De-cat question..

[L18M]

i have read that its best not to put a de-cat unless you have it mapped.
why is this?

my current setup is:
blitz lm intake
fmic
blitz bov
stock tub
down pipe
3" exhaust from tub back inc mid silencer
chiped ecu
fcd

is this gonna be a problem?
my thinking is as i have a fmic, the new exhaust will help spool the tubby quicker so therefore reduce lag. kinda cancel out the fmic.
the tub spools up nicely but the bov does not seem to make much sound when theres  higher levels of boost.
ps have been driving on low boost as precautions until i find my pfc.

[grinder]

the only thing i can think of with that set up - is that if you ECU incorporates a FCD - and then you have another FCD - what the hell is it clamping the voltage at ??

i ran my TII with decat ( down and main ) , cone filter , fcd , bov and it was fine

[Timmy]

The chipped ecu guessing it is something like re-a has a higher fuel cut anyway by changeing the voltage signal with an fcd it isn\'t seeing the correct boost and not fueling accordingly.
Other than that they say you shouldn\'t use a decat without a remap because if the boost spikes or creeps the ecu won\'t give it enough fuel.
Your ecu should already be mapped for that but was done in japan so the map needs checking really, it\'s much easier and better in the long run to get a pfc.

[Jimi_Hendrix]

Oh man, sounds soooo complicated tuning a turbo car! Lol!

[Swanny_UK]

Well, I\'d air on the side of caution mate.  I work on the principle that if I change something, to remap, therefore do mods in batch\'s.  You might not be able to guage what sort of performance increase you get from each individual change, but it\'ll save money, yet be safer.

[L18M]

hmm.. mixed opinions lol
the chipped ecu.. tbh i dont even know what its chipped for. i got it as my ecu that came with the car was not really making the front rotor do what it was ment to be doing...
i poped over to haywards n matt had a spare so i got his ecu. he said he got it chipped from rotechnics back in the days. he was using a fcd also so i assume the chip does not incorporate the fcd.

[interloper393]

as above fitting a decat will cause boost spikes so will run lean and damage the engine.. but with the mods u already have you should already have an uprated/remaped ecu

[Brett]

The TII runs rich as standard,providing you are limiting the boost to 0.9-1bar then the stock pump and injectors will cope.  Probably best to set the boost controller to 0.5bar, remove the FCD and then increase the boost in steps until you hit the chipped ECU\'s fuel cut - then you will know what it\'s been mapped for :wave

[L18M]

The TII runs rich as standard,providing you are limiting the boost to 0.9-1bar then the stock pump and injectors will cope.  Probably best to set the boost controller to 0.5bar, remove the FCD and then increase the boost in steps until you hit the chipped ECU\'s fuel cut - then you will know what it\'s been mapped for :wave

boost controller.. err.. i not got one yet
hmm.. maybe i remove fcd to be on safe side..
i thought it would be better to keep fcd on so it wont run lean on high boost..?!?

[Brett]

I\'d recommend getting something in there to controll the boost, TII\'s can spike upto 1.2bar in 4th and 5th gears on WOT - not a good thing. (Well it feels like a good thing until you get the comedy shaped apex seals after a few high pressure runs)

[Prof]

boost controller.. err.. i not got one yet
hmm.. maybe i remove fcd to be on safe side..
i thought it would be better to keep fcd on so it wont run lean on high boost..?!?

In theory - the logic is revered.  The standard ECU will cut fuel to the rear rotor when the boost hits 8.8 psi give or take.  The idea is that it will at least try and save the engine.  Never to sure whether this is such a good idea and opinions are varied.
 
What an FCD does is to \'cap\' the boost level seen by the ECU - so when you make 10 or 12 psi, the ECU thinks it\'s getting 8psi of boost.  That means you don\'t get fuel cut, but it also means no maps for the higher boost either.  Almost all chipped ECU\'s take that fuel cut away so an FCD is redundant and will in fact stop the chipped ECU from correctly fuelling past 8 psi.
 
If you make intake mods or exhaust mods that \'promote\' better flow then you will make more boost

[L18M]

if theres no fuel then isnt that the same as running lean..?

[Prof]

if theres no fuel then isnt that the same as running lean..?

Not quite - fuel cut is no fuel - so no combustion.
 
Lean is too much air / not enough fuel - combustion and knock and possibly detonation
 
In actual fact, there is one exception to the fuel cut to the rear rotor - if you hold the accelerator to the floor (WOT), then the ECU does fuel cut to start with, then gives up and just opens the taps - it feels like a little kick in the back and is a little disconcerting - it will only happen on the stock ECU at or near the boost cut limit.
 
As many have said - get a proper standalone or at least a good piggy back in there and then you can be sure of what\'s going on with fuel and timing - your in the dark without some logging tools.

[pdtaylor18]

Totally agree with the chipped ECU and standalone FCD, I had both on my white one and had all sorts of problems, iliminated the FCD and all went away, I just never realised that the ECU had it built in. You can have a decat and all the other mods but then driving around like an old woman going shopping is hardly going to be your style.  You MUST have a boost controller with all your mods, its the number one priority.

[L18M]

Totally agree with the chipped ECU and standalone FCD, I had both on my white one and had all sorts of problems, iliminated the FCD and all went away, I just never realised that the ECU had it built in. You can have a decat and all the other mods but then driving around like an old woman going shopping is hardly going to be your style.  You MUST have a boost controller with all your mods, its the number one priority.

i dont mind driving like a \'old granny sat close up to the wheel on a sunday\' when its super foggy out there lol

tbh.. my fc is more of a house ornament atm =(
trying to source a pfc from japan.. n gonna get boost controller also. not sure to go for profec b or apexi avc-r...