61 replies to this topic

[Rap]

Don't they have sun deflectors that you put in the front windshield? I have never used one so I do not know the effectiveness of course.

[Blau]

4 miles is 15-20 minutes on a bicycle. Would that not work for you every other day? You can drive the car if you ever really need to....

[rxter]

I'm not a track guy by any means, so I can't discuss lap times. Neither do I have a clue as to the subtleties involved with various suspension set ups. Those threads are way over my head. What I can tell you is that Bob and I dropped the D1R chassis brace and lower brace into a low mileage cab. It corners so much flatter and hooks up so much faster that I am sure that those small changes would translate to reduced lap times. Probably a lot of tightening that you can do in your coupe.

[Cloud9...68]

Well, I've had time to digest all the great inputs to this thread, and to sleep on it a few nights, and have all but decided that I'm going to keep the car, and turn it into predominantly a track car. I guess as long as I keep the shiny side up, and the tires on the paved part of the track, the degree of abuse seen on the track isn't really a whole lot worse than what one can run into during the course of the daily commute.

As far as my getting to my vanpool pick-up point, I'm not interested in riding my bike. The drive from my house to the pick-up point is anything but bike-friendly, plus I need to carry my lunch back and my gym bag (we have a gym on-site at work that I use almost every day, so I really don't need the extra exercise from riding my bike). Plus there's the matter of my co-rider. So, the only reasonable solution is to drive the 968 on the days it's my turn to drive, and put a car cover on it during the five-month-long Central Texas summer. If I'm going to turn it into a track car, I will most likely add a plexiglass rear window anyway, which will take care of the hatch delamination issue.

Now, as far as my plans for the car, here are my thoughts:

1. Remove the clutch and flywheel, replace the rear main seal, install an 18 lb single-mass flywheel, and a new clutch. I've already started on this.
2. Pull the oil pan, replace the connecting rod bearings, obviously the pan gasket, and possibly add a windage tray. I'd also like to install a three-piece cross-member, to make future excursions into the oil pan drastically simpler.
3. The lower balance shaft seal is very acccessible with all stuff needed to get to the oil pan removed, so its replacement, normally a royal pain, is simple.
4. Re-seal the power steering pump and steering rack, and install and RS Barn rack tack
5. Install the D1R AC and power steering pump tensioner kits
6. Remove and rebuild the head, and obviously install a new head gasket, and new belts and variocam pads and chain
7. With all the stuff needed to remove the head out of the way, access to the tear in the firewall should be greatly improved. I know a guy at work who welds, so I'll invite him over to my house to fix the gash. By then, D1R's new "corrective" firewall brace will hopefully be availabe, and I'll go ahead and install it.
8. After consulting with all the experts, come up with the appropriate suspension mods (starting with coil-overs for sure), and install these, since much of the front suspension will be off to get to the oil pan.
9. Remove rear seats
10. Install the D1R chassis brace (if I can convince Flash to make one for me), harness bar, and harness.
11. Install lightweight racing seats (from what I hear, this may be the most difficult part of the entire project!)
12. Install RS Barn cat-back. Sure wish I could come up with some ways to take weight off the front; it's so much easier to take it off the back...
13. Remove passenger side airbag, and add a sports steering wheel

14+. I'm debating whether I should go ahead and pull the pistons, replace the rings, and install heavy-duty connecting rods. My hesistance is the apparent need to pull the crank to have it and the new rods balanced as a unit. Can the crank be removed without removing the engine? And if I do all this, I'll replace the main bearings as well. The rings and main bearings, however, are quite expensive, so I'm going to really have to think this one over. This may be the point where the slope gets a little too slippery...

Based on Craig and Flash's inputs, with the right set-up, I should be able to significantly lower my lap times below where they were when I left off. As I wear out my tires, and gain driving skill, I'll go to R-compound tires. Then, the next step will be the supercharger. Having been with my company since around 1890, I get a ton of vacation, so I'll be able to take enough to hopefully knock this formidable-looking list of items out in a reasonable amount of time. I sure look forward to getting back to the track - I've developed a terrible tick from the withdrawal that has resulted from being away for so long...

