Adjusting DIY system pressure??

[PaulRV6]

I put together an alchy system but have some questions regarding the pressure output. When I hit my purge button the pressure jumps to 125 psi and then cycles back / forth at about 90-110 psi, this is with one M10 nozzle. I am also using the Shurflo pump.
Do these pressures look ok? Should I just leave the pump cycle? Thanks

paul

 

[PaulRV6]

I did some more testing and need to correct what I found out on the pressures, they cycle between 40-85 psi. I changed to an M15 nozzle and the pressures were about the same.

That cycling happens very rapidly but seems like it would make the flow unstable. Any suggestions on what I should do?

paul

 

[Steve]

The cycling is common with the Shurflo style pumps and should not be a problem. You will have to let the car tell how much alky it needs depending on your combo and set the alky system up accordinly. You can up the pressure with the screw on the head of the pump. The more you turn it in the higher the pressure will be.

 

[Razor]

The cycling comes from power being applied then released on the head of the pump. Spikes up.. shuts off.. drops pressure .. turns back on. On/off/on/off. It is how the typical DIY setup using the pump in that fashion operates.

You adjust volume to meet the engines octane requirements while tuning. Volume=pressure X orfice(nozzle)

 

[DMan]

You can short out the pressure switch on the shurflo to achieve a steady pressure. You should check to see what maximum pressure builds up to. It will be a function of your flowrate.

 

[Razor]

You can short out the pressure switch on the shurflo to achieve a steady pressure. You should check to see what maximum pressure builds up to. It will be a function of your flowrate.

Doing this can damage the motor as the current draw needs to be monitored. The motor has a current rating, printed on its label. This is there for a reason. All Shurflo motors are different. If the orfice size is too small, overcurrent can happen burning out the motor/damaging its armature. Some pumps feature a thermal limiter to shut power off in case of thermal issues.

 

[DMan]

Doing this can damage the motor as the current draw needs to be monitored. The motor has a current rating, printed on its label. This is there for a reason. All Shurflo motors are different. If the orfice size is too small, overcurrent can happen burning out the motor/damaging its armature. Some pumps feature a thermal limiter to shut power off in case of thermal issues.

Yes true, but you can test to see if the current goes too high for your particular setup. Through my personal experience of many years, I can state that if your flowrates are high enough, you will not damage your pump. I did this for over 4 years with no pump issues at all.

It all depends on your alky flowrate and pressure, and how long you stay in it. During bench testing, I roughly recall my shurflo seeing about 10 amps, and current would start to climb slowly if I left it on for a long time (i.e. >30 seconds). I'm currently using those aquamist nozzles so my pressure was about 175psi, so you could tell the pump was working hard. However, my WOT blasts are never 30 seconds long.

 

[Razor]

Yes true, but you can test to see if the current goes too high for your particular setup. Through my personal experience of many years, I can state that if your flowrates are high enough, you will not damage your pump. I did this for over 4 years with no pump issues at all.

It all depends on your alky flowrate and pressure, and how long you stay in it. During bench testing, I roughly recall my shurflo seeing about 10 amps, and current would start to climb slowly if I left it on for a long time (i.e. >30 seconds). I'm currently using those aquamist nozzles so my pressure was about 175psi, so you could tell the pump was working hard. However, my WOT blasts are never 30 seconds long.

Your assumming he's using the same identical pump you used. And the pumps from 4 years ago are way different than whats currently available.

:wink:

 

[DMan]

Another option to control overcurrent is to build in a bleed circuit from the output of the pump back to your tank. Bob Avellar was doing this years ago.

Either way, I think you need to get away from the pump cycling business. It messes up your AFR. The best way I think is with a progressive controller. But you don't always have to use the best way.

 

[incharge]

I have a DIY kit with the shur flow pump from Northern and I removed the pressure switch and cranked the set srew in to the max for constant high pressure ,I fiqure that the pump motor can handle all the voltage that I can throw at it for at least 20 seconds and being that my car runs half that I think it,s fine.. been good for years