Can anyone point me in the direction of fuel cut defencer technical info.? I assume it is used to modify the signal from the MAP sensor to the ECU. Are they solely used to allow boost pressure to be increased?

Cheers,
Leeroy

 

Anyone??

 

http://www.j-w-racing.com
look under dawes devices

 

Thanks m8, but i was after electronic device info.

 

Basically, you're right. But there's not a lot of info apart from that about the place.

It's a gadget that is powered from somewhere that allows the boost cut to be raised by editing the MAP signal. There's an HKS one that effectively works like a variable resistor (its level can be set to different levels) but it varies the voltage everywhere - not perfect! Then there's a DIY, detailed here if you go back a couple of months, but you'd have to build it yourself - clever, though - it 'extends' the returned voltage once the set level is reached, so only the part of the range that you want moved is changed. You can also put a diode in that completely removes fuel-cut but this is a little silly...

The HKS one seems to work fine, though, with no side effects unless you get silly - only minor adjustments are needed to raise the fuel-cut to a sensible level anyway.

 

The reason i am asking is when fitting my AFR meter i found an electronic module fitted in series with the MAP sensor signal, with its own 12V supply. It consists of a voltage regulator and dual op-amp and a trim pot. I don't know the devices origin, so am a bit concerned why its there. However, I am treating this as a good thing that'll allow further tweaking to boost pressure, providing fuelling and ignition timing are optimum.
It also looks to be a relatively professional install, which inspires a bit more confidence!

 

What MY do you have? If 99/00 you could use DeltaDash from ecutek to see what boost the ecu is actually seeing - and if you've got some way of pressurising your system, also whether it's 'lifting' the fuel cut or removing it altogether. It would be nice to know whether excessive boost is catered for, lol

Richard

 

Does it look DIY, if so it's probably a DIY FCD as posted by John Banks on this very BBS. Check the IC's if they are LM7111's then it is for sure.

I made one myself and modified it for a Pre96 ECU.

The 2 trim pots adjust the levels seen by the ECU.

The MAP sensor sends the ECU a linear signal which relates to the boost level.
The FCD will produce a stepped voltage, so that the ECU see's a false reading.

One of the pots sets the 'Step-In' voltage i.e 3.4 Volts. The second pot sets the 'Step out' voltage i.e 4.2 Volts.
The ECU will adjust the duty cycle of the Boost Control Solenoid if the voltage is above specified limits, therfore maintaining standard boost levels i.e 11psi.
The ECU will also apply fuel cut if a specified limit is breached, normally about 15psi(ish).

The DIY FCD allows you to fool the ECU so that you can run higher boost, by adjusting the tension on the Actuator, but also allows you to set where you want the fuel cut to occur.

Ideally the lower level is set just below the normal boost level and the upper level is set 1psi above your target level, therefore if you exceed your target, fuel cut will still occur.

If you want more info mail me as I have lists of the MAP voltages for Pre and post 96 cars. And can give you some pointers if you wish to check its set-up :0)