Macca

Walt. Sorry it has taken me some time to get around to this. You asked about NITT as you werent able to access via FB.

Again it was a brilliant event. Four fourth year. Mostly the same "hardcore" crowd from the inaugural event. 20 P cars over two sessions (this time) at Manfield and 30 at Taupo.

The weather held together very well for the drive down to Fielding. Infact it was a corker of a day, bit windy but sunny. Matt and I took the Rangiwahia Road. Great drive, zero traffic, plenty of twisties and only complaint was around 2-3km of recently sealed road around 35mins through the drive.

New motel this year and certainly not up to the standard of our previous years abode, but it did fit us all in including cars and trailers. Next morning I was up at 6am and it wasnt looking great, Dark grey skies and rain. We headed off to find breakfast (McDs only option open - yikes!) and then to the track.

It was wet when we got to the track, but by the time we had set up and had the briefing just drizzle. the track was plenty wet for the orientation lap but the drizzle stopped on our first group out - aircooled. Dave was pretty much lead car for this IIRC, and he was doing very well in the Orange T keeping all and sundry at bay with a nice 3-4 car lead and driving very well.

Then it happened. Just as we watched, he locked up half way through T1 and skidded off the track touching the armco. A light touch but enough to loose a headlight and put come racing stripes and a few ripples down one side of the car. To give him his dues he took it like a man, checked the car over (suspecting a brake line at fault - which may have been damaged prior), got it all checked out and decided to get back on the track. He completed the NITT without further incident. Got the gardening award but in reality should have got the spirit award for pulling his britches up and manning it out. Good on ya Dave!

You would have loved the morning sessions Walt!

Second and third sessions the track started to form a dry line. By mid day it was essentially a dry track unless you wondered too far off the line where you could find it was a bit damp and greasy. I wouldnt say it was the fastest surface Ive seen at Manfield but it was pretty good. Temps were around 18-20C, humidity was a little higher on account of the precipitation and the grass was damp and mushy for those that experienced it. I think the only other incident of the day was Chris B in his new 3.8L re engine ex Seamer 964 hot rod. Easy mistake that one, getting unsettled coming through the Castrol complex (infield) and likely crossing the damp on the edges of the line. New car to him and not yet fully dialed in mechanically either.

By the last session the rain had started to spit again but not enough to dampen my enthusiasm for one last run. I struggled all day with the hairpin. My subsequent AIM data showed just how bad I was running 47kmph to 67kmph through there and very rarely getting it right. I need some tuition for that corner and one other which Im just not getting. Im frustrated because once I cant get something I just keep making the same mistake till Im shown how.

I was happy enough with my consistency on the day. My top 20 laps were between 1.14.24 and 1.14.99 with my fastest single lap being an outlier rolling lap of 1.13.97 and AIM showing a theoretical best lap of 1.11.14 (which is not possible IMO). I think with a little help ironing out those corners and a cooler crisper and drier day getting some consistency in the mid to late 13s is possible for me. After that I think the talent had run out!

The drive back to Taupo that evening was a late one. After gassing up, coffee and air in the tyres. We drove through a thunder shower on the vinegar hill route. We were in a 8 car convoy with myself as lead. You would have been proud Walt, I just knuckled down and drove it like it was dry! Very fun, a bit edgy, but after getting dialed in on the track it just seemed to come together. Chris T and Andrew F (600bhp 997TT) were not too far behind and once we turned onto SHW we never looked back. Had a dream run, little traffic, high average speed, weather cleared and we had a magic drive through Desert Highway, possibly the best Ive had yet just jetting along. We caught up to another 6 car convey (I think they left Fielding 30 mins earlier than us) as we past Taurangi heading up the hill after Hataipi, and had a great final run on the bypass into town where we celebrated with Chris B over a beer at the Hilton. Tania would not have made a good passenger on the 225km drive from Fielding. We didnt stop once.

Sunday was a rest day. For 8 of us that meant a 5 hour back road drive led by Scott H in my old 993. 400km later with some varied terrain and speeds we made it back to base and prepared for Matts BBQ which was a very well organised and catered event as always. The weather stayed good, 20+C until the sun went down then she cooled off quite a bit.

