If you guys (Ed and Al) don't mind, I'd like to propose a test.  At your convenience, and I'm not kidding- don't make any special trips, or go to any real effort.  Could each of you run at low power, below the staging point, maybe 1500 rpm, and enable only one set of injectors at a time.  I'd be interested to see what position on the mixture knob you have to use for each set.  On mine, I have to turn the mixture knob to about 9:00 for the Mazda 550's, and about 3:00 for the MSD's.   

 

The test will be interesting, since (as I recall) Al has Mazda 550's as primaries, and also has the same MSD's that flow about 500 as secondaries.  I can't recall if I've ever seen the physical layout of these though.  Are they all the same distance from the rotors?

 

 

Sorry, it will be months yet until my engine runs again.  It ran on the dyno, now waiting to run on the airplane.

 

RC Engineering measured 570 cc/min on my Mazda injectors that I used as primaries.  I have no measurements on the MSD 2013s.  You can see on the attached photo the 570s are in the rotor housings and the 2013s are out in the TB.  

 

I’m not surprised at your mixture knob settings.  Mine were even more extreme.  I don’t recall ever running on the MSDs only below the staging point.  For the 570s I had to turn the mixture knob as far as it would go to get enough correction at idle, and then it may still have been a bit rich.  But I was running with a constant pressure fuel regulator at 40 psi.

 

I’ve changed to a MAP referenced regulator, and I’m planning on switching the wiring to run the MSDs as the primaries (if my wiring harness allows; I have completely separate wiring to the two sets coming from different sides).

 

BTW; a plug for TWM Induction.  I returned my constant pressure regulator and they very promptly swapped my old fittings into a new MAP referenced body and returned it to me – NO charge.  A bright spot in my day.

 

Al