[PNW987.1CaymanS]

Hey everyone, first post on the site.

I will have to get an introduction post up soon. I was trying to figure out what autocross class my 2006 Cayman S would be in, as I am about to order the class magnet panels. I have done a lot of searching and can't quite decifer what class my car would fall into.

The car had a number of modifications on it when I bought it. It was previously owned by a PCA track day instructor.

The current mods on the car are:
Borla exhaust
Quaife LSD
Softronic Plenum with 4.1 flash
GT3 strut hats and front brake ducts
Girodisk front brake rotors

From what I can tell, it seems that the intake plenum will bump me from street touring to street prepared. This is pretty frustrating, as a highly modified 2006 WRX STI with a STU index has been dominating fastest time of the day. A turbo car can crank up the boost and get an extra 50-100 hp, but my intake plenum that gets me maybe 20-25 HP earns me a much harsher class index penalty.

The club that I race with has a Pax class that uses SCCA index ratings, as sort of a catch all class. It looks like a fun class that usually has 15+ cars in it.

My other option is (Sport A), which is a class specific to the club, but usually has 2 cars in it at most. I don't really want to race in a class by myself or with only one other car.

Street prepared is also pretty vague as to what class I would be in. There is a listing for lightly modified vs heavily modified. I'm not wanting to run tires below 200 treadwear, or have to change tires at the track.

I wish I could just run STU, if not for the intake plenum issue. I'm not going to buy a stock plenum and install it. I like the way the powerband is and am not willing to make the car drive worse for the sake of autocross classification.

I've got a set of Apex wheels on the way. Originally wanted to run Yokohama A052, but since they are impossible to find for the time being. I am thinking of getting the new Bridgestone RE71RS once they are available in June.

Sorry for the rambling post. Any input that you guys have would be much appreciated.

 

[GT3Twenty10]

The one time I Auto x my car it was ASP on street rubber… I use to do this Sport for years and got burned out only using 1&2 gear..

my car is pretty modded… I didn’t even mention the 3.8. I’m sure it would be AP
Not sure why a plenum would bump you up, those things don’t do anything

 

[red_stapler]

my intake plenum that gets me maybe 20-25 HP earns me a much harsher class index penalty.

It is harsher because the index expects every car to be prepared to the full extent of the rules, which for street prepared means having a .2 engine and Hoosiers.

Right now your car is legal for ASP, BSP, and SSM.

I personally would run the car in ASP since it has the softest index.

 

[Apex1]

PNW987.1 welcome.

 

[PNW987.1CaymanS]

Thanks for the responses guys. I am wondering if I should just not mention the intake plenum, and run with a STU index. It is a pretty laid back club, and I am not likely to be very competitive any time soon. I want to play by the letter of the rule book, however flawed it might seem. It seems like the rules don't really look at the differences in engine design when it comes to how rules are applied. Most cars have the filter, then intake, then throttle body. Porsche seems to run the intake/inlet after the throttle body.

Thanks for the welcome Apex1.

 

[arthurc604]

Appreciate your desire to follow the rule book! I know the SCCA solo rules may seem flawed, but what they are trying to do is extremely challenging. First of all, they are taking every car sold in America and putting them into classes in an attempt to make the competition as even as possible while trying to cater to "popular" cars (ie. sports or sporty or enthusiast cars). Then you add in the layers of modifications and try the same thing all over again.

Nevertheless, in every class there will always be a very small number of cars (or even one) which will be theoretically the fastest on an autocross course. The thing is - until you get to the top tier of competition, the spread of driver skills way WAY overlaps the performance of those class cars.

My suggestion is to run STU until you are getting competitive and start winning things (trophies, coffee mugs, whatever) and at that point to put yourself into the 100% legal class. Many people put a lot of time, effort and money into the events and IMO a legal car shouldn't be losing to an illegal car.

Like many other sports, it's cheap and easy to participate - it's expensive and very difficult to win.

