Fun Chaos! MSD, Fluke 88, Blaster & Tachs
 

Calling all MSD experts and Ignition Gurus!!!!!!!!!!!!!!!

Mystery:
Fluke 88 shows 950 RPM
Tach shows 950 RPM
Trusty old Engine Analyzer shows 3000 RPM
Car runs awesome (I think).





Here are the tools and units:

Brand new Fluke 88 (calculates RPM from ignition wire)
Electronic, but old, Engine Analyzer (calculates RPM from coil)
MSD 6AL
MSD High Vibration Coil
1983 911 SC
1982 911 SC

History:
MSD 6AL and HighVib Coil installed on the '83. Hooked up old Engine Analyzer to determine RPM and analyzer's RPM matches car tach's RPM. Super fun and pretty happy with the results -- especially the experience.
Scraped $$ and bought Fluke 88 to replace old Engine Analyzer,
MSD6AL, HighVib Coil, new caps and rotors for the 1982 SC.

Installed units on the 82, fired her up, no problem and very happy with the results.

Mysteries...... and I NEED HELP!
My old Engine Analyzer must now be connected with the black wire to negative and the red wire to the positive side of the coil. On both 82 and 83 SC! I have had this unit for 20+ years and prior to MSD, I connect the opposite (black wire to ground and red wire to negative post of coil). Although I am not worried, what gives with MSD as far as the reversal of polarity? And yes, I dug up the manual and it is black to ground and red to negative coil post.

On the 82 SC, my tach and the fluke 88 both show about 950 RPM. However, while the old engine analyzer shows about 3000 RPM (three thousand). What's going on with the coil?? This worries me a lot!!!

Thinking I have a faulty engine analyzer, I hooked up the engine analyzer on the 83 SC. Now, the tach, engine analyzer and fluke 88 all show almost same numbers.

What is going on with my reading on the 82? The car runs fine. Is my distributor faulty? Is my coil on the 82SC firing 3 times more than what is required? Help!!!!


p.s.,

On the MSD, I did cut the right wire for 6 cylinder cars (red wire).

The polarity of the connections on the ignition coil doesn't really matter.
It only determines how the electrons will flow at the spark plug, e.g. from
the center electrode to outer (body) electrode.

Remember: The MSD produces multiple sparks (6 to 10) below 2000 RPMs
and decreases as the RPM increases. This causes any test device that's
connected to the coil to indicate an incorrect RPM, i.e. a higher RPM than
the actual value. Your tach signal has a special output from the MSD which
produces only one pulse per cylinder fire.

Loren/Fellow crotch rocketeer,

Thanks for the 'warm and fuzzies...'

If you have further input, could you explain why on the 83 SC, the same setup resulted to same 950 RPM off the engine analyzer, tach, and fluke

Put a scope on each and you'll probably find that multiple sparks occurred in
one setup and not the other. Check your setups and MSD connections closely.

Any tester placed on a coil which has multiple sparks will indicate an incorrect
RPM. The tester doesn't known that each cylinder is getting multiple sparks,
so it can't adjust the indicated RPM for the multiple sparks which vary with RPMs.