burglar

Out of those, which would you choose and why?

BS 987.1 Cayman S with PASM and XRR sized wheels? Does sport chrono get you anything?

mopar bob

I would pick a Boxster S 897.2 I fit that. Yes Sport Chrono helps with throttle tip in. It also changes the rev limiter, with out at 65k it starts to soften the RPM's and with it's a hard limit at 72k. At least that is what I think I remember from when I bought mine 997.1.

Grantsfo

987.2 isnt a choice unfortunately. ...or is it? Were there 2008 model year 987.2? If so that would by my choice.

Im wondering if 2012 base Cayman with PASM, PDK and sport chrono might be the car? Also wondering if LSD was available on base 2012? 987 S manuals do struggle when things get slow. PDK perks things up.

mopar bob

I just read the fast track and it's a 987.2 base not S I missed that. I was wrong once but I was wrong about that. I would pick a 987.1 S for BS. Or a 04 Boxster S 550 spyder for CS.

XPC5

987.1 S with sport chrono and pasm. SC changes rev limiter behavior, throttle map, and also psm intervention threshold. All the things you want. This would be a good ProSolo car for sure with the launch, and just a nice car to own and race in general. Run it on short rear tires like 285's to help the gearing. There may be a unicorn combo with the sport suspension (non pasm) like the '08 sports. If that gets you lower, without the electro shocks, that would be cool.

sjfehr

987.1 Cayman S will be absolutely fantastic in BS and actually competitive with C5- if you're buying a Porsche for autocross, that's the one to get. And they're cheap, too!

I'm really disappointed 987.2S isn't moving to BS with 987.1S. No chance again C5Z/C6Z, and now they're moving the Elise down from SS as well so I can't even get lucky with a tight course.

mopar bob

What about a 08 987.1 S RS60 can that run in BS?

PedalFaster

Yes, but the RS60 was effectively an appearance package -- nothing about the car makes it significantly more appealing for BS than any other properly optioned Boxster or Cayman.

mopar bob

Yes it has 7 HP more power WOW. But if you look these are the cars that have the options that we are looking for. Sport Chrono PASM and sport seats. OK at lest half of the ones on Autotrader do. This car may have the best chance of finding one with X73.

grey ghost

I am thinking of a 986 S for c-street, having driven a 2000 with 030 and TCM and a 2004 550. I would run the 2000 model, the 550 PSM interferes by coming back on if ABS is actuated.

I would start with the 245 square set up and with a GT-3 front bar. Been looking for one with TCm at
a reasonable price, been hard to find.

I would basically run what I did in 2000 and 2001 in SS to a 2nd and 3rd at Nationals.

burglar

I wish you good luck, those NDs look untouchable.

edfishjr

GG, I haven't been around the national scene for long, so I had to look you up. What you did back then was, frankly, amazing.

I also think that the Boxster S can match the ND on sweeper courses with a couple of digs. May be my direction as well next year. Looks like you haven't been to Nats in forever. If we both go this route, let's meet there in 2017. I'd love to hear the story of 2001.

PedalFaster

Why do you think the Boxster will do relatively better on sweeper courses? With its lack of camber and relatively narrow front wheels, I figure (based in part on personal experience with two of them) that Boxsters will actually suffer on sweeper courses relative to NDs.

Regarding digs, they'd either need to be in the ~30 mph range where the Boxster can use first gear but the ND has to pull second, or above 50 mph for the Boxster to have an advantage:



After building the ND's thrust chart and comparing it to the other CS options, I pretty much gave up hope for anything else in the class. The ND's acceleration looks to be as good or better than the Boxster's throughout the core autocross speed range in second gear. I'd love to be wrong though.

edfishjr

I don't have my spreadsheet with me at work, but I'll try to comment.

What I did was to calculate peak thrust in 2nd gear by using spec gear ratios, picking tires for the rear OD (285/30-18 for the Boxster S) taking 86% of rated peak torque as the delivered torque and taking the spec weight plus 200lbs for driver as the weight. When I do that, the peak thrust in 2nd for a 2003 to '04 BS was well above the ND peak. So, something is screwey somewhere, or assumptions are vastly different, because your thrust curve shows the ND peak higher than the BS peak in 2nd by a considerable margin. Need to get to the bottom of this because it is the key reason I think the BS can out-dig the ND.

