How to run large shots without burning up your tires
Most of us start with a 50 shot, love it, and soon up the shot to 65, 75, etc. Pretty soon it is obvious that pumping an extra 75 whp out of your engine, while impressive on the dyno, doesn't do much for you ETs except for put a higher mph next to 14.xxx. A 100 shot should put a 5 spd H22A euipped prelude way into the low 13s, but without traction there is no hope.
There are two ways to put a large shot of nitrous to the ground. The first being nitrous controllers, which are expensive, but provide the most control of your nitrous kit. The second way is through a two stage kit, which provides two different size shots to the same engine.
Nitrous Controllers
Progressive controllers work by rapidly clicking the solenoids so that only a given amount of nitrous can get into the engine over a given period of time. The more often the soleoid clicks the less nitrosu gets through. This is particularly helpful with FWD vehicles which have a hard time putting down anything higher than a 75 shot on street tires. The idea is that you have a small precentage of your total shot(ex. 20% of a 75 shot) at 3k rpm and then increase the percentage by 20 for every 1k rpm after 2k rpm. Therefore you'd have 40% @ 4k, 60% @ 5k, 80% @ 6k, and the full shot at 7K. Of course this is just an example and the actual percentages would need to be adjusted for each car and track conditions.
The cons of progressive controllers is that the rapid clicking of the solenoids causes the rubber seals to wear out very rapidly. This can be fixed by ordering tougher seals from NOS, but the seals tend to run around $100 a piece. These seals will nto wear out, but they also do not seal as well as their rubber counterparts, which makes it necessary to have the car running whenever you open the bottle so that whatever nitrous may leak through the solenoid will not collect in the motor.
One safety measure that must be taken with progressive controllers is the use of a back up solenoid. This solenoid should be wired to open when the nitrous kit is activated, but to not be affected by the progressive controller. The rapidly changing current in the solenoid coils can cause them to fail over time and if they get stuck in the open position you could blow your motor. The back up solenoid will prevent the nitrous from reaching your motor is your primary solenoid does fail.
Jacob's Nitrous Mastermind (JNMM)
The JNMM retails for around $225 and is on the low end progressive controllers. It is a durable unit however and features a rev limiter, automatic timing adjustment when the nitrous is in use, a fuel pressure safety switch, and a progressive nitrous controller. Crane makes a similar product.
NOS and NX units
These units tend to run around the $500 mark, but are much more specialized in their ability to control the nitrous flow. The nitrous can be controlled in relation to time or RPM. These are top of the line products, but they are quite an investment for most people.
Two stage set ups
The theory behind two stage kits is to use a small enough shot in first and second gear that you can retain traction and as you get moving you can use a larger shot while still retaining traction. Think of it in terms of tubing. If you are hanging onto the rope and the boat comes tearing by you at 30 mph you won't be able to hold on. In contrast, if you are already going 30 mph and the boat speeds up to 60 mph you should be able to hang on much easier.
Since most FWD cars have trouble putting down anything more than a 75 shot in first gear. Therefore somewhere between a 40 shot and 60 shot would be ideal. Once you're into third gear or the top of second, you activate the 2nd stage and hang on for the rest of the ride.
Different two stage set ups
There are way too many different combinations of kits and ways of running multiple stages of nitrous that I'm only going to go into depth on the one I believe is the simplest to do.
Several users are running the NOS 05030FI kit, which is a four cylinder direct port kit. This kit is used to run the second/higher stage.
For the first stage we will use a single fogger set up. we will need two AN style Ts, six pieces of SS braided line, the appropriate fittings,one nitrous solenoid, one fuel solenoid, one fogger nozzle, the appropriate jets, and the wiring/relay. Undo the fuel and nitrous lines from the "IN" port of the solenoids. Place a T in each line. If you are running a purge kit, like you should be, place it directly upstream from the T in the nitrous line, unless you want to buy two purge kits. Next connect the two T's to their respective solenoids via the SS braided line and fittings. Tap the intake 7" from the throttle body, screw in the fogger nozzle, put in the right jets, and connect the fogger to the second set of noids via the last two pieces of SS braided line.
The wiring is a bit tricky and will require two arming buttons and two relays. This is NOS's wiring diagram for their two stage kits:
The NOS part # for the second relay is 15605S. .