Project GTI: Cooling Down
Winter’s Here

I’m fully convinced that Ireland has the sneakiest weather system in the world.

Just when you think you’re over the worst of it, it plays the ‘one more thing’ card and either dumps snow on us, or batters us with wind and rain just as we start to get our hopes up that we might have just had a soft winter. (For the sake of his short rant, I’m going to conveniently ignore that it snowed at pretty much the exact same time last year. Shush.)

There was a slight difference this year, in that Project GTI & myself were ready and waiting for snow. While the snow didn’t quite make it to my doorstep, I was able to hunt some down on my favourite local driving roads to see just how much of a difference the Wavetrac and Michelin Cross Climate+ combination made.

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Long story short? It was tremendous fun.

Okay, it was a pretty light dusting of snow all things considered, but it didn’t stop others from getting stuck (including a quattro B5 Avant, presumably on full summer tyres). It did provide plenty of entertainment for me, so really, that’s all that matters. An AWD car on full winters would probably (well, definitely) have been faster, but I doubt it would have been that much more fun in the conditions.

What has this got to do with this update? Absolutely nothing. The next bit, however, is where the real substance of this story is. Believe it or not, this was the planned final piece of the Project GTI puzzle. So, by the time you get to the end of this feature, Project GTI will be complete.

Heck. I better get cracking, so.

Man’s Not Hot

So, let’s pick things up from where we left off in January’s update. My plans for the winter involved tightening up a few areas on the car (which we achieved with the Tyrolsport rear hatch brace and rigid collar kits) along with coming up with some cooling solutions for the GTI’s first generation EA888 and its DSG transmission.

The MK6 GTI is a bit of an oddity in the GTI lineup. It’s essentially a (heavily) face-lifted MK5 which shares a lot of the same underpinnings, but with a slightly different 2.0-litre turbocharged engine (EA113 TFSI in the MK5 versus the MK6’s EA888 TSI).

I say it’s an oddity, because to me, it always felt like it was filling a gap between the MK5 & MK7. It started production in 2008, but with the MK7 arriving in showrooms in 2012, its lifespan was shorter than most other Golfs. Add to this that the MK6 GTI’s production run was during the peak of a global recession, which goes a long way towards explaining why they seem much rarer than their siblings either side.

While lots of parts from the MK5 will fit, there are still certain things with which you have relatively limited choice. Oil cooling is one of these things. Because of this, I spent a lot of time researching what my options were.

With some kits, you would need to run either modified TSI or 1.8T oil filters, which I just outright didn’t want to do. With limited space at the front of the car, and with an air conditioning condenser, intercooler and water radiator sandwiched together, I wanted to minimise the amount of space that the oil cooler would occupy in front of these.

My oil temperatures on track last year peaked at 130°C (266°F), so I was quite keen on reducing these by as much as I possibly could with the aforementioned limitations taken into consideration. What I believe worked best for me was to use two different kits to make one perfect solution.

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With that, I ordered a HEL Performance kit from eBay along with placing a separate order with CSF for one of their small universal dual-pass oil coolers.

The kit came with a take-off plate, 90°C (194°F) thermostat, braided lines, fittings and a small single pass 13 row oil cooler. I’m sure that the cooler supplied with this kit would be fine for most ordinary applications, but my car isn’t exactly ordinary anymore, which is why I added CSF’s dual-pass cooler into the equation. By CSF’s estimates, the dual-pass cooler should result in a further 15-20% reduction in outlet temperatures when compared to a single-pass cooler.

With everything on the bench, it was time for the strip down to begin…

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As I wanted to continue to use OE and non-modified oil filters, I didn’t choose a traditional sandwich plate which would have attached to the oil filter housing. Instead, the take-off plate would replace the factory oil heat exchanger, which is located – inconveniently – beneath the intake manifold.

Thus, a fairly thorough strip down of the front of the engine and car requiring the intake manifold, catch-can, throttle body, fuel rail with injectors, water pump, bumper, under-tray and splashguards amongst others to be removed. It was during the removal of the under-tray that we discovered a hole in one of my intercooler’s boost pipes. Another thing for the list…

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This is the rather inefficient factory oil ‘cooling’ solution. You often hear people stating that surely the manufacturer knows best when building a performance car, but this is a great example of the compromises that have to be made for a car to make it into production. It’s perfectly adequate for the majority of owners, but if you intend on tracking your car, it should be a mandatory upgrade.

