Hondata

I have a NA ls/vtec. Type R replica. I recently built the motor and went for its initial test drive. Looking at the lap top I notice the AFR hunting quite a bit during driving. The car seems to run fine, so I assume this to be normal? At start up, it settles into a nice idle at 850rpm and `14.7 AFR. Only problem I've noticed is that when you push the clutch in to come to a stop and it is coming down from anything higher than 2k rpm, it goes past its 850 idle and dips so low that it stalls. So question 1 - is it normal for AFR to swing between 11.5 and 16.5 when driving? Question 2- why is the idle going to low when coming down after the clutch is pushed in? The ecu is a Hondata p28 using a plx wideband. Setting is on closed loop wideband. Thanks

Do you have a lightweight flywheel?

Yes

That is the most likely cause and that is not something that tuning can really fix as there is just not enough inertia to keep it spinning when it tries to idle down. You can try to target a higher idle.

That makes sense. Thanks

Post your calibration. What wideband are you using? Turning the over run fuel resume up usually fixes the coming down to idle stalling issue as long as the target idle speed/duty is correct. The default rate of change values for closed loop are not good which can explain the huge swings in A/F.

Its a PLX-SM

Try this. Make sure the voltage offset for the wideband is correct and use D10 input for the wideband and remove R136 and R138. Set the voltage offset so the wideband and software read close to the same.