De-Cat and Lambda question

[K9]

Sup. I'm ordering a Milltek DP de-cat and already installed milltek cat back non res. Question is now when fitting de-cat it will thriw the engine light up, that need to be coded out, can  i do this myself with vagcom or a mapper need to code it out? As i already have a custom map. Will i need a whole new map or will the old map be enough?

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[Dan_FR]

Map needs adjusting. Its only a few values within the minu wont take your mapper more than 10 minutes

[K9]

Map needs adjusting. Its only a few values within the minu wont take your mapper more than 10 minutes

okay cool! good that i don't need to pay the price of a new map. Will it work with the lambda cutted off if i install the cat for MOT again?

[Dan_FR]

No need to cut lambda off. Can leave both installed. Primary lambda will be fine with a cat fitted  for MOT purposes

[K9]

No need to cut lambda off. Can leave both installed. Primary lambda will be fine with a cat fitted  for MOT purposes

so it will work fine after the lambda is coded out for the de-cat to work fine? and no coding needed when re-fitting cat for MOT?

[K9]

A friend to me told me its possible to pass mot without cat. True?

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[Dan_FR]

No need to cut lambda off. Can leave both installed. Primary lambda will be fine with a cat fitted  for MOT purposes

so it will work fine after the lambda is coded out for the de-cat to work fine? and no coding needed when re-fitting cat for MOT?

If the map (emissions threshold) is adjusted correctly, you won't get an EML with the de-cat. The primary fuelling lambda is unaffected so it will be fine, and you will be fine to re-fit the cat for the MOT

A friend to me told me its possible to pass mot without cat. True?

Writen with my fingers

No. It will fail on a visual inspection (as it is missing) and it will also fail on the emissions. It will not pass a legitimate MOT with a de-cat fitted

[K9]

So the map need to be tuned as i already have the custom one. And if correct i will not get EML light and it will run as normal? Where is the primary one? Do u have a de cat fitted?

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[Dan_FR]

To get the most from the car, the map will need adjusting to take advantage of the increased flow potential, but it is not essential. This could be some adjusting to your existing map or a whole new one - talk to your tuner

To stop the EML coming on the map will need adjusting to change the cat efficiency threshold map. This is still a map adjustment but is more of a patch to the software already on there, it will not affect the running of the car in any way

There are two lambda sensors, one before the cat, and one after. The one before is the primary fuelling lambda. The second one (after the cat) is simply there to monitor the efficiency of the cat and is the cause of the EML when fitting a decat. The adjustment to the map changes the threshold that triggers the EML (or they simply remove the DTC all together - either way)

And yes I have a decat and Revo software (Stage 2+)

[K9]

To get the most from the car, the map will need adjusting to take advantage of the increased flow potential, but it is not essential. This could be some adjusting to your existing map or a whole new one - talk to your tuner

To stop the EML coming on the map will need adjusting to change the cat efficiency threshold map. This is still a map adjustment but is more of a patch to the software already on there, it will not affect the running of the car in any way

There are two lambda sensors, one before the cat, and one after. The one before is the primary fuelling lambda. The second one (after the cat) is simply there to monitor the efficiency of the cat and is the cause of the EML when fitting a decat. The adjustment to the map changes the threshold that triggers the EML (or they simply remove the DTC all together - either way)

And yes I have a decat and Revo software (Stage 2+)

What arw the gains when fitting a de-cat? And it will be fine when re-fitting old cat for MOT?

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[Dan_FR]

Impossible to put numbers on it, depends on whether you're K03 or K04, the mapping, stage of tune/other hardware fitted etc. It will definitely open up the higher RPM though regardless. Have a read of the TFSI stuff on Niki's site - covers various stages of tuning and gains: http://r-techperformance.co.uk/ (make sure you look at the right sections for K03 and K04)

It will be fine if you drive it normally/off boost, but I wouldn't advise hooning it all the way there, and hooning it all the way back

[Paradox1]

@Dan_FR  - Do you have a catback on your car or just the decat?

[Dan_FR]

Full turboback system including 3" downpipe

[K9]

Impossible to put numbers on it, depends on whether you're K03 or K04, the mapping, stage of tune/other hardware fitted etc. It will definitely open up the higher RPM though regardless. Have a read of the TFSI stuff on Niki's site - covers various stages of tuning and gains: http://r-techperformance.co.uk/ (make sure you look at the right sections for K03 and K04)

It will be fine if you drive it normally/off boost, but I wouldn't advise hooning it all the way there, and hooning it all the way back

So i should not hooning when the oem cat is fitted with the lambda coded etc? But can hoon when de-cat is in place?

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[K9]

Should a lambda spacer be fitted to?

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