[Diy_efi] Magesquirt vs D- jetronic

[John Nevius]

Thanks for your clarifications, Adam, you are correct I blurred the distinction between speed-density and mass flow.

FWIW, Bosch L-Jet through the late 80's (Volvo, BMW, Saab) only had a very crude accomodation for throttle position sensing.  They could read throttle closed (idle) and WOT only.  IIRC Saab was the first to use a "real" throttle position sensor.  They relied upon the AFM to trigger an increase in the fueling.  Generally these cars are considered quite driveable :-)



Cheers!

John N

Adam Wade wrote:

> --- John Nevius <jnevius at spiritone.com> wrote:
> 
> > It can operate as a true mass flow system (it knows
> > the amount of O2 being sucked into the engine by
> > knowing the temperature of the intake charge and its
> > absolute pressure)
> 
> It's my understanding that MS operates as a
> speed-density system, which is what you described. 
> Mass airflow requires a hot film or hot wire sensor,
> as I understand it.  I don't believe there are any
> home-brew MAF systems out there, although I suppose
> there is no reason you could not write code for the MS
> that would allow use of a MAF sensor.  Initial
> calibration would be a bit of a bear, I'd guess.  And
> MAF sensors are quite costly...
> 
> > Mass flow is normally better, however engines with a
> > high cam overlap sometimes produce erratic vacuum
> > readings.
> 
> MAF is more accurate EXCEPT when speaking about
> transitory airflow after rapid changes in alpha. 
> "Better" is sort of vague.
> 
> > There are variants available that allow
> > you to run alpha-N at low RPMs and mass flow at
> > higher RPMs.  
> 
> Again, ITYM speed density rather than MAF.  There
> would be no reason to use alpha n main metering if you
> had a MAF sensor, unless you were running a big cam;
> I'd recommend a straight alpha-n system for really
> lumpy cams.
> 
> > Throttle position can be used with mass flow to
> > simulate an accelerator pump on a carb'd car
> > (momentarily increase the squirt when the throttle
> > is opened).
> 
> In fact, it's required if you want the vehicle to be
> drivable.  All systems of which I am aware use an
> "accelerator pump" feature for transitory airflow
> after large/sudden changes in alpha.
> 
> > and intake air temperature (for the mass flow
> > calculation).
> 
> MAF is measured, not calculated, and a MAF sensor has
> built-in temperature calibration for the resistive
> elements.  Speed density requires AAP and AAT to
> determine density mathematically.
> 
> | 82 Honda CX500 Turbo (Cassandra)  90 Kwak Zephyr 550 (Daphne) |
> | "It was like an emergency ward after a great catastrophe; it  |
> |   didn't matter what race or class the victims belonged to.   |
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> 
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