I've already posted this in Civic/DelSol subforum but got no answer... Maby you guys can help me?

I've just checked my AFR and it is quite weird... As soon as VTEC kicks in AFR reaches 13.8... a moment later it gets too rich... 11.7 - 11.8 and stays like that all the way up to 8200 rpm. The setup is: B16A2 '2000, CAI, SuperSprint header+exhaust, stock ECU no piggybacks. Any ideas what's wrong with my engine? How can I diagnose it? Thx

BTW I was using a wideband AFR meter.

 

it is supposed to be richer in vtec.

 

Yes, but definitely NOT 11.7. It's too rich!

 

actually i just saw a thread where it compared the dyno results from a stock itr ecu and a kenji chip. it had the a/f reading on the bottom of the dyno sheet and the stock one ran rich. i think it is a safe guard thing that honda uses.

 

It's normal for it to lean out momentarily when it kicks over to the HI cam before it settles into whatever AFR it's supposed to be at according to the HI cam fuel map.

The reason it happens is because of the sudden change in the cam profile and the extra volume of air coming in. It's the same concept as the motor leaning out when you have a steep throttle tip-in with no form of throttle-dependent enrichment in effect.

 

Stock honda ecu's run pig rich.