[mikeo]

Its been several years since I was active on the forum so I thought I would enter the pool as a "New" guy since there are going to be quite a few of you who don't know me.  My credentials are in the garage, a guards red 1994 968.  I would say it is heavily modified due to the turbocharger, Electromotive engine management and aftermarket track suspension.  I used it as a street car and track day car until 2009 or so when the stock market was in the toilet and the car refused to start.  Having been the technician that installed the TECgt and harness, I suspected a wiring flaw.  There were a LOT of wires. I couldn't find anything wrong and I decided not to send the TECgt to Electromotive for fear of a giant bill to repair.  Plus I had already decided that this was not the time to spend the bucks on tracking the car.

 

Now its 2019, I'm retired with time on my hands so its obviously time to resuscitate my #52.  I've done the easy stuff.  The TECgt has been repaired by Electromotive (only $201 + shipping and insurance) an the injectors have cleaned by Mr. Injector and are perfectly flow matched.  Now I'm putting together a list of the other things to do before I turn the ignition key to start. So far, this is my TO DO List:

 

1.  Brake System purge and bleed (the reservoir is empty, don't know where it went)

2,  Timing belt

3.  Drain fuel and flush lines

4.  Swap out transmission.  The spare has a limited slip diff.

5.  Check all of the electrical stuff that can be checked before turning the key

6.  Replace the coolant.

7.  Battery has already been replaced

8.  "Hand Prop" the engine to verify all is well

 

What else?  Feel free to pile on!

 

  

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[MCL968]

Have you ever replaced the line from the alternator to the starter? Mine was toast, and it was about to turn the whole car into toast as well.

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[az968]

1 Variocam pads,depending on mileage, since you are changing the timing belt. The side you can't see is twice as worn as the side you can.

2. Balance shafts belt

3. Misc drive belts


Turbo, sweet!


Pics?

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[mikeo]

MCL968,  All the heavy power cables were replaced with a kit that was sold by a R.L. member back around 2008.  The cables I removed really needed to be replaced.  There are less than 3000 miles on the replacements.

 

AZ968,  The pads and belts have about the same mileage as the cables so I'm not concerned about the pads.  The belts however are ten years old so they probably need to be changed.  There were pics on the forums back in the day.  Try searching for my older posts.  

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[Cloud9...68]

Welcome back - nice to see another track guy on the forum - we're in woefully short supply these days for some reason.  What sorts of suspension mods have you done?

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[mikeo]

Posted in 2005  

 

In January, I decided to proceed with my suspension project. I had already replaced the front sway bar with the Weltmeister, installed KLA rear drop links, Dynatech STB, and Racers Edge control arm spherical bearing bushings (they are holding up just fine), and rear sway bar bushings. For the 2005 project I replaced the stock M030 control arms and struts with Charlie arms and Ledas/450# Hypercoils and added the Dynatech camber plates (yes, I know what they cost) to add a little vertical axis compliance compared to the full race (cheaper) camber plates. While I was there, I installed the big blacks with Pagid blue pads clamping on OEM perforated rotors (Please, no debates. See the old threads if you are compelled!). A 5/33 proportioning valve replaced the stock unit. In the back, I went full coilover with Ledas/500# Hypercoils, replaced the torsion bar bushings with Racers Edge Delrin, and the bars with 10 mm diameter ones. The rear brakes were not changed, the Pagid blues have been there for several years with almost no wear. That may change with the new proportioning valve. Time will tell.

The ride height was reset to be the same as the Club Sport (lowest factory ride height for 968 NA models). I've been running at this height for 3 years now and the splitter is as close to the road as I want it to go. When weighed at Roebling last month, the diagonals were only 13# different. Total weight with 5/8ths of a tank and yours truly was 3350#. I always have liked the full figured type. 

Replacing the proportioning valve required removal of the windshield washer reservoir. With it out of the way, the job was easy.

Removing and reinstalling the torsion bars was a PITA, mostly because of my "read the instructions once and go do it" approach and the fact that I was working to a deadline. Indexing the 10 mm bars was not important since the spring rate is inconsequential. Under those conditions, I was doomed to miss a step or two and I was barely finished in time for tech on Friday before the DE weekend. If you decide to do this, read the Elephant Racing write-up on R.L.. You do not have to drop the entire suspension to do this job. The 968 is even easier that the 944 because, after removal of the aero fairings the torsion bars can be pulled straight out without tilting the torsion bar tube as described in the Elephant Racing description.