Anyway, get out there and have fun! This is my first "serious" year with my 987.1 and really looking forward to it.

 

[PNW987.1CaymanS]

Thanks for your input Arthur. I think I will try running STU to start. With some Sport A thrown in, if I've got some competition. I've got my second event with the car coming up in 2 weeks. The first event, was pretty wet (still lots of fun).

Running pilot super sports, I was just a bit faster than all of the cars in Super Sport. I think that they had too much power for the conditions. Sounds like you are about a year ahead of me with your car. I am just getting a feel for the car this season and getting it set up.

Which tires are you running? I found a great group buy on some forged Apex wheels. I was able to get 19" for the price of 18". They are the tiniest bit heavier than the 18s, and the 200 treadwear tires are shocking less expensive in 19" for the widths that I am looking at.

 

[Apex1]

Actually, Ryan Clark won the SCCA B street solo a couple of years ago in a 2007 Cayman S. He stuffed RE71R's 265/35/18 f and 285/30/18 r into his car. He was just fast all year long. This photo is from Porsche wheels and tires, and a sub group called Porsche wheels and tires that worked on P9 page 13. That year he actually beat the A class guys in their Corvettes by a few hundreths of a second for 3 days of total time. I would think you could compete without anyone checking your car until you start winning. Ryan inspired me to compete, but like you I bought someones race car with that exact Softronic race Plenum and 78 mm throttle body so into a modified class called GT3 in the Porsche autocross class. Its ugly, a national champion Keith Brown in his modified GT4 is the winner most of the time.

 

[arthurc604]

I'm on some very old RE-71Rs. This year I am focusing on learning how to drive the car and improving my driving technique. Actually last year I was autocrossing on the actual rims and tires in Apex1's photo. The car ended up owned by a local member and I eventually managed to buy Ryan's wheels off of her as she wasn't autocrossing any longer.

My current rims are also from Ryan - some Work Meisters which aren't particularly light but look unique on the car and are at the optimal legal size. In both cases though I do run the 285/30R18 which gives the car ridiculous fender gap but really helps with improving wheel torque.

I was able to set top PAX/2nd raw at our club's first event and I can definitely see areas where I can be driving better so hoping to have a successful year in our points championship.

@Apex1 - I've raced against Keith many times in G Stock and his MINI S back in the mid-2000's. Great guy and great competitor!

 

[Apex1]

Keith Brown and Ron Bauer along with a few others who are at the top of the time charts each weekend in my area. So if you happen to be in their class, that's too bad as I don't have the seat time over the years to be that competitive. It takes a lot of dedication to be racing both days on the weekend, one day for SCCA and another day for Porsche autocross. I road bike and snow ski, so that takes a big toll in time allotment even during the spring time.

 

[arthurc604]

Yeah, in addition to them you have many other SCCA national champions in your region. I like to do the Packwood National Tour from time to time for #1 the amazing venue and #2 to get my clock cleaned and to know where I really stand in terms of ability.

 

[PNW987.1CaymanS]

These showed up today. I still need to figure out what tires I am going with. I have a single A052 (275/35/19). I was hoping to find the other 3 tires, but they are on backorder with no idea if and when they will be available.

Thinking of starting with 255/35/19 in the front on a 9" wheel, and 275/35/19 in the rear on a 10" wheel. I would like to go a bit larger eventually, I will see how much more I might be able to fit, and what might need to be done to make something wider fit.

I'm leaning towards trying the new RE71RS, that look like they will be available in about a month. It looks like Kumho, Falken, or Hankook could be options as well. What do you guys think? I'm hoping to have these good to go by the 3rd weekend in June.

I'm also thinking of doing a wheel stud conversion. The thought being that I would be able to run different spacers (mostly for stock wheels), and not need serveral different sets of wheel bolts. My stock bolts are looking pretty sad these days as well. I would like something that could handle about a 15 to 20mm spacer. I saw that a 78mm stud can handle up to a 20mm. I'm not wanting an excessively long stud, just enough to suit any spacer that I might need.

