simon's learning what to do with the polo thread

[sambb]

hey I remember you said you'd put droop limiting straps in it. If you jack the car at the right rear jacking point to simulate 3 wheeling, its not hanging off the strap is it? Yeah I reckon rear toe out with lots more rear neg camber will really help it rail around corners like that - did with mine. I'm at 2 or 2.5mm (cant remember) total rear toe out and 1.75 neg camber and i'll be going for more of both next stab at it with the shims.
Slicks mean more grip = more lateral G's = more roll angle, needs more spring. My 390lb/in (7kg/mm) fronts = 315lb/in at the wheel can be on the uncomfortable side of fun when commuting but I am from Sydney where goat tracks are frequently called roads so it might not be too bad for you. I guess what I'm trying to say is that despite the fact that more spring than 350lb/in might work better with the slicks, running more than 350-390lb/in on the front at every other time wont be exactly plush.

[Sydneykid]

thanks guys

I've been told where I can get 2nd hand slicks for a good price, and given I'm in the same class as some cars that are basically out-and-out race cars on semi-slicks it doesn't really matter if I put myself into the race car class. I just want to go faster... is 350lb in the right ballpark for them too? does a stickier tyre require a stiffer spring?

Daughter took some really poor photos; this is a reasonably flat corner where the inside rear doesn't pick up as much as the big sweeper. I think it also shows that I do need more rear camber, something I've been putting off

The problem with a full slick is that are very particular about set up, they only operate within narrow windows. For example the spring rate has to be right and will vary from track to track and with conditions. They also have a narrow tolerance level for camber and caster, get outside of that and they will overheat, blister and tear themselves apart fairly rapidly. It takes me almost a full day of testing to get a new car on full slicks in the 95% window. Plus I will kill at least one set getting there.

In comparison semi slicks are far more tolerant, they have much wider window in which they will still operate quite well. I can get a semi slick shod car in the 95% window in a couple of sessions without damaging the tyre at all.

That's with fully adjustable rigid chassis race cars, for a flexing road car with all of the compromises that brings personally I'd stick with the semi slicks.

I'm gradually getting Sam to setting up the rear with 6mm of toe out and 2.5 degrees of neg camber, mm by mm.


Cheers
Gary

[simon k]

That's with fully adjustable rigid chassis race cars, for a flexing road car with all of the compromises that brings personally I'd stick with the semi slicks.

Okie dokie - good advice

I'm gradually getting Sam to setting up the rear with 6mm of toe out and 2.5 degrees of neg camber, mm by mm.

maybe that's a job for this weekend then... it's only 1.5mm and maybe 1.5° neg.

My mini has 12mm toe out at the back, it's a twitchy little thing, especially with a 2.2 turn rack and power steering. I came 5th out of 110 at the mini motorkhana nationals on the long weekend, very happy with that

[sambb]

12mm toe out! I need to man up. I'm ordering another set of the shims tonight.

[simon k]

12mm toe out! I need to man up. I'm ordering another set of the shims tonight.

yep, 12mm, I even checked. I'd adjusted it to give 1° each side but never actually measured how many mm that meant.

It's a lot of fun to drive on dirt, very easy to make it turn, but also very controllable. When doing a khanacross I can basically toss it sideways and get it to drift from one point to the next.

On a straight bit of 100kph road it twitches like it wants to swap ends on every little bump in the road, but it doesn't. You can give the wheel a little tug and it changes direction, then kinda sits at the same attitude. I guess that's what we want our Polos to do hey - not sure I ever put 2 and 2 together...

[Sydneykid]

Minis are always " lively" even when set up correctly, they have a skinny track and very short wheelbase plus it's tricky to get the camber curves (particularly the rear) correct and removing the bump steer isn't easy (hence the twitches over bumps). Overall, that's what you get from 60 year old chassis engineering.

Cheers
Gary

[simon k]

I bought some 6kg springs for the front and spent yesterday afternoon putting them in - a while ago I bought a 36mm socket to undo the CV joints. Taking the whole strut out of the car like the manual says is way easier than f*cking about trying to do it under the mudguard like I did last time

I also cut the domes off the top of the strut tower - did the driver's side first "nah, I don't need to pull that bit of the wiring loom out of the way, I'll be careful" then proceeded to run the angle grinder straight into it, 12 wires cut or damaged... so I was under the bonnet soldering today. I don't think I'll ever truly learn to not be stupid and cut corners

I went for a little drive (also bedding in new front brakes) and ride doesn't seem a lot harsher which is good. I'm getting new tyres tomorrow morning so won't be able to do a "like for like" run around my test corners on the way to/from work but never mind.

