Hello,

I would like to ask you Evo gurus here (both question concern low load/RPM, while in cruise under vacuum):

1) when EX MIVEC is much retarded (), exhaust gases are sucked back into chamber and mix with fresh air, right?

2) when IN MIVEC advanced too much, can be exhaust gases be pushed to intake manifold during exhaust stroke and sucked back while intake stroke?

Would 1) or 2) or both influence AFR readings?

 

No. AFR will only be affected if you are pushing fresh O2 air out into the exhaust.

The reason you suck exhaust air in the chamber is to not have high vacuum while cruising. The exhaust gas lacks oxygen, therefore it doesn't mess with your AFR.

 

Thank you,
how about no#2)? Could it help with pumping efficiency in cruise? Will not low fresh air in chamber cause need for wider throttle open?

 

You MIVEC should be configured that way already. The stock tune is pretty good in the cruise range.

 

thanks