As water will heat faster than oil, this factory heat exchanger allows coolant to flow through it in order to help oil temperatures increase from a cold start. When the oil does get hot, it depends on the normally lower coolant temperatures to try and cool the oil.

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The new take-off plate still allows coolant to pass-through to assist in warming the oil, but also sends and receives the oil from the new (and soon to be front mounted) dual-pass oil cooler.

As a small aside, I was able to inspect the valves after having them cleaned nearly two years ago to check if the Integrated Engineering PCV bypass and catch-can setup were proving effective. The valves had only a light coating of dry carbon on them, and not the heavy, oily sludge that they had before. I guess that definitively answers the question if catch-cans work on these engines.

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With the take-off plate installed, John started working on figuring out an optimal location for the thermostat. Packaging on these cars is quite tight, so you’re limited in where you can install these.

After fabricating a neat, small bracket, the thermostat was attached amongst the front crash structure on the face of the driver’s side chassis leg.

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We (John) were able to make use of the brackets supplied with the other kit to mount the CSF oil cooler, albeit with a couple of small modifications.

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A fairly central position was decided upon, in order to allow the braided lines running from the thermostat a chance to flatten out before connecting to the oil cooler, after they had rounded a relatively sharp bend at the front.

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To ensure the lines were connected correctly, we needed to briefly turn over the engine to double check the direction of oil flow from the thermostat. As luck would have it, we (again, John) had it right first time.

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There were a couple of trial & error front bumper fittings to ensure that the oil lines weren’t fouling on the inside of the bumper (or anywhere else for that matter). Once perfect fitment was achieved, it was time to put everything back together.

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This was a pretty comprehensive installation, and certainly not something I would have ever attempted at home. With everything buttoned up, we started the car and let it idle up to temperature in order to check for leaks or any other issues that might raise their heads.

We obviously changed the oil filter and oil during the process, and as far as I remember, the car only required maybe an extra litre of oil. Even this extra litre on its own will play its role in helping to reduce oil temperatures.

It was a late finish, which provided the perfect conditions for a speedy journey home.

The difference in oil temperatures were immediate, with an instant reduction of over 15°C at motorway cruising speeds and a reduction of 20°C under other driving conditions. On a spirited drive, where I was previously seeing peaks of 115°C (239°F), I’m now consistently below 100°C (212°F).

These reductions on the street bode very well for on-track shenanigans, where I’m aiming for an oil temperature window of 115°C (239°F) to 120°C (248°F). This was just part one of this story, as it would be a few weeks before I would be able to get back down to Stone Motorsport for part two…

Some Time Later

In fact, it was around three weeks before we commenced the final work on Project GTI. It was just enough time to order a new boost pipe and have it shipped to Ireland from the USA for maximum ‘sure, while you’re at it…’ convenience, along with swapping back onto my RAYS Volk Racing TE37 Saga summer setup.

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The primary purpose of this second visit was to upgrade the factory DSG cooler. As per last year, the ‘box went into limp mode after a relatively prolonged session on track resulting in reduced shifting speed in order to protect itself.

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Similar to the factory oil heat exchanger, the factory DSG heat exchanger works in pretty much the same fashion where the engine coolant helps to get the gearbox oil up to temperature, before being depended on to keep temperatures in check.

This was a trickier upgrade to research, as it’s a much less common one to make. There were no aftermarket solutions that I could find for the MK6, so I took to researching the Volkswagen parts bin to see what my options were. I went deep down this particular rabbit hole.

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I can’t recall precisely how I found this information, but in Russia, there are some hardcore Škoda Yeti enthusiasts who have had issues with overheating DSG transmissions while off-roading. As luck would have it, the Yeti uses the same (or least very similar) factory DSG heat exchanger as the MK6 GTI, and their solution to the problem was to use a larger one from the AWD Golf MK5 R32.

So, that’s what I ordered.

