I recently installed a zex nitrous kit on my 02 mustang gt i started with the 75 shot jets first and everything was fine then i put in the 125 shot and when i spray it sputters really bad i have zex spark plugs in it which are 2 degrees colder and i have the timing retarded 3 degrees so i had a friend look at it and he thought it was getting to much fuel so we tried putting the 100 horse fuel jet in and the 125 nitrous jet in and it didnt sputter near as bad so then we tried the 75 fuel jet and the 125 nitrous jet and it seems fine i did a couple passes and pulled the plugs and the tip is a bluish purple color is this a normal color? i did a search for sparkplug tip colors and i didnt see that color on there i just want to make sure im not running lean any help would be great thanks

 

Sounds like your bottle is either cold or emplty and your running rich. Mis-matching the jets like that is not a good idea at this point, unless you are really experianced with nitrous.

 

75 fuel jet and 125 nitrous jet??? WTF are you thinking? Why don't you just drill out the nitrous jet on the 125 a little? Or why not just run an open -4 line to the solenoid? Jet it back to the manufacturers recommendations and trouble shoot from there.

 

so i put the right jets back in and its sputters again my bottle pressure is at 900 and i just filled the bottle so i know its full i have a heater on it but it never gets it much higer than that should it be higer maybe? when im not spraying the car runs fine what all controls the fuel pressure? is it just the regulator that i had to hook the zex box to?

 

Do you have a fuel pressure safety switch? If you do it is probably dropping too much fuel pressure (with the bigger jet) and it is fluttering the solenoids. Ideal pressure with a heater is 1000 to 1100 psi. And as far as the plugs the color should go to the bend in the tip, if the color is closer to the base then it is too hot, if is closer to the tip then its too cold. You might also try cleaning the screen on the nitrous line. Just dont mix the jets, you can go ultra lean and burn everything in the motor. You will need to look down into the ceramic part of the plug and see if there are any shiney specs on it. If there is, it is aluminum deposits from your pistons.

 

OMFG dude do not ever mismatch jets like that! The jets that zex sent you are that way for a reason . Your job is to work around their jetting. This means if your running rich on their jetting, then you need a dyno tune to lean out the fuel. Just because the car feels like its running alot better, could mean its running dangerously lean. Bluish color on the spark plugs is bad. You are looking for a blackish color all inside around the base of the white porcelain in the very dark bottom of the plug. The white porcelain on the spark plug should at least be somewhat dark colored and not just bright white. Look for shiny tiny little bubbles forming on the ground strap after spraying the car. This is sign of detonation. It will also cause a the white porcelain to become covered with black "pepper". Bad thing.

Right now you need to make sure your car has a good stock A/F ratio to begin with. Make sure your stock tune isnt bieng affected by some of the bad cold air kits out there. Change your fuel filter and run a full tank of fuel injector cleaner through, and fill with a fresh tank of 93 before you start using it.

ZEX a/f ratios untuned are perfect with their 75hp (60whp)shot. The 100(75whp) is somewhat safe. Their 125 (100whp) needs to be tuned because its crazy. Stick with 100 shot while untuned. you could switch to an NX kit, and run 100whp safely on their jetting.

 

As stated before, DO NOT mismatch the jets man. 75 fuel jet w/ 125 nitrous is asking for a blown engine. Get it Tuned ASAP and good luck

 

Im going to go get it tuned this weekend and see what they can do and ill have to pull out the plugs and check them again, thanks for all the help im glad i got on here and got some good help before anything bad happened to my motor no one around here seems to know what their talking about ill let you know how it works out

 

When your friend said the plug looked like it was too rich, he was probably comparing that to what an N/A plug would look like. Since you are adding more fuel to make more power, the plug will naturally be darker colored anyway. While n/a your not burning as much. Its a good thing if your plug is almost black after spraying, while untuned this is a good thing. As long as your not smoking fuel out the tailpipe, it will be safer untuned. My plugs get pretty black sometimes.