Edited by Cloud9...68, 04 February 2011 - 08:52 AM.

[flash]

sounds like a pretty decent plan

i recommend tinting the windows and using a windshield screen to keep heat out - that may eliminate the need for the cover

you can always move the battery to the rear, but since you have a hardtop, you will need to use a gel type battery to avoid outgassing - making this move transfers 35lbs from the front to the rear, which rebalances the car

as for the brace, in a couple of weeks i may be in a place to do one-off units - i won't be doing any more batches though, as it is just too complicated and time consuming

[Cloud9...68]

In Texas (as well as Arizona, where I lived before moving here - my next move will be to someplace cooler ), tinted windows are as necessary to survival as food and water, and my 968 is no exception, so I'm covered there. I'm more worried about the impact of the sun's UV rays on the paint, and of the heat on the rear hatch seal, but a car cover, which I already have, should take care of that. And it would only be every other working day; the rest of the time it will be comfortably stored in the garage.

I've thought about moving the battery to the trunk, although I'm waiting for the general availability of affordable lithium ion batteries to really cut down on the weight. I already have the smallest, lightest conventional battery I could find, since we don't have a whole lot of need for massive cold cranking amps around here, the current cold snap notwithstanding. I guess I could remove the AC, but that would really decimate the car's utility, and the supercharger isn't available with AC delete. Besides, the compressor sits nice and low.

The only other ways I can think of cutting weight out of the front of the car would be a lightweight hood, lightening of the front bumper as you have done, and a fixed headlight conversion. I know hoods are available, but the quality seems to be spotty, and we all know that fixed headlight conversions remain largely vaporware, and probably don't save a whole lot of weight, anyway. In the back weight savings is easy - removal of the spare tire, jack, and tools, a lightweight cat-back exhaust, and a plexiglass hatch easily take out over 80 pounds, conservatively.

Back to the primary topic of the thread, I have to say my decision to keep the car has been driven largely by the sense of community of this forum. Plus, I'm already so familiar with the car, that there's a certain amount of inertia involved with moving to something else. And there's just something very intangibly cool about owning a 968.

Edited by Cloud9...68, 04 February 2011 - 01:35 PM.

[StephenHallman]

Just make sure your car is consistently clean when putting on the cover. I'm sure you've heard the stories of scratches from dirty cars with covers. I think you'll be able to pull quite a bit of weight from the car while keeping many creature comforts. I would definitely think twice about removing the AC. Even here in Southern California I'm not sure I could live without the AC(yes I'm very fragile).

I hope the car brings you much happiness and meets all your needs. It's definitely unique enough to make you think twice about selling it.

[Cloud9...68]

In a way, all the work I've been doing to the car has kind of made me fall in love with it all over again. But I'm not sure I agree that pulling weight out of it is going to be easy. Once you get past the removal of the spare, the cat-back, lighter seats, plexiglass rear hatch, and single-mass flywheel, it starts getting harder, and more expensive, in a hurry. I'd love to see it around 2600 pounds, but I don't see how this is possible without some major sacrifices...

[craigawoodman]

Cloud,

Invest in a second set of rims (nothing flash - no pun intended) and a set of track tyres. Not sure how far it is to the track and back, but you could even do your daily 4 mile run on the tyres.

If the track is technical and only 0.7 milrs long, brakes might be an interesting option - I run the Big Blacks front along with a different biasing valve.

If the track is twisty, a LSD will help put the power down enormously. This will stop the inside wheel spinning up under hard cornering forces.

As you allude to, on this sort of track, power will not be everything, handling and balance will win out, so you need grip and balance.

So for an intial round of modifications, track tyres first and then a LSD to see the difference in lap times.

On a short track like this, track tyres might give you 1 sec a lap once warm and will wear much better over numerous laps.

Another good investment is a small car video camera. You can watch your corner entry and exit, if you have lots of road width left when exiting a corner, you can possibly carry more speed through it (as long as this does not hinder your entry into the next corner).

