Forum » Understanding AFR » Tuning acc. to a spot

Tuning acc. to a spot

Understanding AFR

Discussion and questions related to the course Understand AFR

Page 1

General question is that should the fuel table have sequentially increasing or decreasing values all of the time? Can a big jump harm injectors or so?

I have an engine bucking at low rpms like 2500 esp in 2nd or 3rd gear. All of the mechanical symptoms checked and it turns out to be the stage 3 cams having a high degree.

So can I specifically tune this spot regardless from usual lambda targets in order to eliminate/smoothen the problem since lambda will show only the burnt fuel ratio?

We need more details. What engine, what ECU, what kind of injection? Does the ECU use VE based calculations or pulsewidth calculations. Is the bucking during tip-in (moving the pedal) or holding speed and load steady? Can you post a screenshot of a log showing the problem? It could be lean air fuel ratio, but if you have high overlap cams sometimes it needs more spark timing advance.

built sti 06, Link v10, 1000 cc injectors (dont know brand) traditional fuel setup, holding speed at ~2500 rpm (no issues under acceleration).

here is the picture. hope it helps.

Attached Files

any ideas? deteriorating afr at that stage did not help.

So can you get to the area that's bucking in a steady state (on a dyno, or on the road) and adjust fuel and timing to see if it needs more fuel or more advance? Basically if you have to tip in to get there, it's a lot harder to tune because you have to tune the transient fuel (acceleration enrichment) and the base VE.