Pelican Parts Forums - Is the MSD Blaster igntion coil compatible with the CDI unit in the 1973.5T 911?

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- - Is the MSD Blaster igntion coil compatible with the CDI unit in the 1973.5T 911? (http://forums.pelicanparts.com/porsche-911-technical-forum/897276-msd-blaster-igntion-coil-compatible-cdi-unit-1973-5t-911-a.html)

Quote:

Originally Posted by rick-l (Post 8953397)

That "I" core has a pretty big air gap

Which is why the ampere turns using an "I" results in less magnetic field strength than an "E & I" core.

Quote:

Originally Posted by wwest (Post 8953424)

Which is why the ampere turns using an "I" results in less magnetic field strength than an "E & I" core.

An inductor (or a flyback transformer) will typically have an air gap where a transformer will not. What point are you trying to make?

Quote:

Originally Posted by rick-l (Post 8953396)

That would be great if any of the systems discussed here had a Royer oscillator. All the systems discussed here have a flyback. The energy is returned to the battery.

Where are the 60% losses due to eddy currents you discuss?

Never said anything about eddy current loses.

Eddy current loses result from the molecular structure of the core material and induced current flow in that material.

The subject matter regards the amount of magnetic flux vs ampere turns.

Example: 1 ampere turn with an "I" core transformer or inductor will be produce "N" levels of magnetic flux, whereas 1 ampere turn in an "E & I" core transformer or inductor will produce "N" * X levels.

In the linked document X = 1.6

This is all very interesting but what is the answer to the ORIGINAL question?

Can I safely use a MSD Blaster coil?

Quote:

Originally Posted by HarryD (Post 8953720)

This is all very interesting but what is the answer to the ORIGINAL question?

Can I safely use a MSD Blaster coil?

Yeah, what he said!

There is no data on any of them so it is just an opinion.

But what fun is that when you can rewrite scientific laws?

I think when you get by all the dick swinging the answer is yes.

Quote:

Originally Posted by Sunroof (Post 8943233)

My car has been known to suddenly die after a long run on the road and I thought it might be fuel related. Lately though someone suggested that the MSD Blaster ignition coil I installed might be overheating and causing the shutdown after a nice run with the car. The questions came up as to whether I was using a non-resistor rotor? does the Blaster has an internal resistor? or I have external ballast resistor?

I do use the 6500 rpm cut off rotor, which I just realized is not the "non resistor rotor". I will switch to the non resistor rotor, but can anyone shed any light on what's going on with this system set up. And yes, I have bought the silver made in Brazil coil, which failed me miserably after purchase.

thanks

Bob
1973.5T

Post having the tach jumping, over-voltage episode, new alternator installed, my '78 acted as you say. Engine shut-down randomly after a period of running flawlessly.

Discovered that cooling the CDI box, garden hose water spray, would result in the car starting back up right away. Your CDI box may be overheating, or the MSD blaster. The latter becomes more probable if you non-resistor wiring and/or sparkplugs.

Quote:

Originally Posted by HarryD (Post 8953720)

This is all very interesting but what is the answer to the ORIGINAL question?

Can I safely use a MSD Blaster coil?

Found this old thread (http://forums.pelicanparts.com/porsche-911-technical-forum/653610-911-sc-no-start-perma-tune-question-2.html) where various
CDI coil values are indicated and linked to in post #29. Maybe helpful in choosing
a replacement CDI coil.

Quote:

Originally Posted by wwest (Post 8953004)

"I" core: That 60% energy level loss due to magnetic field "leakage" will be dissipated as HEAT with in the coil structure.

(Page 48)

http://www.worldphaco.net/uploads/CAPACITIVE_DISCHARGE_IGNITION_vs_MAGNETIC_DISCHARG E_IGNITION..pdf

I have no idea where you got the 60% number from that article. The referenced refers to 16% or 28% efficiency transferring energy from the capacitor to the inductor which was derived on page 42. If the core heats up it is due to the resistance of the windings not leakage inductance.

Page 48, figure 34, Bosch GT40 cannister coil, 17mj.

Page 49, figure 35, Bosch GT40T transformer "coil", 28mj

http://forums.pelicanparts.com/uploa...1452626150.jpg