Thankfully, the DSG heat exchanger is infinitely more accessible than the original engine oil heat exchanger, being located behind the air intake and sort of beneath/beside the battery. You lose a little coolant during the installation, but that’s pretty much the worst of it. The larger heat exchanger is approximately 10mm taller than the previous one, allowing it to hold more coolant while also having a larger surface area inside to transfer heat from the oil to the coolant.

I think it’s an upgrade which should offer a small improvement, rather than a complete revolution.

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As luck would have it, just across the workshop, was a proper Seat León Supercopa racecar. These are 330hp 2.0TFSI FWD factory-spec racers that were run in a one make series in Europe for several years. They utilise a lot of factory production car components, including the DSG transmission.

For me, it was most interesting to note what Seat’s motorsport division deemed adequate to control transmission oil temperatures. According to the part number, it’s the very same DSG heat exchanger that we had just fitted to my GTI not 20 feet away. If it’s good enough for one of these, it’s almost certainly good enough for me.

Also, take note of the triple-water radiator setup on these, with an extra radiator at either front corner with ducting and venting into the wheel arch. Interesting.

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Finally, it was a straightforward case of swapping in the new boost pipe, which was thankfully easy to access. The punctured pipe is pictured in black and white above.

There was still one more thing to come…

Talk To Joe
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While not strictly necessary before a tuning session, I hugely appreciated Rob offering to give the GTI a proper wash before it headed into the dyno cell. It reminded me that it’s been almost three years since the car was last polished, so it’s perhaps a tad overdue a detailing session.

While I’ve always maintained that this isn’t a show car, it’s nice to look after it as much as possible.

Anyways, with everything installed and the car mechanically perfect, it was strapped down onto the Dyno Dynamics rolling road. Joe Power of TDR Performance custom tuned the car for our piss poor Irish fuel in January 2018, resulting in a peak power figure of 308hp on a fairly conservative map.

I was supposed to call back after a couple of weeks to finish the tune, but the car was behaving so well and driving so nicely, that I kept putting it off for another day.

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Time does tend to pass by much quicker these days, so after over a year of putting it on the long finger, I made the arrangements for Joe to book me in and give him some time with the car again.

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I’ve got to know Joe quite well over the last 12 to 18 months, and he’s given me some fantastic advice for the car during this time. He currently works on LMP2 race cars in the European Le Mans Series, including the prestigious 24 Hours of Le Mans, so my humble GTI is in very safe hands.

Also, as he’s familiar with the car, myself and what it’s used for, he’s been able to tune it specifically for what I need. To be truthful, I think he knows what I need, better than I do.

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On its first run in over a year, with probably 15,000kms more on the clock and a few trackdays under its belt, it made 297.4hp with mint AFRs. I would deem this to be a more than acceptable deviation from the previous 308hp run over a year previous, when taking differentiating factors such as temperature, air pressure etc. into account.

Essentially, Project GTI was very healthy and, pretty quickly, that number started to increase as he made his refinements.

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“I’m not going for big numbers” he advised me from my own driver’s seat, as if to temper my expectations. It’s in situations like this that I’m glad I have no input, mostly because I’m an idiot and would just set everything to 11 and hope for the best.

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Thankfully, his goals for this session were far more rational than mine. Taking power/torque delivery, heat management and reliability into account, the final tune saw a peak power figure of 332hp and just over 400Nm of torque. This was at a peak of around 1.6 Bar (23psi) which is pretty much middle of the road for a K04. These turbochargers are typically boosted to between 1.4 Bar to 1.9 Bar (21psi to 28psi) on this platform depending on fuel, tune etc.

Most impressive, was the perfect AFR line on the dyno chart demonstrating that the car was comfortably supplying enough fuel into the cylinders without the risk of running lean.

Of course, part of me would love to know what the car is capable on proper fuel (as stated before, we only have the option of 95RON in Ireland, equivalent to 91 in the US), but I guess you just sometimes have to suck it up and play the hand you’re dealt.

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As heat soak started to creep in, the power figures started to tail off but the AFRs and power curves stayed consistent.

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This was one of the final (hot) runs, which demonstrates the really smooth power delivery along with the AFRs along the horizontal line. The linear power curve is particularly advantageous on a two wheel drive car, as there’s no sudden onset of boost which could result in a loss of traction.