Everything else was pretty straightforward. Good tools, a set of pry bars, an air impact gun and air ratchet were very handy. 

All of my suppliers were great! Here they are:

Dynatech Scott Reynolds Camber Plates and STB
Sunset Porsche Jim Brakes etc
HRM Jason Lee Charlie Arms
Racers Edge Karl Poetl Ledas, Hypercoils, bushings, rear coilover adapters, t-bars
Frozen Rotors Bill Groschen Cryogenic treatment
Paragon Products Jason Burkett Pads, fluids, tools
Porsche of N Orlando Jim Alignment
Zotz Garage Donnie Mechanic

After double checking all of the torques, I had the car aligned by Jim at Porsche of North Orlando. Here is the before and after.

<a class="" href="http://www.968forums.com/uploads/post-33-1115086926.jpg" title="Alignment.jpg - Size: 136.92KB"></a> 

I made a mistake when I had the camber set at -0.75 deg. The camber plates provide 2 deg change so my max at the track would be -2.75. I will change the street setting to -1.5 so that I have -3.5 available for DE. Toe changes as the strut is moved through the camber range, 1/4 inch in my case. So we set the street toe at 1/8 inch toe-in. At max camber its 1/8 inch toe-out. I have not decided to change this or not.

Ride is firmer than M030, there should be no surprise here. Its 270 miles to Roebling from my house and I slowed down in the same spots that I always do. I don't want to hit an unexpected pothole, but that is no change from before. Road noise is definitely increased. The stereo would have to be turned up to painful levels to drown it out, so I didn't. After about 400 miles I didn't notice it so much. So, if you like peace and quiet in you 968, I would not recommend these mods. If your wife/GF likes a Caddy, she won't like this.

At the track, first session: HUGE understeer! I'm back in the paddock after 4 laps. After resetting the camber plates from street to track settings I was ready for session #2. This time the understeer was minor and I was able to remove most of it with small adjustments on the Ledas. Braking was changed in that less pedal pressure is required to evoke ABS. The brakes modulate fine, the car was not tail happy, and fade was non-existent. I expect to see reduced wear rates in pads and rotors as a result of the brake mod. Compared to my last session at Roebling, lap times improved by 2 to 3 seconds. I believe my 1:28 on about 6 different laps compares favorably with the PCA F stock 1:22 to 1:31 qualifying times posted at Roebling in 2004. I hope to rapidly become more confident and squeeze out a little more as the seat time piles up. 

Of course, the turbo install this summer may cloud future improvements due to the suspension.

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[Cloud9...68]

Thanks for the summary.  I have a lot of the same stuff on my mostly-track car, with a few differences.  You didn't mention your wheel sizes - I'm running 17 x 10.5" Signature SV103's with 275/35-17 Maxxis RC1 tires all around.  I'm also, on Karl's recommendations, running much stiffer springs than you - 700 lb in front, which gives a spring frequency of about 190 cpm, which I realize is too high.  I was origionally running 1000 lb springs in back, but the car was a twitchy, hyper-oversteering mess, so I softened the rear springs to 800 lb, which gives a theoretically optimal spring frequency of about 135 cpm, due to the very low motrion ratio (0.65) in back.  I also have the Weltmeister adjustable sway bar in front, and the M030 3-way adjsutable M030 bar in back, which I've been running at its softest setting.  I'm still fighting some oversteer, which is making it difficult to put the power down early enough coming out of the turns, which is costing me lap time, so most recently, I've disconnected the rear bar altogether, and am still working on sorting out the roll center heights, spring rates, track width, and sway bar stiffness to eradicate the stubborn oversteer my car has had (which has lled to many off-track excursions) since I did all the mods.  At least I'm learning a lot through the process!

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[Rap]

Where are  you braking coming into the turns? Early or late?

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[Cloud9...68]

Braking?

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[Rap]

You mentioned oversteer coming into the corners. Is your braking not done when you start to rotate the car! Are you trailbraking?

