whats this - FCD??

[TRex]

Stu, this may help...

 Fuel Cut Defencer is any device that prevents the stock ECU from cutting fuel(in Rotary engine) to the rear rotor when the boost exceeds a preset boost level. This maximum safe boost level and behavior is written into the engine management unit (map) and can not be changed without reprogramming the ECU.
 The maximum allowed boost pressure is about 8.6 psi. The way an FCD defeats the fuel cut is by \'lying\' to the ECU about what the boost pressure is. The FCD is placed between the boost sensor and the ECU where it modifies the boost pressure signal by some amount so that as the boost pressure rises above the preset "safe limit", the ECU continues to see a signal that is below the limit.

[Grizzly]

Well put !!

[Grizzly]

So we have decided with the correct checks first 10psi is within the bounds of a stock T2.

Now just to throw a spanner in the works how much would an exhaust or a set of Decat pipes change the fueling?

What i\'m saying can you still run 10psi with an Exhaust and Air filter (bolt ons) fitted?

[FD3SNuttah]

well then dont you need the fcd as it wont cut fuelling as you get the spkies when you upgrade the exhaust thus preventing it from leaning out

[Grizzly]

So you can\'t up the boost then?

I will tell you know that i had a stock t2 running 10psi of boost and it didn\'t lean of as much as my stock vert when i put the 3" exhaust on it (without including spiking).

[Grizzly]

well then dont you need the fcd as it wont cut fuelling as you get the spkies when you upgrade the exhaust thus preventing it from leaning out

The idea is not to exceed 10psi. i have seen exhausts spike 2psi and creep more in some cases so what i\'m trying to say is its one or the other. You can\'t raise the boost and fit and Exhaust and expect not to have problems.

[TRex]

So we have decided with the correct checks first 10psi is within the bounds of a stock T2.

Now just to throw a spanner in the works how much would an exhaust or a set of Decat pipes change the fueling?

What i\'m saying can you still run 10psi with an Exhaust and Air filter (bolt ons) fitted?

 Chris do you not sleep m8....  :spank

 You have thrown a spanner there actually, because \'Yes\' once you open up engine breathing (unrestrictive intake and exhaust) then the engine will naturally flow more Air, as there is no suffocation at the Intake and no backpressure coming out.
 So the Turbo will boost a lot easier, hence why \'boost spikes\' occur!

 If I were these chaps doing light mods(basically cheap mods) just trying to get a wee bit more from the standard motor without spending(as this seems to be the factor), I would go this route first!
 1. Proper Boost gauge -- you need to see whats happening, especially as this is your main point of pushing power. Never guess or work blind.
 2. Form of proper Boost control - not really to push the boost up yet, but to aid in controlling Boost for the next mod stages.
 3. De-catt -- no point trying to get more power with a big sponge stuck up your zorst
 4. Improve Intake flow -- done after zorst as it\'s no point pushing more air if it\'s not allowed to exit as quick as it comes in.
 5. Cooling the charge air --- but now we are going into alot bigger cost from here.

 The list goes on, but so does your costs...
 Somewhere along in there I would probably throw in a FCD, mainly because the T2\'s do go into \'Fuel Cut\' easily and will deffo need one....

 Point to note, this above is all well and good providing all the basics checks are done ensuring the car is properly tuned and serviced first. Also making sure all connections are secure and hoses - from water to vac lines are decent and in check.  Basically the car is not a sh!tter to start with.....

 disclaimer, these are my thoughts at almost 2am when I should be asleep!

[Grizzly]

He he...

[Brett]

Ok then,  so do we know what the FCD is tricking the ECU into reading?  Is it a directly proportional reading, or does it simply cap the output signal from the Pressure sensor at (for example) 8psi?

[FD3SNuttah]

how would the ECU know what pressure the turbo is running at? it could boost all the way to 15psi! the ecu would still be thinking its running at only 8psi!? that sounds dangerous! does the ecu still run the actuator when it hits the highest stock level of pressure?

[Brett]

As far as I\'m aware (going on the red book) even with the loop pressure being bled out the Wastegate should be starting to open around the 10psi mark.
 If the ECU is programmed to give maximum fuel at xxPsi then I\'d imagine thats where the FCD will \'cap\' the boost reading to the ECU?

[FD3SNuttah]

thats alright then. 10psi is plenty, but are we runnig lean? anyone had a go on the rolling road with the exhaust/filter/decat/fcd? did it run very lean when spiking? i suppose it shouldnt run dangerously lean as the rotor runs pretty rich anyway?

[Grizzly]

I have had it hooked up to a wideband. Yes it does start to lean on a stocker at 10psi on a coldish day.

But this is without a De-cat or Exhaust fitted that alone makes it a diffrent ball game. I know what the Exhaust on its own will do at stock Target boost, it acts like you\'ve wound the boost up basicly spiking to 10psi then droping back if you keep it WOT.

As for Filter and other bolt ons etc i never ran it as i fitted a EMS,Injectors Pump etc at the same time so it would not be a fair test.

BTW this is all for S5 T2\'s if you have a S4 with the single waste gate then you will find Spike/Creep alot more of a problem.

[Brett]

So do we think its a yes to the FCD modifying the output signal to read a max of 10psi or something? I\'ve no put a meter on there yet, but I\'m presuming its just a voltage scale thats used as the output?

[Grizzly]

On a stock car!!!

If you fit a Big Exhaust you may have to have a FCD becouse of the Spike but i would not run any more boost.

Its one or the other, Boost or Exhaust. Simple as that. On a good stock car.