[T3] Spark Plugs & Ignitions

[Daniel K. Du Vall]

I agree on the CDI. I run an MSD 6A on my 72 right now and also gap them more than stock. I ran the w7-w6 on my cars in Arizona never had a problem but then again getting up to temp was never a problem there either ;-)

Engine performance and diagnosis was my best and favorite subject in school so I am always tinkering with it. Can't wait to get to tinker with the Mega Squirt and the many options there are with it.

Daniel Du Vall
72 Squareback
74 (Standard) bug
04 Golf TDI
99 Chevy Z71
Destination unknown!



-----Original Message-----
From: type3-vwtype3.org [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: Saturday, June 28, 2014 8:44 AM
To: type3 at vwtype3.org
Subject: Re: [T3] Marigold's story

On 28 Jun 2014 at 4:13, Daniel K. Du Vall wrote:

> 	 I would have to agree on the use in more modern cars. One thing I 
> know is that when used in modern ignition systems they tend to last 
> longer. I got well over 100k on a set in my 99 Chevy and could never 
> get that on an older HEI system in my 77 Chevy. I tried them in my bug 
> years ago and they seemed to ware much faster.  Maybe this was a fluke 
> but I tend to lean on what I have observed.  I run Bosch coppers W6 or
> W7 on my air cooled and Sometimes NGK I have a set of ND Right now 
> only because I had them and they were new seem to run just fine.

Why not W8, as that's what's recommended? I'm guessing those are colder plugs that may not get up to the proper self cleaning temp. 
Unless you're racing or doing exclusively very high speed driving, colder plugs are counterproductive. I used to do this, too, until I learned what the heat range actually meant for a spark plug. I still have some Bosch W175T1s if anyone wants them. (That's the next colder plug from the previous Bosch numbering system. Standard was W145T1.)

Any car with a Capacitive Discharge Ignition (CDI) system will get long plug life. The difference is that the CDI spark is extremely short, so there's less time for the electrode to ablate. As a rough estimate, the CDI spark is about 10% as long in time, so we would expect to get about 10x the mileage out of them.

I'm not sure about today's standard HEI systems, whether they are similar or not, but I think it's a reasonable guess. Our '96 Taurus had a 100k service life on it's platinum plugs and I don't think I got around to changing them until about 120k. At that point, I'd have to say that they were still just fine.

I've had Bosch Platinum plugs in both standard (Kettering) ignition system cars and cars with CDIs. They work just fine in either one, but I expect to get much longer lifetime in those cars with the CDIs. 
Most of the time, I frankly don't see much difference in plugs. They all seem to work about the same.

BTW, it took me a LONG time to figure out what to look for to determine if a plug was worn out. I finally realized that there are 2 things to look for:

1) Look at the insulator. It should be light tan. If it's brite white it's either too hot a plug and/or the engine is running too lean. If it's black, it's either too cold a plug and/or the engine is running too rich.

2) Look at the corners on the center electrode and the edges of the ground electrode. You want them to be nice and square. As the plug fires, those corners get ablated away and get rounded. Once you see those corners get "soft" it's probably time to replace the plug.

A CDI or HEI will fire those plugs long after a Kettering spark will no longer jump the rounded corners, so that also adds to plug life.

A few years ago I had a squareback that I had not serviced for several years that began to start hard even though it had one of my Delta CDIs. When I finally got around to looking at the plugs, the center electrode was fully hemispherical and mostly recessed below the top of the insulator. Those were standard Bosch W8ACs. That demonstrated how good my Delta CDIs were and how much better they fired than the standard ignition.

Yes, I buy, refurbish, repair, and resell the old Delta CDIs. I have them in all my old VWs. I've been using them since 1966 and they are great! I have a number of them ready to sell right now. Prices range from $100 to $150, depending on the model and whether it is used or NOS.

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