How to Properly Set Pump Pressure
 

I decided to build a temporary pressure gauge to more accurately set my pump pressure after I originally tested my setup with different pump pressures. I'm interested in learning what the specific pump pressure should be after the affect of check valve jets and maximum boost pressure at wide open throttle. I've been told to leave the pump pressure alone (leave at 165psi) but after check valve jets and high boost levels I want to know if it needs to be adjusted. Should it always be 165psi at the pump while check valves and boost decrease this pressure or are we aiming for 165psi at the nozzle after check valve jets and boost? This will help me more accurately set the failsafes since I've already determined how to adjust the board trimmers properly.

Setup:
HFS-4 system
Four .4mm direct port injection check valve jets
One .6mm post intercooler check valve jet

Pressures:
Pump pressure = TBD
Single check valve jet cracking pressure = 15psi
Maximum boost pressure in upper engine rpms = 25-28psi

Calculating My Setup:
I plan on flow testing all of the nozzles for a more accurate measurement but first I wanted to look at the online Aquamist Pressure vs. Flow chart and see where I landed. I calculated my methanol content, OEM fuel injector flow rate and each check valve jet.

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Pressure Gauge:
This is a simple pressure gauge with a 6mm push fit connector on one end and a 4mm push fit connector on the other end. I disconnected the 6mm line from the FAV inlet and inserted it in the 6mm push fit connector on the gauge. On the 4mm push fit connector end of the gauge I ran a short 4mm line with a .6mm check valve jet spraying into a laundry detergent bottle. This pressure testing bypasses the FAV (I still removed the FAV jumper on the HFS-4 board to be safe) and only has to overcome the 15psi cracking pressure of the one check valve jet.

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https://farm6.staticflickr.com/5573/...f939de08_z.jpg

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Notes:
-I reset the pump pressure as per the Aquamist instructions; turn the tiny allen screw clockwise until it clicks then turn it counter clockwise one full rotation to set the pump to 165psi.

-When I first put the jumper on SYS to turn the pump on I noticed the pressure gauge bounced around 150psi. I'm assuming this is the 165psi less the 15psi cracking pressure of the check valve jet. Add in max boost levels of ~25psi and the pressure would drop to 125psi.

-When I turned the tiny allen screw counter clockwise one more full rotation and jumped the board, I noticed the pressure gauge bounced around 120-130psi.

-When I turned the tiny allen screw clockwise two full rotations until it clicked again and jumped the board, I noticed the pressure gauge bounced around 180-185psi.

QUESTIONS:
-Turning the tiny allen screw clockwise increases pump pressure?

-If so, then turning the tiny allen screw clockwise where it clicks is the highest pump pressure?

-Should my pressure gauge shows 185 psi (tiny allen key screw turned fully clockwise until it clicked) so my nozzle pressure is at 145psi (185 pump - 15 cracking pressure - 25 max boost)?

-If my pressure gauge shows 165 psi then are my flow calculations on the above Aquamist Pressure vs. Flow chart (red vertical line at 120psi) correct and is this what I should be running at even though I still show a slight amount of timing correction in the upper rpm range where I could use a little more flow?

Re: How to Properly Set Pump Pressure
 

Yes, your questions are correct. When running that much dead head you can set the pump to max pressure to get the most at the jet face.

Anything higher than 185psi and the valve will have issues with slower opening which is a bad thing.

One thing to keep in mind is not to get too overly concerned with the exact cc the system is putting out, but to see how the car responds to what you have. If you need a little more on the top end turning the gain up a little should help.

Re: How to Properly Set Pump Pressure
 

Thank you Jeff, so I'm safe to leave it at the 185 psi (pump Allen key clicking point)? As for the top end, the red 95% IDC light comes on at 4,000 rpm and I see the minor timing correction at 5,200 rpm, gain is fully maxed out BTW.

Re: How to Properly Set Pump Pressure
 

This is a good write up.

The click indicates the "max adjustment" has just been passed. In order to obtain the "nearest" max setting, just advance 3/4T after the click.

If you require higher pressure, you need a shim behind the by-pass valve or a longer set screw. It is OK to maintain 185psi to offset the manifold pressure.

Re: How to Properly Set Pump Pressure
 

Rich and Jeff, thank you so much. As soon as I get my new .4mm CVJ I'm off to log the car then hopefully off to the dyno.

Re: How to Properly Set Pump Pressure
 

So does this mean that the set screw just keeps going around? (i.e. you can't strip it or turn it too far)