Thanks guys.
This weekend I managed to put some time into injectors and pumps - I finally confirmed our stock pump versus the Walbro and the SL55. I've been looking for reliable curves for months...and today I finally got undermy car and confirmed my stock pump details.


I have an engine model I've developed over the past 3 years - I still think its a little heavy on the air and subsequently the fuel requirements, but is getting closer to the mark.


See the chart.....


I am suprised the Walbro doesnt perform as well as I would have thought.
I'd be aprehensive in installing one, given it has little margin unless you put in the larger 550cc injectors so you can continue to run a 3.8bar rail. It doesnt look like it would cut the mustard if you put in a higher rail pressure. Like I said, my calcs may be a little heavy on the air (=fuel) and I believe some have installed it with some success to 20psi simply with the Bosch 0280156304's.


I think to be safe I will be going with the SL55 option + a 4.5-4.7bar fixed rail pressure and Bosch 0280156304's.
You could make the stock ones work, at 5.5bar, but I'd be concerned about the bottom end tune then.
The excess fuel from the SL55 pump back to the tank (recycle line) will be required to spill back twice as much fuel but this shouldnt be too much of a problem.


I'd like to simply use a suitable 400L/hr line filter with a 400L/hr 4.5bar pressure regulator downtream. and hook the spill back line back into the existing line back to the tank. + Plug the stocl vent line up.
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I've also added a couple of tables to adjust the injector capacity for the boost.
I looked at the Bosch 0280156072, Bosch 0280156304 and the DeutschWerks 550's sold by Needswings.
Of course they are normally rated at 3bar (for sale purposes) - however with a 3.8 bar rail pressure hitting a 1.36bar (20psi) manifold pressure - they will only be operating at a dP of 2.44bar not 3bar....so their capacity needs to be reduced accordingly by "the rule of squares".
.............eg: New cc's = rated 3bar cc's X SQRT(2.44bar) / SQRT(3bar)............to work out lb's divide by 10.5 seems to be standard number but there have been comments around different fuel densities etc....I didnt go there.


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Now I need someone to correct me - I'm thinking if I simply go with this setup, the duty cycle will look after the rest....but I still havent gotten my head around LTFT's, STFT's and their effect on open loop WOT where the damage can be done.


Appreciate any comments.


I hope someone appreciates the pump curves.