Project GTI: Preparing For The Final Evolution
Diagnose

It’s been over two months since Project GTI last made a proper appearance on Speedhunters, not counting a brief cameo in April.

The truth is that the car has been boringly reliable the last couple of months, especially since we sorted out the niggles that I had let build up. It starts first time, it’s running perfectly, it’s smooth, it’s reliable and it’s still pretty fast.

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Although I haven’t gotten out as much as I would have liked in recent times, I do still get to enjoy the occasional aimless drive. Whether fast or slow, the Mk6 is an absolute pleasure to drive. There’s lots of feedback through the wheel, the car is compliant enough without being harsh and uncomfortable, and if the mood takes you it can both scare and impress in equal measure.

When commuting, the DSG box is smooth, the in-car entertainment is perfect, and it’s easy to drive in traffic. I really don’t have any complaints about the car. I will have owned it for two years in a couple of weeks, and it’s usually around this time that I should start getting itchy feet and begin to look for its replacement. The thing is, I can’t find anything that ticks so many boxes, except for a new GTI, which seems sort of pointless as it’s not an upgrade as such.

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We did diagnose one thing that was maybe responsible for causing some of the aforementioned issues which I’ll get to in a minute, and which this post is primarily about, but I’d like to talk about the future of Project GTI just for a brief moment.

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The car has come a long, long way since I first bought it as a completely stock used GTI out of a dealer. Suspension, brakes, cosmetics, engine, transmission and interior having all been addressed in one way or another. The aim of keeping the car balanced between daily driver and making the most of what’s available is still key, but there is one last area of potential that I want to exploit.

June will see Project GTI get a sizeable injection of horsepower, and I’m aiming to bring the updates almost as soon as they happen. I’m not chasing horsepower figures, but I do want the car to become all the car it can be.

I am tremendously excited about this.

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Now, to get back to what this post is actually about…

If you remember, the car suffered braking issues after a track day earlier this year. Over the course of a session, they began to fade and developed a pretty severe vibration. The vibration issues were diagnosed and solved, and the fade issue was partly addressed with a fluid change. We thought there might have been some air in the brake fluid, which reduces the fluid’s boiling point, but there was a much more obvious cause which needed to be rectified.

Resolve
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We identified the issue during the last visit at Stone Motorsport, but seeing as I wouldn’t be doing any track work in the meantime, we left it until the next service to resolve.

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I’ve been maintaining a pretty consistent 10,000km (6,200mi) service interval (which I actually set on the car’s on-board computer instead of VW’s 20,000km interval through VCDS) which results in around two services every year.

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On the recommendation of others whose opinions on performance VWs I trust, I changed my oil from 5W30 to 5W40. It still meets VW’s standards, but should result in less oil consumption (currently around 1 litre per 10,000km) and a slightly quieter running TSI motor, which are notoriously diesel like on idle. A genuine VW filter was also used, and I’ll be sure to keep an eye on everything to see if the change makes any difference.

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And finally, onto the actual reason I was here: brake overheating. I know lots of people who run Tarox setups on their track day cars and never have problems with overheating, so something was definitely amiss.

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Inside the front wheel arches are large openings which I thought – wrongly, as it turned out – were supplying the brakes with cold air.

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When viewed from beneath, you can see that these openings even have a dedicated channel which should funnel air running under the car towards the brakes.

The issue here is that air cannot be effectively routed into this channel. The grill beside the fog lights is solid, and there’s a considerable lip which sits behind the front splitter that obstructs any air from entering the channel into this faux brake duct.

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You can maybe see it best from here, where the plastic lip – which itself is around an inch thick – is actively preventing any air from running through the channel. After a thorough inspection, it’s obvious that there’s no effective brake cooling on the GTI from factory, which is a little bit disappointing. My diesel BMW 3 Series saloon had more adequate brake cooling.

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Another view through the front splitter, which shows how the plastic lip blocks air flow. Any air that makes its way through here, is just going to stall when it hits that lip.

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Lots of discussion, measurements and cardboard mock ups were had in order to figure out how to best solve the issue. Eventually, we decided that the simplest solution was the way forward and to make the most of what was already in place.

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Using a cardboard template, a 2mm piece of alloy was roughly cut that would connect from the bottom of the splitter to the bottom of the vent in the wheel arch and act as a bridge of sorts.

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The plastic lip which was previously stalling the air was trimmed to suit the new configuration.

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Using the mounts of the splitter as a guideline for the width, you can see where the lip remains on the left and where it was trimmed on the right.

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Now, air that passes through the front splitter should have a direct route onto the brake caliper and the back of the disc. It has to be an improvement on what was not there originally.

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With everything measured twice, it was time to finalise the design and install it on the car. Bryan cut the alloy to shape and smoothed the edges before painting the finished plates black.

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The splitter was drilled and fitted with countersunk rivet nuts, which would provide secure mounting for the finished alloy plates.

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Again, rivet nuts would be used on the wheel arch side for the same purpose. It also makes the plates easy to remove in future, as they’re not permanently attached to the underside of the front bumper.

