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

 

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.

 

PNW987.1 welcome.

 

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.

 

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.

 

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.

 

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.

 

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!

 

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.

 

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!

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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?

 

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

 

PNW Wider is better, even 265/35/19 f and 285/35/19 r if they are available. Not totally sure that setup will fit. I do know that 265/35/18 f and 285/30/18 work. You may need to use a 255/35/19f and a 285/35/19r. On slick tracks like concrete, more rubber is better, just more grip. If you are road racing, then other factors come into play, but you are just using 1st and 2nd gear. I don't have a reference point for your front using the larger tire in 19 inch. At the outside you can use a 5 mm spacer to get the tire away from the shock or spring on a coilover.

 

I went ahead and ordered a set of Bridgestone RE71RS. 255/35/19 front, 285/35/19 rear. I got a text after ordering saying that there is a 30+ day wait on the back order. Hopefully get them with a few events left this year.

Going to get the wheel stud conversion ordered soon. Leaning towards motorsport hardware. Anybody have any experience with those?

 

PNW, I checked out Tirerack research on the RE71RS tester review. They were using a BMW 430I 2020 Grand Coupe and square 245/40/18's. They had some interesting comments about the tire,

"Interestingly, in the wet the Potenza RE-71RS held an even larger advantage in lap times, but our drivers universally preferred the old Potenza RE-71R for subjective characteristics. The new tire's most obvious strength was its amazing ability to put the power down at corner exit. It continually challenged our drivers to apply more and more throttle, yet the rear end seemed to always remain firmly planted. The counterpoint to that was its rear axle behavior through the slalom. When dealing with the more-abrupt lateral transitions through that element, there was very perceptible movement at the back of the vehicle. Adding to the equation, the front end grip couldn't match the dominance of the rear, which created a strong tendency to understeer at corner exit and required that the driver ensure the nose of the vehicle was pointed in the desired direction before committing to the throttle. Lastly, even though the Potenza RE-71RS led the 50-0 mph braking objective results by a considerable margin, it still didn't seem to scrub speed as effortlessly as it built speed, which created an imbalance and made it difficult to accurately judge braking zones. Even so, when dealing with Extreme Performance Summer tires, what really matters are lap times and objective results, and in that regard, the Potenza RE-71RS was the clear winner once again."

I was thinking about 265/35/18 f and 29535/18 r, but after reading the above statement about causing a strong tendency to understeer at corner exit, I'm going down 1 size to 255/35/18 f and 275/35/18 r which is what I have been using for years. My class allows Hoosier A7's so that is my race tire. But, I need to replace these old RE71R's so that's the size I'm going to use for the street and rainy days at the track. You might be getting yours before mine. Let us know your thoughts.

​

 

I'm hoping that I get them before too long. The A052s that I was planning on using are not available until who knows when. I was planning on 255 front, 275 rear in a 19". I will try getting them once they are available, as I already have a single new 275/35/19 that I got deal on.

I have an event next weekend, my second with the car. The last one was a single, 4 run session that was pretty wet. It looks like the weather should be good for this next event. I am currently on Michelin Pilot Super Sports 245/40/18 front, 275/40/18 rear. I have seen some conflicting information, but what tire pressures would you suggest?

It's good to see that the new Bridgestones are getting good reviews. Visually, they look like a big departure from the previous model.

 

We will see in Lincoln, Nebraska this fall at the Solo Autocross SCCA Nationals, which tire comes out on top. I believe the new RE71RS will again be the favorite for the top line drivers. My thinking is that Bridgestone has waited until they got the tire rubber matrix correct for the American market. i would be surprised if the American tire does not have a different rubber compound than the current RE71RS tire in other markets.

 

I believe the new RE71RS will again be the favorite for the top line drivers.

https://m.tirerack.com/tires/tests/testDisplay.jsp?ttid=285

.3 seconds faster on a 30 second autocross

The new tire focuses more on track use than autocross competition,
with specific emphasis placed on dry traction, consistency over multiple laps, and wear.

less precise and didn't offer the feedback of its predecessor.
The lack of feedback meant it was harder to
read and didn't communicate its limits quite as well

our drivers universally preferred the old
Potenza RE-71R for subjective characteristics

...rear axle behavior through the slalom. When dealing with
the more-abrupt lateral transitions through that element,
there was very perceptible movement at the back of the vehicle.
Adding to the equation, the front end grip couldn't match the dominance
of the rear, which created a strong tendency to understeer at corner exit

if someone isn't happy with the way the new tire feels, they're almost
certain to forgive that shortcoming when they see their improved lap times

 

Agreed, as it has been for the 20+years I have been AXing, tires are the BIGGEST factor in determining standings at the end of the race day.

