Injection Time v Running Lean/Rich

[PhilW]

Hi,

I'm tryin to understand the relationship between lambda values, MAF values and its related injection on time.

As a rough calculation A/F ration is calculated as (100*Inj period[ms] *RPM)/120000

So if MAF values are low inecjor times would therefore would be low in proportion, which tends to be the reason why people run lean with a stuffed maf?

What adjustment does the precat lambda sensor have on the injector time as well as how is the injector time calculated?

But in certain circumstances would a/f ratio (derived from above calculation) be running lean if the oxygen sensor was seeing a rich a/f in the downpipe?

Also, would an air leak before the first 02 sensor account for lean conditions?


Thanks.

 

[Uwe@Ross-Tech]

If MAF values are low compared to the true air flow, then ECU will reduce injector times because it's trying to match the amount of fuel to the amount of air it *think* your engine is getting. But it doesn't take long before it notices that the lambda sensor is telling it it's running lean. This will result in the part-load fuel trims going positive, and as a result, the injector times will come back up. Still, once those fuel trims hit a certain threshold, you'll throw a lean code.

-Uwe-

 

[-pseudonymous-]

You seem to be getting the opposite problem to me Phil. Im beginning to wonder how accurate these calculations are. I certainly dont think the calculations in block 032 give a clear indication as we dont run the wideband lambda's as said before. Im seeing figure's around the -10% region on mine and an A/F Ratio as low as 12.3 on boost. It seems to be running like a bag of poo bit it might just be me. I've given up trying to solve the problem now.

Also you seem to be getting very healthy MAF readings, whereas im seeing 167g/s max...

 

[Uwe@Ross-Tech]

The values in Group 032 are "long term" / "learning" values. That means they are not intended to be accurate in real-time.

-Uwe-