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[Cloud9...68]

The oversteer is primarily coming out of the corners.  And yes, I trailbrake in almost all of the corners.  I also left-foot brake in all corners that don't require a downshift.  As usual, I thought my disappointing lap times were because of my crappy driving, so I let the track owner, a retired pro whose last right was with a Ferrari factory GTP team, drive it.  He pulled in after two very slow warm-up laps, and told me it's impossible to drive the car fast because the oversteer is preventing him from putting the power down coming out of the corners.  He estimates this is costing two seconds a lap, out of a ~1:03s lap, so it's pretty significant.  Disconnecting the rear sway bar altogether really helps get the rear planted, so I'm driving that way for now, but I don't want to have this be the permanent soluton, as it makes it more mushy in the rear than I'd like.  I have to admit that going from a staggered to a square set-up is probably largely to blame for the oversteer, so I'm working with Dale Thompson to sort the car out.  I'm sure it's all doable;  I just want to make sure I don't create other problems while solving this one.  I'd love to know what understeer even feels like, as this is a completely foreign concept to me, at least in this car.  I've entered all the required measurements (spring and sway bar motion rations, front and rear roll center heights, front and rear weight, sprint rates, etc.) into his spreadsheet, which will give me some quantitative data to go along with car feel, lap times, and data from my DA system.

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[Waylander]

Soften the front a bit, that should induce some understeer

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[Cloud9...68]

Soften the front a bit, that should induce some understeer

Nope - other way around.  Reducing roll stiffness at a particular end of a car increases the grip at that end.  More front grip is the last thing I need.   

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[Rap]

Do you have any aero on your tail?

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[ds968]

No need of an aero for me , I drift through all turns ;-) ;-). Thats on the street of course . But on a serious note, for a change, I regret not having tracked the car after Flash changed pretty much my entire suspension, just to see how different the car would have driven compared to when I tracked it with the stock set up. The change was very noticeable on the street but Id think on the track that would have been even more magnified. Sure I push it on twisty roads here now and then, but its just not the same.. I was reading this thread and so many technical references are over my head , it may as well be written in greek. But I admire how knowledgeable you race guys are about all the nuances of the cars specs and their effect on handling .

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[Cloud9...68]

Do you have any aero on your tail?

Nope - just the stock spoiler.  The track I drive on is very tight - I can barely top 80 mph on the longest straight, so aero is a non-factor for me.  Also, the oversteer is primarily coming out of the corners, by which time the car is moving way too slowly for aero to be a factor even on a faster track.

 

I'm really sorry I brought this up.  This isn't an issue that can be troubleshot over the internet.  If it were as simple as changing a single factor like a front or rear spring rate, or slapping on a spoiler, I would have solved it years ago.

 

Rap, I appreciate very much your introducing me to Dale Thompson - he's a great guy who has worked in suspension dynamics for a living for decades, and I just finished making all the measurements needed for inputs to his weight transfer worksheet.  I plan to start working with him next week to review the factors (and there are a lot of them) to find a combination that corrects the oversteer without inducing other problems.

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[Rap]

I wish you the best on that. I just ask because you’re another 968 track guy and I’m always trying to learn from what others are experiencing. Last October I blew my tranny. I had my replacement put in. Then Jeff Coe got back to me and told me the original tranny wasn’t a limited slip. This of course answered the question I had as to how I could spin a tire going through turn 2 and 7 at the Glen. The replacement tranny was off my red car and does have lsd. I find my aero increases grip in the corners. I just don’t have the cojones to find out its limits. I found breaking at high speeds caused the rear to be a little squiggly with the the stock spoiler. Again good luck with your mods!

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[Cloud9...68]

Thanks - I didn't mean to sound like an a$$, but handling is something that everybody experiences, and is therefore a topic everyone has an opinion on, and there is great temptation to share these opinions even when all the facts are not known.  I'm sure I've been guilty of it myself.

 

Interesting about your tranny.  I have a Guard torque biasing diff, and while I'm the farthest thing from an expert on the subject, there is a school of thought that says a clutch-type LSD is more effective for track applications than the gear-type unit I have.  So, switching to an OS Giken to similar LSD is somewhere on my list, but it's pretty far down because of the cost, and hopefully Dale and I will be able to sort things out just by optimizing roll center heights, springs, sway bars, and shock calibration.

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[Waylander]

Sigh

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[Cloud9...68]

Sigh... 

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