[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]

Re: [T3] Fuel Pump Specs

--- Russ Wolfe <russw@classicvw.org> wrote:
> On Mon, 2005-02-14 at 15:14, James Montebello wrote:
> > Pumps don't deliver "pressure", they deliver
> "flow". 
> > A  restriction in the line after the pump (like
> the
> > fuel pressure regulator) is what makes "pressure".
> > The pump merely has to be able to pump fuel
> against
> > that pressure to operate.  Increasing the flow w/o
> > touching the FPR will increase line pressure. 
> > Twisting the adjustment bolt on the FPR will alter
> > line pressure w/o altering pump flow.  So, the two
> are
> > related, but can be adjusted independently, so you
> > can't really get pump flow from the pressure w/o
> > knowing the restrictions.
> This is not entirely true. Some fuel systems are
> "returnless" systems.
> The pressure is regulated right at the pump, and it
> maintains a constant
> pressure in the fuel rail at the engine. The
> regulator senses the flow
> and adjusts the pressure in response to demand.
> There is not regulator
> on the downstream side of the engine.
> Bosch builds one of these systems for the JEEP, and
> the SeaDoo Jet Skis
> Walbro/TI builds them for Chrysler/Daimler, and
> Mercedes.

I really don't want to get into a semantic pissing
match here, but what I said was perfectly true.  A
fluid pump does not generate pressure.  A regulator
does. If the regulator happens to be built into the
same housing as the pump doesn't mean the pump itelf
is still generating pressure.  This is basic

Some pumps are electrically "throttled" by regulating
the voltage to the pump itself to reduce its flow. 
This is how the Chryler "returnless" pump works,
anyway.  In this case, there is no mechanical fuel
pressure regulator.  Instead, a pressure sensor and
some electronic method of regulating the pump voltage
based on that output of that sensor is used.  I
wouldn't be at all surprised if more recent pumps
don't integrate the sensor and electronic regulator
into the pump housing itself.  I felt this was far
enough off topic to not be worth mentioning here, but
there you are.

Still more pumps are deliberately designed to be weak
against line pressure, and will simply stop when line
pressure reaches some rough point.  Many "interrupter"
style pumps do this (Lucas made a number of these). 
These types of pumps are mostly for carb use.

None of this answers the original question, which was
the approx. flow rate of the stock T3 pump.    

Do you Yahoo!? 
The all-new My Yahoo! - Get yours free! 

List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]