Pump adjustment screw

Terry Syd · 02-29-2008

I've read on the forum where the pump adjustment screw on top of the pump housing will only change the pump pressure 15psi. How many turns out from the full inward position does it take to reach the maximum amount of pressure change?

I ask because I have changed the position of the screw several times and would like to put it back in the "mid" position.

Terry Syd · 02-29-2008

I've read in the sticky on pump pressure and nozzle size that a complete revolution of the screw is equal to a 5 psi change in the shut off pressure. I've also read advice about turning it out 7 revolutions, which would be a 35 psi change. That is a significant difference from 15 psi.

Is the change 5 psi per revolution?

How many revolutions of the screw can be made before the screw no longer adjusts the max pressure?

What is the stock setting from Devilsown?

dvldoc · 03-01-2008

You can turn that 7 times you won't see more than a 15psi change, The nozzle size is the main factor in the pump pressure. So if you are running a M3 you will not be able to reduce it less than 200psi. The pressure switch really does little to effect the pump pressure. The only real way to reduce pressure is to PWM control the pump like our controller or reduce the voltage going to the pump. Most vehicles put out about 13.8v while running you can reduce that down to 12v and that will knock off much more pressure than turning the screw.

Or just get a smaller nozzle

Terry Syd · 03-01-2008

Hmm, a rheostat in the pump power line, that could work. That would allow very fine tuning for whatever nozzle a person was running. If you changed your methanol blend, you could then just tweak the rheostat to compensate. You could also get the vehicle up to speed and then fine tune the WI for your cruising speed.

Anybody have any idea about what size rheostat it would need to have in order to provide a good tuning function?

My basic question for this thread was where is the stock pump set at. Is it set at 3 turns out?

Terry Syd · 03-02-2008

I've just done some more calculating. I've read that the pump uses 7 amps at 12 volts to crank out 150 psi. If my memory of Ohm's Law is correct then that is 1.7 ohms though the pump windings (correct?)

I don't want to drop the voltage too low or I'll get into an overheating condition, thus the use of pulse width modulation for the controllers so that low rates of flow can be achieved. If I limit it to a 20% drop in voltage I end up with a rheostat of .34 ohms.

This would allow a 13.5 volt regulated system to be varied from 13.5 volts to 10.8 volts.

Does anybody see any problems with this idea or my math?

Rocket468 · 03-02-2008

The problem with reducting the voltage to the pumps is around 10 v the pump will not operate. This is why we do use pwm so the pump see full voltage all the time. This min voltage is going to be your limiting factor when using a rheostat

Terry Syd · 03-03-2008

Yeah, that's got me a bit worried - that I might drop the voltage too low for the pump to operate. I might have to try a little bit bigger rheostat in series with the pump and then monitor the pump and the voltage drop across it as I wind up the pot. When the pump stops pushing water through the nozzle, then I find out what the voltage drop across it is, then add one move volt for insurance. Then run it up again and measure the resistance of the pot at the point the voltage reaches that 'insurance voltage'.

If I can get a 20-25% change in voltage (disregarding the dynamics of the change in flow through the nozzle at different pressures), then I can probably tune the basic system for my usage.

I'm running the basic on/off system without a controller. However, I am only running 9 psi boost and the WI system has now been set for around 6-7 psi. I really can't justify a controller for 2-3 lbs of boost change.

On the other hand, around town the engine is usually running in the range of 2400-2500 rpm when on boost. Out on the highway the revs sit at 3000-3100. That is a little more than a 20% increase in air flow. If I tune the nozzle and pot for 2500 around town, I can dial up the pump pressure for 3000 rpm when I get out on the open road.

I will be able to optimise the flow for off-road and around town, and then use another setting for out on the open road. When I come to hill on the highway the WI will kick in at just the flow rate I want. - At least that is the theory.

Terry Syd · 03-08-2008

I looked at the price of various rheostats (potentiometers, variable resistors) and the prices for a 10 amp device was way too expensive.

Since I want a simple two voltage system, then a STDP switch using a resistor in one circuit seems more logical and less expensive. The pump windings measured 2 ohms. If I use a .5 ohm resistor in series with the line voltage, then I will have a 20% drop in voltage across the pump.

I tried a .47 ohm resistor in the line and it worked fine. I'll be wiring in a double pole switch so that one circuit is the alternator voltage to the pump and the other circuit is alternator minus around 20% (depending upon what works best).

If someone has a simple basic system for their vehicle that they want to fine tune, then a resistor in the line to the pump can help them fine tune the pump pressure. A person could use a .1, .22, or a .47 ohm resistor. If they wanted they could put a couple in series, say a .1 and a .22 and come up with a .32 resistance (or put a couple of 1 ohm resistors in parallel to come up with a .5 ohm resistance).

02-29-2008	#1 (permalink)
Terry Syd Alcohol Holic Year: 1990 Make: Toyota Model: Hilux Join Date: Nov 2007 Posts: 104	Pump adjustment screw I've read on the forum where the pump adjustment screw on top of the pump housing will only change the pump pressure 15psi. How many turns out from the full inward position does it take to reach the maximum amount of pressure change? I ask because I have changed the position of the screw several times and would like to put it back in the "mid" position.

