Dear Walter,


At 20.02 2011.11.26, you wrote:
>
>
>Electron wrote:
>
>> At 11.42 2011.11.25, you wrote:
>> >
>> >>  The trick, I imagine, would be building a
>> >> carburetor for a more efficient engine.
>> >>
>> >
>> >The current engine controllers have efficient carburation. They use
>> >fuel injection with a model of the relationship between time of the
>> >incoming air and its location during detonation.
>>
>> What does have detonation to do with normal combustion? When detonation
>> occurs, the ignition time is retarded and/or the A/F ratio is made less
>> lean. When detonation is not detected, it doesn't enter into the equatio=
n
>> of the injection (or of the ignition) at all.
>
>When detonation is detected the mixture for the next few cycles at that
>point is leaned to oxidize the carbon particle the usual cause of detonati=
on.

While carbon spots are often the cause of preignition (thus possibly also o=
f
detonation), leaning the A/F ratio will very likely cause detonation itself=
..

My experience is with racing motorbike engines, not cars, however I think i=
t
applies to a good extent.

Could You please quote some doc online where they say that when detonation =
is
detected they actually advance, instead of retarding, the ignition?


>> >The fuel metering is adjusted every 2-4 microseconds to get uniform mix=
ing.
>>
>> What? 2-4 microseconds means 30000000-15000000 RPM, while the A/F ratio
>> is adjusted at best every revolution of the engine (2 on 4 strokes).
>
>The fuel flow rate is being adjusted every 2-4 microseconds on some cars
>actually many cars. The days of simple one shot injectors has essentially =
gone.

While I know that some modern automotive injector "spray" more than once ev=
ery
engine revolution (to improve pulverization), how can a mechanical valve (s=
olenoid
or even piezo) move that quickly?

Specifically, injectors I know that open in less than 1 ms (which is alread=
y a
very fast injector!) tend to cost a lot.

Moreover, a fast injector that opens and closes multi-times per cycle would
improve pulverization and homogeneity of mixture a bit, but 2-4 us, even if=
 it
could be achieved (I would be grateful if You could point me to an injector=
 on
the Net that does it) what would improve? You need to bring A/F mixture int=
o
the cylinder in the inlet phase, four strokes (even more SUV ones) don't re=
ally
have any problems with "normal" injectors.. racing 2 strokes would benefit =
more,
but 2-4us per "spray" is an unbelievably (and apparently unnecessary) short=
 time
for a mechanical device.

With kind regards,
Mario

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