Mapping HSV duty cycle against speed / load / inj Dc??

[max_torque]

Hi,

I am about to set up a full system (race pump, accumulator, HSV, 4 x 0.3mm jets, DDS2) on my turbo rally car, which runs with a MoTeC M8 engine management system.

Basically i drive the HSV from a spare PWM driver, and i can select what parameters i use for the 3D maps axis.

1) Option 1: speed and load. X axis is engine speed, Y axis is MAP. This would be a direct mapping of HSV duty verse these to axis, allowing me to tailor the water injected percentage to meet requirememts against plenum pressure.

2) Option 2: speed and fuel injection duty. X axis is engine speed, Y axis is fuel injector duty cycle. Effectively map water injection mass as a ratio of fuel flow.

I correct fuel injection using both a wide band lambda sensor & pre turbine EGT (once it hits a my EGT limit) (engine is mapped to LBT (approx 0.89 lambda, and uses EGT sensor to overfuel for component protection as necessary)

If i use option 2, i effectively can map my water injection like my fuelling, i have a target AFR, and i could now use a target WFR, i.e. the water injection mass flow would be corrected automaticaly for changing conditions such as BARO, IAT, etc.

Anyone tried this method?

[CnC]

Fuel injector duty cycle is mapped against load isnt it? So mapping water against fuel injector duty cycle seems to be effectively mapping against load as well. Mapping against duty cycle, and indirectly against load, or directly against load both seem like good ideas.

Mapping againnst fuel injector duty cycle would probably be quickest as you would already have all these numbers from your fuel injector duty cycle map to compare against (just need to scale the flow rate of your injectors compared to the flow rate of your water injector and set the duty cycle of the water system appropriately).

[PuntoRex]

I've been using system 2D for several years.
Recently I added a Digital Pulse Adjuster (http://www1.jaycar.com.au/productView.asp?ID=KC5384&CATID=25&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=347) on signal stream before the 2D controller. So I can adjust the signal it sees, thus the WIDC.

Here is the recent map:
http://home.pchome.com.tw/personal/rexchiou/WI_Adjust.jpg

The 2 vertical dotted lines indicate the approx. WI operating range. I'm running a pretty high w/f ratio of 25~30%....

The whole system still works on the fuel injection pulse signal, & like CnC said, engine load info is already in it.

Now it's working very well.

[CnC]

Is the hump due to the fact that you are injecting more water around peak torque in order to prevent detonation?

[PuntoRex]

Yes :smile:
I found detonation is much more easily heard around midrange.

With this hump, I feel the engine is livelier & midrange detonation is totally suppressed.

Although I have no dyno numbers to prove this, it runs very well with this setting.

[CnC]

Very good, and another good use for the DFA (I have the book Performance Electronics for cars which this kit came from).