Supercharger info

Chris Morriss crsm at oroboros.demon.co.uk
Tue Aug 11 18:24:51 GMT 1998


In message <01BDC554.C86F3D20.dzorde at soanar.com.au>, Dan Zorde
<dzorde at soanar.com.au> writes
>'71 I think, fiberglass and perspex Fiat 850 sport.  The 555 setup will 
>probably be along the lines of what you have come up with although I thought of 
>using a MAF instead of the MAP, altitude won't be a problem as everything in 
>this end of the world is flat as.  Intention is to look at a Ford MAF (think 
>this was the one that was voltage output) and use this in combination with air 
>and water temp to run the 555 (as its purely a race car O2 won't be needed). 
> By using the MAF and knowing exactly how much air goes into the engine, do you 
>still need MAP ?  Can you see any pitfalls in this ?
>
>Dan    dzorde at soanar.com.au
>
>On Tuesday, 11 August, 1998 3:29 PM, Walter Petermann 
>[SMTP:corsaro at brokersys.com] wrote:
>> Dan,
>> don't know zip about turbo's but I'm interested in the 555 circuit and
>> the car. What year is it?
>>
>>   Walter
>

It's difficult to use MAF on a simple analog system if you want to fire
the injectors once per crank revolution.  Imagine that the engine is
loaded such that it requires the same amount of fuel per revolution at
6000 rpm as it does at 2000 rpm.  The MAF at 6000 rpm is going to be
roughly 3 times as much as at 2000, so if you fired once per rev,
without compensation, then you would be overfueling the thing grossly.
You need to divide the MAF by an amount proportional to rpm.
(Analogue division and multiplication can be done, but it's a pain).

Stick to MAP, the fuel required versus MAP curves are much easier to
implement.

Of course, if you were prepared to fire the injectors at a constant
frequency, irrespective of rpm, then you could easily relate the
injector on-time to the MAF.
-- 
Chris Morriss



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