Series 1 to Series 2 in a Mustang | Page 2 | AEM
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AEM_NS
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There is no "dwell" when you

There is no "dwell" when you use a CDI.  As I mentioned before, the dwell usually gets set to 1-2ms to get the CDI to trigger.  The actual dwell time from the EMS to the CDI has no influence over how the CDI triggers the coil.  Usually, most CDI boxes only need a short trigger thus the 1-2ms dwell setting.  Apparently, there may be some issues if the dwell is too long but I don't have first hand experience with that.  The CDI box just needs to see a 0-12v rising edge trigger to fire the coil. 

PC logging the coil channel in the software isn't all that useful.  You're better off troubleshooting these setup issues with an oscilloscope.  If its starts and runs, run it and then figure out the misfire issue.  I don't know what the relevance of the SPOUT signal is now since you're not using it so explaining what the SPOUT signal is and how it's implemented is outside the scope of our discussion.  Have you verified that you have good rotor phasing?  Bad rotor phasing might explain a misfire.  You should also probably check the injector phasing as well which can be done with either a timing light or scope.

azfiveoh
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Joined: 01/07/2015 - 07:39
I've been able to get back to

As always, thanks for your reply.  The start of the new year has been busy and I've finally been able to get back to messing with this project.

I don't have an o-scope so I'll need to get one before I can do the testing you recommended.  In regards to the SPOUT signal, the reason I had asked is because there wasn't any kind of misfire or issue when the CDI box was triggered via the TFI.  Once I bypassed the TFI and used the coil output from the EMS to trigger the CDI the misfire issue started.  I wasn't certain if the TFI's output in some way different from that of the EMS and as a result was causing the issue. That does not seem to be the case according to your explanation.  I have checked the rotor phasing and injector phasing, both of which appear to be fine.  The car starts and idles normally, the misfire occurs when the engine RPM is increased.  Changing the coil dwell settings causes the misfire to move in the RPM range, which is why I inquired about the coil dwell.

I'll continue to mess with it and see what I can come up with.

AEM_NS
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Looks like the CDI get's

Looks like the CDI get's wired into the coil primary circuit output from the TFI so what the CDI sees is "downstream" of the SPOUT signal.  The coil primary signal should be exactly the same coming from either the TFI or the EMS with it set to do a rising edge output.  

azfiveoh
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It's interesting that the

It's just strange that the engine revs smoothly when the CDI is triggered from the TFI yet with the same settings it misfires, badly, when the EMS triggers the CDI directly. I'll reset the dwell settings and verify the timing, just to be certain those elements are not creating an issue.

AEM_NS
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Compare the trigger signals

Compare the trigger signals with an o-scope to see if they're different.

azfiveoh
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So I made some headway here

So I made some headway here by changing the coil dwell from Ford TFI to All CDI Systems in the software. Making that change allowed me to rev the engine, with no load, almost all the way to redline where it was breaking up almost instantly with the Ford TFI settings.  The wizards sets the coil charge time to 3ms and the coil I am using calls for 1 ms charge time based on 6-7 amps coil charge current, primary inductance of 1.7mH, 14vdc supply voltage, and a primary resistance of 0.23 ohms.  I want to set the coil to fixed 50% duty cycle so I'm setting the dwell max to 1.5 teeth (based on an ignition event every 3 teeth due to a 12 tooth wheel and 8 cylinders) and the dwell min to 0.1 teeth.  In AEM Pro I would have adjusted the coil dwell factor to 10 based on a Dwell vs Batt Volts setting of 50 and a Dwell vs RPM setting of 100 to create a 1ms fixed charge time.  Would you please explain how to accomplish this in the AEMTuner software?

Thanks for your help.

