Fwd: eddy current brake

[John Hess]

The way these systems actually work is a whole lot simpler than that.=20
 They simple fire 360 degree pairs simultaneously.  In other words,=20
the fire one cylinder at the actual point required to ignite the=20
mixture in the cylinder, while firing its twin, simultaneously,. at or=20
near the end of the exhaust stroke.  No attempt is made to break this=20
up into 8 firing cycles, 4 is quite adequate for an 8 cylinder=20
engine.

John


----------
From:  Bob R. McElroy[SMTP:rmcelroy at midcom.anza.com]
Sent:  Friday, December 13, 1996 6:39 AM
To:  'diy_efi at coulomb.eng.ohio-state.edu'
Subject:  RE: Fwd: eddy current brake

With a 4-point crank wheel and one sensor for that wheel, you would=20
have 4 pulses, each 90=B0 apart.  A sensor wheel could be constructed so =

that it gives a rising edge and a falling edge four times per=20
revolution, with the falling edge 45=B0 out of phase with the rising=20
edge.  This provides the 8 points necessary to have a resolution of=20
one event  every 45=B0.

I'm responding to this post because it took me a couple seconds to=20
understand what was intended.  I first thought a wheel with four small=20
(a couple degrees wide) teeth was being described.  I then realized=20
that Tom was describing a wheel with teeth that spanned 45=B0 each.=20
 However, I'm still puzzled when he states "2 revs =3D 360".  One=20
revolution equals 360=B0.  Two crankshaft revolutions, however, does=20
equal 360=B0 of camshaft revolution (oh, now I get it.  Never mind.)

When you start talking about PLL, however, I'm lost.  What exactly=20
does a PLL do or tell you?  Sorry if everyone else considers this=20
question trivial, but I only studied basic electronics in college.  I=20
was lucky enough to take a class on internal combustion engines, but=20
that mainly centered on the thermo-chemistry involved with combustion,=20
and not many practical exercises (like most of my engineering=20
courses.)  On the plus side, I did get to use the Heywood text book=20
that I see listed under the recommended reading list for EFI=20
information.

Thanks for any help.

Bob McElroy

----------
Lessee, 600 at idle to 6000 is 10:1, which is enough for me.  With a=20
4-star
crank sensor, you get a pulse every 45 degrees, since 2 revs =3D 360,=20
right?
Then, if you PLL'd the freq by 45, you'd have 1 degree pulses, by 90,
.5 degree.  Am I right?  I think I understand the need for=20
'reasonable'
accuracy with firing, but you've already got a hardware (crank) 45=20
degree
reference.  The PLL jitter shouldn't give but only a few tenths of a=20
degree
error, if that much.  Capture shouldn't be a problem, as I don't see=20
how you
can rev or decelerate the engine fast enough to lose lock.

Remember, I'm just positing here -- never actually tried this.


Tom Cloud <cloud at peaches.ph.utexas.edu>