Briggs&Stratton Injection

[Ville Ollikainen]

At 21:24 27.1.1998 EST, Ccskidmore writes:

>To the collective:
>
>I am gearing up to put together a small analog control system on a Briggs &
>Stratton
>5 HP engine with a generator.  The scope is a fuel injector using speed as
>feedback(1800rpm)  as well as an O2 sensor to trim for emissions and fuel
>consumption.  I have examined the archives, and found small bits of
>information on past projects but no definitive proven results.  
>
>     Especially to those of you who have experimented with these small
>engines, I would appreciate any guidance and suggestions; especially
>information on particular physical setups; injectors, size, part numbers,
>pulse width, driving circuit (LM1949?).  Also experiences with EGO sensors
>(probably need to be heated?) or alternatives for emission feedback. Also
>thoughts on rpm feedback...inductive, frequency, external(package bought from
>NEWARK or somebody)????


I have modified a 10cc OS 60FS engine for fuel injection. I made a wire
wrap board around Motorola 68HC711K4 controller, using fixed parameter
tables for ignition timing and injector control. This engine is made for a
supermileage vehicle (for more information of the concept, see
www.sci.fi/~fmmc). 

Running your B&S engine with a generator makes things simple, I guess you
could leave out feedback and get the parameters from a fixed table as well.
The fuel consumption should not be the issue: Very few - if any -
supermileage vecihles are using O2 sensors, yet figures like 4000 MPG are
not unusual.

The fuel system is pressurized by compressed air.

In my project the biggest problem this far has not been the electronics,
but the injector. The pulse width is awfully short, even at full throttle.
I modified an old Kawasaki injector by reducing its valve opening (from 0.7
to 0.4 mm). I should reduce it further to use longer than 1 ms pulses. With
a new coil (1 ohm resistance and small inductance) the injector became
barely fast enough. The driving circuit is an open collector power
transistor protected by a slow 3A fuse, very conventional...

If you know a fuel injector made for small engines, please let me know. The
use of this modified injector is not too optimal: I do not recommend a
similar modification for anyone, if an alternative exists. In your case the
engine volume is a lot bigger, so there are better chances to run it with a
standard part.


best regards

Ville Ollikainen
a proud member of Finnish Mileage Marathon Club