UK-POLOS.NET - THE VW Polo Forum

Hey guys,

I've been quoted by what I believe to be the best garage near me for parts to upgrade the performance of my GTI 1.8 2016 6c car with a remap/parts.

I'm fairly new to adding anything to a car, I believed what the garage was recommending was good as I seem to be able to reflect this onto what I can find online.

Basically, they suggest these upgrades:

Racingline Performance Intake System

Upgraded clutch, flywheel, release bearing (don't have the specific ones but it comes to £1500 Inc fitting costs for this alone.

Airtec Intercooler Upgrade

NGK R7438-8 Spark Plugs

Remap (they offer more gains than any other garage near me).

I already have installed a Scorpion Non-resonated cat back system

--

What I was confused about, (this is the question). Is I told the garage I want to keep my car MOT compliant.

They advised against getting a Scorpion Exhausts Sports Cat Downpipe or any other downpipe involving the catalytic converter as this may cause an MOT failure other than the obvious MOT failure, a decat, something to do with heat temperatures of a sport catalytic converter. Yet, this seems like a suggested part other garages would recommend in upgrading the car. Would this drive down the performance substantially, and/or is this guy on the ball?

I'd rather not fail MOT it would give me far more issues than it's worth, which is why I requested to spec my car purely to what wouldn't give me any bother hence, why maybe the downpipe is recommended by places but not advised if you don't want to fail an MOT?

I'd recommend a sports catalyst and not a downpipe without a catalytic converter. Your car will smell and also fail MOT due to CO emissions.
If you want to go a bit more on the power line, you could consider a turbo inlet elbow, turbo muffler delete (or both) and even an upgrade to an IS20 or IS38 turbocharger.

iichel wrote: Sun Mar 24, 2024 12:12 pm I'd recommend a sports catalyst and not a downpipe without a catalytic converter. Your car will smell and also fail MOT due to CO emissions.
If you want to go a bit more on the power line, you could consider a turbo inlet elbow, turbo muffler delete (or both) and even an upgrade to an IS20 or IS38 turbocharger.

So you mention a sports catalyst. What I was looking at is a "Scorpion Exhausts Sports Cat Downpipe - Volkswagen Polo GTI 1.8T 6C" and/or "Scorpion Downpipe with high flow sports catalyst Polo Gti 1.8T 6C 2015 - 2017", Is that what you'd be referring to?

The person I'm in talks with advised against it, alongside the exhuast I mentioned I do have already without a downpipe modification.

His exact words are:

"The modifications you mentioned there would be great for the car – However even a sports catalyst can fail an MOT if not up to the right temperature.



I would recommend upgrading the intercooler over replacing the catalyst – this keeps performance up and the car road legal."

I was just a bit confused, all stage 2 maps for example follow having a sports cat downpipe unless another part is involved with that as well that I'm missing?

I'm just trying to get clarity, I have time between the modifications install and the remap as I need to do 750 miles to settle in the new clutch to ensure it doesn't slip as well, according to them so figures if it's a substantial difference I could get it done with my remap later.

As well, makes me wonder if the car would be throttled by not getting this modification at all?

Firstly, welcome to the forum

I too have just recently started to do some actual power mods and it's also the first car I've done some to.

A decat will be an MOT fail if noticed during inspection, if not it will then almost definitely fail emissions. It will also make the exhaust louder and as mentioned will smell of fuel.

MOT handbook:
https://www.gov.uk/guidance/mot-inspect ... on-8-2-1-1

The garage is also potentially opening themselves up to DVSA enforcement if they're fitting a de-cat as they fined AET Motorsport back in November for doing so. There's also then the issue if you get pulled and they decide to have a look around they could revoke the current MOT and require a retest. But the likelihood of this happening is quite low frankly. A 100 CEL sports cat probably won't offer much restriction, obviously more than a de-cat but probably a lot less than the factory cat. Definitely something to speak to them about if it's of concern to you as they'll hopefully be the experts. Most sports cats will pass but as you've mentioned as long as they're hot.

