[Diy_efi] Re: idle control strategy for SD systems w/o bypass air control?

[Marcell Gal]

Hi Jerry, 

> A lot of DIY and I suspect some aftermarket EFI systems have no 
> bypass air control. 

so they have a small fixed bypass-air path? 

> chosen RPM? I know, adjust the injector timing, But on what 
> do you base your decisions, and how fine grain do you need
> to be, and what do you decide?

I guess you have to lean the mixture,
controlling it for RPM using eg. a PID controller (algorithm).
(you measure RPM anyway) 

potential problems (IMHO):
 - if the bypass path is too narrow, it cannot flow enough air
at some conditions (air conditioner turns on, which happens rarely
on motorcycles)
 - if you make the mixture too lean, the exhaust temperature
can get too high (maybe this is not that big of a problem
with small flowrates and RPM) 

 - the uncloseable bypass path might cause unwanted turbulence
at higher flowrate (depends on aerodinamical engineering). 


It seems to me that there is a tendency
to control all air electronically,
where throttle is all electronic. This enables engineers to
implement desirable throttle-pedal characteristics
and have high efficiency at most conditions. 

Cell 

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