Jump to content
Sign in to follow this  
Guest Anonymous

Coil ballast resistor combo?

1 post / 507 viewsLast Reply

Recommended Posts

Guest Anonymous

Helping a friend track down an elusive high speed miss. His modified tii was running the ubiquitous blue coil along with a CD unit. The ballast resistor, which appears to be original, was bypassed. I decided to swap coils with the original black coil from my 72 and reconnected the ballast. (Engine ran the same except high speed miss disappeared.) Since I pulled out several coils (just in case) and I had my fluke handy, I decided to measure the various coils and ballasts for their resistance and my results were a bit different then what I expected.

______________________________

Two "black" coils (from a stock 02 and a 73 e9) each coil measured 1.3 ohms.

Two Bosch "red" coils, each measured .8 ohms.

Two Bosch "blue 227" coils each measured 3 ohms.

One yellow accel 8401 coil measured 1.2 ohms.

Three ballast resistors (including the bosch ballast resistor mounted on the tii ALL measured .8 ohms.

_______________________________

I have read Zenon's comprehensive review of the various Bosch coil offerings Black, Blue and Red. http://www.bmw2002faq.com/content/view/69/32/ I have also read other's analysis and interpretation of what is supposed to work and what really works. http://www.ratwell.com/technical/BlueCoil.html and http://www.356registry.org/Tech/coil-blueblack.html http://rb-aa.bosch.com/boaa-pl/Product.jsp?prod_id=70&ccat_id=32&language=en-GB&publication=1 Now, I am not so certain there are any absolutes given the advanced age of these cars and their installed ignition components.

Zenon's post recognized that some of the early black coils and ballasts resistors were .9 ohms. This might account for the some of my measurements for the ballasts, but not the black coil measurements. Again, the black coils measured twice the resistance reported by Zenon, but maybe they were newer "post 72" coils. Zenon also suggested the red coils would need more resistance and might need two .9ohm resistors in series to prevent damage to the (red) coils.

Since the measured resistance of the red coil matched the ballast resistors on hand, it seemed the simplest and most logical route to use that formula. Are we missing something?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  



×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.