Date: Wed, 3 Jun 2009 14:36:11 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Why does the fuel pump cycle twice?
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re
"I assume they only are operated
for a fraction (one quarter?) of the duty cycle to get the proper charge."
no sure what that means, but the injectors are held open for so many
milliseconds.....that is the only variable on them .........
fuel pressure is fairly constant ..........how much they'll flow is constant
.....it is only how long they are held open by the ecu that determines
mixture .
the ecu uses it's inputs to decide how long to hold the injectors open each
time they are fired.
inputs of course are coolant temp, air temp, throttle position ( rather
crude, it only recognizes closed throttle and WOT ) , air flow meter input
and rpm signal. ............and I think that's it. The ecu doesn't even
know the position of the engine .........just that it's turning, and how
fast it's turning, and what those inputs are. Someone might think of
another input or two ....but that's all I can think of right now. It's not
a lot of inputs at all.
And if there's no oxygen sensor ........like non-California air-cooled
vanagons.........the ecu doesn't even have any feedback to know what result
it's outputs are producing ! First time I saw that .....I though , how can
that work ? ..............the ecu is just trusting that how long it told the
injectors to be open is right.
Very crude. Subaru engineers would puke into their sake and laugh their
asses off if studying the earlier electronic german fuel injection systems,
they're so crude compared to what occurs in the 90's and onward.
Scott
----- Original Message -----
From: "Kenneth Lewis" <kdlewis@NORTHSTATE.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, June 03, 2009 4:51 AM
Subject: Re: Why does the fuel pump cycle twice?
> Gregor,
> The injectors are wired in parallel so they all fire at the same time. I
> agree, it doesn't sound very efficient. I assume they only are operated
> for a fraction (one quarter?) of the duty cycle to get the proper charge.
>
> Ken Lewis
> http://neksiwel.20m.com/
>
> On Tue, June 2, 2009 9:51 pm, Gregor Brandt wrote:
>> If the FI fire everytime a spark fires, and there are four plugs
>> sparking at different times, does that mean 3 times out of 4 we are
>> throwing fuel into a cylinder that is not firing? Where does that
>> fuel go, is it wasted?
>>
>> Gregor
>>
>>
>> On Tue, Jun 2, 2009 at 7:32 PM, Ken Lewis <kdlewis@northstate.net> wrote:
>>> Robert,
>>> That sounds like normal operation. The injectors fire every time a spark
>>> plug does. The fuel pump runs for a few second every time an injector
>>> fires.
>>> When the engine is running the pump never times out and runs
>>> continuously.
>>> Ken Lewis
>>> http://neksiwel.20m.com/
>>> in statu viae
>>>
>>
>>
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