As for the rest of the car, what they've recommended all seems good. I'd personally add a fuel filter, coil packs, an uprated dogbone/pendulum mount and an oil change to that list. If you want to go even further you could consider replacing the PCV and fitting a stronger rear main seal from 034 Motorsport or iABED while the flywheel is off.

The low-pressure fuel pressure regulator is built into the filter and a fresh filter will also put less load onto the fuel pump which you'll be asking more of once mapped. MANN WK69 will fit and typically sub £30.

I was advised by MRC that old coil packs are known to fail at higher power levels. The current revision is K (full part number 06L 905 110 K). You could also use uprated coil packs from the RS3, or those from APR, Racingline or 034Motorsport.

As for the clutch, yes you will need to bed it in. I've just had a Sachs SRE Organic installed and need to do a minimum of 500 miles of town driving and no full throttle to bed it in. Not sure if others are the same but I found the clutch to be significantly heavier than stock but it is getting lighter with use. The bite is much lower and the engagement window is also smaller so once it's at the bite not long after the car wants to go. It takes some getting used to. Also, double-check with the clutch manufacturer which release bearing they advise to use, some use the stock, part plastic release bearing while others seem to use a full metal one more akin to that in the mk5/6 golf. The main difference between the two is their depth. My Sachs SRE came with the latter.

A fresh oil and filter never hurts and is only £60-£70.

An uprated dogbone/pendulum mount will help stop the engine from twisting as much, if the downpipe you choose is bigger than stock there's a risk of it contacting if yours is worn. I've chosen to replace all of the mounts with VibraTechnics and I don't think I'd recommend it as there is quite a bit more engine and gearbox noise transmitted into the cabin but doing just the dogbone won't have much effect.

A new PCV and uprated rear main are purely preventative. One of the symptoms of a failing/failed PCV is blown oil seals in areas such as the upper timing cover, cam magnets, exhaust cam adjusters, oil cap and at worst the rear main. If you've had any blow recently consider replacing the PCV. I took the point of view that for £200~ I could reduce the likelihood of ruining my expensive clutch through oil contamination if the rear main failed and the flywheel was already coming off anyway so it was right there.

If you fit a turbo elbow, you'll need the Golf-R style PCV hose. Part number 06K 103 213 J. An aftermarket elbow can reduce the effectiveness of the PCV but that's a whole other discussion/topic. If you want to have a read lookup mk8 PCV retrofit. iichel helpfully has a post
viewtopic.php?t=78017&start=90

Ian095 wrote: Sun Mar 24, 2024 5:56 pm I was just a bit confused, all stage 2 maps for example follow having a sports cat downpipe unless another part is involved with that as well that I'm missing?

An upgraded cat/decat will increase exhaust flow by reducing back pressure/restriction which could also reduce exhaust temps. An upgraded intercooler will reduce intake temps, improve flow if designed correctly and take more to heat soak. Both improve performance/consistency but in different ways.

It's also generally advised against to drive a car with a downpipe if untuned.

I'd also try and get a dyno done before and after so you can verify the tuner's claims of power/torque increases. It will also allow you to see that the car is running correctly in its stock form.

Finally, make sure you inform your insurance. I haven't had any of my mods increase my premium, like with new quotes, putting the date out helps reduce the cost.

Some links:

Fuel Filter
https://catalog.mann-filter.com/EU/eng/ ... er/WK%2069
Coil packs
https://www.awesomegti.com/apr-ignition-coil-mqb/
https://www.awesomegti.com/034motorspor ... x-engines/
https://www.awesomegti.com/shop-by-car/ ... a888-gen3/
Dog bone/Pendulum
https://www.vibra-technics.co.uk/vw/pol ... _torq_link
https://www.powerflex.co.uk/product-det ... /2065.html
PCV Hose
https://progressiveparts.com/product/ge ... 08640-2017
https://clptuning.co.uk/product/genuine ... ther-hose/
Sports cat vs de-cat:
https://www.youtube.com/watch?v=qEcVHJ7QDyI
Rear Main Seal upgrade:
https://www.awesomegti.com/shop-by-car/ ... -0t-ea888/
Turbo elbow:
https://www.youtube.com/watch?v=18hQlygnX_o
https://racingline.shop/product/racingl ... 12p1gtis38

Bepis wrote: Sun Mar 24, 2024 10:46 pm

First of all, wow! Thank you very much this is very comprehensive so I greatly appreciate the time and effort you put into this for me.

