RS3 PFL Decat but no map?

[teddyrs3]

Hi,

Having a debate with a friend and wanted more experienced views on this...

I’m under the impression on the Rs3 8v if you have a primary decat fitted am I right in thinking it will chuck the eml on and limp mode? I have read that the turbo spools too much with a decat and therefore causing limp mode unless mapped is this correct?

On my old s3 I ran a decat without a map for a few months without it causing any problems but was told same can’t be done on the rs3. My friend however disagrees and believes a decat with no map will fine .

What are your opinions?

Thanks guys

Teddy

 

[Jonessy95]

Hi,

Having a debate with a friend and wanted more experienced views on this...

I’m under the impression on the Rs3 8v if you have a decat fitted am I right in thinking it will chuck the eml on and limp mode? I have read that the turbo spools too much with a decat and therefore causing limp mode unless mapped is this correct?

On my old s3 I ran a decat without a map for a few months without it causing any problems but was told same can’t be done on the rs3. My friend however disagrees and believes a decat with no map will fine .

What are your opinions?

Thanks guys

Teddy

Secondary or main?


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[RS03_SEN]

Hi,

Having a debate with a friend and wanted more experienced views on this...

I’m under the impression on the Rs3 8v if you have a decat fitted am I right in thinking it will chuck the eml on and limp mode? I have read that the turbo spools too much with a decat and therefore causing limp mode unless mapped is this correct?

On my old s3 I ran a decat without a map for a few months without it causing any problems but was told same can’t be done on the rs3. My friend however disagrees and believes a decat with no map will fine .

What are your opinions?

Thanks guys

Teddy

Try it, see what happens.


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[teddyrs3]

Secondary or main?


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Apologises I meant main cat.

 

[teddyrs3]

Try it, see what happens.


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I do have a spare main cat laying around lol. Might bash it out and have it fitted

 

[Jonessy95]

I do have a spare main cat laying around lol. Might bash it out and have it fitted

One on the downpipe will deffo need mapped , secondary you can get away with but will eventually burn out the 02 sensor as it’s happened to mine like 8 months after

 

[DW81]

One on the downpipe will deffo need mapped , secondary you can get away with but will eventually burn out the 02 sensor as it’s happened to mine like 8 months after

I didn’t think the 02 sensors are fitted after the secondary cats on the PFL model, but further along the front of the exhaust.
Been running my secondary decat pipes about 16 months now, no problems thus far

 

[T-800]

I didn’t think the 02 sensors are fitted after the secondary cats on the PFL model, but further along the front of the exhaust.
Been running my secondary decat pipes about 16 months now, no problems thus far

Correct no 02 sensors near or on Second cats.

Just the main cat.

 

[T-800]

People with MY19+ though will have the full monty

 

[Jonessy95]

Yeah since it’s decat it’s burnt out the sensor over time , the eml light comes on me car saying catalyst below threshold bank 1 which is the 02 sensor before the cat


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[DW81]

Yeah since it’s decat it’s burnt out the sensor over time , the eml light comes on me car saying catalyst below threshold bank 1 which is the 02 sensor before the cat


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I take it you have a full decat exhaust system then. PFL or FL ?

 

[Jonessy95]

I take it you have a full decat exhaust system then. PFL or FL ?

Pfl and secondary decat , resonator cut out and welded in straight pipe , valves unplugged and carbon fibre intake , am still on original map


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[DW81]

Pfl and secondary decat , resonator cut out and welded in straight pipe , valves unplugged and carbon fibre intake , am still on original map


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I’m at a lost, as I mentioned earlier I to have removed the secondary cats and replaced these with the through pipes from the FL model. I too have the exhaust valves unplugged with those vw international plug adapters.
Standard intake still and not mapped either.

Someone with more knowledge may be able to give you an answer for the burnt out 02 sensor perhaps

 

[Jonessy95]

I’m at a lost, as I mentioned earlier I to have removed the secondary cats and replaced these with the through pipes from the FL model. I too have the exhaust valves unplugged with those vw international plug adapters.
Standard intake still and not mapped either.

Someone with more knowledge may be able to give you an answer for the burnt out 02 sensor perhaps

Am guessing it is the lambda sensor coz it says catalyst below threshold bank 1 , engine light comes on and flashes on cold starts now and then , av went to Audi and bought a lambda sensor bank 1 gonna fit it tomorrow see how it goes


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[Jonessy95]

This is what the 02 sensor looked like


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[Nickyc]

I dont understand how changing the secondary cats would cause this, anyone shed some light on it ?

 

[Jonessy95]

I dont understand how changing the secondary cats would cause this, anyone shed some light on it ?

Am puzzled aswell , my cars getting on a rolling road Dyno tomorrow to get the air fuel ratio checked see if me car is running right


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[Marshy]

I dont understand how changing the secondary cats would cause this, anyone shed some light on it ?

Removing the secondary cats can’t cause this.
I have heard of some cars where the primary cat has started to disintegrate which causes the same efficiency code condemning the cat or lower lambda sensor.
I think Audi know this and carried out an update which reduced the pops and bangs as this is a known feature that destroys a catalyst over time.

