View Single Post
Tyson Schmidt Tyson Schmidt is online now
PRO Motorsports
Tyson Schmidt's Avatar
Join Date: Nov 2001
Location: Burbank, CA
Posts: 4,404
Paul, the only way you can eliminate that box and have your car run right, is to remove the frequency valve and turn your CIS system back into K-Basic.

That brain, even with the oxygen sensor unplugged, runs the frequency valve at a default setting. Usually 60% If I remember correctly.

Without the frequency valve operating at this default setting, you'd have to adjust the mixture to compensate, and it would throw off the accuracy of the mixture throughout the range. In other words, it may be in spec at idle, but go lean at higher revs for example.

So either convert the whole system back to K-Basic, or leave it alone. BTW, have you verified that it is working? If you unplug the little aluminum ice-cube relay next to the brain, does it run worse? If it runs the same when unplugged, then it isn't operating. That's your original relay BTW. The new replacement relays are black plastic. I bet the date stamp on that relay is '79 ot '80.
'69 911E coupe' 2.7E MFI (retired 911-Spec racer)
'72 911T Targa (Formerly "Scruffy")
2004 GT3
Old 01-30-2004, 07:57 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)