[sambb]

ha ha yeah I was worried about doing the same when I did mine. Didn't cut any wires but did manage to nearly set the firewall deadener on fire.
I haven't removed the driveshaft to do it before. Since I got coilovers I just wind the spring collars down until the springs are unseated and then bang the hub off like before except now it just pops off.
Keen to hear how the 6kg/mm springs go. What were your previous fronts?

[simon k]

I haven't removed the driveshaft to do it before. Since I got coilovers I just wind the spring collars down until the springs are unseated and then bang the hub off like before except now it just pops off.

I wonder if your struts are shorter than mine... if I do that, the driveshaft hits the lower control arm before the hub is anywhere close to coming off.

Keen to hear how the 6kg/mm springs go. What were your previous fronts?

the previous fronts were 275lb / 4.91kg, I kinda get the feeling I'll end up on 7kg fronts like you.

hey I remember you said you'd put droop limiting straps in it. If you jack the car at the right rear jacking point to simulate 3 wheeling, its not hanging off the strap is it?

didn't answer this earlier on - pretty sure it's not, the big mother rear bar takes care of that

[sambb]

6kg/mm (335lb/in) will be 271lb/in at the wheel so a decent jump. RE possibly going heavier again, is it still getting over onto the outside front a fair bit or is it just that you feel that ride/comfort-wise you could tolerate stiffer?

edit: oops my comment re getting the struts out wasn't entirely accurate. I remember now that I have damper stroke adjustment on the bottom collar and also ride height adjustment on the spring collar. With BOTH of those backed off the strut isn't hardly pushing into the hub at all and so is easy to get out.

[simon k]

6kg/mm (335lb/in) will be 271lb/in at the wheel so a decent jump. RE possibly going heavier again, is it still getting over onto the outside front a fair bit or is it just that you feel that ride/comfort-wise you could tolerate stiffer?

a bit of both I think - I'm surprised that the ride doesn't feel a lot harsher than it was, and I can still feel the inside rear wheel lifting. Unfortunately the next local sprint isn't until mid-September so it'll be a while before I can try it out. There is one at Winton on the 24th of this month, but they want everyone to wear race suits so it gets expensive quickly

[simon k]

I put a muffler on it on the weekend - 14" long, 5" round and straight through - it's been a 6+ months since I've had a muffler but I reckon it's as quiet as the stock one. I really wasn't expecting it to make so much difference

[simon k]

I've been a bit quiet haven't I!

Not much has been happening with the Polo - just a bit of a whistle under boost that's been a little bit annoying but not annoying enough to do something about fixing. Middle daughter turned 18 in Jan and used it to get her license... otherwise just commuting to work

A new year of motorsport has started so I thought I'd better get to and replace the front springs, I went to 8kg/450lb and after today it seems like I might have hit the sweet spot.

There was a sprint at Winton today, and another at my local track on 8th March. I was tossing up which one to do but the family want to go to Melbourne on the 8th March weekend so today was it. Through the week a lady in my local club offered me some used A050s for cheap, I said yes, but that was before a big bill on Thursday to replace brakes on the family Subaru... so I asked her to sit on them for a few weeks, which meant I had to do the sprint today on a set of 2nd hand Nitto NT01 that someone gave me. I've used them a couple of times and found them really greasy so I wasn't expecting much today. On top of that I got 25 minutes down the road and realised I'd left my helmet at home. I hate to be late for things and I'd left home with plenty of time to get there early - I got there *just* in time for the drivers briefing

The practice this morning confirmed the tyre greasiness, as did the first session... I had the pressures at 30 hot, talking to a fella who had done 1000's of laps of Winton in the last 25 years said maybe they'd like a bit more so I set the fronts to 30 before I went out again, which became about 35 hot. The tyres were much better as evidenced by a 1:42.7 time which I'm very happy with. I would expect that to become a 1:41 or better with more track time and on A050s.

