Ignition testing

[Jimvr4]

The stock ignition system was tested way back in the summer of 2003 by tom93vr4. Since then it seems like no one has ever repeated those tests. Now that we have Chrome ECUs we should revisit these tests to see how far we really can push the stock ignition.

Stock ignition with stock (75% dwell)

Here are the results with a stock powered primary side at 75% dwell. I didn't measure the stock voltage level supplied to the coils but others have measured mid 12s at idle down to high 11s at WOT.

I measured the primary side current. The scale is 10mV per Amp and the waveform is inverted because I'm measuring at the input side of the coils.

Here it is at idle, 714 rpm. Note the dwell time is a little over 5ms and the current charges up to about 5A


At 3333 rpm the dwell time starts to diminish as does the charging current. Now we see less than 5ms and around 4.6A


At 6000 rpm the dwell is significantly reduced as well as the charging current. Here dwell is only about 2.5ms and current is about 3.6A


Stock ignition with stock (90% dwell)

Now let's see how it improves in Chrome with the dwell set to 90%.

Here it is at idle. No change at idle since the full time is already spent charging the coils


At higher rpm the 90% is still similar to the 75%. Around 4.6A charging current is reached.


At about 6666 rpm the dwell time is still around 2.8ms and charging current is around 3.8A. So the coils do get a bit more time to charge up.


So how can we improve the spark? We need either a longer charging time or a higher charging rate. Fastbikes76 coil hot wire mod improves the charging rate. I'll be testing that soon to show how much.

Fundamentally it is clear that the charging time cannot be improved. It is just as clear that the coils cannot reach their energy potential with such a low charging rate provided by the stock system. Further the current levels are GREATLY reduced at high rpm due to the limited charging times. A much higher than stock primary voltage could be used at high rpm to reach the 5 to 6 amp current level that is achieved at idle.

So, what we need is a modification that increases the coil supply voltage as a function of rpm! Hmmm

[fastbikes76]

Great info and thanks for taking the time to look into this. Certainly interested in the hotwire results too see if on paper it works as well as it does in reality.

[LeRoyDL]

Curious, add dli too. Maybe someday :-)

[KeithMac]

The joys of wasted spark!.

[Greg E]

So, what we need is a modification that increases the coil supply voltage as a function of rpm! Hmmm

Adam and I had talked about that a couple years ago as another "chrome mod" but the general community seems happy with just a simple DLI amp so I never bothered.

[futurevr4man]

Thanks for taking the time to look into this! Always love a good data-based approach to these things. I'm anxious to see the results after the coilpack hotwire!

[ChargerX3]

Thanks for looking into that Jim. Would be great if we can find a work around.

[Jimvr4]

Test setup

I'm using a Lenovo Yoga Ultrabook running Windows 10. I have Picoscope 5000 plugged in and I have a Hantek CC-65 current clamp hooked up for the current measurement.


Here you see the current clamp hooked up and set to the 1mV/100mA scale (10mV/A)

Curious, add dli too. Maybe someday :-)

Right now this investigation centers on the performance of the primary side of the stock inductive system. I will leave DLI testing to someone else. I'm trying to show that we can achieve a strong spark without spending $400.

The joys of wasted spark!.

It is true that the coils have less time to recover because they are used every third firing instead of every sixth firing.

Adam and I had talked about that a couple years ago as another "chrome mod" but the general community seems happy with just a simple DLI amp so I never bothered.

I don't think chrome by itself would be capable of doing this. It has no way to increase the coil supply voltage on it's own.

Thanks for taking the time to look into this! Always love a good data-based approach to these things. I'm anxious to see the results after the coilpack hotwire!

I should be able to get some more time in the garage soon. I've been hesitant to cut my harness but interrupting the supply voltage without cutting requires a couple of connectors and wiring and costs too much. Right now my plan is to cut it and install a pair of mating spade connectors.

I also want to get a BNC extension cable so I can pull the Picoscope into the car along with the laptop. Then I can do testing under load. Might need a helper to run the laptop and save images then.

Thanks for looking into that Jim. Would be great if we can find a work around.

I certainly hope to

[Greg E]

I don't think chrome by itself would be capable of doing this. It has no way to increase the coil supply voltage on it's own.

I'm sorry. I was talking about an ignition amp that works similar to the Keen-Bell boost a pump that would have a high/low switch triggered by the ECU which the user could set in chrome.

[bradrs]

Good to see actual data. Too bad none of the changes upped the amperage beyond the stock at idle. I'm really curious about whether or not it has the current limit in the transistor.

That looks as if that adjustment you are making isn't exactly a 75% and 90% dwell time, but rather the values you are putting in are the max dwell duty cycle permitted. It probably still calculates dwell vs battery voltage, then compares it to that maximum value. That would explain why at idle, the actual dwell time did not change.

You may be able to up the actual dwell at lower RPM in another table, if you know where it compensates the dwell vs battery voltage. This is just a guess though.