nxcoupe
01-03-2007, 02:41 PM
Ok, so I thought I would contribute a little to this section by posting up how I run a 225+ hp dry kit without boosting fuel pressure, or 'fooling' the mass air sensor.
First, I use a dry single nozzle nitrous kit. For this example I have an .082 nitrous jet in it. The way I have it set up is I use a piggy back engine management system, this one called a PMS, but there are lots of them out there including AEM. Most of the systems have a programmable input and output array. What this means is that the input allows the computer to 'see' the voltage flowing into the nitrous relay or solenoids. I use the main power wire coming into the nitrous solenoid, ran parallel into the solenoid and into the computer. When the solenoid is activated, meaning 12V flows through the wire, the computer then looses it's ground signal and sees 12V coming into it. This closes a mini switch that tells the computer to switch tables and use either a global fuel multiplier, global timing multiplier, or whatever else you enable for it. MSD uses a similar wiring strategy for it's nitrous retard built into it's Digital series units and seperate nitrous retard.
Deciding what fuel multiplier to use is the catchy part. I went with a recomendation from a manufacturer that turned out to yield a 19 to 1 a/f ration on my new engine. Nice. I had to just start from scratch and went with a 2.1 multiplier, which means if the commanded injector pulsewidth is a .2 ms, then it will become a 4.2 ms pulsewidth, so you can see this allows much more fuel to be delivered to enrich the nitrous.
The only drawback to this method is the size of injectors you may need for your individual application. I had been using 42 lb injectors with mine, flowing 42 psi of fuel pressure, and I ran out of injector after making some changes. This was both a good and bad thing. It was good because it needed more fuel, which more fuel means more power. It was bad because my injectors were already at 100% duty cycle and couldn't deliver any more fuel, resulting in a holy piston and three pistons with swimming pools(detonation pits), and melted spark plugs out the ying yang.
The best route for selecting a tune is to go way rich and slowly lower your fuel multiplier down until you see the a/f ratio come up. I typically run over 10.5 and under 12.0, can't give you all my secrets ;).
First, I use a dry single nozzle nitrous kit. For this example I have an .082 nitrous jet in it. The way I have it set up is I use a piggy back engine management system, this one called a PMS, but there are lots of them out there including AEM. Most of the systems have a programmable input and output array. What this means is that the input allows the computer to 'see' the voltage flowing into the nitrous relay or solenoids. I use the main power wire coming into the nitrous solenoid, ran parallel into the solenoid and into the computer. When the solenoid is activated, meaning 12V flows through the wire, the computer then looses it's ground signal and sees 12V coming into it. This closes a mini switch that tells the computer to switch tables and use either a global fuel multiplier, global timing multiplier, or whatever else you enable for it. MSD uses a similar wiring strategy for it's nitrous retard built into it's Digital series units and seperate nitrous retard.
Deciding what fuel multiplier to use is the catchy part. I went with a recomendation from a manufacturer that turned out to yield a 19 to 1 a/f ration on my new engine. Nice. I had to just start from scratch and went with a 2.1 multiplier, which means if the commanded injector pulsewidth is a .2 ms, then it will become a 4.2 ms pulsewidth, so you can see this allows much more fuel to be delivered to enrich the nitrous.
The only drawback to this method is the size of injectors you may need for your individual application. I had been using 42 lb injectors with mine, flowing 42 psi of fuel pressure, and I ran out of injector after making some changes. This was both a good and bad thing. It was good because it needed more fuel, which more fuel means more power. It was bad because my injectors were already at 100% duty cycle and couldn't deliver any more fuel, resulting in a holy piston and three pistons with swimming pools(detonation pits), and melted spark plugs out the ying yang.
The best route for selecting a tune is to go way rich and slowly lower your fuel multiplier down until you see the a/f ratio come up. I typically run over 10.5 and under 12.0, can't give you all my secrets ;).