Originally Posted by
kingtal0n
Well it sure sounds like you know what you are doing. Vacuum test, check. Vacuum reading, check. Vacuum reservoir volume/rate, check? At this point I would tentatively suggest (not sure its worth doing or even possible but it is an lightly engineering consideration) if you're going to go through all the trouble of increasing the vacuum capacity using external reservoir: Perform some calculation to find out roughly how much pressure and how much volume the brakes use per 'stroke' in a worst case scenario and determine the necessary volume for each available pressure scalar. For example 12" with 2L capacity might work for 3 full braking strokes but 18" with 1.5L might also work similarly. Then you could find the minimum volume which would maximize the pressure signal per unit mass evacuated from the reservoir. In other words pressure drop derivative (rate of change) is maximized at some minimum volume given a constant flow rate supply source. The vacuum pump for example would much more quickly supply 18" to a small reservoir than a large one, but I am not a braking expert and no idea how the pressure vs volume plays a role at the pedal feel and braking influence. It may respond more favorably to a large volume of mediocre pressure or a small volume of very low pressure. Thats where the arduino comes into play- you can test various MAP start points for the pump and find the ideal setting with minimum pump run-time (wear) much easier done empirically than mathematically I guess.
