simon's learning what to do with the polo thread

[sambb]

Ok so pedal was ok at the track but felt like it had gulped some air afterwards. Yeah I'll have to get high temp fluid in mine before I hit the circuit again. I've always run standard stuff as the hillclimbs don't stress the fluid and was perhaps lucky at Wakefield and south circuit. Car will be quicker now so the brakes will be getting a bit more of a hiding.
Did the cars balance feel ok.... a good front end and not too scary rear end?

[simon k]

Ok so pedal was ok at the track but felt like it had gulped some air afterwards.

hard to say what it was like on the track, or when it went soft - the pedal is only ever being pushed through the floor - it felt normal again today

Did the cars balance feel ok.... a good front end and not too scary rear end?

There was only one corner where the tail wanted to step out (turn 11 on the map below), otherwise the tail was following the front all the way around. I could use a bit more oversteer still. I was getting braver with the sweeper (turn 5), braking at the start of the day to nearly holding it flat

I did have a scary moment, I was tailing a GT4 celica and went past him on the inside of the exit from turn 9. At the same time an RX3 that was behind me went through between us. Imagine the celica on the left side of the track, me on the right side and the RX3 in the middle. I was over to the right as far as I could go, and the RX3 had enough room for the braking area and to turn in for turn 10. Except that just before the braking point he decided to jump across at me - I went for the grass, swearing profusely. I found him afterwards and he apologised, he said he was going to come and find me to say sorry - he said thought he was past me and the celica was on his inside... it was the other way around, the celica was long gone and I was still beside him. There must've only been an inch or two in it, back in the pits I checked for green paint, I swear I heard a crunch...

[sambb]

Ive never seen Winton in map form - only ever on TV. It does look like a brake killer. Yeah I couldnt believe the toss bags Ive encountered on the few circuit days I've done. I had a guy (2 seconds slower than me) wave me through coming on the straight at Wakefield but when I drew along side him he sped up again forcing me to go two abreast through the kink and squeazed me big time. I squeazed him in the next session - he'd staged up in front of me in the dummy grid but when the flag came to head onto the track I somehow got in front of him. That's why I like hillclimbs - balls out and only yourself to blame if something goes crunch.

After all the effort where are you at? Happy with the improvement or thinking it could have gone better?

[simon k]

After all the effort where are you at? Happy with the improvement or thinking it could have gone better?

I'm OK with the time I got for where it's at - it's no faster than last time I was there, but a lot of suspension and tyre changes.

I'm chasing down the fastest lap time in the performance thread, I have a couple of seconds to go which I'm not likely to get without a few more laps under my belt and a bit more grunt. I'd like to say the car has a 1:39 lap time in it... I'm catching the cars that are doing those sort of times on the corners, but they're walking away on the straights.

The cooling problem is annoying, but as you said in your PM the restricted exhaust would be impacting it at least a bit. Not going to go any faster without an exhaust so might as well do that before doing anything about cooling

[Sydneykid]

Winton is tough on brakes, right angle turn, short straight, right angle turn, short straight etc. Boiling brake fluid produces gasses which (just like air in the system) causes the brake pedal to go spongy as it compresses the gas. After a day so so the gas rises/works its way up to the master cylinder and the pedal isn't so spongy any more. But once it's been boiled it has lost whatever it gave off in the gasses, a byproduct of which is often a colour change to a dirty brown. Plus it often smells "burnt". New fluid required.

I assume you have removed the backing plates, if not do it, it's well worth it. One of the side effects of wider wheels is less airflow gets to the brakes. Before the full on brake ducting on the Skyline and EVO I used to run these;



Easy to bend up out of alloy sheet and a couple of hose clamps as retainers.

Cheers
Gary

[Sydneykid]

I'm chasing down the fastest lap time in the performance thread, I have a couple of seconds to go which I'm not likely to get without a few more laps under my belt and a bit more grunt. I'd like to say the car has a 1:39 lap time in it... I'm catching the cars that are doing those sort of times on the corners, but they're walking away on the straights.

It takes a lot more BHP to drop 2 seconds, whereas with driver improvement and car handling upgrades 2 seconds is not all that difficult.

That said a decent exhaust is always worth doing on a turbo car, not just for more power but turbo life as well.

Cheers
Gary

[sambb]

Simon I spoke to the guy who has some TT bits. Apparently the recall meant changes to the control arm, but not the upright. The uprights were constant throughout the mk1's. Apparently there was a Canadian company that used to make reproductions with even lower balljoint points but they are like hens teeth. I'm going to keep my eye out. I'll ask him if mk4 golf driveshafts fit. I was thinking I can just call mca and find out if the diameter of the strut tube base has the same dimensions between TT and polo. My mca's have a threaded / removable base for stroke adjustment and it's possible I guess that I could just thread another base on there.

