Hi. I just installed a skunk2 70mm throttle body and intake manifold on my 2000 Civic Si. its a 1.6L DOHC Vtec, and I installed this about a month ago. There are no oil leaks, no vacume leaks, everything is tight and runs fine. Its just that i have had this car for a while and before i installed these 2 mods, the vtec would always engage at 5500rpm. Now it doesn't engage until 6200rpm. Is there a possibleity that the extra air would change the air/fuel ratio causing the vtec to change?? I am lost and have searched for this forever. I have heard of a few posts on other sites where the manifold caused a problem with a secondary runner or something and the vtec would change?? i don't know. I am just curious if there is a fix for this or if I need to change the timing advance/retard or if its right in front of my face and i just don;t see it...... any help would be great! thanks

 

i've never heard of a ecu reprogramming itself to change the vtec engagement point.

 

you could always get it tuned, then get your vtec set to engage whenever you want