Quote:
Originally Posted by bonner
cheers lads didnt realise this can cause det!! some serious stuff then! i best lay off the boost myself appoligies mate!!!
|
Don't get scared too much by what's being said above.
The key factor is to ensure you do not generate any more boost then it would of done prior to the decat or sport's cat being fitted.
Therefore, keep the throttle movement light and slow. You don't have to drive like your 65 (how old is Big'E' now ??), just be careful if you do decide to pull a quick overtake.
If you have a boost gauge, keep it under around 0.7-0.8bar.
They don't tend to run lean so much, the problem is more the peak torque boost spike and increased held boost you can get once decatted, which needs to be re-calibrated during the remap.
The increased boost can cause detonation both at peak torque and high rpm due to too much ignition timing advance for the boost being produced.
The 'load' induced on the engine also changes and causes the calculated load value used in the ECU to be different, therefore you end up in a completley different region of the mapping, which can cause some leaning out, but only by a small margin. This does however not help with the risk of detonation.
It does however depend on the car.
Early cars were alot more tolerant to a decat and many people, some of us included, ran decat UK classics for many years without issues.
Classic STi are a bit more borderline depending on the model (STi 1 RA being the worst)
Newage STi do overboost / spike quite bad. The worst spiking I have seen after decat was on my own Hawkeye.
The 2.5 litre has another 25% air to spin the turbo, therefore once decatted is will try and boost it's tit's off.
The recalibration process has to reign in quite a bit of the boost control to get the boosting back to acceptable levels.
The advantage of this though is that you can generate near to, or full boost at 50% throttle, which makes for a great drive.