CIS v. EFI

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <s510dfcb.032@mannlawfirm.com> Bruce Aukerman writes:

> Scott J, you may well know [or understand] more about CIS v. EFI than
> some of us.  Is that what the question was?
> 
> When the topic came up, you said mods were avail for CIS that [in
> essence] made EFI irrelevant for our cars.  Great.  I asked what the
> mods were.  No answer.  So, I ask the second time.  No answer.  Then
> the thread died.

I'm not sure that EFI is ever _irrelevant_ - but it is possible to achieve more 
with existing CIS.  The problem that we're chasing in the UK with our MB 
engines - close to a hybrid of the MC-1 and MC-2 but without emission controls 
is proper control of full throttle enrichment.

The existing CIS-E system is a mixture of mechanical (air mass sensor and fuel 
distributor plunger) and electronic (OXS sensor and fuel frequency valve) 
systems.  There are performance curves for both of these systems - but both are 
only really designed to cover the performance curve of the engine as shipped.

If you change _anything_, you change implicit assumptions in the system and 
have to compensate.  The mechanical part of the system is to some degree self-
regulating - but we suspect it ceases to have any effect during peak load 
situations, and there is no excess capacity to be used by mods.  The electronic 
part has some scope - but we don't know the relationship (e.g.) between duty 
cycle and enrichment.

Modifying CIS-E turns out to be pretty much a one-off business.  Personally, 
I'm beginning to suspect that even manufacturing tolerances (such as 
compression) make a huge difference.

-- 
 Phil Payne
 UK Audi [ur-]quattro Owners Club