Pel

Macca why are you running MPSC2 instead of Trofeo R, Continental or Dunlop option? All seem to have a sub 100 treadwear rating, Is it a cost vs life thing or something else?

Macca

Pel. Mostly personal choice to date.

TW rating is a useless guide between brands. Its only really an indicator between a companies own tyre products. For example MPSS are 300 and MPSC2 are 180 and Id say thats a reasonable guide. Infact Id say teh MPSS guide is generous and the MPSC2 conservative even between those two TW guides on the same brand...

TrofeoR and Dunlop SportMax are the same cost fitted to the 991 GT3. Around 3350 NZD. The Dunlops are NO Porsche factory fitment the Pierelli are not. The Dunlops have a reputation to be a bit better in teh wet but wear very quickly on the shoulder, I dont think Id get more tahn 2 days out of Dunlop compared to 4-5 for the MPSC2

CCS keep telling me that the TrofeoR will save me 1s a lap at HD. Im not sure I believe that. They have a vested interest in the Pierelli product after all! Leong hasn't found it so and the guys on the RL 991 GT3/4 board who have run them either love them or hate them. More dislike than like. The di have the propensity to be quicker for a PB lap, I dont doubt that but they are very fussy with tyre pressures, they have a great operating range once heated up and stay on longer than MPSC2, life on the track is similar but the rears wear quicker than the fronts which is opposite to MPSC2. They have a stiffer sidewall (not NO/N1 tyre) so they need less pressure 28-30 hot all four. They are a bigger liability in the wet and on the road they wear faster although as said they last as long on teh track 4-5 days.

I will probably give them a go in 2017 as Im finding the "peaky" nature of the MPSC2 a bit of a pain (first and second lap before they start warming up, next four laps they are "on", last four laps they are progressively going "off", then cool down lap). They have quite a lightweight thin tread carcass and the heat fluctuates alot in the tyre during a single lap compared with the Z221 or what I know of the Trofeo R. I think Ill enjoy them for their heat stability and slightly quicker times in ideal conditions, but they like more camber which Im not keen to do (I dont want to spoil the cars street manners) and they suit a situation where you dont need to drive 200-700Km return from the track each day out (so 15km return in Taupo would be good!)...

996tnz

Will leave Macca to confirm/deny, but my understanding is that MPSC2s are almost as fast (within a second anyway on a track like HD) of those others and last twice as long. Similar argument applies to the Nitto NT-01s - even new, they are a bit slower again but last really well past 20 heat cycles and can generally be run down to the cords.

Crosspost - MAcca's already nailed it.

Macca

Walt. How would you evaluate this, same driver?

993, 1320kg, 285 bhp, 260lbft, HKZ221, 1.18.80 Manfield (dry and cool), heavily revised chassis/suspension.
991 GT3, 1460kg, 475 bhp, 324lbft, MPSC2, 1.14.24 Manfield (dry a bit warmer/humid). Factory geo, chassis, DSC controller etc

For arguments sake lets say 4.5s a lap difference similar to the 991 GT3 Cup but in the other direction.

The 993 is 140kg lighter, but 190bhp down on power and 64lbft torque (more importantly). The 993 has gripper rubber but far lower Vmax.

Id have to say power followed by chassis, with tyre advantage to 993. However none of it makes much sense really when you consider the metrics on stand alone imperical merits.

I think we are stabbing in the dark here. It probably largely "is what it is" as systems are working in integration with one another (i.e. chassis with suspension and suspension with tyres, braking as a function of tyre patch and tyre grip etc).

Macca

Heres a lap on youtube of Craig Baird in a 997 GT3 Cup in 2009 on slicks during a big meet Manfield running in the 1.08s-1.09s (although the fastest lap of the weekend was Matt Halliday was just under 1.08 in ideal conditions during qualifying).

Gives some clue to the lines.

996tnz

Using my earlier estimates as a guide (and I'd used similar research to your own in coming to those ones), we'd get:

~win 0.5-1s from the Z221s (soft or medium?)
~ lose 2s for the missing 180HP
~ 0s from race suspension, alignment, ride height vs the 20 year younger GT3 with its 4WS etc.
~win 0.5s weight loss
~lose 0.2s aero (likely worse Cd than the 0.33 of a stock 993 and 991 GT3, offset by the 993's smaller frontal area, but much less downforce won from that drag than the 991 GT3 achieves)**
~0s brakes (bigger brakes, on our cars at least, make for easier and more repeatable laps plus much less pad wear but don't directly lower best lap times IMO).
Lose 1 sec to narrower track?
Lose 0.1 to 0.2s per upshift = so around 1.5s a lap
Lose maybe 0.5s a lap to trick PSM/DSC/smarter diff/better ABS in GT3?

Total laptime loss estimate = 3.7s-4.2s a lap

But yes, they're just (mostly) informed guesstimates.

**Cd x A is 0.614 for a stock 993 versus 0.672 for a stock 991 GT3. But tyres contribute disproportionately to Cd and also a little bit to frontal area, so if you were running wider rims and tyres for instance on the 993 she'd lose some the aero advantage the stock car has. It looks to generally only make for a 1.5% to2% worse Cd and CdA per extra inch of width though, provided they still fit in the wells.

Macca

Some salient points there Walt and ones I probably missed with the 991 GT3 Cup example. Mainly being aero/downforce, tyre patch and track width.

I always used Z221 C70 (soft) with that car, uprated sizes to 235/265 x 18. So Id take the 1.0s advantage. I counter that by saying the power/torque advantage would probably give more like a 2.5s a lap advantage.