The next day was Taupo. The sun was up and the sky was clear. It was a fairly hot day but the wind was up (30+ kmph). Managed 7 sessions on the International A1 track. Personally I found the track not much to my liking. The wind pushes pumice dust across the track randomly. I was having traction issues out of corners, it was random from lap to lap. My car was very underteery, I think in part because the front tyres were wearing low, but also my tyre temps were very peaky. Id go out on 28 all round, easy into it with a bit of oversteer till they got to 32psi maybe 3 laps later, then they would
work well for around 3 laps 32 F and 32-35 R then Id find the rears got 36-38 and the car was back to oversteer. A bit frustrating. Others were having issues finding traction and fast laps too, with Jake, Matt B and Leong all struggling to get anywhere near previous best lap times let alone consistency.

Regardless of not liking the surface that day, and it being fairly warm (24C) I did lay down a dozen or laps between 1.40.45 and 1.140.90 with a best outlier lap 1.39.67. But realistically I was struggling to get in the high 40s. Again two corners elluded me completely, and for those I will seek some in car tuition as i simply cant get my car working with those corners and Im repeating my mistakes. I didnt get much faster during the day which is unusual for me too and I think for this the increasing ambient temperatures and the wearing front tyres (just above WOF level on the fronts by the end of the day) were partly to blame. The track was not the quickest surface Ive experienced there. I should think mid 1.39s with some consistency is possible with the right conditions and a hand with a couple of the corners.

There were no incidences at Taupo although Chris T did a fair bit of gardening during the day. I dont think anyone beat their PB but everyone had fun and brought it back in one piece which is the main thing.

So that was NITT 2016. A great event with 30 like minded blokes (and one lady - Patsy). Really looking forward to NITT 2017. Hope to get some practice in at Manfield and Taupo before that event and knock off a few personal performance goals on those tracks in 2017 before deciding if I will keep the 991 GT3 or move it on....

I didnt take alot of pictures but here a dump of some that may be of interest...

996tnz

Great write up Mark, and many thanks for that. Super pics too. Raised major nostalgia, right down to the deluged run along the eastern side of Lake Taupo recalling the last NITT I was on.

From the few sentences posted here before, I'd picked up on Dave's T - and Dave's spirit - being harder to kill than a cockroach, but it's good to have that extra background. Not hard to have that happen, even without suspect mechanicals. Between coldish tyres and chasers filling my mirrors, I've spun the 996T in similar circumstances before, but was luckier in getting away with nothing more than some bubbled rear tyres. I guess Dave's T will be getting the love she needs though and be back stronger than ever.

That GT3 of yours is a weapon and you are obviously pedalling it well too going by those times. Know what you mean by the Manfied hairpin being a bit awkward as too often I was tending to find myself coming in too hot and/or braking too late and then getting cramped on the exit too.

It's about 8 months since I was last there but IIRC, that left-hand hairpin is placed hard on the heels of a fast left-right S complex, so cars tend to still be overly weighted to the wrong side when entering the braking zone, reducing braking efficiency and/or making for a sharper weight transition during turn in. Maybe it's as simple as recognising that and sacrificing a few kph through that preceding right-hander to allow the more settled car a better turn in for the hairpin? I haven't experimented with that too much yet as I hate trading off speeds unless there's no other way to solve the problem, but that might be where I end up if I can't find a better way to do it, since hairpin exit speed out onto the straight is obviously more important there. Your car is better sprung and has stickier tyres than the ones I've run there, so you may well not need to trade off that right-hander anyway. As you mentioned, a bit of coaching there would probably be the best medicine for us both.

Got a huge kick out of NITT last time and if it had looked like it was going to be wet enough, I was very tempted to put the yellow terror forward as a replacement for any car that might want to pull out at the last minute. But I was, and am, just too flat out on too many fronts just now. Could do with more of your dolce far niente...

Macca

Hi Walt. "Dolce far Niente" is under pressure here right now as well!

Yes - that's the corner (I think referred to sometimes as Goodyear - just after the Castrol esses). My problem is exactly as you describe. The GT3 has too much traction and contact patch to be rotated at lower speeds like the 993 and this is what im struggling with. For sure I think i need to slow down the entry not going so hot at teh end of Castrol, turn in earlier but carry more speed through the Goodyear corner and come out a bit wider on exit. My speeds in Goodyear varied by 20km across the day, but its not as simple as looking at the times lost just in that corner as there are trade offs as you know with the sector before and after. Ive highlighted it on the attached map.

To be fair I think its my single biggest problem on that track, although there are likely a few tenths tiding up a few lines here and there. Coming into Castrol is one area. I think I can turn in later and more aggressively keeping on the accelerator in longer riding more over the inside rumble strip (assumes dry) cutting a straight line. I did start to get it semi regular, but its an un-natural one as you are pulling real G into that tight left hander. I had it down pat a few years back with the 993, but as speeds increase so does the G there.

