Suggested Scaled N2O Fuel Trim Firmware 1.1.58>

[Sprocket]

Firmware version 1.1.58 onwards suports Fuel trim in N2O settings which is great ( this setting alone has made me change back to the 1.1.xx versions after suffering running issues previously. Yet to test it)

Perhaps this could be further enhanced by introducing scaled fuel trim. Monitoring the cylinder pressure with a transducer or just a manual potentiometer mounted on the dash. 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




I run a small 1275cc engine with 100bhp normaly aspirated. I now have a 50hp hit of nitrous ontop and suffer with rich missfire when the ambient temperatures are lower. There is no suitable jet to remove only the required fuel to move out of rich missfire and I have to trim the fuel with Vems. This means connecting a PC.

[MWfire]

you can use mat input for NO2 presseure, and then you have MAT(pressure) depending table.
But, then you don't have correction for temperatue of intake air(10C lower temperature and you need 2% more fuel).

[Sprocket]

you can use mat input for NO2 presseure, and then you have MAT(pressure) depending table.
But, then you don't have correction for temperatue of intake air(10C lower temperature and you need 2% more fuel).

That would be an idea, however, the point of the N2O settings is that it is switchable. You do not need the correction all the time, only when N2O is activated.

Its simple enough, but it would depend on how much config bytes it uses and some one writing the code.


One other thing that is desirable is progressive activation. A basic Duty cycle ramp to 100% over time with a fixed PW. This will allow the use of higher levels of N2O without the strain on the transmission while reducing wheel spin at the same time. For instance, my engine (53hp standard, 100hp modified) could easily cope with 100hp nitrous, but a 100hp hit would certainly break the gearbox and spin the wheels in third gear.

Suggested settings

Start DC
Finish DC
Ramp time
PW


One step further could use the gear selection with the speed sensor restricting N2O activation to higher gears


I think these two simple controls for N2O would be a good selling point. Any more complex than this and it would be wiser to use a controller specific for the job. I say this as im sure I spotted Tony C's Capri in Trevor Langfileds (Wizard Of NOS) book on Nitrous Oxide Injection. A Vems instalation with Nitrous system in a published book

[MWfire]

you can use boost pwm table for NO2, so you just set 50% at 5000rpm and ramp up to 100% at 8000rpm.
In version 1.1.47 you can do that dependining on rpm and gear.

[Sprocket]

I like that Idea (I suggested it on the Wiki some time ago ) and I have decided to give it a go. I have started a thread over on the Wizard Of NOS forum. I need to set the PWM period to 25 - 30hz which I believe is ~0.04ms. Minimum DC of 20% and max of 80% dependant on Pulsiod optimisation.

Two concerns Trevor raised was the driver current capacity and the back EMF.

I do not have any FETS in this ECU, they are all IGTBs (long story). The IGTBs carry 14 amp continuous and the solenoids are fused at 15amp. It has been suggested to use two outputs, strap them together for engine damage limitation, in the unlikely event of one driver failing.

Will the transient surpression diode on its own be man enough for these big solenoids, more to the point, will the IGTB survive with them. Would adding an external flyback diode to these two chanels help disipate the flyback voltage before it reaches the transient surpression diode?

Other than this I think it will work.

I realised that there is gear dependancy setting in N2O config in 1.1.58, so I can use the boostDC table (top line??) to modulate the power level of the N2O and activate only in 2nd 3rd and fourth gears between 3500rpm and 6500rpm above 95% throttle with ignition retard of 4 degrees and fuel trim of around 90%. starting the DC at 30% up to 100%

I think thats a plan 100hp jets here we go ( that will make for a 4x output of a standard engine )

So while the suggestions I posted above are still a usefull addition, I will plod on with what we have I need to fit a speed sensor somewhere now

This could get complicated, so I know I will be back asking questions