Question about fuel with dry kits??? [Archive]

Injuneer

06-23-2002, 08:32 PM

<font face="Verdana, Arial" size="2">Originally posted by Hood_Lum:
I'm running a NOS dry kit with 150 shot.
How does the car know when to add extra fuel?
Oliver</font>

Is it the NOS 5176 dry kit for the LT1?

If so, you have two nitrous solenoids in series. In between the two nitrous solenoids, on a "tee" there is a blue "pressure regulator". There is a line from this pressure regulator to a "tee" you added in the vacuum line to the fuel pressure regulator.

When you open the nitrous solenoids, a small stream of nitrous flows through the pressure regulator and applies a pressure to the vacuum port on the fuel pressure regulator. That pressure closes off the fuel return line more, and raises the fuel rail pressure. The increased fuel rail pressure increases the amount of fuel that flows through the injectors for any given pulse width.

In effect, the stock PCM does not even know the nitrous is flowing. It is still calculating the injector pulse widths on the basis of an N/A motor. It is just the combination of these pulsewidths and getting the fuel pressure high enough to add the extra fuel required for the nitrous.

As a guide, when you raise fuel rail pressure, the fuel flow increases in proportion to the square root of the pressure ratio..... increase the fuel pressure to double... 43.5psi -> 87psi, and you increase the fuel flow by about 41%. 41% of a 300HP N/A motor is an extra 123HP.

If you have a setup other than the 5176 kit, let us know. I run a dry system with an aftermarket PCM... in this case a MoTeC. It has a program for running N/A, and then a set of supplemental fuel tables to increase the pulse widths when it senses the nitrous system is activated. But the stock PCM can't do this.

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Fred
94 Formula A3: 381/TH400/N2O
Detailed Mod's List (http://members.aol.com/InjuneerZZ/Mod.htm)
11.513@115.59 on motor; 11.162@127.67, 1.643 60' on a 125-shot. Going with a 275-shot this year