best ignition coil to use with CDI+ classic retrofit

[matt2000]

Hi guys,

quick questions for the users of classic retrofit CDI+ :
which ignition coil are you running and did you need to change any of the base settings on the CDI+ ?

I understand the bosh one is best, but that reliability is terrible. So I am looking for a viable alternative.

Best,

Matt

[QueWhy]

Original Bosch is the best and most recommended. I just continued to use the dreaded silver coil my car came with. Two years later the CDI+ and silver coil are still working just fine.

This thread Coils for CD+ ignition has a lot of good info. Unfortunately the thread title keeps it from being found via search.

[Sunroof]

Sent you a message Matt........................

[Jonny H]

CDI+ requires a genuine Bosch CDI coil part number 0221 121 00X (where X could be 1 to 6) or equivalent when used with the default settings.

Why? The characteristics of the original coil allow it to charge and discharge at a rate faster than other coils available. This allows us to fire two sparks with an interval of just 400us (microseconds).

Other coils can take almost twice as long to recover from firing which makes the additional spark too late in the firing cycle to gain any performance benefits.

Other 'slow' coils can be used with CDI+ but it requires increasing the spark interval using the software (which is on our website).

Why does my car run on other coils with a Bosch CDI but not CDI+? This is because the coil is too slow to react, CDI+ second spark effectively 'cancels' the first one. Symptoms: sometimes the car will idle but not pull under load, otherwise not start or run at all.

[digitaldgp]

I bought this and it works great on my 1970 911. After John Walker told me I needed a new coil for a better spark.

https://www.************.com/p-1586-cdi-ignition-coil-by-************.aspx

1970 Porsche 911 CDI Ignition Coil by ************ parts classic.

[matt2000]

Thank you all for your advice. it seems that there is indeed one coil to rule them all ;-)

Matt

[WelchW]

Thanks for sharing, I found a lot of interesting information here. A really good post, very thankful and helpful that you will write many more posts like this one.

[donbecker1234]

Another vote for _P_ arts _K_ lassic coil. I read a ton of threads and couldn't find anyone complaining about that one.

[Jonny042]

Originally Posted by Jonny H

CDI+ requires a genuine Bosch CDI coil part number 0221 121 00X (where X could be 1 to 6) or equivalent when used with the default settings.

Why? The characteristics of the original coil allow it to charge and discharge at a rate faster than other coils available. This allows us to fire two sparks with an interval of just 400us (microseconds).

Other coils can take almost twice as long to recover from firing which makes the additional spark too late in the firing cycle to gain any performance benefits.

Other 'slow' coils can be used with CDI+ but it requires increasing the spark interval using the software (which is on our website).

Why does my car run on other coils with a Bosch CDI but not CDI+? This is because the coil is too slow to react, CDI+ second spark effectively 'cancels' the first one. Symptoms: sometimes the car will idle but not pull under load, otherwise not start or run at all.

I'm using the P-Klassik coil, with fantastic results, but have nothing to compare it to. They advertise that it has a 100 to 1 turns ratio, Jonny, do you know if it indeed compares to the genuine Bosch part in it's ability to charge and discharge quickly?

[blucille]

funny. not really. I bought 2 of the p-(k)lassic coils, they both failed in just a few years. I reached out to PK to see if they've updated their design to fix whatever issue is causing the failure, and got no reply. I then searched and found some spare old Bosch black coils and have been running these ever since.

[mysocal911]

Originally Posted by Jonny042

I'm using the P-Klassik coil, with fantastic results, but have nothing to compare it to. They advertise that it has a 100 to 1 turns ratio, Jonny, do you know if it indeed compares to the genuine Bosch part in it's ability to charge and discharge quickly?

This problematic issue only relates to the very marginal second ignition pulse of the CDI+, and to a lesser extent to the shorter first pulse
when compared to either the Bosch or MSD ignitions, thus providing a questionable ignition replacement benefit.

Please consider reading how a CDI ignition functions and what are the critical design parameters. There're many insightful threads here on the Pelican Parts Forum
over the last 15+ years.

[groovydude]

Specs on the P-Klassic Coil vs Bosch (from P-Klassic):

Inductance 100 uH
Leakage Inductance 18 uH
Capacitance 15 uF
Primary Resistance .4 Ohms
Secondary Resistance 160 Ohms
Current Rise Time 4.3 uS
Duration 30 uS
Peak Current 106 Amps

Specs on the new Bosch coil:
Inductance 908 uH
Leakage inductance 402 uH
Capacitance 918 uF
Primary Resistance .6 Ohms
Secondary Resistance 749 Ohms
Current Rise Time 7.15 uS
Duration 56 uS
Peak Current 54 Amps

Although there's no spec for time it takes to recharge and fire again, the faster current rise and shorter duration would suggest that the P-Klassic coil is up to the task.

[Jonny H]

The PK coil is indeed pretty close to the spec of the Bosch CDI coil and it does have the rapid charge/discharge characteristics. They do work well with our system but we did have some longer term issues with robustness.

[WelchW]

This works really well for us, thank you! Facing same issue here. Help is appreciated.


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