MSD6AL little issue , help needed please mates !!!

[cdrik915]

Hi !!!

I post here this problem for a friend , sc owner 's (and SWDP member)

A MSD6AL has been installed on his 911 SC , all works great and the engine seems to be more punchy.

BUT , i've a doubt concerning the MSD model : is PN 8910 the good version for a 82' SC ???

Or is PN 8910 EIS the good one ???


The trouble is that the REV counter goes up without problem to 3000 t/mn , and start to jump after.

Could you please help me ???

[James Brown]

Yes the MSD 6AL p/n 6420 has a rev limiter on the bottom of the unit, check what RPM it is limiting to. Also, a SC does not require the tach adapter, remove it if it is installed. The coil should be the high vibraition Blaster coil. Other than that, the 6AL is the correct unit for a SC.

[DUK]

3000 rpm is where the multi-spark quits, I had the same problem and had to use the 8910.

[cdrik915]

Thanks , and could you precise me HOW to connect the 8910 please ????

Thanks per advance ,

Ced'

[JFairman]

Did you cut the wire under the little round cover to calibrate the rev limiter to a 6 cylinder motor?

Thats explained in the instructions and by default they are set up for 8 cylinder engines.

cut both wires under there and it's calibrated for 4 cylinders

[James Brown]

Yes cut the RED wire, if not already done. You can visit msdignition.com and download the installation instructions for free. But, the wiring diagram is on the back of the unit, if it's not, the heavy red wire goes to a constant 12V source like the starter, heavy black goes to a good ground source, red goes to the ignition switch, orange to the + on the coil, black to the - on the coil, violet and green to the distributor, white-do not use, purple wire from tach. to the plug on the MSD unit. Thats it.

[James Brown]

Crap, sorry, didn't read the WHOLE story!!!The 8910 is the TACH ADAPTER. the 911sc does not require the adapter, just plug the violet tach wire into the MSD unit (like I did) and it should work. The tach adapter is for old tach's that can't read a square wave digital signal.

[cdrik915]

Really thanks guys !!!

I'm trying all that !!!!

[haycait911]

the MSD tach output doen't work with all SC tachs. try the output first, if tach isn't operating properly you'll need the adapter installed. my SC tach needed the adapter.

cutting the wires for the number of cylinders is only so the RPM pills work correctly. the unit will work fine with any wire cut but the rev limit pill will be off.

[cdrik915]

Ok.

Now it's more clear .

Thanks.

Subsist an issue : the tachmeter works great and perfectly on the 1/2/3 gear , going normally to 6000 RPM.

BUT , and the problem is there : on 4 th gear or 5 th gear , it runs up to 3500 RPM exactly and seems to becoming crazy after this precise value , but ONLY ON 4 AND 5 TH GEAR !!!

Could it be an internal problem of welding failure???

Your thoughts ???

[LUFTMAN]

replace porsche tach (not very accurate) with a autometer unit problem solved.