John McM

A good non RSG day but you'd find it hard to recognise the difference. Hot as any other day over the last year. Many spins, albeit not our group.

O2GO

Nice one John. I always get home and think "wish I'd taken some photos".

I was happy with the day getting a decent number of laps in the 1:20.5/6/7 range in the early part of the day. As it heated up it knocked off 0.5-1.0 secs. I wonder if thats the reduced air density or the heat in the track or the tyres really hot or all three.

Racing Ray was working hard to teach me to double apex #10. He recons it will save a second when nailed well. Pity I got the lesson on the last run. A few weeks until I can practice it

Macca

That little Targa SC is a really interesting Targa buy for 36K. Id say that would be very compelling motoring.

Wow. Love the red commodore. Hope you guys kept it honest. How did the Martin 911 go? Looks a real nice car.

Doug. You got slower as the day went on or faster?

Macca

John. How did you go with the lap times today? Im sure you go plenty of useful advice from Ray/Steve....

gt38088

Its pretty hard to get a gt3 engine into boxster/cayman. That's why very few have done it. One raced at the N24 hrs a couple years ago. Would be a very big budget...to solve all the engineering issues. Awesome outcome though.

Macca

Bugger!

John McM

Four sessions. Driver training, Prestige, Slow normal and Fast normal. I think the Commodore ran in fast normal. I tried one session there, but very hard to concentrate on lines with cars coming through quickly (pit lane woman controlled outgoing gaps strictly so first cars lapping before last cars out) so ran slow normal after that.

The Martini was brought in for the Targa and left behind for Steve to work on. He spent a reasonable amount of time trying to work out what had been done in the US to it and how to make it work better. Apparently a lot of nice parts which need to be understood.

I struggled to get a rhythm going. Steve and Paul helped with tows but I think running shotgun with Steve in the last session showed me the theory more than anything. He ran 1.15.31 in the 964 with me in it. My 100kg would have affected the car, so that number is very likely sub 1.15 with a lighter load.

Not sure what the time impact of the heat was. My tyres came to temp very quickly. Also given I don't have a lambda sensor I would not have had compensation for the thinner air. But the reality is I need to rebuild my approach to get lower times. Steve brakes quickly then accelerates through the corners. As long as his front grip is ok, the acceleration takes care of rear grip. I coast too much, hence lower grip. Fastest time was a disappointing 1.24.4. Who ever took half a Dave and 2 Macca's can give them back on 14/12!

Macca

Hi John. Good overview. The 964 race car of Steve's will run mid 1.14s in heat of battle (so he told me). Its very light.

Love to know whats in that Martini Targa car.

Your lambda would have made no difference under track conditions. over 60% on TPS = WOT = revert to open loop (i.e. alpha N tables). In laymans terms when your on the gas your lambda isnt being used. Thats part of a closed loop system (cold idle partial throttle). Your Throttle Position Sensor when receiving input greater than 60% reverts to a closed map. Porsche Motronics became and area I had to learn by necessity to tune from scratch the LINK G4. Handy as I know much more now about how the engine inputs work now.

I think the C50 medium tyres would be better in 30 degree + heat but the C70 should wok ok up to that temp...

Yes, you need to lay those picks on real hard all at once as late as possible. First time I took a ride shotgun with an instructor in my own car I thought he was going to kill us. Once you can invoke the same fear in a passenger youll know your on the right track LOL!

John McM

Martini car start up

John McM

Braking in Steve's car was manic. I had to tighten my harness straps 3 times. No way you can run that hard without good restraint. Biggest revelation is as I mentioned was seeing how the slow in fast out theory really works. I've nailed the braking part now to work on the attitude under throttle. Not so sure about Steve's sawing action on the steering wheel. It works for him but not sure I want to play at the edge until I know where it is.

As for the impact of heat, there definitely seemed to be an impact on my V max. I'll look at what Paul ran to see if his car was affected as well.

peterC2S

I found the same thing with heat yesterday - was a full half a Dave worse than last time out yet not much difference from the driver. Don't know whether it was tyres (only second session out on new 221s and they still stick like glue).

I found times deteriorated as the day went on (got hotter). Might do some reading onto the theory there.

Or I could just be imagining it - though the AIM doesn't lie!

peterC2S

Quick update re next Sunday's run and meet up - discussion seemed to favour starting and finishing earlier as a few people have other commitments in the afternoon. So I think Doug has a cunning plan that he will post up separately - but best have an early night Saturday!

Doug - over to you...

John McM

For those not there on Sunday, I think it's good to mix it up with other cars from time to time but it's definitely harder work.

Older cars with road tyres skidding a lot. Less obvious lines being followed. Also found out it pays to record your laps on video. Didn't need it in the end to prove my innocence but the single seater suspecting me of rear ending him and breaking his diffuser was an insight into other drivers' perceptions.

We shook hands but not good to be accused.

356Downunder

Here's a rather nice 993 Targa.....and yes, great fun for sure......especially in weather like we're having right now!!!
Its mine and its open to fair and reasonable offers ....only reason for selling is a 993 C2S purchase.

http://www.trademe.co.nz/Browse/List...x?id=648753147

Macca

The hotter (relative humidity) it is the less volumetric efficiency a combustion engine will make. The phenomenon is more obvious on on forced induction engines were the induction multiplier makes it just so much more obvious.

My hunch is the above played a small part but your tyre temps played a larger part. Ive looked at the heat characteristics of those C70 and they are a winter shoulder season tyre for us really. The C50 medium compound starts to take over around 20C as you can see below. Also if you use a pyrometer probe you will see if you are cooking the insides up too much.

You may recall I sent an email around a month or so ago asking who wanted Medium Z221 for NZ. It was in anticipation on a hot summer track.