Originally Posted by Ben
I'm thinking something along the lines of a mbc that vents through a needle valve instead of a standard port. Then you could control the pressure dump pretty precisely. Whatchya think?
I spent a little while thinking about this. Essentially the concept creates a rising rate fuel pressure regulator with 2 stages of rise. 2 stage linear, not progressive like I wrote in an earlier post. The first stage would be absolutely identical to a current FMU where the FMU builds fuel pressure with MAP linearly where the rate of fuel pressure rise is controlled by bleeding pressure to atmosphere at the needle valve. The second stage would start at the point when the pressure relief valve opens. When the prv opens, we can then vent additional pressure to atmosphere at a time determined by the prv's pop open point and a rate determined by the second needle valve.
So let us assume that we set our stage 1 needle valve bleed to rise fuel pressure at the rate of 8 psi to every 1 psi of boost pressure. Let us then assume we set our pressure relief to open after 4 psi of boost pressure, and we set our second needle valve to increase fuel pressure at the rate of 3 psi to every 1 psi of boost with any boost over 4 psi
Result of above assumptions:
1 psi boost pressure --> +8 psi fuel pressure
2 psi boost pressure --> +16 psi fuel pressure
3 psi boost pressure --> +24 psi fuel pressure
4 psi boost pressure --> +32 psi fuel pressure
5 psi boost pressure --> +35 psi fuel pressure
6 psi boost pressure --> +38 psi fuel pressure
12 psi boost pressure --> +56 psi fuel pressure
Bear in mind my assumed rates are arbitrary, so observe the data as conceptual/hypothetical, but not necessarily correct for the application.