Originally Posted by
waldig
Remember that the boost is reducing the pressure differential across the pintal limiting your fuel available. I have run a car without a fuel pump, at idle when the manifold vacuum actually sucked the fuel from the injector. Open the throttle and it dies though.
If you have a rail pressure of 60 and a boost of 20, you only have a 40 psig differential to fuel the engine. I did testing and posting showing how raising the rail pressure solved it all.
I used the boost to feed back into the regulator fitting and at high boost got 80 psig on the rail and consistant 9:1 F/A ratio. Way too much, on my car I only needed to boost the rail pressure a few pounds to keep in the proper range. This is why I did not choose to try changing the injectors.
Enjoy, Woody
I was surprised to learn this. On the turbo cars I've had experience with the OEM fuel pressure regulator is referenced to the manifold pressure/vacuum. Thus the fuel pressure across the injectors is constant, the spray pattern consistent, etc.
As long as the pump is up to the task (i.e. Walbro, SL55, etc), I would think the stock injectors could provide all the fuel you'd need with an adjustable boost/vacuum referenced fuel pressure regulator. Sounds like your results Woody already proved it.
All things considered, a fuel pump and regulator upgrade is pretty cheap and easy. And maybe throw in a looped fuel rail to assure even distribution. You would need to get a TUNE specifically for the variable fuel pressure though.