Fuel Pressure

[Seth]

On Fri, 5 Sep 1997, James Weiler wrote:

> 
> 
> On Fri, 5 Sep 1997, Dick Protus wrote:
> 
> > 	I've noticed that the fuel pressures I've seen have seemed low.  
> > I know most of you are doing conversions and using stock components, but I'm
> > used to seeing 5+bar, not the 1.7-2.0 bar most of you seem to be using.
> > 	I've seen injectors rated to 30bar (probably would have to go an F1 
> > team to find those in use though).  I was just curious why/how everyone 
> > choose the pressure they did.  Safety? Convience? Or another reason.  
> > 
> I'm sorry Dick did you say 5 bar ??? that's 75 psi????  wow, what kind of 
> applications are you dealing with?  CIS ?? Diesel?
> 
> jw
> 
I am not speaking for Mr. Protus, but 5 bar doesn't seem that high to 
me.  Beetles run at ~38 psig or 2.5 bar, CIS cracks the injectors at 
48psig, or just over 3 bar.  A good bosch pump will do 90-125 psi, 
depending on who you quote.  From memory, mechanical injection for 
gasoline, into the ports is on the order of 10 bar, and the mechanical 
injection on mercedes 300 racecars with in cylinder injection, was 20 
bar.  Here at the VRI we have run direct injection with EFI injectors at 
100 psi.  The new unit electronic injectors for diesels are quoted at 
just under 2000bar, or 28,000psi.  The advantage is better atomization 
and reduced unburnt kernels in the diesel exhaust.  So most of that is 
academic, but I am planning on running my rail pressure as high as 
possible for my second stage injectors, as they don't have the luxury of 
spraying on the back of a hot intake valve.  They are a few inches 
upstream.  Hoping that will reduce the wall wetting.

I don't know what the upper flow rate for a bosch roller vane pump is at 
75 psi, or 90 psi, and driving 4 injectors at 80% duty cycle might reduce 
the rail pressure. I don't have information on that, but I am planning on 
bench testing the system, so I should be able to find out ahead of time.

Seth Allen

ps, anyone know of a free/cheap cross compiler from a 68k mac to a 68HC11 
for "C"?

thanks in advance