Looking at my data there is a good 20 laps within 0.5s of the PB 1.14.24 - accounting for in and out laps and the first 2 sessions which were wet or damp its probably 40-50% so I think its a good base. Next year I will put someone like Ray in the passenger seat for a session or two and see if I can get that PB around 1.13.80 with similar consistency. After that, for me, I dont think there is much left in it.

Taupo is a different kettle of fish. There is still at least a second left on the table there and probably more. More technical track, longer and Im making more mistakes per lap in more locations than Manfield. Ill have to make it my goal in 2017 to get consistently in the mid 39s there. After that, again talent runs out.

It becomes more obvious how much harder the car is being pushed to achieve these times. High 11s, HD, 13s Manfield, 39s Taupo and you are cycling tyres, pads and rotors at an alarming rate not to mention life cycling everything faster like CL hubs, fluids etc. Im now getting 4 days max from a set of MPSC2 and have had to move to RT RE10 pads to get rotor life above 8-9 days and pads lasting more than 6-7. At 3350 for tyres, 2200 for front rotors and 600 for front OEM pads you can see where this is all going. You pay to play if you are going to go hard with the car all day. Im going broke slowly so will have to slow down soon!

The 9 track days I have done in the GT3 in 2016 have all been running fairly hard. On SITT it was pushing on to with high 5s best rolling lap at Teretonga and mid 6s with some consistency. The car had held together fine, but we are doing oil changes now every 4 track days, SRF brake fluid same and there are a few additional preventive items on the list such as CL locking pins, a transmission fluid and clutch fluid change coming up shortly about 1/2 the recommended time etc.

Macca

Here some data from Manfield may be interesting to compare with your mental notes on the yellow beast there. I think a cooler drier day would have benefited Vmax by 2kmph but you'll get the idea (I break 200kmph in three sectors of the track in the GT3, but im pretty sure you would in the 996TT too!).

gt38088

I haven't ridden with either of you Macca and Walt at Manfield so following comments are blind to that extent. But having done a few laps there and seen a few different lines into the hairpin you refer to - make a couple of general comments.
You definitely want a late (ish) apex into the LH elbow at the beginning of the esse complex.
Coming out of that corner you end up over on the RH side of the track, ideally not all the way over because the next part of the esse is turning right but within half a car width in my mind not critical. Key thing is to be flat all the way around the right if you can. Lots of ppl hug the right side of the track leading into the hairpin but in order to keep gas flat I have seen many ppl let the car drift over to the left side before braking for hairpin. Sort of like double apex. It takes some of the flip flop weight transfer away and so braking should be a bit more controlled.

Macca

Thanks for the tip Graeme. I think I need you to ride in the car with me there. Here is a lap where I think I get it better than most other times, but probably not perfect.

gt38088

For lap time (but in racing some need to block there) probably a bit narrow on the left hand elbow which means you end up on the right side a bit earlier than best line. In turn you then need to lift of the right hand curve. If you hit the rh curbing a little later here and also let the car drift further to left side afterwards on entry to hairpin (looks like you are in the middle of the track) you may be able to stay on the gas. And the wider radius means the car might settle a bit quicker before stoppers can be full on - less lock to unwind or you are unwinding a bit earlier.

easy to say from the comfort of my laptop :-)

996tnz

Yes Mark, your hairpin trajectory mirrors my own recollections of often struggling to hit that apex and of not having the car rotated enough to get good power down early for the following straight. And I think Graeme is onto it with recommending later apexes through the preceding esses so the car is entering the hairpin's braking zone straighter, more balanced, and with more unforced room to get her turned before apexing.

As for my Manfield speeds, I was on street Sumitomos last time I had her at Manfield so while I may have got her over 200 at a few points, my cornering speeds were well down on yours (as were my costs by the looks of it - that's quite some committment). My biggest kick is pushing on and improving my driving, and I expect you're the same. So as long as the brakes and tyres don't get in the way of that progression, I'm happy to leave some seconds on the table when it comes to hardware and footwear.

I only threw her some R-comps at her relatively recently for instance because I was destroying roadies too often on dry tracks (eg square inch chunks of tread coming off, exposing the cords in multiple places when only half worn). Those NT-01s are just a cheap used set, but the downside is that while I'm running HD over three seconds faster than the 1:18s she ran at stock power on roadies, I can't get a good feel for my own progression as a driver over time.

