REGULATOR BLEED/BYPASS SYSTEM

I have done extensive Flow bench testing with air bleed/bypass jets on the second stage nitrous system. On my Flow bench when the first stage comes on and the fuel pressure drops to the set level, the second stage Holley regulator creeps up to the line output pressure of the fuel pump 18-PSI. When the second stage is activated it takes from .62 to 1.29-seconds for the fuel pressure to drop down to the 7-psi flowing that it was set on and stabilize from the 18-psi that it had creped up to. So for .62 to 1.29 seconds after the second stage is activated it is extremely rich. I ran a 0.018-inch bleed jet off the second stage regulator with a Nitrous Flare jet fitting, #6AN fuel pressure 1/8” n.p.t. Fuel port fitting and a #4 braided line back to the top of the fuel cell (opposite the inlet side of the cell). I put a #4 Bulkhead fitting into the top of the fuel cell to attach the #4 line from the bleed jet to. On the opposite side of the #4 Bulkhead fitting inside the cell I cut a piece of ¼” tubing off and attached it with a #4 tube nut to the bulkhead fitting inside the fuel cell. The tubing/ “dip-tube” needs to be long enough to always be submersed in fuel in the fuel cell to prevent it from pulling in a LARGE amount of air into the main fuel line when the fuel pump is not running.

Without the “dip-tube” in the fuel cell I found that when I turn off the fuel pump and nitrous system after a shot on the bench the bypass line/air bleed jet from the regulator would suck air into the main fuel line through the bypass jet & #4 line out of the fuel cell. When I would activate the system and use it almost immediately thereafter it would spew a large amount air and fuel out of the nozzles and the spray-bars for a couple of seconds until the air was all purged out through the system. All the air did not exit back through the bleed jet in the short amount of time before I activated the system. A large amount went through the nitrous systems fuel enrichment circuit. So be sure and install a “dip-tube” when using and air bleed/bypass jet.

With the 0.018-.0.020inch bypass jet the second stage would not creep but a ½-PSI to 1.0-PSI higher than the 7-PSI flowing that the second stage was set on. It would creep to 7-1/2 to 8-PSI at the most. The second stage would drop from this level to the set Flowing level in a few tenths of a second when the system was activated. So this arrangement stabilizes the second stage nitrous-to-fuel ratio more efficiently and is closer to optimum upon activation.

When using a 0.018-inch bleed jet for each nitrous stage’s Fuel pressure regulator you can use a 3/16” to 1/8 N.P.T. compression fitting in the fuel pressure take off port fittings on both regulators as a nitrous jet fitting. Remove the ferule and nut from the compression fitting and throw them away. The 3/16” to 1/8” n.p.t. Compression fitting will need to be drilled out with a 3/16” drill bit to make the inside diameter large enough to except the 0.018 to 0.020-inch nitrous flare jet. Connect a –3 AN Braided line to the jet fitting in the regulators and run the two –3 Braided lines into a Y-Block (Product Engineering and Magnafuel make some nice Y-blocks for this application) and then run a Number- 4 line from the Y Block to the bulkhead fitting you installed into your fuel cell. In front mounted fuel cell applications you can run the –3 return lines back to the fuel cell. You will have to install two #3 Bulkhead fittings into the fuel cell and make “Dip tubes” for each one.

Using a 0.018- 0.020-inch bleed jet on the first stage regulator could also be an advantage on cars that can take a harder “hit” to the tires because it will cause the nitrous-to-fuel ratio to be closer to optimum upon activation at the launch and this will make more power quicker into the run. Although if you’re blowing the tires off at the “Hit” not running a bypass jet on the first stage may be an advantage because the nitrous system will be a little rich for approximately .62-1.29 or more seconds that it takes the fuel pressure to stabilize from being deadheaded. The larger the gap between the static deadheaded line pressure and the flowing fuel pressure to the nitrous system, the longer it takes the system to make maximum horsepower. When a car has tire spin, static line pressure can be raised to calm down the launch by removing the 0.018-0.020-inch jet and putting in a blank jet. In my opinion it is also an advantage to use a 0.018-0.020-inch bypass/bleed system on Pulse applications (Progressive controllers). The rapid solenoid cycling can make the fuel side momentarily too rich. The bleed jet will help keep the fuel pressure more stable by continuously returning a small amount of fuel back to the fuel cell bleeding the system so it is ready for action. 0.018-0.020-inch Bleed jets reduce pressure spiking and system pulsation and Cool fuel is continuously circulated from the fuel cell.

Although a single 0.018- 0.020-inch jet on each of the regulator’s outlets is the easiest way to accomplish a bleed/bypass system you can also use (2) 0.014-0.016-inch nitrous flare jets on fogger applications right at each of the fuel solenoid inlet fittings instead of the 0.018-0.020inch-flare jet at the regulator. (Although I feel like the single 0.018-0.020-inch bleed jet at the regulator is sufficient and the simplest way). You simply install a 1/8” N.P.T. Female “T” fitting and use a 3/16” to 1/8” n.p.t. Compression fitting as the flare jet fitting at each fuel solenoid connect a –3 AN Braided line to each of the jet fittings/0.014 to 0.016-inch flare jet at the fuel solenoid’s and run them to a Y Block and then run a #4 braided line back to the fuel cell. Twin direct port systems with 0.014- 0.016-inch bleed jets at each fuel solenoid can route the #3 lines back to a Nitrous style distribution block and then run a single #4 line from the distribution block back to the bulkhead fitting in the fuel cell with the “dip tube” installed. I also like to orient the bleed let fitting so that it is pointing upwards to help bleed the majority of any air pockets that maybe in the fuel system.

There are several important reasons why a bypass/bleed system can be used on high performance fuel systems -

1. Bypass systems allow for a constant flow of fuel throughout the entire fuel system, making the pump and regulator(s) more responsive to the demands of the system

2. They help maintain fuel pressure to within 1/2 lb.

3. They reduce pressure spiking and system pulsation.

4. Cool fuel is continuously circulated from the cell or tank to the engine/nitrous system.

5. Installing a bypass/bleed system enables regulator pressure adjustments simply replace the 0.018-0.020-inch bleed jet with a .073 jet and hook an Accurate fuel pressure test gauge to a gauge port fitting off the fuel regulator and activate the pump and set the pressure. Remove the 73 jet and replace it with the 0.018-0.020-inch bleed jet and remove the gauge and cap of the gauge port

Good Luck this season!

Robert Lane

Any questions for Robert Lane please go to his forum @ http://excoboard.com/exco/index.php?boardid=18653

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