ShadyRacing

reading through here: http://fc3spro.com/TECH/FM2W/power.htm

a question came up regarding the fuel cut defensor and raising the boost.

as i understand the fcd tells the ecu its less boost than its acutally is. wont that cause lean running situation? or does the ecu and boost cut works different than the mazda bp-t engines i am used too?

i am looking forward to upgrade exhaust, fmic, airfilter and fuelpump.

what boost level i will be save to run with that mods and a fcd.

regards

martin

Sideways7

iTrader: (7)

If I remember correclty, fuel has nothing to due with boost, only the amount of air entering the engine.

NZConvertible

No because the main load input is the AFM, not the MAP sensor. The FCD only affects the MAP sensor's output. The ECU sees less boost but the same airflow, so fueling is not affected. Ignition timing is though, so the ignition timing is not retarded any further once the FDC activates. FC's have quite conservative ignition timing maps, so as long as intake temp is kept down and you don't go silly with the boost this is okay.

Those engines use basically the same EFI system as the FC, so it's a safe bet the FCD has the same effect on both engines.

Anything past 12psi is going to shorten the turbo's life considerably due to overspeeding. That's what I'd aim for, but not until the fuel pump and FMIC are in place. If you're going to stagger those mods, you'll need a FCD before you put a decent exhaust and intake on or you'll hit fuel cut, and I wouldn't install the FCD without upgrading the pump first. I'd keep boost at 10psi until you upgrade the intercooler. With a big exhaust you won't be able to keep the boost that low without porting the wastegate, particularly if you have a 86-88 model.

Note that the very first mod you should do is to install a proper boost gauge. You need to know how exactly how much boost you're running and the stock gauge is totally inadequate when modifying.