View Single Post
RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
RarlyL8's Avatar
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,577
Goran - that is the type of information I am looking for. Did you personally check over or tune the CIS prior to changing over to EFI?
That is a critical point. If the CIS is not verified as being tuned well the data is useless. Much the same as if the EFI is not set up correctly.
There is no doubt that EFI has the capability of being a more precise system, I want to see exactly how much more precise.

There is also the difference between stock CIS and optimized CIS. EFI by its very design must be optimized or it will not work well. Stock CIS works just fine in a stock application. This is where a lot of the bias against CIS comes from. EFI is so much better than stock CIS that it is easy to dismiss CIS as old junk.

Mark - the A/F ratio pattern of stock CIS is pretty bad. It was designed to protect the engine and "fuel cool" with mileage not being a consideration. The A/F takes a dip as soon as the throttle is touched and takes a dive to around 10:1 when boost is initiated. It then recovers and can actually go lean at the top end on a modified engine. So yes, you do need the ability to adjust your WUR if you wish to better straighten the A/F ratio throughout the range. Your LM-1 will tell you where the trouble spots are and then you will know what tuning is needed to remedy.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-01-2007, 06:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #74 (permalink)