If this doesn't apply to you then I apologize, but I feel the need to share this because I was confused about this for a couple days. I installed my ZEX dry kit this weekend and got the bottle filled at a local shop. It was the "universal" kit I believe, as it was used. It had jets for 50-75 HP, so I used the 75 HP jets as recommended in the online setup guide for a 4 CYLINDER, which is the jetting the kit was supplied with. I figured for a given HP setting the jetting would be the same regardless of displacement or # of cylinders. After a few impromptu runs down my favorite "track" I was rather disappointed with the performance of the system. It worked, but not as well as I thought it should. I checked my jetting, and it was right, or was it????

I did some more looking and discovered that the recommended jetting for a V-8 was completely different. I called ZEX to try to clear this up in my mind, but the guy on the phone had no idea what he was talking about. He told me that the smaller fuel jets lean out the mixture, and you want to use smaller fuel jets as you go up in HP because it is the nitrous that makes the power and not the fuel. WTF??????

I ordered the correct jets for 100 and 125 HP, which came in today. The system works great now, and I have no complaints. After a little looking around and educating myself I finally figured out exactly how the system and jetting work. The smaller the "fuel" jet, the more pressure will be applied to the FPR, richening the mixture. Using the 4 CYL jetting was bosting my fuel pressure to the sky, and with 8 injectors instead of four I was getting twice the fuel needed.

So, the point of this post is let everyone know that you absolutely need to get the correct jetting table for a 4, 6, or 8 cylinder engine, because the jet requirements are drastically different for all. I'm sure many of you already know this, but I wanted to pass this information on in case someone was experiencing lackluster performance with this system. Hopefully someone out there will benefit from reading this. Other than my complete misunderstanding of dry nitrous kit operating principles, I have to say that the ZEX kit a great kit. Easy to install and use, and the power comes on nice and smooth so it doesn't blow the tires off when it's activated. First gear is still completely usable in my car, albeit on concrete. Thanks for reading.

 

The only time you are messing with fuel jets is in a wet kit, not a dry kit. I believe you are still a little confused as to alot of stuff with nitrous.

Im glad you are enjoying your nitrous however. But if you have both fuel and nitrous jets, then you have a wet kit. Dry kit just sprays nitrous only and depends on your car to add extra fuel. A wet kit sprays both fuel/nitrous in a fog, therefore adding its own fuel to the mix.

 

I know what you're saying man, and you're right to an extent. A dry kit on an LS-1 is mounted in front of the MAF, and depends on it to tell the computer to add extra fuel. On an LT-1 the nozzle is mounted behind the MAF, so fuel needs to be added another way. ZEX accomplishes this applying pressure to the fuel pressure regulator to raise fuel pressure. The injectors are still at the same pulsewidth, but the increase in fuel pressure compensates for the nitrous. The ZEX kit uses a nitrous jet as a "fuel" jet to regulate the amount of pressure that is supplied to the fuel pressure regulator. The ZEX control unit has a vacuum line going to the intake, and one going to the FPR. In the ZEX control unit there is a circuit that bleeds nitrous pressure to the FPR. The amount of pressure applied to the FPR is regulated by bleeding some of the source pressure to the intake manifold, so a smaller jet bleeds off more source pressure thereby increasing the pressure to the FPR, which in turn raises the fuel pressure, and vice-versa. When the system isn't activated the FPR is connected by the control unit to manifold vacuum, so it operates normally. The only drawback that I can think of is the inability to tune the A/F ratio(unless you REALLY know what you're doing), since changing the "fuel" jet will increase/decrease the amount of pressure sent to the FPR AND the intake manifold. However, I've been told that the setup is slightly rich to err on the side of safety. The kit is considered dry because the exttra fuel is supplied by the injectors, rather than through the intake. The nice part about the system is that fuel pressure is regulated according to bottle pressure, so the A/F ratio stays the same until the bottle is empty. Of course there will be a slight loss in performance as pressure goes down, but the the A/F ratio is constant. It's actually a pretty slick system. I hope that clears it up a little bit. If you want go check out www.zex.com and read their description and look at the pictures it might be a little more clear than my explanation. I hope this helped.