Reply to "Stroker Motor Questions by Dave F #5972"

> Dan, Here I have to disagree with you. In the case of Weber 48 IDA's on an
> IR manifold, camshaft overlap needs to be limited as much as possible.

I was referring to IR EFI which has no such limitation. Webers and non-timed
mechanical injection have that problem because they are constant flow. But
with SEFI, the fuel is not injected on the overlap pulse. I know guys running
260 degree duration (at 0.050" lift) cams with IR EFI and they have no problems
with reversion.

> The reversion from the valve overlap pushes the raw fuel back out of the
> stack.

Not if there isn't any fuel there to begin with. It also depends upon the
length of the stack (i.e. the harmonic you choose to tune). If you pick a
stack length that tunes at the first harmonic, the effect is strong in a
narrow RPM band. Tuning to the second or third harmonic is less sensitive
and broadens the RPM spread.

> What I interpret that as saying is that they (Hilborn) have written a fuel
> map for you. Since you don't have a computer, or need a computer, you don't
> change it, or you simply can't change it.

The Hilborn system uses a computer to perform the fuel injection and requires
tuning but does not use a laptop as the user interface. My guess is it's like
the SDS (Simple Digital Systems) or the PMS (Programable Management System)
which use a handle held interface with buttons. This is a simpler but less
flexible approach.

> I think I started the "no 02 Sensor" stuff when I posted this quote from
> Hilborn a few days ago

There are three popular EFI control schemes:

1. mass air flow
2. speed density
3. alpha-n

None of them require an O2 sensor. A friend runs a mass-air Ford EEC-IV
without O2 sensors, for instance. All of the above control schemes can be
used with or without and O2 sensor. They differ primarily in the way they
sense engine load. Speed density systems use manifold vacuum via a MAP
(manifold absolute pressure) sensor to sense load. Fuel is metered using
the MAP input, engine RPM, and volumetric efficiency tables. Mass air
systems use a MAF (Mass Air Flow) sensor to directly measure the amount of
incoming air. Those sensors typically use wires that air exposed to the
air flow. As the air flows over the wire, it changes the voltage drop
across the wire. Tables in the computer convert the voltage drop to air
mass. Alpha-N systems are the simplest, using only RPM and throttle position
to determine load. Note that a MAP sensor can be used with Alpha-N, but it's
used as a barometric pressure sensor to detect altitude changes. You can
also blend the authority of Alpha-N and speed density by weighting the
authority between the throttle position sensor and the MAP (manifold
absolute pressure) sensor.

> How did the performance change on the classic mustang when switching from
> carb to EEC-IV. Did you get smoother running, more power and better fuel
> economy??

When the stock long runner Ford 5.0L EFI intake is swapped over, you
generally get better low end torque at the expense of higher RPM power.
A shorter runner intake can gain the high RPM power back. Part throttle
fuel economy is generally improved but highway cruise fuel economy can be
slightly better with a well-tuned carb. This is because the car can be
tuned to e lean under those conditions. This can be done with the Ford EFI
system but requires some modification. Cold start-up and idle are generally
improved.

> Just how common is this stuff in breakers yards in the US?

Very common. Ford went SEFI on it's Mustang 5.0L in 1986. It's a straight-
forward swap on early Mustangs since they use the same engine. With a similar
overlap cam and displacement, little to no tuning is required. If you
substantially modify the engine or use a larger displacement engine, you'll
need one of the tuners (PMS, EECtuner, TwEECer, etc.) to get the maps correct.

Dan Jones