I had a quick thought today - what if we removed the main secondary throttle plates, plugged the holes, discoed the linkages and used advancing throttle body vacuum to actuate the cold-start secondary plates which would now be used as the main secondary throttle?

theoretically, depending on timing of throttle actuation, low end torque would be increased from a higher velocity intake charge at low rpm due to higher manifold vacuum. should make a N/A RX7 more "streetable" with virtually no affect on top-end response / power-band.

kinda like a carter AFB or holley with vacuum secondaries on a V-8.. It's commonly known that on street cars vacuum secondaries are ideal, especially for larger cfm carbs vs. smaller cid engines due to secondary actuation by sustainable manifold vacuum. mechanical secondaries are recommended for drag / race engines.

has anyone done this / heard of this? post you thoughts ~rich

 

1st Gen carbs have this system, and most people remove it to improve throttle response. FC Turbos also have a system that slows the opening of the secondary throttles, and again most people remove it to improve throttle response (TB mod).