Nitrious control with VEMS - possible in several ways, PWM-ed or ON/OFF
ON/OFF
PWM-ed
- possible with boostcontrol (fully mappable "boost-alternate" output PWM table), see MembersPage/GergelyLezsak/NitrousPWM
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.
What is the current status of the Nitrous Controller function?
(i cant see it in MT)
Would be also nice to control PWM Nitrous valves,so power increase is not so sudden (you may experience traction problems if all 100% is applied,even with 4WD,so so we in the Lancia,where we had to set it constatly increasing from 70% to 100% in 2 secs,
at WOT.
My suggestion:
settable
-AFR (leaner than setpoint and N2O wont activate,protecting the engine from running lean)
-starting point RPM
-starting PWM %
-time between start and end where PWM increases linear
-final PWM % (does it makes sense to set it to 100%? Fuel injectors dont like that...)
-Max allowed running time,after this,N20 is not applied (in a tipical dragrace you can set it to your 402m time)
-in any case (dry or wet) ignition retard is needed
-if dry system is used,Fuel enrichment is also needed.
-of course input switch (with MT confirmation,like ALS)
Note that this is how a working N2O computer works.
Firmware Version 1.0.78 has N2O control. This firmware also has an open loop boost DC control which could possibly be used as a N2O controller.
Possible Idea is to use the N2O control feature to enable the system and retard the ignition. This will energise a relay, switching 12v onto the N2O solenoids. The solenoids are then grounded via an injector channel that is controlled via the open loop boost DC controller.
In this mannor, N2O is fed in at the lower rpms ( set for your shift points? ) giving a softer hit. Could also be used to flatten out the torque curve, more at the bottom end and less at the top end. The result would be more akin to a torque platau, than a curve
Firmware version 1.1.58 onwards suports Fuel trim in N2O settings.
Perhaps this could be further enhanced by introducing closed loop fuel trim. Monitoring the cylinder pressure with a transducer. Simple linear scaling of fuel against analogue input voltage.
This would be a FAR!! more useful function as Nitrous Oxide systems calibrate the Nitrous to fuel ratio by fixed oriface jets. Cylinder pressures change with temperature resulting in a change of the N2O/fuel ratio. While it is favourable to run Nitrous systems in the very rich areas of engine operation, any change that results in a richer still condition can introduce rich missfire, and like wise, any change that results in a leaner condition could end up potentialy damaging to the engine.
Suggested pressure transducer http://www.noswizard.com/product_desc.php?id=154
Suggested config settings
Input channel
No Fuel trim volts
Full Fuel trim volts
No fuel trim enrichment (biased at 100% for zero fuel trim)
Full fuel trim enrichment (biased at 100% for zero fuel trim)
This should be restricted to trim only. Base Nitrous tuning should be done with the Nitrous system Jets.
-- It sounds like you have problems heating your bottle to correct temperature, you always jet the nitrous system to have the same pressure, for example 900 PSI. below 650 PSI you get a very bad result, as the nitrous will start flowing in gas form instead of liquid form. There is no way to compensate for this with your ECU
The fuel trim is only for small adjustments or small dry systems, not increasing horsepower by 50%.
//Emil
//Emil
- No bottle heater which is why the cylinder presure changes. I dont understand why the liquid will flow as a gas below 650psi. I use a Wizards Of Nos kit, which by nature, is a world apart from every other kit. Im not doubting that a bottle heater is the answer, but why is removing 10% or even 20% fuel by the ECU, if that is what is needed, a problem? Trust me, the system is set up correctly, it just lacks a bottle heater. I could fit a pressure regulator on the fuel feed and achieve the same result, I could fit a smaller fuel jet, and achieve the same result. Those are more involved.
- I am not using the fuel trim to add 50% of engine hP worth of fuel and I never implied that i was or that is what could be done. The trim is being used to 'trim' the fuel and that is what it is for is it not? not to supply the full amount of fuel.
Thanks for the input