De-Cat / Stage 2 Question

HHS3

Phantom Black S3 - R-Tech Stage 2+
Hello,

My S3 is currently Revo stage 2 with a Revo CAI and stock exhaust but the downpipe is modified with the pre-cat material removed.

I'm getting a BCS downpipe with de-cat fitted on Wednesday, I'm not expecting an EML to come on as I've already got stage 2 software.

I've been informed that running a de-cat will cause it to run lean without an update despite having stage 2 software.

Can anyone elaborate on this for me please?

If so, would this have to be a Revo map update (so only a Revo dealer can change) or can any garage update the necessary parameters on the ECU?

I'll be calling R-Tech this week to get booked in for stage 2+ but that won't be until late March/early April, so would running lean due to a de-cat for over two months have a detrimental effect? I know that running too lean can cause damage but I'm not sure how lean (if any) a de-cat would cause, my guess is it's only marginal so I'd be ok to leave as it is until the new remap.

Cheers.
 
Depends if your stage 2 software is for running a decay or if it’s for running with a cat/sports cat sounds like the map was made with a cat in place?
Tbh I’d run the map whilst it was decatted. I did previous for a few month after I melted the sports cat on the drag strip and swapping it out for a decat. But I know others will disagree with this
 

prt57

Registered User
Whilst it may be too late now but I understand the BCS sports cat is so big that there is no restriction to the flow so the only benefit from a decat is the cheaper price.
Could you not call in the morning to see if they can weld you a cat in place then you would have no worries or hassle at MOT time?
Alternatively, why don’t you send RTech a message asking the question.
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
Depends if your stage 2 software is for running a decay or if it’s for running with a cat/sports cat sounds like the map was made with a cat in place?
Tbh I’d run the map whilst it was decatted. I did previous for a few month after I melted the sports cat on the drag strip and swapping it out for a decat. But I know others will disagree with this

I told VAS Motion when they were doing my Revo remap that I still had the stock exhaust but with the pre-cat material removed in the downpipe, so they would've adjusted the fueling to accommodate for the cat then I guess.

Whilst it may be too late now but I understand the BCS sports cat is so big that there is no restriction to the flow so the only benefit from a decat is the cheaper price.
Could you not call in the morning to see if they can weld you a cat in place then you would have no worries or hassle at MOT time?
Alternatively, why don’t you send RTech a message asking the question.

Pricing was the only reason I went for the de-cat BCS downpipe and I can get the MOT passed ok, plus it should have a little more presence as I can't afford the Powervalve WRC cat-back for quite a while.

I'll be calling R-Tech this week to get booked in for stage 2+ so will see what they advise.
 

paddy

Registered User
Just out of interest guys if i fit a BSC down pipe and sport cat or a BCS full system do i need to get the thing remapped or can it live on revo stg 1 until i get a fuel pump without the dash lighting up like a christmas tree :) ?
 

samuelh_888

Registered User
Just out of interest guys if i fit a BSC down pipe and sport cat or a BCS full system do i need to get the thing remapped or can it live on revo stg 1 until i get a fuel pump without the dash lighting up like a christmas tree :) ?

Hi @paddy - the majority don’t get any error at all but I’ve read on here one or 2 said they did; this really was the minority of those who’d fitted the BCS. Prior to fitting my I spoke to Dave @BCS and he said it would all be fine. I had it fitted and drove the 30 miles or so to Unicorn and it was perfect, no errors at all.
 

paddy

Registered User
Cheers Sam i notice you are looking at a loba, i was just looking at an Autotech, i just had a new pump about 4k ago so i might just upgrade the internals of that.
 

prt57

Registered User
Pricing was the only reason I went for the de-cat BCS downpipe and I can get the MOT passed ok, plus it should have a little more presence as I can't afford the Powervalve WRC cat-back for quite a while.

I'll be calling R-Tech this week to get booked in for stage 2+ so will see what they advise.

RTech will advise to get the none valved system. I’ve seen a few threads elsewhere mentioning this.
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
RTech will advise to get the none valved system. I’ve seen a few threads elsewhere mentioning this.