 

[Jonessy95]

Removing the secondary cats can’t cause this.
I have heard of some cars where the primary cat has started to disintegrate which causes the same efficiency code condemning the cat or lower lambda sensor.
I think Audi know this and carried out an update which reduced the pops and bangs as this is a known feature that destroys a catalyst over time.

Yeah everyone says the secondary cat won’t do this , I have also a resonator cut out , valve a and b unplugged and also air intake with standard map , I think my car is running too rich


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[Marshy]

Yeah everyone says the secondary cat won’t do this , I have also a resonator cut out , valve a and b unplugged and also air intake with standard map , I think my car is running too rich


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Secondary cats and resonator delete and valves permanently open will affect back pressure but shouldn’t affect lambda readings as both sensors are way before all of that.
Running an air intake if anything would make it run lean since there’s no mass meter.
Fueling is done by the top lambda sensor so fueling should be within parameters, sounds to me like you either have a faulty lower lambda sensor or a degrading primary catalyst.
If it’s the cat you’d be as well going stage 2 and fitting either decat or sportscat.

 

[Jonessy95]

Secondary cats and resonator delete and valves permanently open will affect back pressure but shouldn’t affect lambda readings as both sensors are way before all of that.
Running an air intake if anything would make it run lean since there’s no mass meter.
Fueling is done by the top lambda sensor so fueling should be within parameters, sounds to me like you either have a faulty lower lambda sensor or a degrading primary catalyst.
If it’s the cat you’d be as well going stage 2 and fitting either decat or sportscat.

Yeah I changed the lambda sensor in bank 1 coz I got the eml light on saying catalyst below threshold bank 1 , pulled out the sensor and it looked like that from the picture above , hopefully this Dyno run tomorrow will see what’s wrong with me car


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[Marshy]

Yeah I changed the lambda sensor in bank 1 coz I got the eml light on saying catalyst below threshold bank 1 , pulled out the sensor and it looked like that from the picture above , hopefully this Dyno run tomorrow will see what’s wrong with me car


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Be interesting to see what the outcome is.
If the car performs perfectly on the dyno then it’s telling you fuelings good and it’s the cat at fault.
Usually when the cat is faulty the car still runs and pulls perfectly, the only symptom is the warning light.

 

[Jonessy95]

Be interesting to see what the outcome is.
If the car performs perfectly on the dyno then it’s telling you fuelings good and it’s the cat at fault.
Usually when the cat is faulty the car still runs and pulls perfectly, the only symptom is the warning light.

Yeah definitely will post the figures! And the light came on 6 months ago , then misfires accrued , changed coil packs spark plugs and now 02 sensor , hopefully not the fuel injectors but surely by now I would know this, car still drives perfect and hasn’t broke down or anything , just now and then it sounds like it misses a beat


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[Jonessy95]

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[Marshy]

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Looks like it’s made good figures.

 

[Jonessy95]

Looks like it’s made good figures.

Definitely! The guy said it hasn’t got a misfire but he says it definitely needs mapped


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[Marshy]

Definitely! The guy said it hasn’t got a misfire but he says it definitely needs mapped


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It does sound like the primary cat is faulty causing the code.
Stage 2 next then

 

[Jonessy95]

It does sound like the primary cat is faulty causing the code.
Stage 2 next then

Could be! Was gonna go stage 1 first! And he says the code comes on the dash and affects the way the car runs, car fuelling was perfect and boost was


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[Marshy]

Stage 1 is only any good to you if you can find someone to map out the cat efficiency code otherwise you’ll still get the warning light on

 

[Jonessy95]

Stage 1 is only any good to you if you can find someone to map out the cat efficiency code otherwise you’ll still get the warning light on

Yeah definitely , think mrc will do that for me


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[Marshy]

Sounds like a plan

 

[Jonessy95]

Sounds like a plan

Yeah can’t wait! Hopefully sorts it out


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[Marshy]

I’m running Apr stage 1 with hg Motorsport intake pipe, makes a lovely difference to the car

 

[Jonessy95]

I’m running Apr stage 1 with hg Motorsport intake pipe, makes a lovely difference to the car

Sounds good! What power did yours make? And what did it make before the map?


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[Marshy]

Sounds good! What power did yours make? And what did it make before the map?


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I didn’t put it on the dyno.
Just the butt dyno I’m afraid

 

[Jonessy95]

I didn’t put it on the dyno.
Just the butt dyno I’m afraid

Oh a see! Will definitely be good gains tho! Torque looks a massive increase


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[Marshy]

Yeah it can certainly lift its head

 

[Kaine19]

I made 331hp at the wheels standard and 389hp at the wheels with MRC stage 1, secondary decats and hg motorsport pipe. Just received forge intercooler, starting to get bits for stage 2 now

 

[AudiNutta]

I made 331hp at the wheels standard and 389hp at the wheels with MRC stage 1, secondary decats and hg motorsport pipe. Just received forge intercooler, starting to get bits for stage 2 now

That is well down on power to start with, did they complete a few runs to try and get that up?

 

[Deleted member 117185]

That is well down on power to start with, did they complete a few runs to try and get that up?

That’s at the wheels, not the fly like everyone else quotes. That’s about 440 at the fly.