Hi, I'm a french owner of a RX7 TT (94) and I am wondering on fuel system :
my car is equipped only with the purple piggy back Peter ferral's and a Walbro 255 Lph (+ HKS full exhaust en suction kit). Then can I install the injectors 850 Cm3 (secondary) in the place of the primary injectors (550 Cm3). Can the ECU it adapt or must I invest in a Apexi Power FC for exemple ???

thank you

 

You might get more responses in the engine management section of the forum. Im not familiar at all with the PFS's system.

 

From what I recall, the PFS Piggyback cannot change the injector ratio (550/850). If you upgrade the primaries, you have to ugrade the secondaries to keep the stock ratio.

If that wasn't the case, I'm sure someone will pipe in.

 

Just so you know, we typically refer to injector size in CC's - it's the same thing as cm3 (cubic centimeter), but that's us Yanks.

Anyhow, running larger injectors with Peter Farrel's box is VERY hard. A buddy of mine (Carlos) pioneered it some time back, running 850cc primaries and 1200cc secondaries. The problem is you can never really get the transition when the secondaries come on tuned in properly - that's why he ran those sizes, since it's close to the stock ratio of injector size. It's just a problem with the PMC - since it's reliant on the stock ECU, that brings lots of limitations with it.

The PowerFC handles all kind of injector sizes VERY easily, though.

Anyhow, just upgrading the primaries will result in an impossible to tune out stumble when the secondaries come on. If you upgrade both, it will get better, but you'll never get it just right.

Dale