Very interesting to hear, do you know why they advise this? As BCS say that their Powervalve system should be the best of both worlds (on/off boost) performance-wise. I'll be having an in depth conversation with Niki about everything, just interested to know beforehand.
 

ch1z64

C'mon you's bhoy's in Green
VCDS Map User
Silver Supporter
Just out of interest guys if i fit a BSC down pipe and sport cat or a BCS full system do i need to get the thing remapped or can it live on revo stg 1 until i get a fuel pump without the dash lighting up like a christmas tree :) ?
Paddy i have the same system as Sam and have never had any ereors come up on the Dash , mind i am only stock at the moment
 

prt57

Registered User
Very interesting to hear, do you know why they advise this? As BCS say that their Powervalve system should be the best of both worlds (on/off boost) performance-wise. I'll be having an in depth conversation with Niki about everything, just interested to know beforehand.

I'd be interested in knowing this also. You don't happen to have any links?

I recently sold my standard S3 intercooler and the chap who came to pick it up had been to RTech to chat about the way forward for his GTi including the BCS. Essentially he told me that the Powervalve is a disc with an 8mm thickness. So when the valve is open the disc is horizontal and so there is an 8mm bar in the middle of the exhaust flow. Only tiny but the ordinary sports system does not have this.
 
I recently sold my standard S3 intercooler and the chap who came to pick it up had been to RTech to chat about the way forward for his GTi including the BCS. Essentially he told me that the Powervalve is a disc with an 8mm thickness. So when the valve is open the disc is horizontal and so there is an 8mm bar in the middle of the exhaust flow. Only tiny but the ordinary sports system does not have this.
8mm thickness is a lot I’d say especially for just a flap
 

Hp_S3

Registered User
I just had second hand powervalve system fitted 2 days ago to a standard car and I also do not have any problems with errors. TSR did say it wouldn't be a problem Unless it was a de cat version.
 

Kaine19

Stage 2+ S3 8P now gone. Hello 2016 RS3 :)
Another question, i will be decatted on wed but not into rtech until mid feb. I expect light on the dash but is it ok to boost around?
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
I personally wouldn't boost around mate as it'll definitely be running lean on a standard map with a more free flowing TBE, especially decat.

Even though mine's already running stage 2, it's going to be running a little lean now that I've got a decat fitted so I'm trying not to redline it until I visit R-Tech next month.
 

Kaine19

Stage 2+ S3 8P now gone. Hello 2016 RS3 :)
Yeah. Dont mind not doing. Had no problems with the miltek downpipe but it does have sports cat
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
Oh really, interesting to know! Means I haven't got to drive as cautiously which is handy because even adding the BCS DP to replace my old modified DP has made a very noticeable difference at stage 2.

Called R-Tech up earlier and managed to get booked in for next Monday the 29th :tongueclosed:
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
Yeah I fiiiiiiinally will be! Way earlier then initially planned but my stock HPFP is faulty so have got a new one ready and a nearly brand new Autotech internals came up for £250 so bought that too, then my flexi pipe split so thought F it I may as well get a BCS DP and go the whole mile as got the Nurbergring in April for a stag.

It's going to be tight as hell for a long while but will definitely be worth the pain!

You're getting your custom TBE fitted Wednesday and then stage 2+ with R-Tech mid Feb right?
 

Kaine19

Stage 2+ S3 8P now gone. Hello 2016 RS3 :)
Yeah way earlier than you planned. Silver lining after all. The ring for a stag thats amazing haha. Yeah exhaust on wed. Pick it back up thurs then down to Rtech on the 13th. Am actually off all that week so no doubt i will be out testing it
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
Indeed haha! Doing a road trip with a few cars in a convoy to the ring, hopefully stop off at Spa on route but will see, should be good fun.

Nice one mate sounds good, bet you're the same and can't wait! I got to drive a 2018 RS3 the other day which was rapid, but know I'll be quicker come Monday :sunglasses:
 

Kaine19

Stage 2+ S3 8P now gone. Hello 2016 RS3 :)
I was in audi the other day looking at a Q5 for her. But naturally i went off to look at rs3 and rs4 haha. I think the rs3 is something i will aim for as the rs4 is or this one was 77k
 
Indeed haha! Doing a road trip with a few cars in a convoy to the ring, hopefully stop off at Spa on route but will see, should be good fun.

Nice one mate sounds good, bet you're the same and can't wait! I got to drive a 2018 RS3 the other day which was rapid, but know I'll be quicker come Monday :sunglasses:
I’m afraid you won’t be the 2018 RS3 is 400bhp...
 

S.

Save the manuals

HHS3

Phantom Black S3 - R-Tech Stage 2+
I’m afraid you won’t be the 2018 RS3 is 400bhp...

