Crazy idea?

Thor Johnson thormj at iname.com
Sat Mar 21 05:39:40 GMT 1998


> >Hi everybody.   I just joined, have some FI experience, but I'm NOT an EE
> >(in other words, I'm easily lost in circuitry)
>
> That's okay, I for one have lots of electronic experience, but am lost in
> fuel injection (I know what gasoline smells like <G>)

Hey... that sounds familiar ;)

> >I know there are problems with injector mis-timing due to acceleration /
> >deceleration, but it's got to be better than firing them all at once.
>
> I think what you are proposing makes a lot of sense - however there is
> something to consider aside from timing - is the injector size.
---
> In order to achieve the "X" you'd have to drastically increase the
> pulsewidth, increase the fuel pressure on the rail, run larger injectors,
> or a combination of all three.  This gets a little complex for me, but you
> need to achieve the volumetric equivilent of the six injector pulses "X"
> with your one firing of the injector.

I'm not sure whether I was reading/remembering this right so, here is what I
gleaned from
here/experience on the topic of SFI vs Batch:

Batch:
  * Worse Idle performance due to fuel puddling (little effect on hi revs...
air moves quickly)
  * Can use smaller injectors (acceptable injection time is 100% of the
crank rev time)
  * Easier? (I output but it has to be beefy)
  * ONE uP output (for those running out of outputs and PWM counters)

Sequential:
  * Better Idle performance
  * Have to use bigger injectors (Tinj < 25% of Trev)
  * More complex (just imagine if you got the time *completely* reversed)

Note that the big/little injector might be a GoodThing (tm);  I was
injecting a 600cc Honda
bike motor, and the calculations came out to be *real small*, so I used SFI
+ Methanol.  Nothin
like changin your fuel when you can't find the parts ;)

Aside:  During the competition, one of my drivers blew out.  I reprogrammed
the thing to Batch
mode and slaved the "dead" injector off a good one; I can fry 3 more drivers
before I hafta
replace the board- built in fallback.

-Thor Johnson





More information about the Diy_efi mailing list