Pads and rotors haven't been a big problem for me luckily. Endurance pads are easy on rotors at the expense of some bite and feel, but aren't getting in the way of my driving yet, nor is the higher compressibility of SRF (though that might be next on the list).

I worked out some cost forecasts per event some years ago but that's on my other computer. Risk and insurance (if any) were included, but excluded mortal/medical risk. Between entry fees, consumables, repairs, accelerated maintenance, transport, accomodation and potential crash damage I think it roughly worked out to around $1200 a track day, $1800 per Targa Tour day, $2500 or so for a Sprints day, $600 for an Ardmore gymkhana (destroys tyres), and about $300 for a Gymkhana day. Plus maybe about $500 or so probably for a drag day. Still pay to play obviously but minor in comparison to the GT3 by the looks. Actual spend could usually be less than half of that for many events, but one bad day levels it up again eg, Sprints may only cost $800 or so on a good day, but a bad one will hurt the pocket big time. Probably doesn't pay to factor in those personal risks either (roughly multiplies those figures up by a factor of two to three) or we wouldn't be driving uncaged cars.

Macca

I agree Walt I think Graemes recommendation is a good one. I took Marty (Graemes mechanic and someone who is familiar with Manfield) around for a session. We discussed this corner I was having problems with. His advice was similar to Graeme. The challnege is you need to change your line for the previous corner (RH elbow) exit to position yourself correctly for the hairpin and get the car as flat as possible for entry. I think you identified this too. I played with the line to get the position on the track right but was always too loaded to get an easy turn in without scrubbing too much off the speed. I think I need to play with the elbow exit line a bit more and the accelerator to get the car to flatten a bit before throwing it in. Currently its loaded on the opposite side of the car than I need the weight transfer and this is causing problems. Hopefully that makes some sense. Its good to have some input on this as I think its given me some good ideas to experiment next time Im out there. Hopefully Ill get to go to Manfield more regularly when Im in Taupo. I do enjoy that track...

As for track running costs, I do have a rough mental per day cost that includes annual insurance and maintenance spread only over 10-12 annual track days (i.e. for road use the Kms are "free").

Essentially the car only gets used for occasional fast back road drives and getting to and from the track etc. Tyres are the biggest factor at $700 per day based on 5 days (Im only getting 4 at my current pace before grip drops off, but I will learn to live with the 5th day of compromise for budgets sake next year). After that its rotors & pads. Im hoping the RT RE10 will bring those costs down by 25%. I think $225 per day for front and rear rotors, $240 for pads, $200 for fuel (the GT3 drinks like a turbo), $240 track fees, $225 for insurance and $250 for services, oil changes, brake fluid changes, alignment, balancing etc. That's $2000 at day! Tyres, Rotors and Pads account for around 60% of that. Some cheaper 20" rubber options along with some Brembo typeIII rotors might save a further $350 a day(18%) but its hardly a game changer. I think the best answer is a Cateram, Lotus or something much lighter with lower tire/rotor/pad costs. By early 2018 I think the question would be for me do I sell the GT3 and replace with a 911 road car and a lightweight track hack or get another GT3. Im very borderline on this right now. $24K pa is alot of money when you arent working (and it ignores depreciation etc) and probably enough to campaign a 944 for a season of Porsche Series if you were careful with your $$$!

996tnz

Macca, any kind of racing is even harder to justify if watching the pennies I think as you're pushing that bit extra in circumstances that are less under your own control. For example, 4 lots of panel damage across a dozen or so hours racing 2K Cup and all four times were from getting hit in the flanks by the car behind, whose drivers were following too close, too sleepy, too optimistic, or too late on their brakes. No offs, no spins (bar one quarter spin at a wet Taupo, and an intentional 1/4 ACW into 3/4 CW spin during practice at HD to stop the car when the brakes gave out entirely). Obviously I still reflect on those situations with a view to reducing the chances of them happening again, but considering that we made about 500 passes with only three mild contacts (pretty much bumper to bumper, no panel damage) I don't think I was reckless. On the flip side, we were passed on maybe 100 odd occasions (mostly in reverse grid races, plus a few cars each qualifying - usually up the straights by gruntier cars). But yes, we got hit hard from behind three times when the following driver stuffed up their braking without actually intending to pass, plus once during an insane late divebomb by the guy behind when it was already our corner. So I think racing crash damage costs can be reduced but not eliminated. But racing is even more addictive than tracking plus it is a huge buzz and teaches a lot, so I'd still say to just go for it in one form or another eventually.