02-29-2008	#2 (permalink)
Terry Syd Alcohol Holic Year: 1990 Make: Toyota Model: Hilux Join Date: Nov 2007 Posts: 104	Re: Pump adjustment screw I've read in the sticky on pump pressure and nozzle size that a complete revolution of the screw is equal to a 5 psi change in the shut off pressure. I've also read advice about turning it out 7 revolutions, which would be a 35 psi change. That is a significant difference from 15 psi. Is the change 5 psi per revolution? How many revolutions of the screw can be made before the screw no longer adjusts the max pressure? What is the stock setting from Devilsown?

03-01-2008	#3 (permalink)
dvldoc DevilsOwn Staff Join Date: Apr 2005 Posts: 1,966	Re: Pump adjustment screw You can turn that 7 times you won't see more than a 15psi change, The nozzle size is the main factor in the pump pressure. So if you are running a M3 you will not be able to reduce it less than 200psi. The pressure switch really does little to effect the pump pressure. The only real way to reduce pressure is to PWM control the pump like our controller or reduce the voltage going to the pump. Most vehicles put out about 13.8v while running you can reduce that down to 12v and that will knock off much more pressure than turning the screw. Or just get a smaller nozzle __________________ Currently deployed to Ramadi 1 battalion 12th Marines see you in 8 months.

03-01-2008	#4 (permalink)
Terry Syd Alcohol Holic Year: 1990 Make: Toyota Model: Hilux Join Date: Nov 2007 Posts: 104	Re: Pump adjustment screw Hmm, a rheostat in the pump power line, that could work. That would allow very fine tuning for whatever nozzle a person was running. If you changed your methanol blend, you could then just tweak the rheostat to compensate. You could also get the vehicle up to speed and then fine tune the WI for your cruising speed. Anybody have any idea about what size rheostat it would need to have in order to provide a good tuning function? My basic question for this thread was where is the stock pump set at. Is it set at 3 turns out?

03-02-2008	#5 (permalink)
Terry Syd Alcohol Holic Year: 1990 Make: Toyota Model: Hilux Join Date: Nov 2007 Posts: 104	Re: Pump adjustment screw I've just done some more calculating. I've read that the pump uses 7 amps at 12 volts to crank out 150 psi. If my memory of Ohm's Law is correct then that is 1.7 ohms though the pump windings (correct?) I don't want to drop the voltage too low or I'll get into an overheating condition, thus the use of pulse width modulation for the controllers so that low rates of flow can be achieved. If I limit it to a 20% drop in voltage I end up with a rheostat of .34 ohms. This would allow a 13.5 volt regulated system to be varied from 13.5 volts to 10.8 volts. Does anybody see any problems with this idea or my math?

03-02-2008	#6 (permalink)
Rocket468 DevilsOwn Staff Year: 2000 Make: Pontiac Model: Grand Prix Join Date: Apr 2005 Posts: 1,103	Re: Pump adjustment screw The problem with reducting the voltage to the pumps is around 10 v the pump will not operate. This is why we do use pwm so the pump see full voltage all the time. This min voltage is going to be your limiting factor when using a rheostat

03-03-2008	#7 (permalink)
Terry Syd Alcohol Holic Year: 1990 Make: Toyota Model: Hilux Join Date: Nov 2007 Posts: 104	Re: Pump adjustment screw Yeah, that's got me a bit worried - that I might drop the voltage too low for the pump to operate. I might have to try a little bit bigger rheostat in series with the pump and then monitor the pump and the voltage drop across it as I wind up the pot. When the pump stops pushing water through the nozzle, then I find out what the voltage drop across it is, then add one move volt for insurance. Then run it up again and measure the resistance of the pot at the point the voltage reaches that 'insurance voltage'. If I can get a 20-25% change in voltage (disregarding the dynamics of the change in flow through the nozzle at different pressures), then I can probably tune the basic system for my usage. I'm running the basic on/off system without a controller. However, I am only running 9 psi boost and the WI system has now been set for around 6-7 psi. I really can't justify a controller for 2-3 lbs of boost change. On the other hand, around town the engine is usually running in the range of 2400-2500 rpm when on boost. Out on the highway the revs sit at 3000-3100. That is a little more than a 20% increase in air flow. If I tune the nozzle and pot for 2500 around town, I can dial up the pump pressure for 3000 rpm when I get out on the open road. I will be able to optimise the flow for off-road and around town, and then use another setting for out on the open road. When I come to hill on the highway the WI will kick in at just the flow rate I want. - At least that is the theory.

03-08-2008	#8 (permalink)
Terry Syd Alcohol Holic Year: 1990 Make: Toyota Model: Hilux Join Date: Nov 2007 Posts: 104	Re: Pump adjustment screw I looked at the price of various rheostats (potentiometers, variable resistors) and the prices for a 10 amp device was way too expensive. Since I want a simple two voltage system, then a STDP switch using a resistor in one circuit seems more logical and less expensive. The pump windings measured 2 ohms. If I use a .5 ohm resistor in series with the line voltage, then I will have a 20% drop in voltage across the pump. I tried a .47 ohm resistor in the line and it worked fine. I'll be wiring in a double pole switch so that one circuit is the alternator voltage to the pump and the other circuit is alternator minus around 20% (depending upon what works best). If someone has a simple basic system for their vehicle that they want to fine tune, then a resistor in the line to the pump can help them fine tune the pump pressure. A person could use a .1, .22, or a .47 ohm resistor. If they wanted they could put a couple in series, say a .1 and a .22 and come up with a .32 resistance (or put a couple of 1 ohm resistors in parallel to come up with a .5 ohm resistance).