This is the greatest 987 AX discussion on Planet-9 I have seen in some time. Can we push it a little further? Is anyone using coil overs with stiffer springs? Is the standard toe-out front and toe-in rear working for everyone?

My current suspension on the 987.1 Cayman Base:
MCA 2-way remote damper with 11Kgf/mm front and 13Kgf/mm rear springs
Tarett top mounting hardware for Dampers
Tarett 26.8mm front and 19.1mm rear sway bars
Front GT3 lower control arms
OS Giken Super lock LSD

The setup:
20mm lowered from stock ride height
Camber front 3.3 rear 2.7
Toe 1mm out each side front, 2mm in each side rear
Sway bar front 3 of 5, rear full soft,
Damper compression (bump) and rebound setting do not have a sweet spot yet, but generally compression is stiff with rebound mid-scale.
I know that the spring rates are aggressive, but my home AX site is Crows Landing, super flat and high grip surface. I am also limited by STR class to 255 tires, so running the same front and rear. Using 18X8.5 wheels front and rear, with a 10mm spacer in the rear to get offset correct for tires tracking square front to rear.

This build was to compete with NC Miata’s & S2000’s and did an ok job with that. Then ND Miata’s showed up and sure destroyed that idea. The SCCA is looking to move the Cayman Base to STU with the S. (Bottom of page 24 Item # 31259 of this Fastrack news April meeting)

I agree that SCCA Solo classing cars is an impossible task. I know a couple of the SFR guys on the committee and they are trying hard. But SCCA is generally not kind to Porsche’s in classification because top tier drivers like to drive them. Also a track change, plenum, is going make a Porsche even less competitive in AX or Solo. Sorry PNW, changing a plenum is not that difficult for an owner to do, the ECU maybe the bigger challenge.

 

...my home AX site is Crows Landing, super flat and high grip surface...

You are so lucky! But your $/run cost for tires must be eye watering.

 

AX 987.1- I have gone down that pathway you describe but ended up in the GT3 class with Keith Brown, a former SCCA national champion, using a sponsored modified GT4. Well its not fair, so second place was the goal in his class over the 12 races for the past few years.

I am using Ohlin R&T and their standard spring set up of 400 lbs/in f and 458 lbs/in r along with Tarett Cup LCA's f and r as well as their down links. I use -2.9 degree camber f and -2.5 degrees r with about 5 minutes of toe out in front and 12 minutes of toe in in the rear. I've had the car corner balanced with 200 lbs weight in the drivers seat and lowered to about 30 mm lower than OEM. I am running Hoosier A7's 255/35/18 f and 275/35/18's on Signature SV104's that are 9 in wide in f and 10 in r, The other tire/wheel set is Titan 7 TS 5's, 9 in wide f and 10 in in r with RE71R's which I will be replacing with Bridgeston's new RE71RS as soon as they are available.

The interesting part of this discussion is I am using my car as my bike carrier, so it gets a lot of use during the week, but even with the suspension camber, I would expect that the inner shoulders of my old RE71R's to wear rapidly, but the rain groves are still in the shoulders and the face tread is not to the wear bars. I have rotated the tires once so that camber is working well for street use after 15k miles. I also use a Wavetrac LSD which does have the ability to almost lock up both rear wheels when the inside tire is lifted. Its not as radical as the clutch LSD's, but I don't need to rebuild it. Not sure how it compares to your OS Giken Super Lock LSD. I also upgraded my motor mounts, using a new OEM front mount with a FF orange insert and the FF Orange transmission mounts. I also use the Numeric shifter and cable system.

This car works extremely well in canyon driving as the balance is very good with great turn in and good traction out of the corners. I'm using OEM R brake pads and GT2 brake ducts f and r. I'm also using the Soul long tube catless headers and a Milltek muffler for a little more power and great sound effects.

 

Loving the discussion going on here. I am several years of development behind you guys. I am trying to keep my car comfortable enough for street use, but I'm hoping to pick up some good info from you guys.

Sadly my car didn't have the Bilstein damptronic coilovers listed in my signature (tried editing my signature, but I can't figure out how to remove that). I made my profile while I was waiting to take delivery of the car. Apparently one of the shocks failed, and it was put back to stock PASM suspension. I am very pleased with the comfort/performance of that setup for now though.

I guess I just can't catch a break weather wise this autocross season. It looks like it is going to be raining again this weekend. I think last time I was running 35psi all around for tire pressures. It was wet without much grip, but it felt pretty good. This was with 245/40/18 front, 275/40/18 rear Pilot Super Sports.

What would you guys suggest? Would it be different in the dry vs wet?