Nitrious control requires little configuration in the ECU
How it works
The output is on/off type (often a relay) controlled by the following condition:\nÿ1ÿ
- nitrous_switch_is_on() condition: it makes sense to install the nitrious switch so it disables the output completely (eg. cuts relay or solenoid power) - the firmware need not know about it; if a switch signal is input to GenBoard, the 2 states are: switched to GND / pulled up to 5V (such as HALL supply or TPS5V)
- The gear select on a VW would be switched ground
Nitrous-oxide injection is a very popular, and simple way to increase hp. But any system, that hasn't got a controller means easily putting your engine to danger. A clogged fuel injector, or any kind of failure that results in going to the lean side, and your engine goes boom...But if properly controlled the system can be very safe, and fun-to-drive.
A nitrous controller should only (assuming a wet system) make the nitrous and fuel solenoid(s) close and open, hence the name pulsesystem.Which means if you do not have a system that is jetted at the solenoids, serious differences occour in flow (nitrous foams when it leaves the solenoid, so if the jet isn't just there [as in typical american systems], than you're metering a foam with the jet rather than a simple flow of liquid).
So a typical Pulse system contols the additional fuel injector, and the nitrous jet. Some of them, that are rather made for handleable performance doesn't even have an oxigen sensor to monitor N/F ratio; what they only do is increasing the amount of nitrous and fuel injected from point A to point B in time C. This is the simpliest solution.
Making it monitor an o2 sensor for safety, maybe a knock sensor for extra safety, instead of the timer solution you can use ASR signals for an ultimate system to achieve max. acceleration, or you can make it gear-referred to protect your gearbox from overwear (I mean less additional hp in first gear and in reverse[ :) ] ).
Mcell suggested:
if(RPM>config.nitrious_rpm_treshold && WOT && N2O_SWITCH_IS_ON()) N2O_PORT = _BV(N2O);
Frank K suggests the following:
Make this system very versatile by doing the following. Create a lookup table for on times based on MAP and RPM. This is quite simple, not to mention it will be compatable with either coldstarts for water injection, alcy injection, nitrous injection, or even 5th injector setups. All we do is require that the user know the nessecary duty cycles of the injector he is using. We will need to be able to change frequencies based on solenoid/injector types. The only other thing I can think of is to have a dual table setup on the fuel side when the nitrous is active. By doing the MAP and RPM table, you can really customize the setups. I also think that will really assist in customizing your setup to minimize turbo lag.
Let's take a look at the competition's offerings:
- Hipower Systems "Maximiser" progressive controller: http://www.wizardsofnos.com/shop/maximiser.php
- Twisted Sanity progressive controller: http://www.twistedsanity.com/prog_spec_sheet.htm
- And a homebrew (but serious) alternative: http://www.diy-nitrous.fsnet.co.uk/index.htm
My Homebrew circuit, Really simple hows this for a suggestion?
Dry Systems:
Dry systems are nitrous only systems. They only inject the gas, and rely on the engine management system to add the extra fuel needed. They are popular because they are slightly easier to install on EFI cars. The problem is that they are limited by the amount of fuel the injectors and pump can flow. If you try to add too much nitrous and the injectors can't keep up, you lean out. Simply adding big injectors can give more overhead, but you might sacrifice idle and low end drivability.
One way to increase the fuel flow is to increase the fuel pressure. It doesn't buy a lot of head room, but ramping up from 3 bar to 5 bar can increase injector flow (to flow_at_3_bar *sqrt(5/3)) by 5lb/hr with 21lb injectors - that's good for an extra 90HP on a V8.
Many pumps can flow more with increased voltage. The catch is that while we're ramping up the fuel pressure at the pump, the regulator is trying to bleed the excess back to the tank. Solution can be tweaking with FPR.
electronically adjustable fuel pressure regulator
FPR is just a spring pretensioned valve most of the time, so a given_pressure * given_area acting against the spring will open the valve and relieve some fuel to flow back to the tank.
It sounds simple to fool the stock regulator by applying extra force with a solenoid
- positive force (adding to the spring force) will result in higher fuel pressure
- negative force (against the spring force) will result in lower fuel pressure
You only want one direction in any given install.
It sounds possible to use a FPR that regulates at 5..6 bar (when it gets no electronic input), that can be decreased to 2..3 bar by pushing the right amount of current through a solenoid. It means the solenoid must act towards opening the regulator valve (pretensioning the spring) towards relieve. We plan to use such a solenoid from kunhke.de but they are quite pricy (35 Euro !). Should be possible to get sg. similar for less.
The other direction is also possible: using the standard spring that is for 3 bar, and adding 2..3 bar worth of spring force by solenoid when needed:
Without monitoring the fuel pressure, this is dangerous (can go lean if the solenoid does not activate for some reason).
An alternative might be to use a stepper motor to screw the tensioner up or down. Most adjustable regulators seem to use a screw type adjustment anyway, so if this was combined with a normal boost/vacuum reference, you might have the best of both worlds.