The 4th session I was stuck behind a V8 commodore that I gobbled up on the corners but would get away from me on the straights. I gave up trying to pass and let him go almost the length of the pit straight, but caught him again within a few corners, very frustrating. I found him afterwards and (in a nice way) said it would have been good if he'd let me go, he apologised and said he'd look out if it happened again... the 5th session I had a Pulsar beside me off the starting line and he beat me to the first corner, I figured I could learn some lines from him so tucked in behind. I was quicker on the straights but he cornered better so we were pretty even. There is a big left-hand sweeper at Winton, and before the sweeper there are two 90° turns and a straight, after the sweeper there is a kink to the right, then a tight right hander. The Pulsar got a bit crossed on the way out of the 2nd 90° so I ducked past, then he came hot on my tail around the sweeper. Approaching the tight right hand I braked hard and Mr Pulsar couldn't quite pull up and he gave me a little tap on the bum. I don't think he expected me to slow down as much as I did... His front bumper did its job and absorbed all of the impact, crumpling a bit, my back bumper has a very feint mark on it. We talked afterwards and there were no hard feelings from either side. I thought it was pretty funny

However, last time I was at Winton I found that the temperature was getting up to 3/4 on the gauge and it was cutting power - 170kph on the long straight down to about 140. I thought about an oil cooler, but Sam suggested removing the exhaust restriction might help - I made a 3" downpipe, but it was the same today.. In a 4 lap session I'd get 2 laps down before it got hot, so I'd take it easy for the next lap and then have another go. It kinda worked... I think next job really does need to be an oil cooler

I have a new noise though, best described as a "choof choof choof" under boost (the whistle hasn't changed). I think tomorrow I'll make a pair of plugs to pressurise the system like PoloGIT and see what I find

[sambb]

That sounds like an action packed day. Bet you were buggered after all that. Yeah the temps are a pain. To be honest I never saw mine get as high as 3/4 on the gauge even before the oil cooler. It went past the happy 90 degree line yes but never that high but then again the hardest its ever been pushed was at Wakefield in 20 degree ambient which wasn't too harsh + that day I had all sorts of dramas with shift linkages and was never doing more than 5 laps at a time.
From my experience the oil cooler does a great job at keeping temps under control. At SMSP south circuit running on a heat exchanger deleted/oil cooler w sandwich plate setup the oil didn't top 110 degrees and the water was bolted to 90 degrees on the OE gauge. The OE gauges are heavily damped - they'll show 90 degrees for an actual temp as low as 72 degrees but I don't know how high it has to go in actual terms before it moves off gauge 90. But either way the water temp was on the line despite being hammered in 10 lap sessions in 26 degrees ambient.
For the street though the oil comes up too slow. I did plenty of measuring when I put the thermostated sandwich plate in and oil comes up to 80 degrees in normal driving virtually the same as stock with the heat exchanger BUT it then kind of parks itself around 90 and doesn't want to get to 100. I've commuted all summer, and its been a hot one at times as we all know. The oil cooler has been blanked off for zero airflow through the core and I could easily stay at 100 during the day and even with a bit of racey action before home it wouldn't be above 105 on the oil. at night though I'd have to travel nearly 25-30km before it'd top 88 degrees on the oil which as Gary has mentioned before aint great if there's water that needs to be evaporated out of the oil. And this is in summer!
The upshot is that without the heat exchanger the water isn't damped by slow to rise oil temps and goes straight up to operating temp very quickly and then when you do give it a hiding the water doesn't follow the oil temps up but stays in the pocket.
I haven't run it this way but when my built motor goes in i'll be going either back to the oil/water heat exchanger but still with a thermostated sandwich plate and oil cooler so that I hopefully get the best of both worlds. Or the other alternative would be to run a thermostated sandwich plate (sans exchanger like I am now) but with a higher stat than the usually provided 80-85 degree one. A 95 degree stat would probably work much better. The thing will be wide open on the track anyway (much the same as the water thermostat) so it'd be engine oil versus oil cooler & engine coolant vs radiator, but would hopefully warm the oil quicker on the street than what ive experienced.
Haven't had Choof in a car in a while ha ha but yeah a boost leak test might be the go. I've got a spare DV if you end up needing one. My Mk6 Gti turbo is very close to going in, didn't quite make Bathurst which is a bugger, but I will have some K03s spares for you soon if you need them.

[simon k]

I pressurised the inlet tract and found a leak in the joiner in my TIP, but the whistle and choof are still there - though I'm going to change the description from choof-choof to chika-chika... kind of a clicking noise. I fiddled around on the way to work, holding my left foot on the brakes to keep it boosting and the noise actually went away the last time, but I was about to drive in to the carpark so didn't go any further. Will see what happens - it'll either get worse or not

you just have a little 10 row cooler like this, yeah? I have a $100 gift voucher with this mob I need to use up soon

Proflow PFEOC10 Engine Oil Cooler 10 Row 340mm x 135mm x 50mm AN10 (1030kPa Max Recommended Pressure)