ScoobLou

iTrader: (21)

Hi All

Currently have a decat fitted to my Scooby Type R V3 and I had the Apexi ECU mapped with this mod.

I have purchased a sports cat as I am sick of the hassle come MOT time and also don't want hassle if I get stopped by the police.

Do I have to get the car remapped again?

EngineMapper @ Group B Motorsport

The sports cat will be a little more restrictive, so is likely to reduce your overall boost level, so in order to get back to where you were before you'll need a brief map tweek. If you can get to me I'll give it a tweak for you.

Graham

Jolly Green Monster

iTrader: (4)

its actually worse than that.. the restriction to the exhaust will mean the scavenging will be worse and therefore there will be more dirting of the charge mix from the previous cycles exhaust gas and will require ignition and fuelling adjustments as well as most likely increased duty cycle on the boost solenoid to regain the lost effiecency lowing the boost. Therefore you risk det without having it tweaked for the exhaust change.

Simon

EngineMapper @ Group B Motorsport

Fair comment! All depends on severity of restriction however and of course how free flowing the original decat was in the first place. I've seen some sports cats flow better than some decat pipes, albeit they were awfully made! Although all map tweeks from anyone should involve a complete map check, afr, ignition, boost and power graphed.

Jolly Green Monster

iTrader: (4)

your first post insinuated OP would just get reduced power.. therefore possibly could have risked engine damaged driving it around for a couple of months before getting a tweak, because we don't know the exact restrictiviness of the new and old exhaust without checking it.

Simon

EngineMapper @ Group B Motorsport

True, I assumed it was a given that if a map teak/remap was needed then the car would be driven under no duress. I also assumed that that was the point of the question. But if that wasn't clear to the OP then it is now!

prodriverules

iTrader: (52)

^^So who's ***** is the biggest then guys?!

ScoobLou

iTrader: (21)

So these people who put cats on just for the MOT then back to decat, how come their engines don't go bang? Luck?

Jolly Green Monster

iTrader: (4)

because the mot requires 2500rpm hold in neutral and idle checks and hopefully they drive it gently to and from the mot place.

Simon

EngineMapper @ Group B Motorsport

To be honest Simon is just giving safe sensible advice. But that said I've not come across an engine detting due to a change from a less to more restrictive exhaust, but maybe Simon has. The scavange effect is much more prevalent in an N/A car than a positive charged car and it's really the headers that make the biggest different in terms of pulse timing and exhaust velocity, which might then dictate the need for an instant remap/tweak.

Graham