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Steady state afr vs Inertia afr

Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning


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Hi Guys, Ive set my afr/lambda in my fueling table to what I want in the fuel table. all good, bike runs fine and makes good power. however I noticed when I do an inertia ramp run the afr is up and down - looks quite lean in spots and rich in others. however when I go back to the sites in the fuel table at WOT the afr is correct to what I set it. my question is - Is it normal to see the afr to look abit "off" on a wot ramp run? Im running a single cylinder 4str 450cc MX bike being used for road racing with "custom cam" and open exhaust ect... Im thinking the exhaust is causing the afr discrepancy.

That's not unusual and may require some sites added between your existing rpm break points. Generally with a bike engine (or any high output N/A engine for that matter) you'll see the AFR move up and down a little at low to medium rpm but once you're up in the rev range the VE tends to smooth out and the FAR becomes more stable. Depending on the magnitude of the swings in AFR I'll often leave them since you move through the rev range so fast.