As for sweeping, it's not that I think the BS can necessarily out-sweep the ND, I just think it will be very close. 1) I plan to not let the BS roll much, thus negating, to some extent, the need for so much front camber. You've heard me on this before: riding on stiff bump stops. (Of course, I may very well just make the car un-drivable.) 2) When I look at which end of each car is limited by tire loading it's the front of the ND and the rear of the BS. When I compare the two, the BS is very close to the same tire loading in the rear as the ND is in the front. So, the front tire of the BS is not the limiting factor, by this measure (neglecting the camber problem) in a steady-state turn. Of course, dynamically things are more complicated.

So, when I create a rating by 1) comparing grip by looking at the limiting tire loading, the ND wins but by a small margin, 2) narrowness the ND win easily, and 3) thrust, the BS wins handily. Added together, but only using 3/4 of the thrust rating, I get the ND slightly on top, the 03-04 Boxster S very close and the NC2 slightly lower.

But if the thrust advantage is not real, then the Boxster S will drop down a lot. I guess I need to do a real thrust chart, like you have, and figure this out in finer detail. There's a sizeable issue somewhere.

Other considerations 1) I get seasick just watching NDs go around the course, they roll so much. I know, a big bar really helps this plus a pile of low-speed compression damping, been there done that, it works, but there are trade-offs, 2) the requirement for the ND to shift to 3rd on any big, fast course, which seems to be more the National Tour norm these days. 3) Boxster S racing weight is lower than indicated in my spreadsheet because if I subtract most of the gasoline the Boxster loses more weight as compared to the ND because bigger tank (bigger percentage of spec weight) and different fill level standard.

edit: I checked the numbers in my spreadsheet. No way the Boxster S doesn't have almost 10% more peak thrust in 2nd than the ND. ND: 2332 lbs, 2.99/2.87 2nd/final drive ratios. 148 lb-ft torque, 24.7" dia tire BS: 2911 lbs, 2.2/3.44 2nd/final drive ratios, 229 lb-ft torque, 24.8" dia tire. Using those numbers and knocking torque down to 86%, thrust of ND = .387G, thrust of BS = 0.421G

Edit: deleted my last stupid, unsupportable statement.

PedalFaster

Yeah, I try not to read too much into thrust charts since the dyno data is unreliable. I only use charts done on Dynojet dynos, and when multiple charts are available, I try to choose ones that are about median for that type of car. Every dyno is different, though, even after correction factors are included, and if I'm remembering correctly I wasn't able to find many charts for either the ND or the 986 when I put this together. Given all that, the dyno data can't be considered absolutely reliable.

Having said that, on assumptions:

I do some cursory research on race weights when I put charts together, and I have 2260 lbs. for the ND (72 lbs. less than you) and 2950 lbs. for the 986S (39 lbs. more than you). I unfortunately don't keep notes on where I got the numbers from, but I'm guessing I got both from build threads. Also, counter to what you're saying, I suspect the 986S number's probably actually optimistic. It likely dates back to the Stock days when Hoosiers (lighter than street tires) and dump pipe exhausts (lighter than conventional exhausts) were still legal. I've seen a lot of race-prepped Boxsters on scales, and even the strippers haven't come close to Porsche's published curb weights. I wonder if Porsche publishes dry weights.

Our dyno numbers are also different. The ND chart I used had a peak torque value of 144 ft. lbs. at the wheels, whereas the 986S chart I used had a peak torque value of 208 ft. lbs. at the wheels.

Lastly, I used a 24.1" diameter tire for the ND.

Math is math -- the reason we got different results is because we plugged in different inputs. Your numbers have the Boxster accelerating harder. My numbers have the ND accelerating harder, which I agree seems counterintuitive. If I have a slow day today I'll try to confirm all the numbers.

I haven't driven an ND yet, but theoretical tire loading comparisons aside, the Boxsters I've driven haven't had a lot of front end grip. Not sure if this is a function of the mid-engined layout, lack of front camber, or relatively poor geometry from the strut suspension.

The 986 is pretty soft too:





That's my car on M030 springs and rear bar, Bilstein HD shocks, and a stock (non-M030) front bar, but on an admittedly undulating lot.

Now I'm curious.

Don't take any of this as me arguing or being belligerent -- just trying to see why our opinions differ so widely on this.

Oh, and if you plan to sell your Corvette, PM me about your shocks.