BOSCH BLUE COIL
BOSCH BLUE COIL
RL Technical Advisor
Joined: May 2001
Posts: 11,870
Likes: 75
From: Portland Oregon
Gents:
That Bosch blue coil has been around for ages, and its intended to increase the output on the old point type systems found in VW's, 356's and pre-69 911's.
Its not for any CD systems as the turns ratio (impedance) is not correct for those ignitions. Use the Bosch coil on CD sytems with either the Bosch or Permatune CD's; 3-pin or 6 pin.
The Motronic coils are different.
You really cannot beat the stock Bosch coil that is found on the CD-equipped cars from the factory for these years.
We only replace the Bosch coils when using MSD CD boxes.
[ 07-09-2001: Message edited by: Steve Weiner-Rennsport Systems ]
That Bosch blue coil has been around for ages, and its intended to increase the output on the old point type systems found in VW's, 356's and pre-69 911's.
Its not for any CD systems as the turns ratio (impedance) is not correct for those ignitions. Use the Bosch coil on CD sytems with either the Bosch or Permatune CD's; 3-pin or 6 pin.
The Motronic coils are different.
You really cannot beat the stock Bosch coil that is found on the CD-equipped cars from the factory for these years.
We only replace the Bosch coils when using MSD CD boxes.
[ 07-09-2001: Message edited by: Steve Weiner-Rennsport Systems ]
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Joined: Jun 2001
Posts: 556
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From: Peoples Republic of Long Beach, N.Y.
Steve Weiner please reply to this:
I would be happy to clear this up for you. There has been confusion due to technical requirements of two completely different ignition systems used in the same engine configuration (911). Just because both the Perma-Tune and Bosch 3 pin boxes will pug into the same car doesn't mean they are copies of the same design theory. Both have the same electrical properties that allow them to work in the 911, the pin connections are the same, the triggering circuit is the same and the current path through the coil primary is the same but they do not work internally in the same way.
The Bosch unit is a fixed oscillator design, which is what you hear when power is applied to the box. The oscillator is working at a frequency audible to the human ear. In essence, the Bosch unit works at maximum operation but only emits a spark when there is a trigger signal from the distributor points. The trigger signal simply releases the next oscillation from the oscillator in the form of a high Voltage pulse to the ignition coil primary circuit thereby creating a spark at the spark plug. The designers of this system matched a specific ignition coil to the ignition box to balance the inductive load between the oscillator and the ignition coil. This inductance relationship is a close tolerance thing so the ignition coil requirements make it more like a transformer than a simple coil. Upsetting the balance by introducing a faulty coil, or the wrong coil, will cause damage to the ignition box and or adversely effect the engine performance. Since the most common cause of failure of these boxes seems to be the result of oscillator failure, a faulty transformer ( coil ) is usually to blame. For this reason Perma-Tune always has recommended the replacement of the ignition transformer when the ignition box is replaced. This is just logical reasoning, you would not install new tires on a car and leave the old valve stems in the rim would you?
By contrast the Perma-Tune is a demand system, is does no work until there is a signal from the distributor. This design is called a monostable multi oscillator. When power is applied to the unit, it prepares to make a spark and waits for the command to release it, and then releases it with great precision in relationship to the command signal. Once the high Voltage pulse is released through the coil primary circuit, the unit prepares for the next signal. The Perma-Tune design creates a very short, fast rise time high voltage pulse to the coil. This design is not as sensitive to the inductive load or even coil primary polarity, it will perform the same. The ignition coil characteristics will determine how much and at what voltage the coil primary signal will be transformed to. The original Bosch coil works really well with the Perma-Tune because it is a transformer as opposed to a coil and does a better job magnetically than a coil. It just so happens however that the electrical characteristics of a simple breaker points type coil works pretty good too, at a fraction of the cost.
Since we started including this and much more information in the installation instructions of our products about 8 years ago, the word started getting around that the Bosch blue coil could be substituted and that is where the confusion came in. That is true only for the Perma-Tune, use that coil on the Bosch unit and you have trouble.
To really complicate things, the stampede on Bosch blue coils left the supply short and other low quality substitutes showed up in the supply chain. That is why Perma-Tune has started making ignition coils to replace the original blue design.
Here is a link to more information on the 911:
http://www.permatune.com/Tech_Support/Porsche/911.htm
Here is a link to the coil:
http://www.permatune.com/Product/Porsche/911SCxtra.htm
Here is a link to new Porsche products:
http://www.permatune.com/Product/New%20Product.htm
Lonnie
RoninLB
I would be happy to clear this up for you. There has been confusion due to technical requirements of two completely different ignition systems used in the same engine configuration (911). Just because both the Perma-Tune and Bosch 3 pin boxes will pug into the same car doesn't mean they are copies of the same design theory. Both have the same electrical properties that allow them to work in the 911, the pin connections are the same, the triggering circuit is the same and the current path through the coil primary is the same but they do not work internally in the same way.
The Bosch unit is a fixed oscillator design, which is what you hear when power is applied to the box. The oscillator is working at a frequency audible to the human ear. In essence, the Bosch unit works at maximum operation but only emits a spark when there is a trigger signal from the distributor points. The trigger signal simply releases the next oscillation from the oscillator in the form of a high Voltage pulse to the ignition coil primary circuit thereby creating a spark at the spark plug. The designers of this system matched a specific ignition coil to the ignition box to balance the inductive load between the oscillator and the ignition coil. This inductance relationship is a close tolerance thing so the ignition coil requirements make it more like a transformer than a simple coil. Upsetting the balance by introducing a faulty coil, or the wrong coil, will cause damage to the ignition box and or adversely effect the engine performance. Since the most common cause of failure of these boxes seems to be the result of oscillator failure, a faulty transformer ( coil ) is usually to blame. For this reason Perma-Tune always has recommended the replacement of the ignition transformer when the ignition box is replaced. This is just logical reasoning, you would not install new tires on a car and leave the old valve stems in the rim would you?
By contrast the Perma-Tune is a demand system, is does no work until there is a signal from the distributor. This design is called a monostable multi oscillator. When power is applied to the unit, it prepares to make a spark and waits for the command to release it, and then releases it with great precision in relationship to the command signal. Once the high Voltage pulse is released through the coil primary circuit, the unit prepares for the next signal. The Perma-Tune design creates a very short, fast rise time high voltage pulse to the coil. This design is not as sensitive to the inductive load or even coil primary polarity, it will perform the same. The ignition coil characteristics will determine how much and at what voltage the coil primary signal will be transformed to. The original Bosch coil works really well with the Perma-Tune because it is a transformer as opposed to a coil and does a better job magnetically than a coil. It just so happens however that the electrical characteristics of a simple breaker points type coil works pretty good too, at a fraction of the cost.
Since we started including this and much more information in the installation instructions of our products about 8 years ago, the word started getting around that the Bosch blue coil could be substituted and that is where the confusion came in. That is true only for the Perma-Tune, use that coil on the Bosch unit and you have trouble.
To really complicate things, the stampede on Bosch blue coils left the supply short and other low quality substitutes showed up in the supply chain. That is why Perma-Tune has started making ignition coils to replace the original blue design.
Here is a link to more information on the 911:
http://www.permatune.com/Tech_Support/Porsche/911.htm
Here is a link to the coil:
http://www.permatune.com/Product/Porsche/911SCxtra.htm
Here is a link to new Porsche products:
http://www.permatune.com/Product/New%20Product.htm
Lonnie
RoninLB
