Date: Sun, 16 Feb 2003 06:45:12 -0800
Reply-To: Mark Keller <kelphoto@HIGHSPEEDPLUS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@HIGHSPEEDPLUS.COM>
Subject: Re: High performance fuel rail system.
Content-Type: text/plain; charset=us-ascii; format=flowed
Greg,
The advantage or improvement with a larger fuel rail, is related to the
localized low pressue variations that occur when the injectors open and
close at high RPMs and High power settings.
According to the Bosch Fuel Injejction, by Probst. It seems
the pulsating effect is more pronounced as the interior volume of the
fuel pressure rails get smaller. Therefore a larger volume of fuel
under pressue in the rail, the less suspectable to localised pressure
drop due to pulsation of the injector cycle, all things be relative to
the rail volume and horspower being made.
Keep in mind that Vanagon systems, all injectors fire simultaneously
and therefore a strong draw on fuel. Starvation is somwhat accounted for
by splitting the left and right cylinder banks with two fuel pressue
loops. The first cylinders on each loop are # 2on the right and # 4on
the left; leaving cylinders #1 and #3 in the downstream postion. Damage
from Fuel starvation probably isn't a concern with a stock motor and a
functioning fuel delivery system. Power drop off to the downstream
cylinders could be as RPM increases.
Just how high high a rpm? I don't know. I do know that thedigifant
fuel injection pulse is nearly full time at 4000 RPM and up. The cause
however isn't fuel rail volume, but rather is due to the low operating
fuel pressue . In other words if the digifant system were to run at 50
psi, instead of 36 psi, then the pluse cycle could be shortend at every
RPM and the increase of atomization would improve the power produced.
Back to the Fuel Rail. Even with 36 psi at high rpm and WOT, lower
pressure whithin the rail occurs because of pulsation because,open
closed cycle of the injectorslower localized fuel pressue being
available to the injector n with . Any drop in fuel pressue and full
power can't be produced. A good first step is to verify that the stock
system fuel pressure at full throttle and 4000 RPM .. 36 Psi is the
value at Wide open throttle, WOT. I believe this is critical to
waterboxer power, since the system is engineered to be just adequate. A
second step could either be a larger fuel rail or higher fuel pressure.
Since stock is generally ok, just keep the system functioning well and
to standards and power should be adequate. I do run a 50 psi system,
and am quite please with it. I've driven well tuned stock systems and
they really do quite well. The problem is that they require someone to
calibrate them.
Sincerely,
Mark Keller
91 Carat
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