Sequential Setup?

Mark Boxsell mrb at mpx.com.au
Sat Feb 10 10:11:02 GMT 1996


>
>The only way to see the effects of the above is to be in constant TRANSIENTS
>which is were our engines spend 80% of their time.
>

>
>Regards
>
>R.S.Sian
>  

Raghbir,
This may be so but not all of us have the exotic equipment to measure
changes to engine acceleration, etc. You must be chasing cycle to cycle.
I tend to stick to Peter Wales comments (providing I don't make a spelling
mistake) however I agree it is necessary to qualify any comments.
I give an example.
We had a single cylinder rotary valve research engine (250cc) using a
"plate" style injector (from "Lucas, prince of darkness" if my memory serves
me correctly) which did not atomise the fuel very well. Changing the
position of injection in relation to the inlet valve window we could get 30%
change in torque at a (constant) test speed of 3000 RPM. We replaced this
injector with a "pintel" type which gave very good atomisation and we could
not measure a change no matter where we positioned the injection period.
Most of my experience is on racing engines. In part throttle "off cam" areas
in the RPM range you can measure changes, you can even hear the difference
however apart from helping the guy drive out of the pits there are no MAJOR
gains to be made from sequential. Emission and OEM development often have
quite different goals to racing so what is important to some may not matter
to others.

To anyone studying this area a useful exercise is to graph the TIME taken
for the inlet period (eg. 240 degrees) and graph this against RPM. The inlet
time in degrees is fixed however notice how the actual inlet TIME changes
quite dramatically.
Then graph a fixed injector duration say 5 milliseconds against the above
graph and you will see there is a interesting comparison between the AIR
FLOW period and the FUEL FLOW period. Since we are trying to get the two to
mix....... 

             regards,
                      Mark Boxsell
                      MRB Design






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