 

[arthurc604]

I don't really have much to add regarding tires (although I'll have to cross that bridge myself later this year) but the stud conversion sounds like a great idea. In case it helps, on my car (stock PASM which will be 10mm lower than yours if you're stock non-PASM) the tires are pretty much flush with the fender lips when wearing:

18x8.5 offset 49 265/35R18 RE-71R
18x10 offset 32 (after spacer) 285/30R18 RE-71R

Your rims are very close to that already, so you might not be able to do a whole lot for spacers. It looks pretty goofy, but I do recommend the smaller diameter rear as it really helps with lack of thrust as compared to other cars you might be competing against.

 

[PNW987.1CaymanS]

My car is PASM equipped as well. With the 19's that I chose, going with shorter tires isn't really an option. The shortest that I have seen are in the 25.6" to 26.1" range. There aren't too many 30 series available. I have heard that there can be ABS issues if the front tires are taller than the rears. Have you ever experienced that?

The wheels that I have are very light weight at least. It seems that the combined wheel and tire weight should be pretty similar to an 18" setup. Front wheels are 18.5lbs each, rear wheels are 19.8lbs each.

The car doesn't feel like it is lacking for acceleration, though I'm sure every bit helps when powering out of corners and staying in 2nd gear for the whole run. Definitely a different kind of power delivery than I am used to. My other car is a BMW turbo inline 6. That has peak torque at just over 3,000 RPMs.

It is fun having to work a bit more to get to the power. Also hard to beat the sound of the Porsche flat 6.

 

[arthurc604]

My car is PASM equipped as well. With the 19's that I chose, going with shorter tires isn't really an option. The shortest that I have seen are in the 25.6" to 26.1" range. There aren't too many 30 series available. I have heard that there can be ABS issues if the front tires are taller than the rears. Have you ever experienced that?

I drive 75 miles round trip to my venue and haven't had any issues with the offset wheel diameters. Ryan Clark also stated years past that he had no issues. At the last event I data logged a ride-along I did in a 997.2 C2S which I think would be a good 90hp up on my 987.1. The graph below shows that on a 3s full acceleration sector I was able to accelerate at the same rate. I might have been somewhat higher in the rev range due to my higher speed and gearing due to the small rears.

 

[Apex1]

PNW, I would use 255/35/19 f and 285/35/19 r RE71RS. Be happy if you can score these as the back order list will be long getting them. I have these older model RE71R's on my car for 3 years now just trying to use them up on the road. I guess I don't put that many miles on my car these days at 20 miles per gal average. I have had them reversed on the wheels once, that really helped the outside and inside shoulders as I use -2.9 degrees camber f and -2.5 degrees rear. The wear on the shoulders is almost the same, as I scrub the outside in turning and wear the inside due to the camber. I also have a set of OEM wheels with Michelin PS4S's with very few miles, but when I do use these wheels and tires, I'm surprised how much grip those older RE71R's still have once they get warm.

 

[arthurc604]

Keith Brown and Ron Bauer along with a few others who are at the top of the time charts each weekend in my area.

Keith's car just went up for sale on Facebook. Here's your chance!

 

[Apex1]

PMW, you don't need to worry about the side wall height of the RE71RS as 19 inch tires come in 285/35/19 while the 18 in only come in 30. Not sure why Bridgestone did this and never modified there tire offerings over the years, I would have used the 18/35/285 in a heartbeat along with a whole lot of other users.

 

[PNW987.1CaymanS]

Do you think the slightly taller gearing that the 285 would give is worth it for the extra width? I haven't ordered anything yet, I should get an order in to save my spot on a wait-list.

Is wider always better? Or is there a point of diminishing returns?

 

[Apex1]

Keith is probably upgrading like a number of other PNW Porsche members who autocross. Not the right time for me.