You can't estimate with just RPM without consider load.

The only absolutely true measure is the air flow throw the throttle body (hence TCR, GT3 racing using air restrictor in their BoP Balance of Performance, which is basically a standard size cone for every team).

Modern engine varies a lot around the ideal 14.7 ratio, even more so for the small displacement turbo with ultra lean (stratified) combustion mode at low load on both low/high rpm.
On the flip side, on high load extra fuels are injected just to cool the engine for both NA/Turbo, just more severe in turbo case.

My car easily varies between 20km+/l to no more than 5km/l.

Rule of thumb, don't think of the rpm, think of your own throttle input (although drive by wire means it is also damped by ECU).

This post has been edited by constant_weight: Nov 28 2023, 12:45 PM

ok, but not always true. Consider overall package, different transmission type can be as big as 3-5%. Tyre, engine oil viscosity, weight, aero all add up.

My 204PS 1.6T is more fuel efficient than 2.0NA, and that's Skyactiv not some ancient old NA.

This is with combined urban/highway usage, long term average speed on trip computer 33-34km/h.

Of course 100-200km/h pedal to metal, the turbo easily consume 2x fuel vs the 2.0NA. But I'm not that crazy to do that day in day out.

The only catch is the current owner long term FC is 0.8-1L/100km more than me, been asking how I did that.
Only explanation is my rather fast corner with smooth steering input, so I need less re-acceleration. Downside is I always get outer tire wear, from econobox to heavy family saloon.

This post has been edited by constant_weight: Nov 30 2023, 10:16 PM

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This post has been edited by constant_weight: Nov 30 2023, 10:16 PM