Fuel charge cooling vs injector deadtime

[Scott33]

I noticed the help on how to tune fuel charge cooling coefficient is similar to how I would tune injector deadtime - vary target lambda and observe actual lambda (well, more specifically measure fuel/air ratio at various injector pulse widths to determine what the pulse width would be for 0 fuel).

Assuming I can't measure my injector deadtime properly, is there a suggested way to determine those two parameters?  I was thinking of changing the target lambda and testing two different load points, under the assumption that deadtime would have a greater effect at lower loads while fuel charge cooling would have a greater effect at higher loads.  I assume I'll have to go back and forth a couple times to iterate on what the answer is.

Or maybe (since I'm doing this on a GDI motor) I can vary the target fuel pressure and use the same load point so I can either have the deadtime be either the major or minor factor in the injector's pulsewidth depending whether I'm trying to measure deadtime or fuel charge cooling.

Also, is fuel charge cooling relevant to direct injection motors?  Is the effect smaller or about the same as port injection?

[Scott33]

To answer my own question -

1. Measuring deadtime is about measuring actual lambdas and pulsewidths at two different settings (same RPM/load, but different fuel amounts), and seeing where that goes.

2. Measuring fuel charge cooling coefficient is about measuring target vs actual lambda and making sure those track each other.

Of course you get to throw in charge temp approximation table too, but that involves changing air or water temp and observing changes in lambda.

Luckily I have a lambda sensor!

 

[Adamw]

To verify deadtime, you can set injection mode to multipoint group and switch the injection rate back and forth between 1 cycle and 1/2 cycle, while at constant fast idle.  Lambda should settle to about the same value on either rate setting.  If lambda changes when injection rate changes then adjust the deatime up or down until lambda is the same with either rate.  Give it a few seconds to stabilize each time you make a change.   

[Scott33]

Can I use multipoint group on a direct injection engine?  It seems like the 2nd firing would be at exactly the wrong time (and probably wouldn't work since I think only one of two injectors can fire at a time, given the needs of the high voltage driver for GDI injectors).

[Adamw]

No, not possible with GDI.  Sorry I didnt see mention of GDI earlier. 

I would set set fuel charge cooling coef to zero and set the deadtimes so that measured lambda follows a change in target lambda.  That will be about the best you can do.  

[RyanG]

On 12/7/2020 at 1:56 PM, Adamw said:

To verify deadtime, you can set injection mode to multipoint group and switch the injection rate back and forth between 1 cycle and 1/2 cycle, while at constant fast idle.  Lambda should settle to about the same value on either rate setting.  If lambda changes when injection rate changes then adjust the deatime up or down until lambda is the same with either rate.  Give it a few seconds to stabilize each time you make a change.   

This setting is locked while the engine is running? I assume it's changed. I had a play around with my deadtimes last night to try and get them closer. It makes it a bit hard to do it when you have to restart the engine.

[dx4picco]

it did work on G4+ but not anymore on G4X