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Here, you can see the channel that has been created which should effectively flow air onto the brakes.

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And a view from the underside. Because of the various depths between the bottom of the splitter and the shape of the factory underfloor, we didn’t run the plate flush to the edge of the splitter as it would have resulted in lots of air stalling or being mis-directed. There’s an edge on the right side of the plate (in this photo) which practically seals the plate to the underfloor on one side, while the left side has been left open to minimise resistance.

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It’s far from fancy, but then it doesn’t need to be. We had looked at creating more elegant solutions, but it was agreed that they would all offer similar levels of performance but just be far more complicated.

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Time will tell if this solution proves effective, and while the real test will be its next track day, brake performance on the road has been faultless since.

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With only the outer most openings in the front splitter delivering air to the brakes, they’re completely invisible. There are aftermarket options available, which typically involve replacing the fog lights and modifying the inside of the front bumper, but these also cost a hell of a lot more money along with losing the functionality of the fogs.

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While it’s a small issue that has hopefully been resolved, it does go to show that even the simplest of things can take up so much time and thought. With this out of the way, however, it means that we can move onto a more exciting – and maybe the final – stage of this project.

I think it’s about time we Integrated some speed into Project GTI.

Paddy McGrath
Instagram: pmcgphotos
Twitter: pmcgphotos
paddy@speedhunters.com

Cutting Room Floor
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56 comments

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1

Now THAT'S a good mod, bravo!
More of these to SH please, it would definitely raise the ever-so-high quality even more. Useful DIY tricks are part of automotive fandom.

Author2
Paddy McGrath

I really hope that I don't have to figure out another solution to a VW created problem XD

3

Haha good one :) Actually i dont think this is a factory created problem tho, a stock brake cooling duct isnt entirely necessary on a Golf imho, even if its a GTI. But your method is nice to have, ofcourse.

Author4
Paddy McGrath

Reading around online, it would seem that a lot of owners are suffering from brake fade. They're not particularly light cars which doesn't help matters.

5

That 3dr Cossie though

Author6
Paddy McGrath

It's a very, very clean car.

7

I'v never understood the point of a faux grille. They look embarassing and would probably be more aerodynamic when replaced with smooth panels anyway...

Author8
Paddy McGrath

It's just a style thing. On a street car, you're not ever going to notice the difference between it being smooth or textured.

9

OR You could wipe off the whole thing, keeping a red (in your case) body colored part over there. For all it's worth, a certain German manufacturer of rear-engined cars keeps their fronts pretty clean...

Author10

There are infinitely better things to spend money on.

11

Calm down, buddy... (I'm totally insufferable and pedantic aren't I?) I was talking about OEMs designing their cars that way.

12

My first thought was that he would drill through all the holes in the honeycomb (beside the fog lights). Doesn't look like they lined up though.

13

Nice job, but, isn´t there any aftermarket grill similar to the OEM one that allows air flow onto the brakes for extra mass of freshness?

Author14
Paddy McGrath

The only one I've seen is the fog light delete. Even if that grill was opened, it wouldn't feed air onto the brakes as you'd have to cut the arch liner to suit. It's just dead space behind it.

15
Christopher Sulouff

Been reading your updates since the start and I never even thought that I got my MK5 GLi around the same time yo got your MK6 GTi. Though I've had more troubles with mine than yours I wouldn't give her up for anything. Question though, did the switch to 5w40 really make a big difference? I use a high mileage Mobil 1 5w30 and I noticed after changing spark plugs it rattles a lot but the revs don't change.

Author16

It's a bit soon to tell, but it's much quieter than before. I'll have to see over time if there's any other differences.

17

"The thing is, I can’t find anything that ticks so many boxes, except for a new GTI, which seems sort of pointless as it’s not an upgrade as such."

This is exactly how I feel about my ED30. 2 years of ownership and the only car I can think of to replace it is another GTI.

Author18
Paddy McGrath

I tried to buy an ED30 before I found my MK6. Just wanted that K04 love.

19

I'l do you a swap with mine... Its going up for a sale soon. I can't believe the money they are selling for at the moment. I'm thinking mk6 as a replacement with a few mods.

Author20
Paddy McGrath

It's okay, what I have in boxes behind me will keep me happy for a long time :)

21

Nice work, but isn't that rubber lip meant to create a low pressure zone effectively sucking air into the brake duct? Sort of like how the front lip on the C5 Corvette works.

Author22
Paddy McGrath

If that was their goal, it didn't work very well.

23

Doesn't look like it was the first point of contact for incoming air. Recessed I think. So yes that was the purpose but it was too high to work. (could be wrong)

24

air suspension and the splitter is still scuffed xD Living the low life!

Author25
Paddy McGrath

Irish back road life XD

26

How did you take the third photo if both your hands are on the wheel?

Author27
Paddy McGrath

The ye old bored girlfriend in the passenger seat :)

28
Matthew Everingham

;) ;)

29

Nothing like some good old CAD haha

30
Matthew Everingham

The simplest solutions are always the best.