This should be awesome on track.

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It cannot be said that the car wasn’t pushed, anyways.

The Finished Product
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It has been the better part of four years at this stage, but I’m finally at a stage where I consider this project all but done. I’m sure there will be maintenance items to address and perhaps even a couple of preventative things that might come up with more time on track, but this is truly the car I pictured in my head when I first drove it off the forecourt all those years ago.

The premise from day one was to extract as much performance potential from the car as possible, while introducing as little compromise into the car’s abilities as a daily driver. I’m not sure there’s anything I would have done differently, as nearly every change and modification was done once, and done right. We all have different tolerances and tastes, and I’m sure you might do something different if it was yours, but ultimately, it’s mine, and it’s about as close to perfect as I can manage.

I drive it every day, I drive it hard, I drive it gently. It goes to IKEA, it brings my groceries home, and it takes me around Mondello Park with a huge smile on my face.

While it might be finished, I think the real story of Project GTI is only beginning. So many projects are completed and then almost immediately sold off. I couldn’t think of a worse thing to do with this, at least not before I get to drive it and do the things I’ve always dreamt of doing with this car.

So, Nürburgring anyone?

Paddy McGrath
Instagram: pmcgphotos
Twitter: pmcgphotos

Cutting Room Floor
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love the GTI, great to see you making progress! do you watch juiceboxforyoudotcom? I say hello to ruben bendover and the boys on occasion you could should have a showdown, GTI vs rusty tureno!


Yes, I know the guys quite well. At the moment, I think I'm faster than Neil's Trueno on foot, never mind in the GTI!


like the irish flash. make em green with envy.


In his defence, it's still a shell XD


then im a shell too.

Arun Beena Mohan

Hey hows that S15 coming ??


It competed for a few rounds in IDC last season, but they're now working on setting it up for grip at the minute.


I love these project GTI updates, very inspiring. You're going about this build exactly how I would for sure. Those winter shots are so dramatic too! The red contrasting with the white, very pretty. Thanks for keeping us in the loop, can't wait to see where you take her this year! Are you one to name your cars by the way? or is she just the GTI?


We tried naming it, but nothing really stuck. It's just referred to as 'the Golf' or 'the GTI' most times.


Car looks excellent! How are you finding the Recaro for daily life?


Not too bad at all, Andy. I've done quite a few long trips and it's been fine. I'd still like to try get it an inch or so lower, but I'm genuinely happy with it day-to-day. The support it offers is crazy.

In saying all of this, I'm tempted to swap the stock seat back in for an upcoming 2,500kms road trip, if only because it reclines and I can nap if needed!

Francis Chartier

Was just about to say: if you have the rear seats still, possibly do a matching re-upholstery job on the Recaro to give it a slightly more OEM feel. Just my 2 cents.
Still, absolutely loved these updates, as they illustrate IMO the perfect OEM++ (few steps past OEM+) build, and thorough coverage of its progress.


I might get the centre cushions trimmed in the correct tartan, or even a spare set. I don't want to go with a whole re-trim in case I move the seat to another car or project in future.


I really love this Golf Paddy. There's something quite Type R about it too (don't throw things at me.....)


I take that as a compliment, thank you!


Now you can run cool while people with properly setup suspension pass you *thumbs up*.


very useful comment


Oh, no. There goes my dream of winning the trackday world championship.

Bradley Johnson

It’s interesting looking at your power graph vs mine Paddy. Same 2.0 Turbo but of the Japanese Variation of a FK2 Type R. My image shows standard which was boosting at 1.5 bar an produced a similar output to yourself, vs what I’m now boosting at 1.8 bar an producing 392hp an 400ft-lb.


Standard Turbo? Cat? Fuelling? Intake? Intercooler? All setups are completely different, so it's a bit pointless comparing them. At the end of the day, I would hope a significantly newer engine design with 100hp more from factory would be more powerful than a decade old TSI, but that's some very strong power :)

I would also take a wild guess that you're not living in Ireland? Interestingly, there was a stock FK2 on the same rollers not so long ago which made 277hp at the flywheel. The ECU was freaking out on 95RON, with knock protection working overtime throughout the rev range (Just to give you an idea of what we're up against over here!)

