Diagnosis needed... (also Bosch fuel pump specs)

[Seth Allen]

> From: Charles <cmorris at ix.netcom.com>
> To: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Diagnosis needed... (also Bosch fuel pump specs)
> 
> Does anyone have the specs for a Bosch GFP-215 pump? It has the 7/16"
> nipple at the inlet and 12 mm female threas on the outlet side.
> 	Specifically I'm interested in the flow rate at 60 psi - my
> system seems to be maxed out, although it could be cavitating on the
> inlet side. Car is a BMW 745i (3.5 liter turbo) with 3.0 bar (43 psi)
> nominal pressure, running 15 psi boost (hence 58 psi fuel pressure),
> two extra injectors with a homemade 8748 controller, and a small
> nitrous setup (one 40 hp nozzle).
> 	When I take off hard, after about 5-6 seconds, there is a
> _severe_ misfiring that occurs. If I lift somewhat, it catches and
> runs fine. Sometimes I can see the fuel pressure drop very briefly on
> a gauge connected to the rail. I have replaced the stock pump with the
> above Bosch pump (GFP215), and run heavy leads to it since the stock
> wiring was too small. Also I have installed a #6 braided Teflon line
> (.42" ID) from the pump and filter to the rail.
> 	I called Kinsler fuel injection for advice. They said my pump
> should be plenty big enough, but that the in-tank transfer pump (rated
> at something like 2 liter/min, which is marginal for 400 hp) might be
> causing a restriction if I was trying to pull more fuel, and to remove
> it. So I did, with basically no improvement.
> 	The tank has a 1.5 psi pressure relief valve to the outside air
> (which also can allow air back in to the tank). It is working
> properly.
> 	What's interesting is that the volume of fuel contained in the
> new fuel line is just about the amount that would be moved in 6
> seconds or so. This is why I suspect the problem is the pump itself,
> or cavitating at the inlet.
> 	Any ideas gratefully received - before I start tearing it (and my
> hair) apart...
> Thanks!
> -Charles
> cmorris at ix.netcom.com
> 
> 
Charles- Not to overstate the obvious, but have you checked the fuel 
filter? I would replace it, if you haven't already.  Next, you need 60 
psi at 0.5gpm, but thats pumping thru a bosch filter, and through 14ish 
ffet of 0.42"id hose.  I bet if you put one or two transfer pumps (in 
parallel) in the back of the car and put the small pressure pump resevoir 
up front, you might get enough flow.  Or you might need fuel filters in 
parallel.  My bosch pump ( for a measly VW golf GTI) is rated at 2liters 
per minute with no pressure head.  I bet you are taxing your pump, as you 
suspect, but i bet you can get by without two pressure pumps.  I bet 2 
liters per minute at 60 psi after a fuel filter might be a bit too much.  
You could also try a couple of accumulators in series after the pump.  
That might be the best bet.  You could get 100-200cc reserve volume for 
those times when you can use 400 bhp, then the accumulators refill.

Good luck,

Seth