×

Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

+/- LTFT+STFT AFR RICH OR LEAN

Understanding AFR

Forum Posts

Courses

Blog

Tech Articles

Discussion and questions related to the course Understanding AFR

= Resolved threads

Author
1787 Views

I'm still confused a bit on what the scanner is representing when the LTFT/STFT are reading -7 vs 7. When its at -7 is the engine actually running 7% rich and removing fuel on its own or is it running lean and adding fuel?

The trim is positive when the ECU/PCM is adding fuel. So -7 is removing 7% fuel, so whatever table is providing the information (VE, fuel table, MAF) is requesting an amount that is too rich, with the LTFT/STFT added, the engine should be running close to the commanded AFR, but without the trims it would be rich.

- LTFT is rich condition .

+ LTFT is lean condition .

- LTFT is rich condition .

+ LTFT is lean condition .

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?