Would a full decat 3" effect my a/f ratio ?
Scooby Regular
Joined: Mar 2007
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From: east kilbride
my 98 classic ran lean with a sports catted downpipe second decat and a 2.5" bore system would imagine a 3" bore fully decatted system would be even more likely to throw the a/f ratio off. sorted with a piggybank ecu from dastek.
Scooby Newbie
Joined: May 2010
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i got 97 wrx turbo, put full decat system on and it overboosts, so cuts out for a split second when in the high revs!! today it was smoking and there was carbon round the turbo to decat so I think it was blowing!! May have to put the main cat back on!!
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Scooby Newbie
Joined: Aug 2007
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Yeah heard alot of people remapping newer cars to make 100% use of mods and keep em safe. Thought they have a built in boost cut off though 
. All i was thinking was that the lambda sensor is before the cat on mine so cat or not it must read the same measurements ?????
. All i was thinking was that the lambda sensor is before the cat on mine so cat or not it must read the same measurements ?????
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THIS IS WHAT DYNAMIX SAID ON A PREVIOUS THREAD I READ
"The standard Subaru map are designed to build boost level by closing the wastegate on the turbo until it is close to reaching what it should be at and then gradually opening the wastegate when at target boost to keep it at the desired level. When you decat or change the way exhaust gases leave the engine it is changnng the speed of the airflow through the turbo and the speed at which the turbo builds boost. It will therefore aim for it's boost target but make boost much quicker than it thinks it would. It will go past the target before it has had time to react and then overcut the boost so you end up with boost jumping either side of the target. IF this is safe it is only by luck but at the very least it feels hesitant or throws a CEL for overboost.
Mapping sets the boost targets a little higher for more power but also the speed and way the boost control works to make it as smooth as possible."
"The standard Subaru map are designed to build boost level by closing the wastegate on the turbo until it is close to reaching what it should be at and then gradually opening the wastegate when at target boost to keep it at the desired level. When you decat or change the way exhaust gases leave the engine it is changnng the speed of the airflow through the turbo and the speed at which the turbo builds boost. It will therefore aim for it's boost target but make boost much quicker than it thinks it would. It will go past the target before it has had time to react and then overcut the boost so you end up with boost jumping either side of the target. IF this is safe it is only by luck but at the very least it feels hesitant or throws a CEL for overboost.
Mapping sets the boost targets a little higher for more power but also the speed and way the boost control works to make it as smooth as possible."
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fatboy_coach
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Jun 18, 2016 03:48 PM
