Decat on stage 1

[PhantomBlackS3]

Hi all, so I've trawled through all the posts i could find on here, and pretty much every other google search has returned nothing.
However whenever i speak to someone I'm constantly getting conflicting answers, i have an 8P S3 on stage 1 and i currently don't have much of a desire to push my engine much more power wise, however the noise from my catback milltek isn't really cutting it.
What id like help with is info from someone who has fitted a decat and downpipe while staying stage 1..i do know that the EML light can be turned off and the decat can be mapped into my stage 1 software. But will that stop the car going in to limp mode? Ive been on demon tweeks looking at some different brands and almost all say they should be fitted in accordance with stage 2 software, again which i don't have the desire to do...any help on this matter would be appreciated as i see people say one thing then i read something totally conflicting for example the advisory on the product purchase information on the website selling them.
Thanks.

 

[samuelh_888]

A downpipe is not required for Stg1. However if you decat your existing setup you’ll get the EML on the dash. I can’t see your car going into limp mode though. The decat alone with the stock dp won’t change the noise too much.

If you decat, to remove the EML you typically get it mapped out as part of the mapping process.

The downpipe can also be fitted at Stg1 or stock but you won’t get any real benefit from it until it’s remapped, as this is boost and fueling is increased so you need to get rid of the exhaust gasses faster.

Who is your current map from and have you confirmed whether they can tweak the map to remove the EML?

With a decat you’ll have MOT issues unless you have a ‘friendly tester’ who can forge the test.

It’s worth noting the S3 is well sound proofed so you’re not going to get a real reflection of the noise in the cabin.

 

[prt57]

As I understand things, you are looking for more noise from your Milltek.
I’d start by looking at the catback. If it is the resonated version, call Milltek and see if you can buy the pipe that replaces the mid silencer box sold as part of the non resonated version.
The downpipe with decat or sports cat will always talk about having a stage 2 map as normally folks who are doing this are looking for more power. A custom mapper would be able to turn the light off but I’m not sure you are thinking of the best solution if you are just wanting more noise.

 

[PhantomBlackS3]

As I understand things, you are looking for more noise from your Milltek.
I’d start by looking at the catback. If it is the resonated version, call Milltek and see if you can buy the pipe that replaces the mid silencer box sold as part of the non resonated version.
The downpipe with decat or sports cat will always talk about having a stage 2 map as normally folks who are doing this are looking for more power. A custom mapper would be able to turn the light off but I’m not sure you are thinking of the best solution if you are just wanting more noise.

Sorry, i should have mentioned my system is a non resonated system, what would you recommend for a nicer sound from the car? As other than the decat and downpipe i feel there are not many more options, i thought about deleting the back box but have since heard that its far too loud.
I have seen one instance where the pipe coming from the centre resonated part of the car to the back box branched off, one pipe entered the backbox and one pipe diverted round, and both met at the rear as normal. I dont know how much if any difference this system would make?

 

[samuelh_888]

The downpipe and cat is your biggest restriction here, for both noise and power.

Get a muffler shop to cut out your cat and replace with a straight piece of pipe. I don’t think it would achieve the sound you’re after but give possible head aches at MOT time.

If you remove the cat you’ll need to get the EML mapped out. If it was me I’d fit a dp and sports cat (or decat) and then get the map tweaked - this will be stage 2, more power but ultimately you’ll have the sound and no EML.

 

[PhantomBlackS3]

A downpipe is not required for Stg1. However if you decat your existing setup you’ll get the EML on the dash. I can’t see your car going into limp mode though. The decat alone with the stock dp won’t change the noise too much.

If you decat, to remove the EML you typically get it mapped out as part of the mapping process.

The downpipe can also be fitted at Stg1 or stock but you won’t get any real benefit from it until it’s remapped, as this is boost and fueling is increased so you need to get rid of the exhaust gasses faster.

Who is your current map from and have you confirmed whether they can tweak the map to remove the EML?

With a decat you’ll have MOT issues unless you have a ‘friendly tester’ who can forge the test.

It’s worth noting the S3 is well sound proofed so you’re not going to get a real reflection of the noise in the cabin.

The stage 1 software was from shark. My tuner has confirmed that it can be mapped into the current software...the MOT part isn't an issue at all.
In your personal opinion would you think that the downpipe+decat fitted to the car on stage 1 wont give much if any benefit in sound? It seems like I've exhausted all avenues in the quest of getting a better sounding car, also tried looking at modified backboxes or as i mentioned before to prt57, i seen a system that looked custom where there was a single pipe that diverted around the backbox and met the pipe exiting the backbox at the tailpipe cutout on the diffuser...but I'm now starting to think that was valved.

