As many of us using big turbos (especially me :), it's a good idea to spool it with nitrous injection.
Unlike with other technics (launch and ALS), I'd like control it a way to stay in traction which is much favourable in street conditions.
My first idea is a dry kit with PWM-able solenoid, like this one:
Interesting part is controlling such a system with VEMS.
"Boost alternate" pwm reference table (1.1.5x firmware), duty(RPM, KPA) can be used to control it (while PID boost can control boost simultaneously).
Existing logic is probably OK to switch configs when N2O is on or off, to handle related changes like:
- ignition advance
- fuel (especially with dry kit)
- other ?
Or alternatively if this is hand-in-hand by nitrous volume (rated by pwm duty) a simple config value is enough information to add extra fuel(?)
If it works, and one strongly prefers boost_alternate to PID boost, we might add another tunable PWM output (IAC pwm or stepper could be used if not used for idle, but not optimal because only linear relationship in function of RPM is allowed).
New page of PWM experiments : MembersPage/GergelyLezsak/NitrousPWM
AFAIK this is not common in other (big brand) ECUs, so it might be a good idea to take advantage and give support for such an advanced (and cheap) control possibility.
Based on existing measurements I can achieve 0.8-0.9G acceleration with warm tires but excessive wheelspin, maybe it would be slightly more with a 5-10% of slip.
Here's a power chart of a first-gear run with launch&wheelspin (black) and with simple acceleration (red):
(Time differences between the curves are scaled)
Based on the blue area, I'll need a maximum of ~70Hp "shot" of N2O.
For a test-drive open loop boost control with ref table (RPM, kPa) is usable I guess, usage frequency of the solenoids ("Pulsoids") seems 8-50Hz.
UPDATE july, 2009
New firmwares (like 1.1.56) have experimental N2O control to switch a simple solenoid and some correction in fuel+ignition.
- This is fine for an ordinary one-stage system
- it should be able to control the finest PWM-based systems described above
- it can control more stages if only one of the stages require PWM. It cannot control both stages if both need PWM. If one is on/off, and the other is PWM, it might be suitable.
- Actually it should be suitable but we should test such 2-stage system on bench. We might need to syncronize 2 actions so both changes in a syncronized way to be on the safe side (one of the actuators usually change slower than the other, so this must be considered and safety maintained).
Write your thoughts here!
MembersPage/GoranJurkovic I second the idea... Nitrous is a very fast way of getting a few extra HP... So not only VE table must be changed on nitrous spraying, but also lambda target and boost target (for turboed engines)...
Safe lambda range for nitrous is 0.7, while engine runs fine on 0.8-0.84 at the same pressure without it..