[ThrottleSteer]

I'm an experienced autocrosser, but am trying to figure out the best approach for solving a couple of issues. The lot we're currently running in is pretty uneven with lots of dips and a few significant bumps. I'm currently running on a stock PASM suspension with Hoosier A7s and find that in Sport mode, the PSM kicks in at least a few times per run. However, this isn't happening because I'm overcooking it or the car trying to break loose. When the car hits an uneven portion of the pavement or a bump, it's sapping a lot of the power to compensate for the minuscule loss of traction. There are a fair number of obstacles in the lot. Even though I know the car well and am confident in my abilities, it's not worth taking the risk to turn off PSM.

My understanding is Sport + has a higher threshold when it comes to engaging PSM from a loss of traction? Since I don't have Sport Chrono/Sport +, is there anything short of turning off the PSM button to counteract this (e.g. suspension mods, turning off the PASM, etc...)? I plan to add the X73 rear sway bar to help bring around the back end and reduce a bit of understeer. Would this exacerbate or help the PSM problem?

I appreciate any insights or previous experience with the same problem.

 

[Ubermensch]

Not sure what the risk really is to turn PSM off for autocross...I mean it's flat, open, and marked with cones, right? Seems like a good opportunity to try it. I'm a track guy so id understand your concern if you were running at a fast track with fixed barriers and little runoff.

If the problem really is dips then a stiffer swaybar will likely make it worse by transferring that dip to the other wheel as well. Seems like a softer suspension is the answer to dips but that hurts you on the rest of the course.

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[ThrottleSteer]

In the past, most of my autocrossing has been in lots that are open and flat. This lot has several sections that have barriers within 25ft or so of the course. It's a reasonable amount of distance, but things can happen. Over the years, I've seen a couple of cars get crunched.

I appreciate the input on the sway bar. It sounds like short of a Sport+ retrofit (probably not possible or financially conducive), it's either PSM on or off.

 

[Squik]

I do most of my autocrossing with PSM on and catch some flack for it. I've had some good runs with PSM off, but have had a couple of snap spins as well. Years ago, I watched a GT3 with PSM off snap a spin and roll backwards 120' into a curb. Major damage, he had to have stayed off the brakes for some reason.

Question: I've been running with PSC2 & RE71-R's, but now have GT3 LCA's and will be running A7's. Do you have alignment recommendations?

For RE71-R users: a camber of -2.7 F and -2.5 R gave me even heat across the tires for the first time. With lesser camber, the inside is cooler, not getting used much.

 

[Walter]

I'm an experienced autocrosser,

the PSM kicks in at least a few times per run.

I know the car well and am confident in my abilities,

it's not worth taking the risk to turn off PSM.

I would turn off PSM (always keeping in mind where barriers are).
I can't push 100% with possible danger near though.

This lot has several sections that have barriers within 25ft or so of the course.

Packwood?

 

[Apex1]

ThrottleSteer- Changing the rear sway bar to a stiffer X-73 bar will reduce your traction/grip in the rear while pushing the balance forward. If PSM is the real issue, then you need to reduce your rear sping rate or swaybar rate to keep compliance/wheel spin with the ground/bumps. This is tricky as understeer and PSM are at opposite ends of the car. I would suggest to change the front to an adjustable Tarett GT bar with 5 holes. If you need additional fine tuning then a rear GT bar with 4 holes could be installed. The front bar is a bear, the rear bar is easy. That would certainly help to change your balance and understeer. If you are running in the bumps and have understeer, I would go with a softer setting in front than the X-73 bar and reduce the rear swaybar for PSM compliance. For a flat course, you could use a stiffer setting in front and possibly in the rear as well. That's the beauty of adjustable bars, in that you can fiddle with the roll balance f&r, one change at a time until its close, then use air pressure depending on the weather. This allows you to drive harder, while controlling the slip angles better (not triggering the PSM) yet still rotate to get better times.

