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-   -   MSD-5. Still an upgrade? Beating Rich Misfire. (https://forums.turbobricks.com/showthread.php?t=346289)

maxitoman007 11-29-2018 05:36 PM

MSD-5. Still an upgrade? Beating Rich Misfire.
Found an MSD-5 ignition box for really cheap right here in the city. was wondering if it would have the same effect as say an MSD-6a. Anybody have any experience using these boxes? My 87 740 Turbo with mods is suffering from weak spark and pretty rich AFRs so I'm currently looking for a cheap solution to light my wonky ratios.

Here's the box:

dbarton 11-29-2018 07:27 PM

I've put a few MSD 6a boxes in my 240s over the last 20 years, but I don't know about the 5. That one looks like an antique.

My reason was to cure spark blowout under boost (over 12 psi) and it solved it each time. Before the MSD I could only reduce blowout by closing the spark plug gap to about half of normal. With MSD I could actually run a much larger gap than normal, but I don't these days.

I don't know if it will help with an over-RICH misfire though.
Dave B

maxitoman007 11-30-2018 01:03 AM

Fair enough. There is an MSD SCI which is has the same guts as an MSD-6a but just a different case colour for quite cheap around here at $90 CAD so I'm thinking that might be the best route.

lummert 11-30-2018 09:28 PM

Have you tried lowering the fuel pressure?

maxitoman007 12-01-2018 02:30 AM


Originally Posted by lummert (Post 5888948)
Have you tried lowering the fuel pressure?

I have not, however my base Idle is around 14.4 which isn't too bad so I figure my issues arise from using LH 2.2 fuel maps without the usual conditions (20psi+). Only tuning I've done is through leaning out the mixture using the MAF as much as possible. It seemed to work for a while and I would get a good burn all the way to red line however it has gotten progressively worse. It started with just a large flat spot in the powerband when the mixture got rich to the point where it couldnt be ignited, however power would come back once boost leaned out the mixture and it was once again able to burn. Now however, it is as if this flat spot is endless...

If you want more info on the issue, I have a thread about it here (I'm pretty sure you made a few posts in there...):

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