Dave's system is a true return system with our 13301 return regulator. Fuel demands are met first with this system and the excess fuel is returned to the tank to maintain pressure. With a return system, the regulator meters the return volume through a variable orifice. As demand increases, the valve meters down return volume to keep the pressure at the set point. This type of system is very stable and pressure drop during nitrous activation is brief at worst. As long as the pump volume is greater than demand the system will maintain a rock steady setting.
The modified holley 12-803 regulator setup is a dead head regulator that is modified to always flow some fuel through it to allow for static pressure settings and keep the system full of fuel. A dead head regulator requires the fuel to flow through a restrictive cartridge and into the regulator body where the pressure may act on the diaphragm. The diaphragm pushes on a ball in the cartridge that meters fuel into the system. This type of system can have a kind o see saw or up and down pressure graph when you look at a data log.
There is a way to set up you system and check the pressure without taking the whole system off. You already use a jet and return line. What you want to do is take the area of your return jet, and add it to the area of the other two fuel system jets in your system. Find a jet that matches that area. Put that jet in the "return" line and set your pressure. This jet will approximate the fuel flow that wil be on the system when both are activated. After setting your regulator, go back to the old jet and you're all set. You may also just add the area of one fuel jet and test and see how the regulator changes. I would set it for worse case though.
Here's some help:

.028 =.000616 "

I'll use .072" for your fuel jets

.072=.004072 " x 2

.00876" of area needed for the jet to test

.106 jet needed

Area of a jet is: jetId * JetId *.7854


When I first posted this my math was hosed.

Area of jets may be found here:http://www.barrygrant.com/bgfuel/def...age=84#Nozzles
I know its a competitor, buts its good info.

 

That is some DAMN GOOD info.

I never would have thought of just swaping a larger jet in to simulate the openings of the others. I will definately use that method and then just set it without taking everything apart.

One last questions, when doing this with a direct port system do I assume the volume of all 8 jets or of just one? Ie...do I use the area of one and then multiply by 8? I would assume multiply by 8.

Thanks for doing some math on a Sat. morning.

 

Yes, on a fogger type system multiply the area of the fuel jets by 8, or however many nozzles you have.
I'm glad to be able to help.

 

You are correct.
The original ones we got did not have diaphram in the cap.The last batch did so to insure proper ventilation we are removing the diaphram.We did a free flow check.We did 16 oz of fuel in 5 seconds.
Dave

 

Well 90gph is respectable gravity feed. I'm glad you took it into consideration. Thank you for developing a well engineered piece that incorporates our product.

 

I prefer to flow my system using the "before" the fuel solenoid method. Flowing after the solenoid into a bucket does not take into consideration engine vacuum
as seen on a running motor. I think most nitrous manufacturers flow/design
their systems using the "before" solenoid method.

Emil

 

You have a great product.
Dave

 

There is no flow in front of the solinoid. The solinoid must open for flow to occur. Every restriction should be accounted for when possible.

 

I disconnect the fuel line from the fuel solenoid and then attach my test line to this line. I have a brass coupler fitting on the opposite end of this line and I insert a flow jet the same area size as I intend to spray with. This end I stick into a fuel jug and turn on the fuel pump and set regulator to desired psi.

The fuel solenoid restriction and vacuum differances are factored in by the nitrous manufactureres when they determine their fuel/nitrous jet size tables.

To be safe, its best to check your plugs after each run and adjust
your pressure/jet sizes accordingly.

Emil

 

Everybody has their way I suppose. The important thing is that at least an attempt is made to ensure proper fuel delivery for reliable, repeatable power.

 

TTT for Dave

For my math I did:

Direct Port (DP) 150 shot = .020 Fuel = .000314 * 8 = .002512

For the Single Nozzle I did:

150 shot (at 10 psi) = .052 Fuel = .002124

Return Line I did:

.028 jet = .000616

Added all together for total area = .002512 + .002124 + .000616 = .005252

Total Test Jet size = .082 (.005281 area)