How much longer is the next track and what sort of car holds the lap record? If it does not have massive straights, then power will not be the issue. The only track where I lose out is Queensland Raceway, which has four long straights. I can carry the same or better corner speed, but get blown away in a straight line (hence the desire for more power).

Remember, brakes can generate around 1,000hp, but engines cannot. So there is a lot of time to be made under braking. Also for power - as speeds get over 100km/h aero efficiency or drag is the most important issue and drag increases by the cube of velocity - so it is a losing game chasing extra power at high speeds - the ultimate gains are minimal. If you double your power - you do not halve your lap time - you might take seconds off.

Keep the car, buy a cheap set of rims and track tyres (mine were second hand and I did not get a new set of tyres for a year - they took at least another 1 sec a lap off as they were gripier). One run through a gravel track and your rims will be looking slightly second hand anyway.

I personally think that the wheel spacers help with cornering speed (larger track - higher G's). So if you can push your wheels to the extremities of the guards it will also help.

When looking for new rims/tyres, possibly larger tyres will also help (I am running 285's on the rear and with the Supercharger may look at reducing the spacers and running 305's.

What is extremely rewarding is posting a lap time that no-one thinks the car is capable of, regardless of power output, etc.

Sorry - a race seat and harness will also add confidence as the driver will not be moving around as much.

[craigawoodman]

Cloud,

On the weight front, if you take all of the seats out and carpets, there has to be more than 100kg (220lbs) simply in that. The front power seats are very heavy. Then there are speakers, sound deadening, etc which can also come out. As per previous posts, there was the 968 which was set-up for tarmac rallying over here which weighed 1,200kg (2,600) with a full roll cage installed. I believe that there was also a list of what weight had been removed from the car (down to 10's of grams). Not sure if I can find the owner and see if he has it, but the guy who built it was obsessive about weight reduction. I don't think that this car had a lightweight hatch or windows, etc.

My car weighs 1,358kg with fuel. This still has all of the carpets and passenger seat, rear seats, etc in place.

Craig

[Cloud9...68]

Craig,

As usual thanks for the inputs. Yes, I was thinking of exactly what you're suggesting: finding a set of cheap, as light as possible (or are these two things mutually exclusive?) rims, and putting on a set of track tires. Would you prioritize this over more track-oriented springs and struts/shocks? My car has a great ride/handling trade-off for the street, but on the track, to be honest, it feels a little mushy, and it sways quite a bit, especially in left-right-left transitions, even though it has the M030 sway bars. I don't mind sacrificing the street ride, as the roads in my town are generally quite smooth.

The track I'm going to do most of my driving on is progressive. The beginner section, which I've technically already graduated from, is flat, twisty, and 0.7 miles. The intermediate section is something like 1.3 miles, and adds significant elevation changes and blind turns to the beginner course, but still doesn't have any long straights. The advanced course is 2.2 miles long, with a couple of long straights added to the back. I'm afraid I don't know what type of car holds the lap record on the intermediate course - I'll have to find out.

I think I'm OK in the brake department. I have enormous 4-piston calipers from an '88 944 Turbo S, Zimmerman cross-drilled rotors, and a Turbo Cup brake bias valve from RS Barn. And I already have wheel spacers as well.

As far as the LSD, the previous owner installed a Guard torque biasing differential, which isn't actually an LSD, and I really have to read up on how it works. I guess you could call it "LSD lite." A real track-oriented LSD seems to be quite expensive (judging by the $2000 OS Super-Lock unit RS Barn sells). Do you think the incremental improvement over my Guard unit justifies the expense? Is there one you recommend that's a little more affordable than the OS Super-Lock? And again, would you prioritize a proper LSD over better springs and shocks/struts?

Great idea about the in-car video camera. I'll have to mount one to the harness bar of the chassis brace I'm going to buy from Flash

Edited by Cloud9...68, 04 February 2011 - 05:14 PM.

