FM O2 signal modifier
 

I'm wondering what type of benefit might be seen by using the FM O2 signal modifier available from FM Protge and a larger fuel pump on a NA car? My understanding is that this would prevent the ECU from going into a closed loop, Meaning the car would be running under the pre-programmed fuel fixed fuel timing maps. Woould this be useful for those who have the Cams and IM?

all it does is make your car run rich under all conditions, which when under boost is good. your car already runs rich, so you would only lose power and see a decrease in fuel economy.

Accually it is a pressure switch activated mechanism that at over 0 PSI, it activates a voltage clamp on you 1st O2 sensor signal wire that keeps the ECU from reading the rich condition. The ECU is made for N/A applications wich tries to keep emissions good by maintaining a 14.7:1 A/F ratio (which is stioch, which means all/most of the fuel and air were consumed by combustion). A turbo'd car needs a ratio of 12.1:1 or lower (I believe) to be happy. If the ECU sees that you are running rich, it has the ability to lean you out to get that 14.7:1 ratio it's looking for by pulling back up to 30% of the fuel you supply no matter what type of extra fuel you are dumping in until it goes into open loop operation around 4500 RPM. That would spell disaster if you ran lean. Abbove 4500 RPM, the ECU runs rich to keep the engine safe in the upper RPM's. The signal modifier in essence fools the ECU into not pulling back fuel when you hit boost.

Anybody know how to make one of these or get one for cheaper than $100?

Is this "modifier" electronic or mechanical?

Just looking to see if there are any alternatives....

Yes, it is both. It receives a pressure signal from the intake manifold and provides a modified O2 signal to make sure you get the right air-fuel mixture.

When it comes to my engine, I wouldn't want to skimp on anything that will increase it's life.