Rpm Independence.

Tom Sharpe twsharpe at mtco.com
Wed May 12 03:18:13 GMT 1999


Let's see... If we add a flapper to the inlet stream to measure airflow and a
needle in the jet(s) hooked to the flapper to control mixture and raised the fuel
pressure/volume with rpm, we could adjust everything with a screwdriver....i think
cheby didit in '63...  Sharpe

PS Good ideas, I'm building a prototype PIC fuel pump controller...  What would
you like the fuel pressure to be????? How would you like to control it??

Robert Harris wrote:

> Once upon a time there was something known as a binary scale.  Lets see 1 bit
> = 0 or 1, two bits 0, 1,2,3 and so on until we have 8,9, or 10 or whatever
> bits.
>
> Now if I were doing this, the input would come from MAF and whatever and a
> binary number would be generated.   This would then be the index into a table
> where the output would be the pulse width.
>
> BUT, not being enamored with the swiss army knife approach where one tool fits
> all, I would not use a single injector per cylinder or whatever.
>
> If the upper bit was connected to a solenoid valve that simple opened a
> calibrated jet that was 50% of the flow, I have just doubled the dynamic range
> of the "injector" without getting crazy.
>
> Now if you were binary enlightened, you might use a number of these jets,
> driven off output bits of your table such that except for a very small amount
> of variable fuel to do final trimming, everything is on fixed jets.
>
> Of course there would be no advantage to run these fixed jets say at 100 psi
> off a bosch pump would there?  And no advantage to staging them so that the
> higher the flow, the further up the manifold runner they are as to allow
> maximum cooling of the charge.  And no advantage to these jets being smaller
> than your little finger.
>
> And if this was a throttle body, totally eliminating the pulse width modulated
> injector itself by using a lambda valve as a high speed solenoid to turn on or
> off the finest jets.
>
> Calculating the flow is simple math since the orifice is fixed and the
> pressure is fixed.  Also can vary the number of jets in each step.  8 "jets"
> generate 256 steps - probably far finer than a real engine needs, but not near
> enough to satisfy the anally retentive who believe that precision to 10
> decimal points is required to run an engine.
>
> But silly me remembers that the basic advantage of pulsed injectors is to
> improve the idle to ~2500 rpm emissions.   And CIS type thinking on the Bosch
> System used in some models by Jaguar, BMW, Mercedes, Audi etc was really
> crappy at idle, had no power, was balky and all screwed up, couldn't
> accelerate or run smooth   -  *** NOT***.
>
> And since the whole damn thing is fixed jets driven off a table - either on or
> off, someone who is not chemically challenged might just arrange for some of
> these jets to be connected to fuels other than gasoline - say methanal with a
> taste of nitromethane - or staged with supplementary gaseous induction like
> NOS.
>
> But that's not going to happen to anyone who loves the swiss army knife
> approach.  Twist your sister and think about it.






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