Pulsed injectors on/off times

[Jorgen Karlsson]

> Well, I did some of the math, and on a 1.8L engine at 500rpm idle
> and at .2
> bar absolute pressure, I get 5 CFM of air. Does this sound right? Any way
> w/ that figure, comes to 4.439 lbs air/hr. At a 14:1 afr ratio that means
> .317 lbs fuel/hr. If an injector has a minimum pulse of 5%, then the max
> flow of the injector should be 6lbs/hr...and I don't think they even make
> those. So are the injectors actually turned off at idle in some
> cars? This
> doesn't make sense to me. How does the engine run at idle, if not all the
> cylinders get fuel. I thought every cylinder must get the exact amount of
> air and fuel at every rpm including idle.
>
> Maybe my question should really be how much is too much? How big of an
> injector can I use [and still have idle] on a car w/ a given engine size,
> rpm, and volumetric efficiency? Any ideas? thanks.


In addition to my previous answer I must make this clear. The injectors are
opened once per engine rev in a batch fire application. Percentages are not
used for anything but maximum usage, the time that the injector is always
measured in mS. The minimum time can probably be said to be equal to the
time it takes for the injector to open.


Ameer, are you planning on installing aftermarket engine management? In that
case you may be interested in my upcomming kits for the 10vt engine. I am
working on the details right now, supply of parts and soo on. It looks like
the alternative engine management systems will be EMS, Haltech and Autronic.
I can also do direct fire on a five cylinder engine, only Motec has made
that that possible before. I can do it with any engine management system,
even the stock system.

Jorgen Karlsson
Gothenburg, Sweden.