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Discussion Starter #1
I was playing around on the dyno today (DynoJet) and thought I would share some of my findings. The initial plan was to test a new circuit board that would modify some of the sensors. While this testing went well (in the mid-range I picked up ~25 hp and ~33 lbs-ft of torque), what really stood out to me was the shape of the curves (very jagged). Based on my past experience it appears that this engine has a weak ignition system and as you push it (with more boost), it starts to misfire. So, next project will be improving the ignition system. As they say - stay tuned.
 

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evospider: I am pretty sure we were the first to encounter problems with this car's weak ignition and we have this issue resolved. On our site you can find three good replacement options. In order of price, they are Okada, Alfa Romeo 4C, and Ngen. All are on our site, the first two are here: https://shopeurocompulsion.net/collections/abarth-engine?page=2 and the Ngen packs are here: https://shopeurocompulsion.net/collections/abarth-engine?page=3

That said, if you close up your spark plug gap a little that will typically solve a minor ignition break up associated with higher boost. I seriously doubt your car needs stronger coil packs at this point.

Greg
 

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I had bought these for my Dart, but never got around to installing them. Guess where they are going now? ;)

 

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Based on my past experience it appears that this engine has a weak ignition system and as you push it (with more boost), it starts to misfire.
Interesting observation, but are sure that it's not a vibration? Engine mounts, cowl shake, tire hop, etc. I also wonder if the stock diverter valve causes any oscillations in the dyno curves. Could the torque curve be smoother with a performance diverter valve?
 

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Can't discount the possibility that the graph is really what the 124 Spider's delivery looks like since I can't find another one for comparison. Would like to see another dyno run from you after you've improved the ignition system.
 

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Discussion Starter #9
I am pretty sure about the ignition breakup based on some other runs I did with different boost settings. Though high performance coils and tighter plug gaps may help on the dyno, they can actually reduce normal day-to-day drivability and fuel mileage. Typical factory ignition systems are inductive (as opposed to CD or Capacitive Discharge) which means a relatively long spark duration but not as intense a spark. CD systems, on the other hand, create a very intense but very short spark (this is why many CD systems are a multi-spark). In normal driving (NOT extended high rpm), an inductive type spark is very beneficial as it will typically ignite (and thus burn) the complete air/fuel mixture.

Going back to the high performance coils and tighter plug gaps, these help by either increasing the available voltage to jump the plug gap (coils) or reducing the required arc-over voltage (tight plugs). What happens in both cases is that you are trading current (amperage) for voltage. Unfortunately, current is what heats the air/fuel mixture to the point of combustion. Case in point - if you have ever been "zapped" by a bad spark plug wire, you probably felt 10,000-20,000 volts but milliamps of current (which is why you are still alive). Conversely, if you stick your finger into a light socket, you would only see 120 volts yet 10-15 amps of current (and may not be alive to read this).

Based on the above, what really needs to happen is to truly amplify the spark (increase power - watts). Think about a good stereo amplifier - same idea. This is what I will be testing in the coming week or two.
 

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I am pretty sure about the ignition breakup based on some other runs I did with different boost settings. Though high performance coils and tighter plug gaps may help on the dyno, they can actually reduce normal day-to-day drivability and fuel mileage. Typical factory ignition systems are inductive (as opposed to CD or Capacitive Discharge) which means a relatively long spark duration but not as intense a spark. CD systems, on the other hand, create a very intense but very short spark (this is why many CD systems are a multi-spark). In normal driving (NOT extended high rpm), an inductive type spark is very beneficial as it will typically ignite (and thus burn) the complete air/fuel mixture.

Going back to the high performance coils and tighter plug gaps, these help by either increasing the available voltage to jump the plug gap (coils) or reducing the required arc-over voltage (tight plugs). What happens in both cases is that you are trading current (amperage) for voltage. Unfortunately, current is what heats the air/fuel mixture to the point of combustion. Case in point - if you have ever been "zapped" by a bad spark plug wire, you probably felt 10,000-20,000 volts but milliamps of current (which is why you are still alive). Conversely, if you stick your finger into a light socket, you would only see 120 volts yet 10-15 amps of current (and may not be alive to read this).

Based on the above, what really needs to happen is to truly amplify the spark (increase power - watts). Think about a good stereo amplifier - same idea. This is what I will be testing in the coming week or two.
Awesome explanation and I'm excited to see what you find out.
 

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Discussion Starter #11
Here is an update since last week:

I took one of my old prototype ignition amplifiers and made a custom wire harness to connect to the coils. I then bought a new set of stock NGK spark plugs and re-gapped them to 1.2mm (0.048") from the stock 0.6mm (0.025"). As a note, don't try to gap these type of plugs if you do not have the correct tools (which I do). Anyway, with the stock coils/ignition but larger plug gaps, the engine fell on it's face as boost came on (as expected). I then hooked up the ignition amplifier and went for a run. First thing was how smooth it takes off from a stop. Next, it pulls fully through the rev range (even though I am running higher than stock boost). As an added bonus, my fuel mileage seems to have increased as well.

I will continue testing and tweaking (I'm going to try different plug gaps and power output) and update with future developments.
 

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Here is an update since last week:

I took one of my old prototype ignition amplifiers and made a custom wire harness to connect to the coils. I then bought a new set of stock NGK spark plugs and re-gapped them to 1.2mm (0.048") from the stock 0.6mm (0.025"). As a note, don't try to gap these type of plugs if you do not have the correct tools (which I do). Anyway, with the stock coils/ignition but larger plug gaps, the engine fell on it's face as boost came on (as expected). I then hooked up the ignition amplifier and went for a run. First thing was how smooth it takes off from a stop. Next, it pulls fully through the rev range (even though I am running higher than stock boost). As an added bonus, my fuel mileage seems to have increased as well.

I will continue testing and tweaking (I'm going to try different plug gaps and power output) and update with future developments.
Why did you gap the plugs up to .048 instead of leaving them closer to stock??...i believe I know the answer but would like to hear your explanation...;)
 

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Discussion Starter #13
The reason to open up the plug gap is to expose more area to the air/fuel mixture. Contrary to most people's thoughts, just having a spark in the chamber won't always ignite the mixture. In fact, it is not the "spark" that ignites the mixture but the heat from that spark. And that heat comes from the amount of current (amperage) that is allowed to flow across the gap.

When a spark is initiated, it is due to high voltage (10k-20k volts typically) but once the electricity has jumped the gap it only requires 500-1,000 volts to maintain. This is where the current comes into play. By "pushing" more current into that spark, you are creating more heat and heat is what ignites the mixture.

Inside the combustion chamber at light throttle, there is very little air & fuel floating around. In order to complete the combustion process you need to heat the mixture to the point of combustion (~485°F in a typical four stroke gasoline engine). That heat comes from the current flowing through the spark gap. The larger the gap, the more likely you are to "find" the air/fuel mixture.

As a side note, wide open throttle is the easiest mixture to ignite while small throttle transition (such as normal takeoff from a stop) is the most difficult.

Hope this helps.
 
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