996tnz

Just looked up my data at home for that same hairpin to compare, and yes, going off our Vmins, you're right, there's a good bit of speed and time for you to find there still.

Comparing our averages - ie my laps in the driest session of that day (less the out and in lap, and I think it had fully dried out by then) versus that of those 7 almost consecutive laps of yours (just lap 9 missing on the set you posted, as well as the out and in) from session 4 - there really is nothing in it: 57.11 kph, versus 57.13kph).

996T+, Sumitomo HTRZIIIs:



991GT3, MPSC2s:



But by rights the hairpin should be a rout on MPSC2 R-comps versus 300 treadwear roadies, as evidenced by the drive you're getting on the way out, where I'm having to a bit more patient getting back on the accelerator and then having to be back on the brakes much earlier, costing me 15 odd kph of Vmax on the straights. So again, as you worked out, there's more time for you to win there. Which is kind of scary really, considering how fast you're getting around Manfield already.

Macca

Walt. When I get a job I may consider to go racing. Single make series. The oldest guy in GT86 if nothing else presents itself before then. In the meantime Ill have to practice going in circles. There is something very cleansing I find in 100 minutes of intense, unwavering concentration during a track day. One moment off the job spells certain high speed disaster. Unlike most of the other minutes in my existence. Now back to Mr Robot LOL!



oops. Looks like I forgot to send the above earlier!

Macca

Thanks for the extra data points Walt. Its interesting.

Im not sure there is a tonne of extra mid-corner speed that can be carried through there without affecting the times for sectors before and after the hairpin. My guess is probably around 4kmph average. Most cars traces Ive seen for this corner including my old 993 are all fairly similar here. I think its actually harder for larger, heavier cars with more traction like yours and mine to get through this hairpin with any real significant advantages over less powerful lighter machinery.

My best guess is there will be 2 tenths I can pick up at the hairpin without too much trouble, just need someone to show me a good line for my car and then get some practice in. After that I know there are a few spots I can pick up a tenth or so just tidying up and braking later or getting on the gas earlier. 19 November was relatively humid (rain) and 20C. I know from many prior experience my car makes more power 10-15C with low humidity and higher ambient mbar.

I think a PB full lap of 1.13.70 with some good consistency (+0.5s) is doable.

I may have to turn the air con off next time tho LOL!

When I think about it this is probably about right. I think the Porsche series lap record for Manfield was last season by Matt Whittaker in the 991 GT3 Cup on fresh Michelin Blue slicks. Someone can correct me if Im wrong but I recall that was about 1.08.00, with a dry track, lowish temps and humidity.

Thats a 6s delta from my laps today. Im guessing his fresh Michelin slicks are worth 3.5s a lap over my 180 TW MPSC2 (these are IMO more on the road car side of the spectrum than R comp side like Z221, R888R etc).

Its hard to say what a 991 Cup 250kg weight advantage would be over a road going 991 GT3 but id have to think 1.0s per lap at Manfield?

Now throw in the stiffer chassis, firmer dampers with corner weight balance and geo, bigger brakes, Im guessing we are talking another 1.5s a lap?

So there is your 6 seconds and we havent taken into consideration that hes a better driver etc.

I think if you could get a GT road car into the mid 13s at Manfield with consistency I think you are pretty much flying as you say - problem is you are likely wearing everything fast and somewhat on the edge so risk increases too. Relatively speaking.

Taupo is where I need even more help. There is definitely 1s a lap on the table there working backwards from Matt Whittakers record setting laps in the GT3 Cup car last season (1.29.60!). With slicks worth 5.0s a lap there and weight 2.0s with set-up maybe 2.5s I think there is a 1.39.00 possible there (I hope).

996tnz

I've left aircon on even in race too sometimes I'm sure. But the 996T and I presume your GT3 route their fuel through the aircon's heat exchanger to cool the petrol (and it probably even cools the whole tank slightly via the return line), so I console myself with that.