AEM_NS
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Adjusting dwell on the Series

Adjusting dwell on the Series 2 is pretty easy/straightforward.  There are two tables: Dwell vs RPM and Dwell vs Battery V.  If you want 1ms of dwell everywhere, the easiest thing to do is to set Dwell vs Battery V to 1ms everywhere and then set Dwell vs RPM to 100 (y-axis is %).  Regarding the dwell clamp, a dwell max of 1.5 teeth won't clamp dwell until 7500rpm at 1ms of dwell.  Another way to reduce dwell is to actually reduce it in the tables.  I usually just set the dwell to 50% of whatever the ignition event time is once it gets below 2ms.  I've run down to .5ms of trigger dwell on V8s running CDIs to nearly 9k rpm.

azfiveoh
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AEM_NS wrote:

AEM_NS wrote:

Another way to reduce dwell is to actually reduce it in the tables.  I usually just set the dwell to 50% of whatever the ignition event time is once it gets below 2ms.  I've run down to .5ms of trigger dwell on V8s running CDIs to nearly 9k rpm.

Thanks for the great explanation!  Would you mind elaborating a bit on this as I would like to follow the system you've used with success on high revving V8s.  When you say reduce dwell in the tables I'm presuming you are your referring to the Dwell vs RPM and Dwell vs Batt V tables.  I also want to make sure I under the ignition event time correctly.  On my engine there is an igntition event happening every 90 degrees of crankshaft rotation.  At 6000rpm, for example, there is an igntion event happening every 2.5ms.  I've set my rev limiter to 6500rpm which results in an ingition event happening every 2.3m so I would be fine leaving the Dwell vs Batt V at 1ms or am I calculating the ignition event time incorrectly?

 

AEM_NS
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Yes, if you're only revving

Yes, if you're only revving to 6500rpm, then setting the dwell to 1ms everywhere should be fine.  BTW I should have mentioned this before... the Dwell vs RPM table is a multiplier to the Dwell vs Batt V table.  When Dwell vs RPM is 100%, you get 100% of the current Dwell vs Batt V table.  If Dwell vs RPM is 50% and Dwell vs Batt V is 3ms, you'd get 1.5ms of dwell.  

azfiveoh
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Thanks for confirming I did

Thanks for confirming I did my math correctly.  As a best practice is it better to leave the Dwell vs RPM table at 100% and adjust the dwell time in the Dwell vs Battery table until such time that the coil dwell needs to be low enough that it demands modifucation of the multiplier?

Our of curiousity, do the Dwell vs RPM and Dwell vs Batt tables in AEM Pro do the same thing or are the functions flipped as Dwell vs Batt Volts is given in %.

As always, thanks for your help.

AEM_NS
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It really doesn't matter how

It really doesn't matter how you configure the dwell tables.  100% and 3ms is the same thing as 200% and 1.5ms is the same thing as 50% and 6ms.  At 1ms of dwell for a CDI, you've basically got nothing to worry about.  It's a special rule of mine to not look at Series 1 stuff any more, sorry.  wink

azfiveoh
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AEM_NS wrote:

AEM_NS wrote:

 It's a special rule of mine to not look at Series 1 stuff any more, sorry.  wink

Haha, no worries...I was just curious about the change and more specifically why the change was made.

I do have another question regarding MAF and the Series 2.  There was a lot of discussion surrounding using MAF with the Series 1 back in the day and it was sort of accepted that while the series 1 had the ability to run with a MAF the intent was to move to speed density.  I'd changed to a smaller cam which is much less "choppy" so there is minimal intake reversion that would cause the MAF to get bad readings.  MAF technology has come a long way and I've got a MAF sensor that has been calibrated to the injectors in the car and to a flow rate that is matched to the max potential horsepower of the engine. The manufacturer claims better than 2% error across the range.  I have a 30 point transfer function for the meter and had it bench calibrated at the voltage points in the AEMPro software so I could be as exact as possible.  Even with all that I was never able to get the MAF to work with the series 1 and finally just gave up. What are your thoughts about MAF on the series 2?  I would like to use MAF for the drivability aspect but don't want to spend a bunch of time wiring the function back in only to find that the system is not really desinged to support high flow MAF sensors.

As always, thanks for your help!

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