Adjustable FPR question.

[Sagaris]

I am running M50 17.5 lbm/hr injectors and a Mark D 91 octane EPROM on my M20 325i.
I have plans to get long tube headers , some basic head work (port matching/smoothing the exhaust runners) , and a mild cam (less than 288), and no immediate plans to do a stroker kit or anything. Do you think I might run lean without further modifications? (planning on running a wideband + gauge for verification). If it turns out that it runs lean, is an adjustable fuel pressure regulator an appropriate solution? or should I also be looking at 19 lbm/hr injectors? Do you have any recommendations on adjustable FPR's. I would like one that is easily adjustable and can be connected to a pressure gauge easily.

[whodwho]

You could use one to make minor changes. I would look at the Accufab or Kirban ones, they are direct fit to the fuel rail.

[jlevie]

I don't expect you to have any problems with the engine running lean. But if you do a WAR chip or similar would be a better solution than an adjustable FPR.

[nando]

What makes you think it's going to run lean?

[Sagaris]

My new ebay electric supercharger kit. :jk:

I don't know how much the Motronic system can adjust for increased mass-flow and I want to be prepared in case it cannot compensate enough.

[nando]

well you can't install a cam and all that stuff and expect it to magically tune itself. Aside from the AFR, your timing won't be optimized. without tuning you might gain 5hp. It's not going to explode and will probably run just fine, it's just going to leave most of the potential untapped.

everyone always worries about the AFR, when they should be concerned about timing. it has EGO feedback so the AFR will nearly always be OK, but it has no way of adjusting timing, which is where 90% of power is made from tuning.

not to mention, you still have the small orifaces in the AFM, airbox, throttle body, and intake manifold to contend with.

[jlevie]

well you can't install a cam and all that stuff and expect it to magically tune itself. Aside from the AFR, your timing won't be optimized. without tuning you might gain 5hp. It's not going to explode and will probably run just fine, it's just going to leave most of the potential untapped.

everyone always worries about the AFR, when they should be concerned about timing. it has EGO feedback so the AFR will nearly always be OK, but it has no way of adjusting timing, which is where 90% of power is made from tuning.

not to mention, you still have the small orifaces in the AFM, airbox, throttle body, and intake manifold to contend with.

Correct. If you do things that change the mas flow and/or cam profile you need to tweak the timing and fuel. To get good results that means changing the maps in the DME, not applying external band aids.