I am running a SMC kit and I have a check valve right before the nozzle and a gauge a bit downstream of the valve. Once off boost the line pressure drops immediatly. What if I were to put another check valve down at the pump to try to maintain line pressure for better response. Anyone try this yet?

 

You can but I wouldn't think you would see any better responce since the lines really don't expand and fluid don't compress. Everything should be pretty instant but if not it won't hurt. You can purchase higher crack pressure valves but this would only be safe depending on the tuneability you have in the car.

 

Thats not going to work with the 2nd check valve. You can do it with a solnoid, which i am not a fan of using them. They tend to break at the worst time. It takes a fraction of a sec for the system to pressrise its not even worth the extra cost imo

 

I cn attest to the solonoid issue. I put together a DIY kit and used the Mcmaster water solonoid tht was recomended in a few DIY online sites. It's plastic body with 3/8 pipe thread in/outlets. Mine would leak through the threads even with very liberal teflon paste or teflon tape. The plastic body evenutally cracked from tightening the pipe thread fitting before it sealed. I replaced it with a metal body NOS fuel solonoid for now. Planning to go with a check valve next.

 

A solenoid will do exactly what you are wanting to do. Just be sure to get one that is designed for that purpose. The DIY ones you see are people trying to 'make due' with easy to access parts. I have hundred's of solenoids being used, with 100% success rate. Not trying to sell anything, just saying to use the right tool for the job.

Thanks,

Greg

 

Don't forget that almost any check valve that is set up in the free flow direction will reduce the nozzle pressure downstream by two values. The first is the spring pressure which holds it shut and the second is the flow resistance of the valve when open. If you can blow through the valve with your mouth in the free flow direction then the valve has a light spring.
With multiple check valves in a line these pressure drops are added together.
Since most of the systems are developed through experience this is not a problem unless you deviate from how it was developed. In the industrial fluid power world one can buy check valves with various cracking pressures from very low to 60 psi or more in special circumstances. If you install a check valve with a 30 psi cracking pressure spring it will reduce your pressure at the nozzle by a little more than that.
The flow will also be reduced by the pressure in the manifold because the flow is mostly dependent on the pressure differential from the pump to the outlet of the nozzle. I can imagine a system with 30 psig boost, a 30 psig check valve and a 75 psi pump putting out very little flow out of the nozzle. Also the flow you see with the pipe open may or may not be similar to the flow you see with the pipe open during testing.
Also, if you have a perfectly sealed line with a gauge in it that you close behind the check valve the line should stay pressurized to the cracking spring pressure. If you don't see that on the gauge then you have a leak in the solenoid valve seat, lines or the check valve is not sealing.

Another interesting fact about nozzles and orifices is that the flow out of the nozzle is only somewhat linear to pressure in the designed flow ranges. Above a certain limit increasing the pump pressure a lot might only increase the flow a little.

I am looking forward to installing one of these systems on my Evo in the near future. I plan on buying a commercially developed system to piggyback on the knowledge and success of the developer.

Theory is great and a guide but real world experience (understood in the light of theory) is best.

 

Great response. Thanks