True it'll have 20bhp more but also 45lbs less torque and 200kgs heavier than mine so it will be a good race! My brother will still have the RS3 for a couple months to compare so I will let you know the outcome:racer:
 
True it'll have 20bhp more but also 45lbs less torque and 200kgs heavier than mine so it will be a good race! My brother will still have the RS3 for a couple months to compare so I will let you know the outcome:racer:
Think it’s got about 360ft lbs ? Could be wrong.

When I had me S3 8p mine was running 367bhp but 410ftlbs and that thing was very fun. I miss mine from time to time. When you first have it mapped it seems stupid fast
 
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Max Read

Registered User
@HHS3 post up your figures with the 2+Map. I’m curious to see how the decatted standard exhaust holds up compared to a full TBE as that’s what I have on mine at the moment. I’m just waiting for my clutch to give up, then booking in to r tech for 2+.
 

HHS3

Phantom Black S3 - R-Tech Stage 2+
Think it’s got about 360ft lbs ? Could be wrong.

When I had me S3 8p mine was running 367bhp but 410ftlbs and that thing was very fun. I miss mine from time to time. When you first have it mapped it seems stupid fast

Yeah it's 395bhp/354ftlbs, the launch control is ridiculous on that thing!

@HHS3 post up your figures with the 2+Map. I’m curious to see how the decatted standard exhaust holds up compared to a full TBE as that’s what I have on mine at the moment. I’m just waiting for my clutch to give up, then booking in to r tech for 2+.

Will do mate, just to confirm that I'm now running a BCS DP (decat & titanium heat-wrapped) with the stock cat-back but with the butterfly valve delete in the left tailpipe.
 

Max Read

Registered User
I didn’t know you could valve delete the standard exhaust! I’m running a scorpion DP and decat. I’m just intrigued to see how the stock cat back holds up.
 

prt57

Registered User
I didn’t know you could valve delete the standard exhaust! I’m running a scorpion DP and decat. I’m just intrigued to see how the stock cat back holds up.
You cannot remove the valve from the exhaust but you can disconnect the valve actuating rod. You then try and position the lever so the valve is fully open and wire it in this position. However, there is nothing to hard wire it against and so it is just a case of adding enough wire to lock it in position so it does not move. I did have a go at this but did not feel that it was a fit and forget situation as you do not want the valve to shut in it’s own especially if you are in WOT.
My son asked me to do this to his TTS a couple of weeks ago but it would need the back box dropping due to the location of the valve. I said no chance as I did want to have to put it back to normal again in a couple of weeks!
 

samuelh_888

Registered User

HHS3

Phantom Black S3 - R-Tech Stage 2+
@HHS3 post up your figures with the 2+Map. I’m curious to see how the decatted standard exhaust holds up compared to a full TBE as that’s what I have on mine at the moment. I’m just waiting for my clutch to give up, then booking in to r tech for 2+.

As requested see below with the related parts, it pulls like a train! R-Tech is the one, don't settle for anything less. Niki said that an uprated Intercooler and Cat-back would see me 380bhp which I didn't need to hear haha but to be honest that 15bhp increase would barely be noticeable so as funds will be tight now for a long while then I'm not fussed. I'll focus on ARB's and ALK next.

I was racing a TTE420 S3 and 2018 RS3 for hours on Sunday of which they only pulled a little bit away during shifts as they were DSG and I'm manual, so I'm more than happy with that.

Audi S3 8P (BHZ)
R-Tech Stage 2+ Remap (Pops & Bangs @ 6K)
Autotech High Pressure Fuel Pump Internals
New OEM High Pressure Fuel Pump (5mm Drill Out Mod)
BCS Downpipe (Decat & Titanium Heat-wrapped)
Stock Cat-Back With Exhaust Valve Delete
Revo Cold Air Intake (Ceramic)
Stock Alloy Intercooler
RS4 Fuel Pressure Return Valve
GFB Diverter Valve+
NGK BKR7EIX Spark Plugs
Spec 2+ Clutch & Steel SMF
42 Draft Designs Shifter Bracket Bushings Kit & Shifter Bushing Kit
Powerflex Dogbone Mount Insert
Forge Silicone Throttle Body Hose
Forge PCV Delete Plate
Shell V-Power Nitro+
Millers Nanodrive CFS NT+ 5W40
Inlet Valves Cleaned & Injector Service

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