NITROUS OXIDE ( nos / n2o ) advice forum

I understand jetting at the solenoid obviously -- but why at the outlet instead of the inlet?

Seems jetting at the inlet would reduce the pressure the solenoid has to operate against which would allow even greater range of response with lower starting percentages at higher pulse rates.

So I must be missing the reason this isn't done.....

Jetting at the inlet of the Pulsoids would pose some problems that jetting at the outlet avoids. Even IF relocating the jet increased the frequency response, the loss of metering accuracy would suffer and precise metering is ESSENTIAL in performance of the system as a whole.

One of many reasons I'll give here is that the volume of the Pulsoid's inner chamber is an additional space that would have to be filled with liquid nitrous to therefore be sent out through the pipework and to the engine. With the piston (or plunger as it's often called) opening and closing, the process of purging out all of the gas would be significantly SLOWER and the flow would be highly INCONSISTENT as the liquid nitrous, disturbed by the piston actuation, would have the opportunity to change phase into a gas and compound the problem. This problem is far worse with smaller jettings as the Pulsoid would then continuously heat up, resulting in further phase change and potential overheating of the coil.

Pulsoid frequency response increases would have to take place in a new design rather than a band aid. With the REVOs being available, the point is moot.

Makes sense -- basically it's the expansion issue rearing its ugly head in a different manner. Knew there had to be a reason I was missing. Thanks

Yes expansion (phase change from liquid to gas), into a much larger volume after the jet, is one of the reasons for my choice of jet location but there is another equally important reasons, which is contrary to your expectations.
Although, a lower working pressure would enable the plunger (piston), to lift more easily, it would also SLOW DOWN the return (shut off) of the plunger, which is equally as important as the opening time. Ideally we want the plunger to follow the square wave electrical signal, to give the most accurate results but what we actually get is a ramped opening and a ramped closing time, which effectively increases the flow through the system, beyond that set in the progressive controller.
To achieve optimum pulsed response from any solenoid, virtually EVERY paramater of the solenoid design (and to some degree other aspects of the system), needs to be adjusted to optimum settings. This is not a practical option, so I and my team determined the optimum design settings, for what we felt were going to be the majority of applications and then gave, as much adjustment either side of that as we could.
Despite having done all that, I doubt even 0.00001% of our customers, have ever bothered to utilise those facilities and that I guess, is a testimony to how well we determined the baseline settings.