[T2] Using 2000cc FI hardware on early 1800 cc bus

[Al Brase]

First of all, the AFM does not measure MASS, it measures volume, and that
would be fine if we only ever drove at the same elevation.But a given
volume of air at 5000ft above sea level has a lot less oxygen in it than
the same volume at sea level. The hot wire systems are properly called
"Mass" air flow meters whereas flapper boxes are not. Some came with a
switch for use above a certain elevation. Of course a later system with O2
sensor will keep it a lot closer.
Having said all that, your 1800 will likely be just fine. The 1975 1800
motor flowed nearly the  same as a 2000 motor anyway. I think it made more
horsepower. Because it had bigger cam and bigger valves. I realize there
were different  ECU's for every damned combination 1.8, 2.0 automatic,
manual, etc. I think the EGR's were different on some. But I doubt you'd be
able to tell the difference. What DOES make a difference is the spring
tension and wiper position  in the AFM. So maybe eventually pop the top and
bump the cog wheel around a little to see if it gets better or worse.
Probably should keep a pad and pen right there to write down and remember
where you are at.
Al

On Fri, Jun 15, 2018 at 11:19 PM, MUTS <muts at verizon.net> wrote:

> I just heard back from Kyle re using a 2000cc harness and AFM and "brain"
> on a 75 bus with 1800cc engine - he claims that the brain is "dumb" and
> will meter out more gas for the movement of the vane in the Air flow meter
> and so run rich- could only affect this by increasing tension in the AFM
> spring and would need an O2 sensor to set this?  I would think that less
> air mass per minute would deflect the vane less if the air flow meters are
> the same in their vane size-and thus compensate for the engine size?
>
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