well it's a dry system because it's not being injected to each port with fuel , but the manifold IS a closed system in that it is plumbed with tubes to the supercharger. as the manifold pressure rises from negative (vacuum) to positive (boost over 1 atm) the nitrous is introduced about mid way in the plumbing - by the time it hits the manifold it has apparently increased the pressure on my gauge by like 25 lbs. this is'nt theory ...it's actually happening. my best guess is that not many people use both forced induction AND nos. it is a closed air induction with no where for anything to go except to the ports , but the nos HAS had a chance to expand / cool / dense - ify the air headed that way for quite a distance (unlike a wet system direct port injection) the only reason i bring this whole mess up at all is because it's so suprizing to me...i never thought that kind of 'pressure' gain was to be expected most anyone ive spoken to has said that a slight increase in pressure like 1 - 3 lbs would be expected. the jets are tiny...no one runs .018 nos jets and expects to get a ton more ponys. it's been explained to me that a ''50 shot'' adding 50 hp by nos could be done with a single .034 jet dry...two .018's is just a hair less than HALF that...and it was described to me that these would be about a 25 hp increase (to play it safe what with some boost from the supercharger) you can feel the nos hit - it IS an increase and probably leaning out the air/fuel mix...who knows the fmu should perceive the pressure and correspond with more fuel.
either way i'm not driving the car with the nos until i get an understanding of how it's possible to see a 25 lb. increase in manifold boost pressure just from two teeny weenie little .018's

 

Ok, let me get this straight.

You have a supercharged w/ intercooler setup, and want to know why you're seeing so much more boost than before?

 

well that makes it sound stupid ...but yea. i had a nos .o34 jet to an AEM cold air before and it motored good , but i never knew the manifold pressure then....only assumed i was addind oxidizer - maybe cooling the air more als and that was about it.
now i have a vortech on it and it's producing about 12 lbs , but only 6 are getting to the manifold....probably due to choked down lengthy intercooler setup AND my understanding is that the air would be colder and as such less active - more dense and would actually lower the perceived pressure even though the engine likes cold air (which is good) so hypothetically maybe 3lbs are getting scraped off due to lengthy piping and the other 3 due to lower temp.

in answer to your question :yea i want to know why at WOT hauing ass and showing 6 lbs in the manifold then the nos hits (again with two teenie weenie .018 jets) the pressure jumps to 30 + lbs. thats it.

 

Is the nozzle before or after the compressor inlet?

If it's before, it's conceivable that the air is condensing quickly and then re-expanding immediately after it's compressed and passes to the intercooler. Definately a lot of thermal shock in the air is bound to happen...

If the nitrous is after the compressor, then I don't know what to tell you.

 

thanks 1st gen that's where I'M at it is after the compressor inlet. interesting that the point at which it is introduced is probably the most choked down portion of the plumbing. off the compressor it's 3'' then to 2 1/2'' at the inter cooler entry (and exit) then to make a necessary corner it goes to 2'' after inter cooling - then back to 3'' to the throttle body. i would think the greatest pressure in the plumbing would be just before that 2'' corner.....and the lowest would be when it opens back up to 3'' to the throttle body. everything from the intercooler to the manifold is experiencing this high pressure due to nos....a very sudden jump from 6 to 30+ lbs.