The sequential/PDK is definitely an advantage over the MT as well as you point out. I think in the case of that old G50 box based on 6 upshifts per lap we are actually talking over 2.4s a lap! Ive worked out shift losses typically 0.4s with that car. Interestingly only 4 upshifts in Leong's data traces with the GT4 from the 19th, each loss around 0.25s as he runs with sport button which rev matches downshifts and rev holds upshifts making far less lost time on an upward shift. This is the beauty of newer manual boxes and their box of tricks, they are far easier to use with many fewer compromises than older G50/15 boxes of past.

Otherwise I think the formula makes for a fair story. I think downforce (thinking the GT3 Cup examples) would make less difference at Manfield than say Highlands, the advantage at Highlands would be into the back straights sweeper...

Macca

Walt.

Here are the 2010/11 and 2011/12 race results for all Porsche series races. This was before slicks were allowed.

Here you can see times at Manfield (two rounds per season) to range between 1.13 and 1.15 for dry days A+ category (usually 997 Cup or GT3RS which we will assume are similar in terms of driver and dynamics from race to race).

Looking at Taupo a good A+ time was 1.38-1.40

With slicks times have changes. Those same 997 Cup cars in 2015/16 season were running 1.10s and at Taupo without the barrier 1.32s.

I think we have to assume for the most part that a set of fresh Pirelli slicks vs a very good set of R comps such as Z214 is probably worth around 2-3s alone at Manfield and 4-5s a lap at Taupo (allowing 1-1.5s advantage for the barrier removal).

We assume those Cup Cars arent having major revisions form year to year other than set up, (i.e. no HP advantages, weight reductions etc). I think thats pretty safe to say as they are already fighting weight cars and infact many of the same cars are still in used in 2016 series with main differences being replacement and higher quality dampers, slicks, small aero tweaks etc.

Interesting looking at how times at places like HD have improved with tyres. The 944s were late 16s on R comps and now mid 14s on slicks during the Jan 2016 festival. I think a few small tweaks at the track have meant a bit more shoulder to use and a slightly faster surface too...

996tnz

Power has a lot less effect on laptimes than seems obvious. Different story for sustained full power metrics like 0-100, 200, 300, quarter-mile, standing km, top speed etc, but if you check your throttle (load) metric over a lap I'm betting you're over 90% open no more than maybe 20% of the time (not distance) max. I upgraded my power around 20%. Primarily for the road so was more than pleased, but was still initially surprised not to win much more than maybe a second, one and a half max on track at HD, until I worked out that the extra push is just not in play most of the time.

A PDK though seems to be worth around 0.4 or so seconds of the 0-100kph for cars like ours, and that typically involves just the one shift!

You may well be right on the time available from new slicks but they heat cycle out so fast I can't see many of us buying them new. Maybe some slick shod racers here can give us a better measure based on back to back testing. That series data has some value but between 3 or 4 years of car tweaking, driver development, track improvements (or even declines), different weather conditions across seasons at each track etc etc it is also only indicative at best.

I'm happy to volunteer if someone wants to chuck me some of course!

Comanche_699

One day I will read this thread from beginning to end. So far it's the longest running thread I've seen since joining Rennlist a few years ago. It's also the only thread I haven't read because I'm not from New Zealand, so figured I wouldn't have anything to offer.

3600+ pages later, I wonder if I missed something?

Macca

Walt, I think it was more like 0.2s PDK vs Manual for the 991.1 NA cars. I note with the new Turbo Carreras they are giving you another 0.2s to 100 if you tick the "sport chrono" option ($2K) when buying PDK, which I believe is an over-boost function. The beauty of going turbo, the marketing guys can cream more margin for code!

The BHP figures are less telling on the track than the torque figures - Ill agree with that. The 993 is down 35% on power but only 20% on torque over the 991 GT3.

When I get my laptop back from Mr Robot tomorrow I will run up the file at Manfield and let you know what percentage of the lap Im at 90+% throttle. It will be interesting to see. I think you are right it will be well under 20%, but if you are talking about 75%+ I should say a little over 20%...

gt38088

[QUOTE=996tnz;13795694]
A PDK though seems to be worth around 0.4 or so seconds of the 0-100kph for cars like ours, and that typically involves just the one shift!
QUOTE]

Launch control is a big part of it remember

Macca

LOL! Thanks for chiming in.

No, you are not missing much, just a bunch of mostly middle aged men from "down-under" shooting $hit about Porsches, life the universe any everything. Well that was how it was before FB I guess.

gt38088

Macca - on the Baird lap you see what I was trying to explain about letting the car drift over to the left side of track on the last part of the esse complex before hairpin, whereas you are mid track

996tnz

Yes, I probably shouldn't have said 'for cars like ours'. What I meant was for cars in the 3s to 4s 0-100 bracket, but that 0.4s was not so much a comparison of 991 manual vs PDK as it was for a 5-speed Tiptronic 996T versus my car with PDK if it were available for mine.

On the power versus torque front I think it depends on how well your gearing keeps you up near peak power when desired on track. I know the saying is "power sells cars, torque wins races" but that was truer in the days of 4 speed transmissions than it is these days with 8 and even 10 speeders coming out. Back then good torque made up for dropping much further down the tacho on an upshift. Or at launch. As Graeme alludes, launch control makes high rpm launches easier and more repeatable these days, so even there engine torque now matters less than it used to.