I will look into all of these, though the garage I'm getting work done at currently only fit parts they supply, which I imagine they will not be able to get all of these so it would be an afterthought. I imagine having my car mapped before any of this is likely to matter anyways, right? Plus it means I'd have to consider something such as a "stronger rear main seal from 034 Motorsports or iABED" afterwards.

I was recommended a garage near me for repairs who is supposedly an expert with VWs, sure he'd maybe fit things for me if it isn't simple enough for me to do myself, though I figure I'd have to source the parts to him (you already done the main part of the homework for me too on what you've mentioned, thank you again).

I've decided to entirely avoid a downpipe with sports cat, could potentially get by fine but it just sounds like more issues than necessary and of course, as soon as I heard what decat is I wasn't keen on that either. Just didn't get the sports cat thing but I believe what it is, requires it to heat up to be more likely to pass which isn't exactly realistically doable in all cases.

You also read my mind, oil change is due in just over 1000 miles. So I had planned to get it done when I get the remap done.

You mention an upgraded dog one / Pendulum mount too, yet I'm somewhat confused to what they actually are, their purpose. More so, what would be causing the engine to "twist". Saying this as I'm clueless behind the physics / logic in why it may want to twist.

All that there is left to say is thanks again though. I can see myself opting to purchase a lot of these for the better good of maintaining my car and not having it fail on me somehow down the line Also, I blankly quoted you as I don't remember how to simply tag someone in a response on these old kind of forum posts but I know the quote would be huge and unnecessary.

The pendulum mount attaches to the underside of the gearbox and the subframe, its whole purpose is to restrict how much the engine can twist. The engine and gearbox mounts also do this to an extent but they're mainly load bearing and to keep the engine in the car.

Video explaining its purpose and what an upgrade can do. Although for a Golf the concept is the same:
https://www.youtube.com/watch?v=5ddRmzGE4M4

Now I'm not a tuner but typically when pushing beyond stage 1 a sports cat or de-cat is advised to allow for the engine to breathe better. In its most basic sense an engine is an air pump, more air in (more boost) means more air out. The factory exhaust system will have been designed for stock power so may become an issue when going much beyond that.

The issue you may face when pushing on a stock cat is excessive back pressure, limiting performance and increasing exhaust temperatures. If not properly managed could cause damage to the turbo or the catalyst material itself.

The whole "stage" of tune differs from car to car and sometimes from tuner to tuner but typically on these cars stage 1 is just software and 99 octane fuel, maybe a high-flow panel filter.

Stage 2 is typically an intake, exhaust, downpipe and an intercooler.

Then stage 3 is turbo and fuelling mods. Typically an IS20 from a Golf GTi or an IS38 from a Golf R/S3 with a Golf R high-pressure fuel pump. For reference, the 1.8TSi in the Polo has an IS12.

From your 1st post, it sounds like you're describing stage 2.

With the concerns you have raised regarding keeping the car road legal, and for the level of power it sounds like you'd like, I'd probably go ahead and install a sports cat as it will be a lot more legal than a de-cat but will just require some extra attention come MOT time. ie going for a decent drive before to get it hot.

Like Bepis has advised, I would speak to your insurer before installing the mods.

I spent over 25 years as a senior manager for a large motor insurer looking after the claims department and looking at your planned mods I cant think of one insurer that wouldn't load your premium or reject you claim if you didn't declare the mods you're planning. I've got a Cobra Sport resonated system and didn't see a premium increase (but then again I'm old enough to remember when the MK1 Golf GTI was the hot hatch). The same insurer did increase the premium on the other family car that has a Stage 1 remap. (some insurers will refuse to cover at any price)

These days its standard practice for body shops to scan the cars ECU to make sure all is running OK before starting repairs which will allow them to read the flash counter etc

I'll stop with the bad news as Im starting to sound like my Dad. Good luck