[simon k]

Winton is tough on brakes, right angle turn, short straight, right angle turn, short straight etc. Boiling brake fluid produces gasses which (just like air in the system) causes the brake pedal to go spongy as it compresses the gas. After a day so so the gas rises/works its way up to the master cylinder and the pedal isn't so spongy any more. But once it's been boiled it has lost whatever it gave off in the gasses, a byproduct of which is often a colour change to a dirty brown. Plus it often smells "burnt". New fluid required.

I assume you have removed the backing plates, if not do it, it's well worth it. One of the side effects of wider wheels is less airflow gets to the brakes. Before the full on brake ducting on the Skyline and EVO I used to run these;

Easy to bend up out of alloy sheet and a couple of hose clamps as retainers.

Cheers
Gary

check - backing plates are still on, hadn't occurred to me till you said it. I even had a stone caught in one a couple of months ago, made a horrid noise after I backed out of the driveway... yep, I'll rip them off

Simon I spoke to the guy who has some TT bits. Apparently the recall meant changes to the control arm, but not the upright. The uprights were constant throughout the mk1's. Apparently there was a Canadian company that used to make reproductions with even lower balljoint points but they are like hens teeth. I'm going to keep my eye out. I'll ask him if mk4 golf driveshafts fit. I was thinking I can just call mca and find out if the diameter of the strut tube base has the same dimensions between TT and polo. My mca's have a threaded / removable base for stroke adjustment and it's possible I guess that I could just thread another base on there.

I looked at my LCAs the other day, and they're nearly horizontal. I've no idea what a car feels like when it has the roll centre in the right spot v's the wrong spot, but I'm keen to find out! everything written about it screams that it needs to be corrected

I'm 99.99% sure the strut body is the same size - 50mm - google is your friend: GABRIEL Shock Absorber Front Axle, Gas Pressure, Suspension Strut — item: G35291. Buy now! Performance Coilover Damper Kit Fits Audi TT(8N) 98-06(2WD) | Godspeed Project

in other news, I spotted a heap of 2.5" and 3" stainless pipe in a metal scrap bin at work today, will see if it's OK to take some tomorrow

[sambb]

Good find. So it says the base is 49mm OD - did you get a measurement off your Billies before they went in? Definitely the same for ours?

[Sydneykid]

I looked at my LCAs the other day, and they're nearly horizontal. I've no idea what a car feels like when it has the roll centre in the right spot v's the wrong spot, but I'm keen to find out! everything written about it screams that it needs to be corrected

If the arm itself is horizontal then, as the outer ball joint is higher than the arm, the roll centre (CoR) will actually be lower than it appears.

There are number of issues that arise as a result of the CoR being too low;

The distance between centre of gravity (CoG) and the CoR is the Roll Couple (RC). When we lower a car say 20 mm the CoG will go down 20 mm but the CoR almost always goes down more than 20 mm. Particularly once the lower control arms get below horizontal, the CoR drops rather quickly in proportion. As the RC gets larger the more effort the CoG applies through the CoR and the more the car wants to roll. Which in turn means the more weight it transfers onto the outside tyre. Of course we can fit higher front spring rates and/or a bigger front anti roll bar which lesson the roll, but the increased weight transfer still happens. This increase in weight quickly overheats the tyre and causes understeer.

There is a side effect of the below horizontal lower control arms (as per the previous post), that being a loss of negative camber as the suspension compresses. This lessons the contact patch of the tyre which as well as not using all of the tyre it also results in rapid overheating of that part of the tyre still in contact with the track.

That's double whammy of understeer. Of course we can compensate somewhat for that by using higher rear spring rates, lowering the rear CoR and CoG, and and/or a larger rear swaybar. But they have the side effect of reducing the rear grip, so the understeer might well be reduced but total car grip is lost. If the understeer is really bad then we have to lose a lot of rear grip to compensate. So th trick is to reduce the understeer as much as possible by working on the front and the rear. Once that is optimised then we can look at sacrificing some rear grip to balance the car out.

The symptoms are excessive front outside tyre wear, blistering, graining and uneven tyre wear (where the outside wears much faster than the inside). Plus of course Understeer that just gets worse as the tyre heats up, lap after lap. That's why even a badly set up car can do 1 or 2 laps at a reasonable pace, but then the tyres give up and the lap times slow. It's also why a well set up car doesn't wear its tyres out so fast.

Cheers
Gary