The other option that I do not have is to add TPC's trick DSC V3 PASM controller to really change the stiffness or compliance in your PASM shocks around the course. That system is a better way of adjusting the PASM controller mapping of car shocks to individual tracks. Check out Mike's Levitis various youtube video's on how to setup the mapping for DSC programing on your own laptop. This is exactly how Williams F1 team won the world's constructors title in 1993 only they did it without springs just hydraulic actuators. Most likely the best $1100 your could spend on your suspension. I would place this system in front of the swaybar upgrade. DSC is the real deal if you have the ability to program it. Lovetoturn added DSC to his 981 S a couple of years ago and never looked back. If you had SC, you could tie the DSC to your magnetic transmission mounts for a more solid turnin, mid corner throttle and even trailbraking assistance. Lovetoturn also added X73 springs to his PASM shocks without affecting the reliability of that system. The spring rate is higher for the X-73 springs than the PASM ones and your car will sit a few mm lower. There are simply too many advantages to that system if you know how to program it for autocross like three different settings at your fingertips. One for flat grippy asphalt, another for bumpy, slippery hot cement and the third for normal driving or rain. The idea is to improve tire grip and traction around the course without triggering the PSM in bumps, dips, uneven patches and transitions.

Packwood is an excellant example of bumps and a slick cement surface in afternoon sunshine, where a softer setup and low tire pressures on RE71R's or Hoosiers A7's really helps.

 

[gremlin]

You apparently can get sport+ without sport chrono, if you know what you're doing. Installing Sport Plus button on car without Sport Chrono - Page 4

 

[lesmurray]

I have a DSC Sport module on my 987.1. What a big difference in handling. I would recommend it.

 

[Jetbill]

I have a DSC Sport module on my 987.1. What a big difference in handling. I would recommend it.

Have a DSC system for sale here if anyone wants it. Good stuff , just sold the car.
https://www.planet-9.com/login.php?a=pwd&u=32162&i=f9ba9ee9e7a3ad28fe4507d0f1116870a35eae61#/topics/238729?page=1

 

[Saabretooth]

On the suspension question

With a DSC controller on the PASM cars

Would the following be necessary?

https://www.sharkwerks.com/suspension/p4670-rss-tarmac-stage-ii-suspension-kit-for-987-987-2-981-cayman-s-boxster-s-spyder-RSSS489


Or I can just excludethe adjustable drop links ?


Cheers.

 

[Apex1]

Depends on what the intended purpose is for the car and the potential mods you do to the suspension. If you feel you will be going to stiffer springs and lowering your car while using PASM, then they will come in handy as the adjustable toe links need bumpsteer assistance on lowered cars. Also, if you install the LCA's what have internal shims for camber increase, that install would be an excellent time to change spring rates as the car's suspension is apart. If tracking is where your intended goal, then even more spring rate could be added like Swift 300 lbs/in f and 450 lbs/in r with just a shade lower ride height, sourced from Tarett. The links then would be necessary do to lowering the ride. They also require a locker plate in the rear.

If you are not changing the ride height or going to coilovers/corner balance, then no need of the drop links. The product descriptor is great describing the issues of a lowered Porsche.

 

[Ubermensch]

Frankly, you don't "need" any of those items to run the DSC with PASM. You'll enjoy the improvement with no other changes, but certainly if you want more control over camber up front, or need to address geometry problems then those other pieces come in handy.

 

[Saabretooth]

Thanks for the great info.

I am looking to have camber, castor and toe adjustability for track work and then switch back to its role as a DD on weekdays.

Car comes with SC and PASM, am going to use the DSC to smoothen things out with an option for lowering springs in the foreseeable future. From what I’ve read up, not more than a 30mm drop


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[Apex1]

Once you start the suspension work, it makes sense to do most of it while the car is apart. X73 springs will work with the PASM, will lower your car about 25mm and cost less than $400. Look up lovetoturn's P9 threads. He also used a GT3 front adjustable swaybar. I would also include that whole RSS package. Then a competition alignment of -2.7f and -2.5r. 2nd softest swaybar front hole and your choice of PASM settings. You will be good to go for about 3-4 years. This suspension upgrade will hold up to include the wider wheels, 9 in f and 10.5 in r and stickier tires, RE71R's 255/35/18 f and 285/35/18 r.

