Re: [DML] Supercharger help

[Marc Levy <malevy_nj@xxxx>]

The idea that " boosts fuel pressure causing more fuel
to be injected based on the same signals" may be
correct on more modern MPFI systems, but I do NOT
believe this to be true on our Bosch systems.

There is no "signal" for fuel. The fuel is regulated
by a mechanical valve which is controlled by air
pushing down on a large disk. Increasing the fuel
pressure will also increase the resistance of this
valve/plate setup. The end result will be LESS fuel
to the injector.

The Bosch people I have spoken to claim that a
REDUCTION in fuel pressure will increase the fuel
flow. (Yes, I know.. this does not seem right at
first glance, but after closer inspection it DOES make
sense.) I have not verified this myself, but there
are some good books on the Bosch fuel systems. 

Similar fuel systems are used in some high HP
applications (on other engines), so it is likely that
adjustments can be made.

My suggestion for this project (assuming I thought it
was a good idea to add a supercharger) would be to
FIRST replace the antique fuel injection system with a
modern EFI system (multi port) that is able to handle
forced induction. This alone should buy you a few
ponies because the stock air meter and intake is very
restrictive.

A list member has already done a good job adding EFI
using a commercial system (Good amount of information
on this in the archives). A cheaper alternative would
be the "MegaSquirt", which is a build it yourself EFI
system.

After the engine is running well with the EFI, then go
ahead and add in your supercharger.

Marc

--- William T Wilson <fluffy@xxxx> wrote:
> On Sun, 18 Jan 2004, mcookwwi wrote:
> 
> > 6) What system can I piggy-back to the existing
> system to control all of this or should I just replace the existing
> ignition and fuel system?
> Just consult someone who's put in an Island turbo system and make
> the same fuel modifications (essentially, this boosts fuel
> pressure causing more fuel to be injected based on the same signals to the
> injectors). An inexact, but surprisingly effective, approach.