Bradley Johnson

Standard turbo and cat, running a cat back an full carbon eventuri intake with some other little DIY mods that are known in the FK2 community. I get what you’re saying regards comparing the two but in standard form I found it interesting to see similar boosts giving similar out puts.

Yeah U.K so 99 is my regular drink of choice for it. Yeah it’s amazing how much 95 can kill the performance isn’t it. Thankfully mine ran a 305 so a smidge under the claimed 306 when it was in OEM form 2 years ago, but that was whilst using 99 octane of course!


It's interesting for sure, and I'm now curious as to the size of the stock turbocharger on the FK. Boost is only one part of the equation, another is how much air the turbocharger can flow. The factory K03 on the GTI was running 1.6 Bar at 245hp, where the K04 is producing almost 90hp more for the same amount of boost. If I was to run something like a GT3076 at 1.6 Bar, I'd imagine the contents of my engine probably wouldn't stay inside for very long!

Bradley Johnson

Stock turbo is good for 420hp as far as I’m aware. Theres a company in Germany who do a 500 an a 550hp mod which of course means hybrid turbo, an then there’s a guy in China running his in a time attack series with something like 620hp.... through the front wheels!
The joys of the K20 series engines being forged we can get away with big powers without interfering with the internals I guess.
Still for road use an occasional trackday I think sub 400 is plenty enough in a fwd car. I have been struggling to get the power down myself in the first 3 gears let alone 2 with the cold temperatures and AD08R’s at this time of year! I imagine you struggle the same now too Paddy!


It's not too bad, TBH. I find having a tyre that doesn't need too much heat to be more beneficial on the street (Michelin PS4) even if I'm sacrificing outright grip on track. The Wavetrac LSD does wonders for traction, too.


Beauty. I had my mk6 for 5 years, no crazy mods like yours tho. Very tastefully done. I've moved on to a 135i now, but I can't say that I don't think of my little GTI every now and then. Enjoy her, keep her happy


Thanks for all these articles of your project. Every time I read them it gives me direction for my WRX. Better, without losing the car you bought in the process. My favourite speedhunters project.


Project GTI is looking good and man those TE37s are the best
My friend and I are doing a Jetta Mk6 build


I’ve been following this project since the first ‘Project GTI’ post here on Speedhunters. Its so satisfying to see it finally mechanically complete as a perfect driver’s car. This is exactly the type of thing I’d like to do with my Audi 90. I don’t ever intend to sell it, so why not make the best of it. If only parts were easy to find...


I have a MK7 GTI as my DD. It's a great little car. Build quality is absolutely top notch. Too bad they're not more popular in the US. They give great value for the money. The interior feels like it came from a much more expensive car.


Good on ya Paddy, well done!


For what it's worth, I've really enjoyed following along with this series and love what you've done with the GTI! I've owned a few different GTIs so far and this is the one I look up to. Amazing work and incredible photos. Thanks for sharing your journey and all the details along the way!


Thank you, Jake.


Great article once more.
Interesting enough, I start missing my Candy White Mk6 R each time I read one of your stories. And I really love the Valencia Orange M135i that came after! But these über Golfs have something of their own...


I wouldn't turn down an M135i, that's for sure.


Be a little sad to see the updates finish for this as I always look forward to reading when I see its picture pop up . Proper real world builds like this that get used as they should are by far the best thing about Speedhunters and they are what got me hooked (and make me read before going to sleep most nights ) all those years ago . Absolutely top work man


Well, while the 'build' part of it is 99% completed at this stage, I do hope to bring some driving adventures with it in place of the upgrade stories. Definitely not going to hide it away!


Thank you for sharing! If I didn't need a truck weekly, I would have to have a replica of your car to drive daily. Keep up the mods, epic photos and don't sell!!!


Thank you, and that's the plan!


My GOODNESS Paddy. I know you're a very accomplished photographer and all, but we should all be so lucky to be able to take such great photos of our own cars. Those winter drive photos are the BOMB, and the feature image with the F1(?) car beside it? *kisses fingers*

BTW we need the backstory on that car too...


As far as I remember, it's a World Series Formula V8 car.

(And thank you)