The next upgrade would be stiffer springs, f strut brace and rear frame brace, bucket seats, sticker race tires and toe out 5 minutes in front, toe in 12 minutes r, with a little more f camber to -3.0. Yet, still be drivable on the street with a change of your race wheels/tires.

This combo with an aggressive PASM mapping will allow you to use most of the benefits of the Cayman and still retain the driveability of a street car by simply switching to a softer PASM map. Give us feedback from Singapore on how these modifications work on your streets and tracks when you get this work done.

 

[Squik]

I'm a little late with this reply, but I ran my 981S Boxster in autocross with A7's, sport mode, X73 suspension, Tarrett lca's this summer. I found that I HAD to turn PSM off to run decently. My theory is that PSM just doesn't understand the A7 traction levels, thus it activates at the wrong time. The most obvious problem was rolling on the throttle while finishing a hard corner - PSM wouldn't allow any throttle. Turn off PSM and the problem goes away.

With PSM off and RE-71R tires, I'd occasionally get a snap spin. With PSM off and the A7's I've never gotten close to a spin.

I can't address PASM or sport+.

 

[Apex1]

your throttle steer mid corner with A7's triggering PSM interfering with throttle exit is totally different than my older 987.1 Cayman. I routinely throttle steer and 4 wheel drift at less than 8 degrees of slip angle not triggering the PSM after the apex. My issue is driver induced too aggressive corner entrance and threshold braking/trail braking to make the apex. At that point I am usually late with the throttle. Just a little more practice, should be good. One instructor told me I should have gone with 265/35/18 f and 295/35/18 r. He thinks more rubber is better. I told him I liked the balance of 255/35/18 and 275/35/18 and can four wheel drift out of most corners onto the limited straights we have. I like the rotation and throttle steer of my setup, not sure about more A7 rubber though.

 

[ledbette]

I'm a little late with this reply, but I ran my 981S Boxster in autocross with A7's, sport mode, X73 suspension, Tarrett lca's this summer. I found that I HAD to turn PSM off to run decently. My theory is that PSM just doesn't understand the A7 traction levels, thus it activates at the wrong time. The most obvious problem was rolling on the throttle while finishing a hard corner - PSM wouldn't allow any throttle. Turn off PSM and the problem goes away.

With PSM off and RE-71R tires, I'd occasionally get a snap spin. With PSM off and the A7's I've never gotten close to a spin.

I can't address PASM or sport+.

If you have a different F/R tire diameter ratio than stock, it can cause PSM to activate more quickly. It detects more F/R rotational speed difference because of the tire diameters which will be interpreted as a greater degree of traction loss/wheel spin.

 

[Apex1]

That is a great explanation to OP's triggering the PSM. I will ask this coming weekend about the 718 S instructor's PSM going off with RE71R's 265/35/19 f and 305/35/19 r. You would think that ratio is completely out of ratio from stock. Not only that but the balance is off a little, yet he is usually in the top 5 times of the day, even without the aid of Hoosier A7's.

 

[ledbette]

265/35/19 f and 305/35/19 ratios are almost identical to stock. Stock is .96-.97, depending on wheel diameter. He's right at .96.

 

[ledbette]

I put together this handy spreadsheet a year or two back to help me evaluate tire size options. You can enter your tire sizes in row 29 or 38 and compare to stock. I also computed the effect of tire wear on this calculation (i.e. running corded fronts and new rears and vice/versa):

https://docs.google.com/spreadsheets/d/1NpPWLGRBXeUziZawyAbYJAn8HvCKpUt_x6r1ISEik40/edit?usp=sharing

Note: A 265/35/19 is not the same across manufacturers/models. Actual tire sizes will vary. Tire rack usually provides specs for actual tire diameter.