 

[PhantomBlackS3]

The downpipe and cat is your biggest restriction here, for both noise and power.

Get a muffler shop to cut out your cat and replace with a straight piece of pipe. I don’t think it would achieve the sound you’re after but give possible head aches at MOT time.

If you remove the cat you’ll need to get the EML mapped out. If it was me I’d fit a dp and sports cat (or decat) and then get the map tweaked - this will be stage 2, more power but ultimately you’ll have the sound and no EML.

I may no be slowly starting to sway from the idea if it means the software tweak is technically stage 2. Unless there are further fuelling tweaks done between stg 1 and 2 in terms of power gains? Or are the gains between both levels of modification made simply in hardware rather than software? My issue is i feel the car has enough power for my application, but not enough sound...and I'm thinking i cant have my cake and eat it.

 

[doce]

EML also can be disabled with one resistor and capacitor on second o2 sensor signal wires. I do not have cat on my A3, already tried a few spacers and catless tune but capacitor/resistor hack is the best option. Tune modify values on first o2 sensor to 0.2V and 0.46V for second so fuel consumption is increased.

 

[samuelh_888]

The stage 1 software was from shark. My tuner has confirmed that it can be mapped into the current software...the MOT part isn't an issue at all.
In your personal opinion would you think that the downpipe+decat fitted to the car on stage 1 wont give much if any benefit in sound? It seems like I've exhausted all avenues in the quest of getting a better sounding car, also tried looking at modified backboxes or as i mentioned before to prt57, i seen a system that looked custom where there was a single pipe that diverted around the backbox and met the pipe exiting the backbox at the tailpipe cutout on the diffuser...but I'm now starting to think that was valved.

A downpipe and decat would give you more sound. But, you’ll need to get it mapped in (tweaked). A dp added to a stage 1 car is essentially Stg2 assuming you have an intake.

Don’t take the back box out just to have more sound, you’ll get droning on the motorway but also look like a tit. There is a lot of sound deadening in the s3 so it’s probably louder than you think.

I may no be slowly starting to sway from the idea if it means the software tweak is technically stage 2. Unless there are further fuelling tweaks done between stg 1 and 2 in terms of power gains? Or are the gains between both levels of modification made simply in hardware rather than software? My issue is i feel the car has enough power for my application, but not enough sound...and I'm thinking i cant have my cake and eat it.

The gains are not just hardware related - the mapped needs to adjust timing, fuel, etc to make the best use of the additional hardware. With stg2, you can force more air in as it’s being removed quicker/more efficiently.

For what it’s worth, I had a full BCS fitted including downpipe but with sportcat when I was on stock tune and I never received the EML. Some haven’t had the EML with a decat too.

 

[paddy]

I use an APR 300 cell cat and it just scrapes through the MOT. I cant see removing the cat as being an option on a road car anymore TBH.

My thinking is stg 1 squeezes a stock set up to get max power by working it quite hard. Stg2 just makes life for a stg1 a bit easier by flowing more air in and exhaust out giving a cooler running engine and Turbo and only a small power increase, what i am trying to say is i think stg2 is really just stg1 done properly. I suspect a stg2 engine is more efficient than a stg1

 

[prt57]

My son had a down pipe and sportscat fitted to a TTS still retaining the standard catback. The exhaust note did become louder and this hardware was mapped in.
So in your situation, fitting a downpipe to your Milltek will make it louder as well. However, with that hardware fitted you will need the map tweaking and your car will benefit from the easier exhaust path.
So as I see it, keep it at stage 1 with the existing noise or go to stage 2 and get more noise and additional engine efficiency and power. Providing you maintain your car thoroughly, you should not have any problems. I assume your tuner knows what they are doing and checked your car before applying the stage 1 map.

 

[PhantomBlackS3]

Appreciate all the input guys, I'm quickly figuring out i didn't appreciate the complexity of what i was wanting to do to the car, although it does seem simple. And id really be playing a game of luck wether id get an EML or not.
Would i be right in saying that with the decat and downpipe without a software tweak, the car would be getting rid of the exhaust gasses too quickly then? Or what is it that can cause the issues other than a light due to lambda removal? From paddys interpretation of it I'm also coming to see that stage 2 might not be all that bad or harsh on the car after all.

