efi555

[dn]

Peter Wales wrote:
> one on a race car and know it works so ask questions when you have problems
> and I will do my best to help
> 

Peter:

And so it begins.  The questions, I mean.  I think I have a pretty
good handle on how this thing would work, but I have a few
specific questions on the circuitry.  From what I have read, the
unit just uses pulses from the MAF to fire an injector with a
fixed duty cycle (at least for now) every X pulses (essentially
every so many litres of air).  Essentially a fixed pulse width,
variable frequency system.  Later, a CPU could be added to
modulate the injector pulse width to compensate for temperature,
acceleration enrichment, etc.  So far so good?

Ok, now for the guts of the thing.  Is the 555 run as a one shot,
triggered by the MAF pulse, with duty cycle adjustable by the 
control pin? 

How do you determine the number of MAF pulses per injector firing?
What kind of frequency range does the MAF put out?  

Since the system is essentially asynchronous with engine firings,
how do you ensure that the engine does not just get a slug of fuel
on one cylinder, then nothing on the next, etc.  Do you fire the
injector many small pulses per revolution, or what?  As the engine
speeds up, you would have more cylinder firings per second, and
also more MAF pulses due to increased airflow with RPM.  Do these
need to by synchronized somehow, or does it not matter?  Or do
you use a 5 gallon bucket for an intake plenum to smooth it all
out?

Lastly, some questions on the MAF sensor you recommended.  I am
not familiar with a Starion, They may not sell the model under
that name here in Canada.  (Then again, I don't follow the new 
car lines much, I'm a 60's +70's vintage kinda guy).  Some details
on what other models, makes, and years used this MAF would be
helpful in a junket to the local boneyard.  Will this thing handle
the required airflow for a V8 making 400+ HP?

I'll try not to pester you too much with this, but it sounds
almost too good to be true.  I'll be hunting down parts over the
next few weeks, and I'll post my results to the list if anyone's
interested.  Thanks in advance for any info.

Regards
dn



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 Darrell A. Norquay                Internet: dn at dlogtech.cuc.ab.ca     
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