BlwnAway, that would be 46-47 psi fuel pressure. I remember reading somewhere the stock fuel pump has trouble keeping 50psi fuel pressure above ~17psi manifold pressure. That also means that these fuel injectors should be an almost exact match to the JCW. Does any one else have fuel pressure readings at wot to confirm? -Jonathan
I'm with you, I understand the association of boost to FP with our systems but that calculation doesn't seem right. I was under the impression that our fuel regulators being vacuum based, worked as such: On positive vacuum, no demand, fuel flow is restricted by the regulator to a specific point, therefore 40 psi to the distribution rail at Idle. On the cusp of pos. vacuum / neg. vacuum (boost) the regulator opens more, therefore 45 psi at even pedal / cruise. With neg. vacuum (boost) the regulator opens more to meet the demand called upon it, dictated by that amount of neg. vacuum, therefore more neg. vacuum/boost more fuel for the system, and with my boost level of 19.5 or so that gave me 66 psi. at the rail. The whole reason I attached my gauge to the fuel rail was to read these changes and see the demand of the engine on the system, if I had attached the gauge pre-regulator, I would have only been able to read the fuel pump psi, which is a constant reading somewhere in the 60's.
Fuel injectors are rated on the pressure over the manifold. So the pressure that the injectors sees is the fuel rail pressure minus the manifold pressure. if i have 66psi rail pressure and 15psi of boost the net differential that the injectors see is 51psi because i have to overcome the pressure in the manifold to spray the fuel. My understanding is that the mini fuel system has a max pressure of 64-66psi at wot, as BlwnAway saw, so any boost over 14-16psi will also start to see an effective drop in fuel pressure. The reference for the fuel pressure is still vacuum based but the actual pressure the injectors see is based on a combination of fuel pressure and manifold pressure. Hope this helps. -Jonathan
Ok some updated information Link to information about fuel injector sizing. http://www.fordracingparts.com/download/charts/Fuel_Injectors_and_Adaptors.pdf The injector i am interested in is the M-9593-MU32 (bosch p/n 0 280 158 060) It flows 32lbs/hr at 39.15 psid and 36.4lbs/hr (382cc) at 50psid see calibration sheet for reference below. http://www.fordracingparts.com/parts/ics/m-9593-mu32.pdf 8 of these injectors can be had for about $300 and will need pigtails and maby o-rings. That comes out to ~$60 an injector. i need to check on the spray pattern but i think it should be similar to the 550cc ford racing injectors all the tuners are using now. the real question is why has no one tried these before? There has to be a good reason. -Jonathan
Price. You can get JCW injectors for $80/apiece online (13-53-7-574-132 link), so why spend time adapting these other injectors and convincing people they work just as good as JCW injectors? Even if you're saving a fair amount of cost, the potential sales volume is small.
never mind, the part number posted above is for the standard injector. http://www.realoem.com/bmw/showparts.do?model=RE93&mospid=51243&btnr=13_0978&hg=13&fg=15 -Jonathan
These part numbers are crazy. I combed through RealOEM, PelicanParts, and IMBM to come up with this: Cooper S 13-53-1-521-390 Superceded 13-53-7-572-995 Cooper S JCW 13-53-0-391-511 Superceded 13-53-7-556-980 Superceded 13-53-7-574-132 IMBM is showing the same price for both the -995 and the -132 injectors: $80.