I was just wondering if you have to purge a Dry system since it is being injected into the air side and not the fuel?

 

Yes, for full effect of the hit, you gotta purge it. i think you may be confused. a wet kit does not put liquid nitrous in with the fuel supply system. a wet kit injects nitrous and gasoline into the intake manifold at the same time. this bypasses the stock fuel system, thus not having to upgrade your injectors for the higher fuel demand.

 

yeah system wet or dry or direct port doesn't matter. you have to purge regardless because all of them introduce the nitrous the same way.... you are just purging the nitrous side and getting the air out of the system so the car doesn't stutter off the line when air in the lines get fed into the intake instead of fresh liquid nitrous...

all you are purging is air out of the supply line so what is sitting at the solenoid is raw liquid nitrous.... when the system comes on you'll get instantaneous power with no hesitiation... the fuel is going to be there regardless of wet or dry....

 

I've never used a purge on dry kits, once in a while I would arm it during the burnout to get the air out of the line.

 

I never ran a purge on my dry kit. Since the nitrous is picked up by the MAF there are no issues to worry about with fueling if you have your nozzle placement dialed in. I kind of liked the softer hit of the system with no purge. If I ever had a purge I would mainly be using it to control bottle pressure.

 

I've never run a purge kit..and really, you'd only need it for the first pass because after that the line is full...

 

that's not 100% true... sometimes the liquid can change to a gas close to the solenoid.... causing small pockets.. usually not noticeable... but there is a reason the big boys purge before EVERY pass... and usually purge ALOT.....

 

Good point....I was mainly refering to myself and some others who use little girl shots..haha

 

Not to split hairs with you, but this is not 100% true.

These wet systems feed off of the end of the fuel rail and do in fact tax the stock fuel system. If your fuel system is not adequate to handle the nitrous kit you may still have to upgrade it. You are bleeding off the stock fuel system unless you run a stand alone fuel setup for the nitrous kit.

 

i see your point, and you are correct. however, i think the point was that the injectors would not have to be changed until a more serious sized hit is used. seeing the type of question asked, im sure this guy wasnt going to throw more than a 150 at it, which im sure the stock injectors can handle. i mean, mine do. thats the only thing i see a novice getting a wet kit for.

 

when i had my dry i did as unstang did and hit on the burnout as the initial hit would bog the motor from what i have noticed

 

Overpowering your fuel system can come in many forms.... sometimes it's volume, some time it's pressure, other times it's line size from pump to rails.... there are many different things that you can be too small on..... Regarding fuel systems for nitrous the main difference is that with dry your injectors will have to be able to handle the HP your motor puts out AND the added HP that you are spraying with the nitrous.... So if your motor puts down 400hp and you're spraying a 150 shot your injectors will have to be able to supply enough fuel to support 550 hp.

With a wet kit your injectors will still have to supply ONLY the fuel for 400hp HOWEVER since you are "sipping" off of the same supply of fuel that the injectors are using (usually off of a valve very close to the end of the fuel rail) NOW it will tax the total amount of fuel you can provide to the motor. Your injectors are off the hook to provide 550 hp worth of fuel BUT your pump, lines, and rails have to be able to provide 550hp worth of fuel.... usually with a wet kit you will not have enough pump at first..... beyond that the stock fuel lines will be too small to carry enough fuel to support the total amount of HP.... I think this happens (at least with LT1's) right around the 600-650hp mark.... The OD of your lines is small to a point that even if you put 1 zillion lb injectors on one side and a 1 zillion HP pump on the other you will never get the fuel VOLUME needed to make more HP. Saw it happen first hand with my last setup. Made 525 RWHP on spray with a TH400 and ran low 10's.... was running lean regardless of pump and injector swaps..... turned fuel pressure up/down and left it alone... nothing helped.... until i went with bigger lines... you can only put so much fuel thru teeeeny lines..... no matter how much press you run not enough liquid will flow thru the lines.... something to think about with wet or dry and the differences between them...

 

Very well put. You also need to consider the size of the Fuel solenoid as well. Those big noids just draw too much fuel when opening causing lean spikes.

 

Very well put, indeed. all of that stuff is a given. im not exactly sure what the limits of the stock setup is, but i thought around 550ish or so. until that point, unless youve got the money to spare, its not completely necessary.

 

For a dry, you really don't have to purge, for the wet you do. If you want to sandbag someone on the dry, thats a good time NOT to purge, for any other occassion, go right ahead, haha.

 

You don't have to have a purge for a dry or a wet system, you don't have to do anything if you don't want to. Its recommended that you put a purge on a wet system, but if you boom the motor doing your burnout its not really needed there.

All playing aside you do not need to have a purge on your dry system, the fueling is picked up by the MAF and it knows whether its just increased airflow or nitrous because thats what the MAF is designed to do, interpret whats going past it and send out a Hz for the pcm to add fuel to. I even went and logged some runs w/o purging my nitrous line before and I had no fueling issues whatsoever. I even went as far to tune my MAF based on nozzle position as I have my nozzle locked in place.

The long and the short of it, don't need a purge. 1st initial hit just won't be as hard.

 

I didn't purge my mustang before running on the street. It was a plate and carb though...But no studdering, and it still left like a maniac...Just with zero wheel spin.