Sam's build thread

[Eddy]

Hoyhoy.

To Improve Me Polo. - Page 10

This did help heaps.
Also make sure any ducting intake has larger & angled intake @ the beginning, trying to make it straight in the first part just makes the air bounce out.

[sambb]

Thanks Eddy. I was thinking I'd change from the OE Gti grilles with the foglight mount to the standard Polo ones like this:
1 Pc Offside Right for VW Polo 9N3 05-2009 Front Bumper Lower Side Grille Cover | eBay

In the recessed part (depending on clearances to IC pipework etc) it'd be good to bury in there a proper bellmouth and run the pipe off that. Looking at wind tunnel airstream pics of cars like ours, I think the stock foglight mounts will just have air running laterally across the face of them and won't actually gulp much air, but bellmouths angled slightly towards the middle of the car in these plain grilles might work better. That's what I'm thinking anyway. To be honest life is pretty mentally busy at the moment and I'm literally going to have about 3 days to do what I need to do (fitting the mediums, ducts, giving the car a once over) that i'll be lucky to even get the ducts in since tyres are the priority really.

[Sydneykid]

Re hardware issues that arise due to ducting, I'm thinking that a blanking plate over the duct intake is going to be necessary, not just to prevent cooling when I don't need it but to stop every bit of wet road grit (especially salt if you are in the UK or something) and crud getting accurately guided straight onto the rotor in normal driving.
The problem for standard rotors for our car seems to be choice. QFM A1RM's need to be shod onto used backing plates, EBC green stuff has been discontinued and they only do red stuff, which pretty much just left DS2500. There's a lot of reasons why I run 15's but the fact that I didn't want to sling more brake hardware weight at it was one of them. That's fine for hillclimbs and sprints but hopefully it won't fade drastically at wakefield 20 min sessions. Whats the g limit for say A050's in 205/50/15 in a 1100kg FWD with my suspension?

Yep, that's the problem with brake ducting, especially melted tyre rubber in the rotors, very hard to remove and smelly. You could run air filter element or foam from Clark Rubber in the vent inlets. Or maybe race tape them up when not at the track.

You'll be lucky to see 1g, I'd expect something around 0.75g at the fishhook.

At Wakefield 20 minutes is going to be hard on brakes in summer in a road car with a reasonable power to weight ratio. It's also going to be hard to keep the tyre pressure (and temperature) under control. A050's are very tyre pressure sensitive so my approach would be to start off at around 24 psi cold (staggered as per previous post), then stop after 5 or 6 laps and adjust to a max of 31 psi all round. Note how much you have to bleed off, if it's more than a couple of psi then I'd stop after another 5 or 6 laps and check them again. I wouldn't do a slow in lap, come it hot, but then do a slow out lap to stabilise the brake temps. It would be good if you had someone to help, do 2 tyres each, that will minimise the heat soak while stationary. You should only need do that in the first session and maybe again after lunch, as the ambient temperature can change drastically during the day.

During the lunch break I'd have a good look at the tyres and see what they are telling you, especially check the left front for blisters.

Tip, write everything down in the book with the pencil that you have with it in the glovebox, after every session, before you forget.


Cheers
Gary

[Sydneykid]

The US is the home for brake pads, so we just need to identify a common model available there with the same calipers. I'm not up to speed with what other VW's your model of Polo caliper is available on, so some research may be required. A US version of a Golf would be good. If not then what I do is get brake pads slightly larger and cut them down to the right shape with the band saw. Using a cardboard cut out of the original brake pad as a template.

Just as a test, this the front brake pad profile from a number of common Golf models, how does it compare to your Polo pad profile?





Cheers
Gary

[metalhead]

So whats the plan Andrew - not going to do Wakefield again till you get the ducting sorted?

Need to do something, have the ducting but I’m still waiting on pads. Getting brake fade after just a few laps and getting the brakes hot enough to smoke and boil the fluid after another couple seems a bit pointless.

Due to their high maintenance and frequent hardware issues I pretty much avoid brake ducting wherever possible, of course for long distance races (3 hours, 6 hours, 12 hours etc) it's pretty much a necessity. But for most of the stuff we do the races are less than 30 minutes. So I spec the braking components such that they are more than capable of achieving top performance over the race distance. Overall braking performance is generally limited by the tyres, for example it's not of much use having brakes capable of generating -2.5g when the tyres won't handle much over -1.5g. It's just adding weight for no benefit, unsprung weight at that.

Being a suspension guy, I also work really hard on maximising the cornering speed hence the need for extreme levels of braking performance aren't as necessary ie; the delta between the maximum straight line speed and the cornering speed is reduced as much as possible.
...

Good points, and makes a lot of sense. If I were upgrading the brakes or building a braking system/car from scratch then I'd look to do that, but I'm hoping to avoid spending big bucks on a brake upgrade, and also avoid changing to pads that I can’t reasonably use on the street. My car could also improve on the corner speed front, and is heavy, but powerful enough to be moving pretty quickly at the end of a straight... I’ve never had a problem with the brakes in hillclimbs, or other short sprint events, but they just weren’t up to the challenge of more than a couple of laps at Wakefield. To be fair, I’ve never even changed the pads in the time I’ve owned the car (as I said, brakes have been adequate until now), so there’s no doubt some improvement to be had.

[sambb]

that looks sick! always was my favourite matchbox car when I was a kid

[sambb]

Temporary ducting is in - well from the behind the foglight facia to the discs at least. The intakes from the facia for the ducts haven't been sorted yet. The ducting is 50mm and the proper silicon, steel ringed, fibre strung stuff. Its run on the leading edge of the control arm along the ridge where the control arm was stamped out in manufacture. Because the tubing is very tacky its actually solid as a rock tied in like it is. After tentatively placing it, I put the front tyres on sliders and went lock to lock and found that only at full lock did the lower caliper bolt kiss the tubing. So its run as close as I can get it really. If air comes directly out of the ducts it'll hit the inner hub part of the disc, some disc face and also a bit of the pad but I doubt the air will flow like that. The end of the ducting does sit deeper into the rim offset than the air that will fly past the inside of the wheel though so it may make a difference. Either way it'll be better than without.
Advice for anyone looking to do it this way, don't go bigger than 50mm. When you go to full lock if you had anything bigger than 50mm the caliper will start to displace the tubing upwards where it could possibly in a worst case scenario meet the driveshaft boot. If you happened to have a loose steel coil hanging out the front of the duct in that situation it could snare/tear the boot causing a wrap up which would be a major drama, so consider 50mm max if you want to run it this way.
The last pic shows where the curved trailing edge of the guard liner in the front part of the wheel well needs to be cut vertical with a Stanley knife so that the up and down movement of the wishbone won't saw the ducting against it. If you ran <50mm you'd probably be alright though.

[sambb]

$7 buck stormwater 90-50mm reducer from Bunnings. Test fit to get the angles right.
If you push it hard enough over the lip that's on the inside of the foglight surround, you can get it to stay put while you run two self tapers through it. Rock solid afterwards and better with some engine enamel that sticks perfectly to PVC.
Finished product. Cones down really smoothly from 100mm+ at the foglight opening to a nice tight 50mm push fit for the ducting. The ducting fits into the back of the reducer so far in that you can't actually see it from the road and you have to get down as if looking under the car before you can see the orange. Now i'll just hole saw a pair of old black thongs and i'll have a pair of blanking plates that will cover the duct inlets for when I don't need them.

[HaydEn]

Nice stuff dude!


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[sambb]

Thanks mate. The R32 any closer to appearing at Ringwood?