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Tuning for Fuel Economy - Logging cc/min?


apoc
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Hi all.

Is there a way to log instant fuel usage via SCT (or hopefully the PCMTec logger when it's released) from the injectors on these PCMs?

I'm looking to do some road tuning for fuel economy, I have the fuelling sorted, but would like to optimise the ignition map for cruise. At the moment it's a shot in the dark, could be over advanced etc.I've been logging it using SCT, all the knock-limited spark tuning I'm much happier with, and it's running much better under throttle so far.

If I can log the average instant fuel usage (injector cc/min?) and average speed with cruise on, over a consistent road, I'll be able to figure out what the engine likes best.

Thanks in advance!

 

*EDIT*

BA eGas engine (10.7:1), FG plastic inlet manifold, custom extractors (modified hurricanes to fit a GQ Patrol), underdrives, BF cams, loom & PCM

Edited by apoc
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Hi apoc, I guess in the other products you would log injector pulse width and back calculate that to amount of fuel being injected. The other methods of logging air mass (Ford calls this Air Charge) and work out the fuel being delivered by commanded lambda is a less accurate means.

Remember to achieve fuel economy the car will be running close loop fuel control and you wont be able to change the commanded lambda as it will be 1.0. The car will be cycling the injectors rich and lean in order to keep the catalyst functioning for emissions.

You could turn off closed loop fuel control to get around this but then you loose the adaptive fuel management and destroy your catalyst.

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The ignition map should never be over advanced for cruise as the MBT table is the maximum brake torque figure, the PCM will never command more ignition than this. Then the PCM will run on the ragged edge of knock (eg the knock sensors will be right on the edge of mild detonation) to get the most timing possible out of the engine.

Now if you mess with the VCT, IAT and ECT spark modifier it is possible you are under advanced (as most people zero these tables out so they don't add timing to full load to make tuning easier).

You can also disable closed loop fueling and command 1.1 lambda (maybe higher) at cruise, the PCM will automatically add extra timing based on the lambda spark modifiers. This will net you the best possible fuel economy however you will absolutely destroy your NOx emissions and catalytic converter, you car will likely produce 10x the smog inducing nitrous compounds as it should if you do this.

As Darryl said logging air charge or duty cycle are a few ways of doing it. We should be able top log something to this effect eg duty cycle.

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Thanks lads, appreciate the detailed replies so fast. Can you turn off closed loop fuel control for particular throttle / rpm ranges only? Or is it an all or nothing deal? I probably wouldn't go to 1.1 lambda, maybe 1.06 or 1.07 ish.

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The reason I'm changing cruise timing is because the engine is pretty modified from a stock BF XR6 engine, mainly the inlet manifold and extractors which would be affecting spark advance and air charge. And I just want to check that I'm getting the right values in there for engine longevity.

 

Edited by apoc
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37 minutes ago, apoc said:

Also would auF1651 - "A/F bias multiplier in PART THROTTLE mode as a function of Vehicle Speed" (HACCKBC) allow me to target a lean cruise condition without modifying closed loop?

Looking at the code it is quite likely it will do what you suggested. Try it and datalog your lambda, curious what happens.

FYI the Open loop transition is based off this table

image.png.2fb2ddc46baef172440953c93cf54a50.png

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