Date: Wed, 3 Jun 2009 14:26:32 -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?
Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=original
looks like everyone has it understood now .......
but just in case......
this notion : "The fuel pump runs for a few second every time an injector
fires." is totally off. The fuel pump runs full time once the engine is
running, of course.
also, fuel is not injected into the cylinders.
it's injected into the intake manifold, right near, even into. the intake
port for each cylinder.
Then the fuel/air mixture is drawn in by piston downward movement - the
intake part of the four stroke cycle.
relatedly.......to me anyway ................
People may find 'waste spark' ignition interesting.
Many modern cars use this. It occurs 'naturally' on a 4 cylinder engine,
( or 6 ) if you are designing an engine, and want to eliminate the
distributor.
Engines like that...........such as the common Subaru EJ22 have a coil with
four spark plug wires coming off it. and no distributor.
It just works out that firing each plug at tdc for all cylinders, whether on
compression, or exhaust stroke works out just fine.
If there's any unburnt fuel still left in the cylinder, or starting down
the exhaust pipe........sparking that plug again helps burn it , reducing
emissions.
and getting rid of a mechanical thing with bearings and so forth, like a
distributor ........that's always a great thing......fewer parts to wear,
etc.
Almost no modern cars have a distributor. - it's a great part to not have
on there.
I have in the back of my mind a plan to run a waterboxer off a Subaru fuel
injection and ignition system ............though so far .........
the easy solution of where to have a camshaft position sensor is .........to
keep the waterboxer distributor and use it for camshaft position reference
to keep the soobie Ecu happy. So there would still be a distributor on the
waterboxer engine in that case........but the subaru fuel injection is
massively stronger and more accurate than the waterboxer fuel injection
system and might be worth the effort.
And subaru uses sequential injection firing of course ............and since
the ECU knows what part of the 4 stroke cycle each cylinder is on ......
I imagine not only is it sequential...........like each cyldiner fired in
order, individually by the ecu at the right time.......it might even be
timed to the beginning of intake stroke , since the ecu knows there the
camshaft is.
On the waterboxer..........all the ecu knows is that the engine is
turning.............and how fast, that's it. There's temp and air flow
meter inputs of course ........
but 'timing wise'. ........waterboxer fuel injection is rather crude and
retarded actually........and I mean 'retarded in the lacking intelligence
sense.
Scott
www.turbovans.com
----- Original Message -----
From: "Dennis Haynes" <d23haynes57@HOTMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, June 03, 2009 2:53 AM
Subject: Re: Why does the fuel pump cycle twice?
The injectors actually fire once each engine revolution or for our engines
every other spark pulse. All four injectors fire together.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Gregor Brandt
Sent: Tuesday, June 02, 2009 9:52 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Why does the fuel pump cycle twice?
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
>