31

Love the build Paddy, been following it from day 1. I recently picked up a Skoda Octavia RS (we lose the v from vRS in Australia) and have been going back through your posts for some more ideas.

Author32
Paddy McGrath

It's only the UK has the vRS, even Ireland is technically RS although no one ever calls it that. Would love an Octavia RS Combi in 4WD, cool cars.

33

10 points from me, that is very clever!!

surely to be overheating monster brakes to the point of warping rotors there must be some serious issues at play, not that a couple of ducts will fix. Dodgy disc material? sticking / dragging pads etc etc.

Author34
Paddy McGrath

I don't believe the rotors were warped, rather they had a build of pad material on them. There was previously no air flow onto them whatsoever, so I'm hoping and expecting that this is the last time I have to deal with the issue.

35
ThosePeskySkids

Nobody seems to have bitten, so... integrated Engineering? are you able to get their parts shipped to Ireland easily?

or am I missing something else?:)

Author36

As it turns out, they can very easily ship to Ireland.

I'll have a full post together after the FD in New Jersey coverage.

37

I was kind of hoping you would go with a full framed turbo. The K04 will still be fun though

Author38

I'll go through it all in detail and the rational behind why we're going the route we are, but a big turbo was considered at one stage.

39

Honestly for a reliable daily and occasional track (road course) time the K04 makes the most sense in pretty much every aspect; reliability, price, and power delivery

40

"The truth is that the car has been boringly reliable the last couple of months"
Wish I could say the same about my MK6!

I totally understand the IE K04 decision, though I was really hoping to see an EFR set up haha
Awesome build all around!

Author41

Cheers, Matt.

42

I had once read that the stock rims on the GTIs (can't remember which Mk) were specifically designed to suck air from under the car and out passed the brake discs, cooling them off. Any chance this could be the culprit?

Author43

I haven't heard that before, but as the stock MK6 GTI wheels are flat faced, I'm not sure how effective they would be. Plus they weigh several tonnes, so they had to go regardless.

44

the fitment is so nice when its fully slammed

45

Your GTI is the most mind changing, mind blowing car , I've ever wanted ^ ^

46

As always great write up Paddy, I follow your ProjectGTI very closely on SH as well as on your Instagram.
I was curious to know what is mounted on your front bumper below the GTI emblem? I may have missed it in your previous posts..
Thanks and keep inspiring!!

Author47
Paddy McGrath

It's a quick release for the front license plate

48

I cant see that even helping with a track day event. With my Mustang the only thing that help was getting brakes ducts with 3in tubes to those front rotor. Now I can keep those rotors under 600F degrees after 20 minutes of on track time. Still need to fix up the rears which still overheat.

Author49
Paddy McGrath

I want to wait and see if it makes a difference first, before going further. I'll run more direct ducting if need be.

50
Richard Clayderman

Dear Paddington P. McGrath,

Where is your empirical data from the wind tunnel? Where are your credentials in fluid dynamics?! Have you not just introduced some front end lift at high speed with the resulting turbulence in that area?

"Enthusiasts" do a thing and take it for a drive and it's always, "crisper throttle response, sharper handling," etc. Emperor's new clothes every time. You never really know.

"Yes I fitted a shark fin aerial from Halfords and I can definitely feel the reduced drag at 80mph and my mpg is 50% better!"

"I put a K&N filter in my airbox and it has much crisper throttle response."

"I got my 330d chipped and it has more power than an M4!"

"You simply must get the Porterfield brake pads or you are an idiot and not doing it right."

( ͡° ͜ʖ ͡°)

Author51
Paddy McGrath

Does your cheek hurt from having your tongue lodged so far in it? :-)

52

Incredible, I was following your Mk6 since you bought it.
Only one question that probably is not in the mind of others speedhunters because they not live in spain. Here homologation restrictions are very hard, this last mod for example, could make fail in our periodic obligatory inspection due to jeopardizing safety of pedestrians if you hit them, or probably it will be illegal only by the reason of adding something to the car without homologation. Here we need a project signed by an engineer and pass an obligatory inspection after install the mod with a certificate signed by a legal workshop.

This is the normal procedure for example to change the stock suspension.

Do you have this kind of problems there? Is quite frustrating modify something on the car in spain.

Thanks for sharing this spectacular evolution.

Author53
Paddy McGrath

There's no issue with modifications here, provided that they're installed correctly. Our cars are subject to an annual or bi-annual car test (depending on the car's age) where they are inspected for their road worthiness. My next one is mid-2018 but it absolutely flew through last year's test with ease.

54

I can't believe that you have overheating with such rims,high end pads and calipers,even in a track.
I'd focus more on false product from Tarox than bad air flow to the brakes.
Let us know if this DIY solution proved effective on track.

Author55
Paddy McGrath

It wasn't bad air flow, there was NO direct air flow. Tarox have been amazing in helping me solve this issue.

56

TO THE RING PADDY! GO TO THE RING!

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