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jasons · 25-12-2007

Originally Posted by kgb

More info

OK, went to fit today but encountered a slight technical problem, I have wired the chip pins 5-8 in reverse!

So just put that right and bench tested.

The idea of it is this...

Run too high boost, and the ECU (after a couple of seconds) will cut the fuel, as in the engine stops, key off for 5 secs or so and re-start, and this can happen at speed.

Basically the MAP sensor is a 2 bar sensor, it has a 5+Volt feed in, and on idle output 1.9V, this increases (linear) as the boost
increases, but if the ECU see over 4.5 (ish) volts it sees an overboost, therefore cuts the fuel.

So the FCD is simply a little circuit board that clamps the voltage, this can be adjusted via a POT for fine tuning, anywhere from 0-5volts.

I will install again tomorrow with it set for 4.5volts and then fine tune it from there, the idea being the ECU never sees above that voltage and does not kill the fuel.
Boost gauge essential!

This way I can finally give the thing full throttle without the worry of keeping 1 eye on the boost gauge to make sure boost does not go over 1.9bar. - it spikes at 2.3/2.4 bar.

25-12-2007	#11 (Post Link)
jasons AO Member Join Date: Sep 2007 Location: Derbyshire Posts: 782 Member car: 156 2.4JTD 200+bhp	Re: Ebay does it again Originally Posted by kgb More info OK, went to fit today but encountered a slight technical problem, I have wired the chip pins 5-8 in reverse! So just put that right and bench tested. The idea of it is this... Run too high boost, and the ECU (after a couple of seconds) will cut the fuel, as in the engine stops, key off for 5 secs or so and re-start, and this can happen at speed. Basically the MAP sensor is a 2 bar sensor, it has a 5+Volt feed in, and on idle output 1.9V, this increases (linear) as the boost increases, but if the ECU see over 4.5 (ish) volts it sees an overboost, therefore cuts the fuel. So the FCD is simply a little circuit board that clamps the voltage, this can be adjusted via a POT for fine tuning, anywhere from 0-5volts. I will install again tomorrow with it set for 4.5volts and then fine tune it from there, the idea being the ECU never sees above that voltage and does not kill the fuel. Boost gauge essential! This way I can finally give the thing full throttle without the worry of keeping 1 eye on the boost gauge to make sure boost does not go over 1.9bar. - it spikes at 2.3/2.4 bar.