j_truong23

Hey guys, i've been doing a lot of research and coming across some threads that have discussed this topic as well. I think i just need a little bit of a better understanding on adjusting this.

Currently: 1997 Mazda Miata 1.8L w/ BEGI 4.2 Turbo Kit
I believe that the car is running a bit rich at the moment as its blowing out some grey smoke from the exhaust, smells like fuel.

What I've Tried: It's currently boosting at about 7lbs, and from the research i've done... fuel pressure at full boost should be around (50psi base fuel pressure) + (7psi boost x 6psi fuel pressure) = 92lbs max fuel pressure.

I've been adjusting this from an idle since the fuel pressure gauge is in my engine bay, and toggling the throttle body cable to boost the car and see where fuel pressure maxes out at. I'm having difficulty in getting a consistent number... Is it a problem that i'm adjusting the car at an idle instead of a driving environment?

Also, I followed BEGI's instructions by first disconnecting the line running into the side of the AFPR to "kink" it and then adjust the "base fuel pressure" to 50psi. Then plug the hose back into the AFPR and then the pressure should drop to about 37 -38psi which it does. After that, it says to start the **** on the side of the AFPR completely tightened, and then going 1/4 turns loosening it until i reach the appropriate max fuel pressure under boost. (Do i need to turn off the engine and then turn the **** loose and then turn it back on in order to get better results?) This is where i'm running into a lot of problems as to getting a consistent fuel pressure. Not sure if i'm close to the correct amount but i'm still blowing out some grey smoke smelling like fuel...

Thanks for any help you guys can give ahead of time!

concealer404

iTrader: (3)

Wait so we're talking about an FMU setup?

Yep, they run rich. Not a whole lot you can do about it since it's a pretty awful way to control fuel.

j_truong23

I believe so, it's the older 4.2 BEGI kit that comes with the AFPR. So it's natural for these systems to run rich?

concealer404

iTrader: (3)

Is it an AFPR or an FMU? Or do you have both?

What AFRs are you seeing on your wideband?

j_truong23

I think it's just an AFPR, not FMU. Haven't gotten a chance to put in a wideband yet. I've just been trying to adjust it based on the instructions its given me to get it running and boosting safely

concealer404

iTrader: (3)

Anyone else know? Is this that weird BeGi adjustable FMU thing? "Normal" AFPRs don't jump 6psi of fuel pressure per psi of boost.

j_truong23

Not sure then... because the formula was for every pound of boost, there should be about 6 psi of fuel pressure from what i've researched. then that is added to the base fuel pressure to get the max pressure