images of the program output and the trigger spec sheet. Clearly the data isnt right because the Primary current charge time (dwell) wont calculate. So the things I am unsure about which are probably screwing the equations are;

Drive Parameters - Resistance and zener avalance voltage (my trigger is just a FET driver as far as I can see)
Spark plug capitance - I am using NGK BR7ES and it measures in the low nano farads and the program wont go that high
Spark burn voltage - 1.2kv is a guess

I tried just adding some numbers as a random test but it still wont find a dwell time.

Any pointers?? I will try the 100ohm trick to see if it makes a difference to the readings.

EDIT. I noticed some errors in the trigger specs so have corrected them.
dwell10.PNG
dwell10.PNG (26.1 KiB) Viewed 4139 times

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