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Project GTI: Preparing For The Final Evolution

Brakes

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.

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

Project GTI on Speedhunters

Cutting Room Floor

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