Good laptime benchmarks can be hard to find Mark. I went through the same exercise some years ago of comparing my then stock 996T (bar endurance pads) on street Sumis at HD versus a modded 996T on slicks driven there by Andre Heimgartner (fastest 996T lap I could find). Researching each factor to better estimate the lap time effect on a ~1m:15 track like HD. He ran a 1:10.6 and I was just under 8 seconds adrift at stock power on my streets. Don't have the analysis to hand now but that benchmark I found was:

~600HP (I thought ~550 earlier but later saw the for sale info for the car) Motorsport Services racecar on slicks, pro driver-
[Slicks, ECU tune, Exhaust, turbos, intercoolers, aero, suspension, weight-stripped etc - lap 199 of the 2011 Racetech 6 hour] - Andre Heimgartner

And IIRC, the estimated time savings were pretty much:
1.5-2s for Rcomps
Another 1-2s from R-comps to slicks
~1.5-2s for the extra 180HP
~ 1-1.5s race suspension, alignment, ride height
~1s weight loss (there's a lot in a Turbo that can come out, and this also includies rotating mass effects from lighter wheels and rotors)
~0.5s aero
~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).
Giving 6.5 to 8 seconds of attributable platform difference. And helping me feel reasonably good about my driving.

But I'm sure at the time he'd have been at least several seconds faster (maybe even 3 or so?) in my car there, and in his car, I'd have been slower by at least a similar margin. So adding up theoretical savings is drawing a bit of a long bow really. Between primarily a few years of driver dev, an extra 80 some hp, and some years-old R-comps I've dropped 3.5s to a 15 flat since (1:15.0 and 1:15.1 bests in my last two sessions). A laptime reduction which does tend to support some of the above effect estimates. But my times were in sprint races rather than his enduro so figuring he'd still have some seconds on me in the same car and conditions.

OK the 991 Gen 1 Cup has 15 odd hp less out of the box than yours but 250kg is a big drop and helps all over the track, unlike improving power-to-weight by just adding power instead, which only helps at or near full throttle, ie maybe a quarter of the time in a lap. So I'd be tempted to double the estimated effect there. In contrast, I think you might be underestimating your tyres Mark, and overestimating the further time savings available from slicks, which I'd guess more around the 1.5-2s mark for you? Not a Porsche thread but from guys that track their F80 beemers:

"The PSC2 is designed for the track and that's where they work best. I haven't done head to head testing in the same car, but I've been through A LOT of NT01's on different cars and I'm pretty sure the PSC2 is faster." http://f80.bimmerpost.com/forums/sho....php?t=1182570

Plus handicapping bodies like the US's National Auto Sport Association already had the old MPSC pegged level with the NT-01, R888 etc:



Michelin quote a 1.8 second per dry lap improvement for the MPSC2 over the old MPSC - based on 997 GT3 testing at the roughly 1m40s Jerez circuit in the dry:



So in terms of laptimes, your MPSC2s have got to be up there near the likes of the Hankook ZDs presumably?

PS: I'm sure they put a Turbo pic next to that GT3 sourced data just for her pretty backside!

Macca

Good stuff Walt.

For my tyre analysis I tried comparing lap times for Porsche series pre and post allowance of slicks (13/14 first year they were allowed many used Michelin slicks I believe). Even in 13/14 many were using Hankook Z214 a tyre already around 1.5s per lap quicker at a 3km course like Manfield over a MPSC2 I would have thought.

What I discovered is generally speaking lap times have fallen around 2s a lap since slicks have been used on group A+ cars in the Porsche series at Manfield. There isnt alot of data to support it and there are many changing variables so I looked at HD times too (Taupo has had the barrier removed in the last 12 months so is harder to extrapolate).

Having used Z221 extensively on the 993 and now on my 5th set of MPSC2 I must say they are night and day with Z221 being far stickier, more progressive and longer lasting (on the track - on the road definitely not!). I have no ability to directly compare them as 20" fitments of anything more serious than TrofeoR are currently rather limited. I think the MPSC2 is a great tyre but its fundamentally a road tyre (I got 10,000km including 3 track days out of my first set!).

Pete or one of the other racers would have a better idea of lap time improvements using fresh Pierelli slicks vs Z214. I may be wrong but Id have to imagine it knocked off almost 2s a lap at HD from mid 16s to mid 14s this last season gone. The Z214s would be a good 1s a lap quicker than MPSC2, I think probably more. Thats 2.7km.

Thats how I can to 3.5s between my road tyres with R comp attributes and fresh Michi Slicks. As you pointed out its not just grip on exit out of the corners but also how that translates down teh straight in accumulate speed, Vmax and then average speed through sweepers etc. Just looking at our tow cars the differences you mostly identified were not the weight or power or weight to power all of which are about equal but the mechanical grip of the tyres and the chassis. I think Slicks working with a stiff chassis and a trick set of dampers set up with the right toe and castor are probably a multiplying factor.

I guess its academic anyways. Maybe the real answer is somewhere between our two estimated (lets say 2.5s a lap). Ill never run slicks on the GT3 to find out!