 

[PhantomBlackS3]

My son had a down pipe and sportscat fitted to a TTS still retaining the standard catback. The exhaust note did become louder and this hardware was mapped in.
So in your situation, fitting a downpipe to your Milltek will make it louder as well. However, with that hardware fitted you will need the map tweaking and your car will benefit from the easier exhaust path.
So as I see it, keep it at stage 1 with the existing noise or go to stage 2 and get more noise and additional engine efficiency and power. Providing you maintain your car thoroughly, you should not have any problems. I assume your tuner knows what they are doing and checked your car before applying the stage 1 map.

Yes mate car was checked before stage 1 was applied to the car, hes clued up and i trust him fully.
Car does no more than 4000 miles per year and I've had all the usual culprits done....replaced cam follower, pcv, dv and personally removed the sump cleaned the pickup and gave everything under there a good clean and fresh oil. The car is my only car but as i only work 5 minutes from the house and do very little through the week...unless i really need to use it midweek it is really just a toy for the weekend as thats the most use it sees..but i like to enjoy it when i drive it..albeit i don't drive it remotely close to as hard as some if not most enthusiasts do, as i said though i do like to enjoy the car when i drive it.

 

[paultownsend]

I cant see removing the cat as being an option on a road car anymore TBH.

Im with Paddy on this one. In today’s world it is no longer socially acceptable to decat a car. The emission hardware is there for a reason. And with a map, a catalyst is even more important. We understand why. Don’t shoot me down with my thinking. I’m as much of a petrol head as anyone. A have an S3.

Put on a decent dp and sport cat. I like what pipeworx are offering.

 

[samuelh_888]

Would i be right in saying that with the decat and downpipe without a software tweak, the car would be getting rid of the exhaust gasses too quickly then? Or what is it that can cause the issues other than a light due to lambda removal?

Nope, you can never get rid of the gasses too quickly. Without the map tweak, with a decat, your o2 sensors won’t be measuring the correct latency of the gas flow (and other stuff I guess, someone more technical than I could explain) hence the EML will come on. It will give a Fuel Rich reading or something.

It’s a minefield right?!

 

[PhantomBlackS3]

Im with Paddy on this one. In today’s world it is no longer socially acceptable to decat a car. The emission hardware is there for a reason. And with a map, a catalyst is even more important. We understand why. Don’t shoot me down with my thinking. I’m as much of a petrol head as anyone. A have an S3.

Put on a decent dp and sport cat. I like what pipeworx are offering.

That i can understand, i wasn't in the belief that i had to kill the planet for more sound mate, id be happy if a sport cat done the job and gave a bit more noise i’d be cool with that.

 

[PhantomBlackS3]

Nope, you can never get rid of the gasses too quickly. Without the map tweak, with a decat, your o2 sensors won’t be measuring the correct latency of the gas flow (and other stuff I guess, someone more technical than I could explain) hence the EML will come on. It will give a Fuel Rich reading or something.

It’s a minefield right?!

Like you wouldn't believe, back in the day before all this stuff it was fit and go! Bring those days back lol!

 

[Davill9]

EML also can be disabled with one resistor and capacitor on second o2 sensor signal wires. I do not have cat on my A3, already tried a few spacers and catless tune but capacitor/resistor hack is the best option. Tune modify values on first o2 sensor to 0.2V and 0.46V for second so fuel consumption is increased.

How is this done mate as I am stage 2 soon but cat section is blowing bad so need de cat fitted this week
Cat already has no internals left y the look of emissions check yesterday so make no difference to eml as I am Resetting daily anyway
Probably about a month till I can get it to Rick @ unicorn as manny is a long way from London
Cheers in advance mate

 

[abmat]

Is your emissions check showing normal levels? If not you’ll fail the mot, definitely if they suspect the cat has been tampered with.

 

[Davill9]

Is your emissions check showing normal levels? If not you’ll fail the mot, definitely if they suspect the cat has been tampered with.

Sorry mate just seen this
I fit a standard cat for mots and remove the same day for another year
Shhhh … to tree hugging protesters with their massive plastic billboards and cotton banners lol

Rick is mapping out the o2 when he does stage 3 map and car isn’t driven hardly ever as it’s being fully restored for a while now but it would be good to get a proper reading for fuel as it says 150m range 25 miles later it’s on reserve maybe talk to unicorn about setting it up properly when re mapped again.


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