Ok, when running a high boost application (upwards of 30 lbs) with nitrous system that has it's own dedicated fuel system, will the pressure differential between the intake pressure -again above 30 pounds, maybe as much as 50 - and the fuel pressure from the dedicated holley blue pump - 15 lbs - inhibit the flow of fuel from the fogger nozzle? If so, do we need to run a high pressure fuel pump or larger jet, or what?

I'd say that in any fogger application, the fuel pressure needs to be at least the same as the manifold pressure. Without any kind of intensifier piston I would think that your fuel flow would be effected. I don't think a larger jet would help in this applicaiton. However, if the fuel pump is a positive displacement pump it would make as much pressure as needed until the pump actually maxed out and was unable to deliver fuel / turn over. Does that make sense? I'm guessing that it's not since most fuel pumps are designed to dead head. I'd say fuel pumps are a centrifugal design because they are designed to move a large volume at relative low pressure. You'll need some kind of FI high flow pump and a boost referenced pressure regulator. I'd also get an in cabin or hood mounted fuel pressure gauge and make sure that it matches the boost gauge. The Mallory 3 way regulator that I have now would probably work very well for you. This is pretty far out of my league and not knowing any particulars about your application, such as pump type, I'm just going off of what I've learned in school.

Ok I did some research and the pump you have, I believe, is a positive displacement. It is internally pressure regulated. You could put a very heavy spring in it to get it up to the pressure that you wanted however, I think that this would cause a huge amp draw and you might burn up the pump or the wiring.

On a side note, mounting pumps inline increases pressure, but has the flow of the lowest pump. Mounting pumps in parallel increases the flow, but keeps the same pressure. To that end a Holly universal inline pump is $140 and that should bump your pressure up to 55 lbs or so. It only flows 58 gph though. If you look a pressure at the nozzle and it never drops below boost pressure or stays 5-10 lbs above boost pressure(what I would say is safe) then the flow is acceptable.

That's the extent of my knowledge. Sorry I couldn't be more help.

very close but not quite. due to the fact that the new pump has relieved the first pump of some of its dutys when it is less burdened it can too flow more. a good example would be a 190 LPH intank pump and a 255 LPH inline pump. by NO MEANS is the flow the sum of the two. But the flow would probably be around 275-290 LPH depending on quite a few variables. for example; at what PSI is the flow rating made? there is a big variable; for example if the 190 LPH were relieved of nearly all of its duty it definitely would become a restricting factor if placed before a 500 LPH race inline pump. then the 190 would restrict it down to like 230 LPH ( depending on many factors) this is why some euro car manufacturers have been doing just this for years.

You should use a manifold pressure referenced fuel pressure regulator for the fuel supply for the nitrous system. It should increase the fuel pressure on a 1:1 ratio to manifold pressure, ie: 1 PSI fuel pressure increase for each 1 PSI manifold pressure increase above atmospheric.
<table border=5 cellpadding=5 cellspacing=5> <tr><td><b>Manifold Pressure</b></td><td>0 PSI</td><td>10 PSI</td><td>20 PSI</td><td>30 PSI</td><td>40 PSI</td></tr><tr><td><b>Fuel Pressure</b></td><td>45 PSI</td><td>55 PSI</td><td>65 PSI</td><td>75 PSI</td><td>85 PSI</td></tr></table>

<center><font size=6>OR</font></center>

<table border=5 cellpadding=5 cellspacing=5> <tr><td><b>Manifold Pressure</b></td><td>0 PSI</td><td>10 PSI</td><td>20 PSI</td><td>30 PSI</td><td>40 PSI</td></tr><tr><td><b>Fuel Pressure</b></td><td>6 PSI</td><td>16 PSI</td><td>26 PSI</td><td>36 PSI</td><td>46 PSI</td></tr></table>



You will need a pump capable of supplying the needed volume at the maximum pressure you'll encounter.
Keep the fuel jet the same size.
A system set up this way will will supply a more consistent fuel/nitrous mix at any and all manifold pressures up to your maximum.

using jets for EFI fuel pressure on the dedicated nitrous side and an FMU to raise the pressure with the boost should maintain the differential you are seeking. I mean even if you already have an FMU for whatever boost you are running then run a second on the dedicated side.

A pressure referenced fuel regulator will get you nothing but a set of melted pistons. You still have aconstant 1000lbs of nitrous feeding the system regardless of the boost in the system. Most foggers run on 6-7 lbs of fuel pressure anyway. A good fogger nozzle like the soft plume or a piranha will use the nitrous flow @ 1000lbs to draw the fuel into the nozzle. @ 1000lbs of pressure in the bottle 30 lbs in the manifold is nothing to worry about. With that type of boost you should be running a dry nitrous system anyway

I actually ended up avoiding the question entirely by running propane as a fuel enrichment for the nitrous system. Works pretty good.

Can you give any details of your system such as orfice sizes etc?