[flash]

rims - the hollow thin spoke 18" 996 rims are pretty light, relatively easy to find, and are not terribly expensive - they come in a 10 and 8 that fit right up

lsd - the guards unit should do fine for quite a while - eventually you may want ot change to the new unit that is out there, but i would put this down lower on the list for a while, and definitely way down below shocks and springs and such

seats - YES! - i dropped nearly 50lbs and i didn't even go with a superlight race seat - if i did, i could have lost another 20lbs

[Cloud9...68]

Flash,

Thanks for the input. I agree that springs and shocks should be a fairly high priority. It could definitely use some firming up.

In addition, since I'm yanking the clutch and flywheel, primarily to replace my leaking rear main seal, I'm going to go ahead and replace the DMF with the 18 lb. SMF that RS Barn carries - this should provide a little more pep. I just got the clutch out tonight - the disk is definitely worn, but it doesn't look as bad as you might expect after 115,000 miles. The flywheel, though, has a bit of grooving. Next step is to get my hands on a Snap-On 12 mm triple square stubby socket, and get the flywheel out of there.

[timbits]

I'm about to do the pressure plate\clutch\flywheel job myself and the last thing I need to get are the triple square sockets for the bolt. I've never worked in there but Erics write-up warns to get a high quality and short driver for the bolts. Looking in Snap-On's catalog their normal line doesn't have stubby triple square drivers, though their Blue Point does. Though I don't know how much of a quality drop there is with the Blue Point drivers.

All this to say that if you find the triple square drivers that are short enough to use and don't cause any issues getting the bolts out I'd love to hear it.

[craigawoodman]

Cloud,

If you have some form of LSD - then that should be fine for now. Everything is incremental - your diff will be better than an open diff and there will most likely not be as much of a gain going to a better diff.

Seats will remove lots of weight. The genuine Porsche powered seat would make a great anchor - they are heavy. A harness will give you more confidence as you will not be rolling around in the car as much. Race seat though are a pain to get into and out of the car with.

Don't forget stainless steel brake hoses and a racing brake fluid. You could then look at better brake pads as well to improve stopping performance. The brake fluid needs to be changed at least every 12 months.

Like you, we need AC - it is too hot to be without it over here.

I find the larger than M030 sway bars help keep the car flat through corners. The original standard suspension had the car leaning everrywhere.

Airbox mod and chip will also be a benefit.

Some retail therapy searching for the next modification will do you wonders.

Keep us updated on how it all progresses.

Craig

[Cloud9...68]

Timbits,

I found what appears to be the perfect tool to remove the flywheel bolts in the Snap-On online catalog: It's a stubby, 12 mm, 1/2" drive triple square driver, part number STSM12SE, and it sells for $27.50. It's a little over 2" long (59.4 mm), but there's about 3.5" between the heads of the bolts and the tip of the front driveshaft, so hopefully there will be room for the driver with the breaker bar. There isn't a picture of the individual 12 mm driver, but here's the description of a five-piece set, with a picture:
Snap-On triple-square driver

Interestingly, the catalog lists another on, part number STSM12SE(2), which is only $10, but is has a much shorter description. If there's any question about the quality, I'll definitely go with the more expensive one.

Others have mentioned buying tools for this job that they had to cut down. I would like to avoid that at all costs. Does anybody have any other recommendations for a tool to remove the flywheel bolts?

Edited by Cloud9...68, 05 February 2011 - 06:45 AM.

[timbits]

That looks perfect Cloud9...68, thanks for the tip I had completely missed that on their site

Their online catalog leaves a lot to be desired but from what I've deduced the $10 versions are just the bit with out the socket driver end. Take a look at the triple square drivers for 3/8" and there's some that show the pictures.

[Cloud9...68]

No problem. I think we should move this to a different thread, as I'm interested in comparing notes on the clutch/flywheel/rear main seal replacement. In the DIY section, Eric K has a great write-up of the job which I've been following. I've gotten the pressure plate out, but now I need to flag down a Snap-On rep to get the triple-square driver. I think we should continue the discussion of this job in Eric's thread. Thanks, and best of luck with the job.

Edited by Cloud9...68, 05 February 2011 - 08:24 AM.

[craigawoodman]

Cloud ? Flash,

The RH drive 968's have the battery located in the LH side rear side pod at the back of the car as standard. Mine is a regular lead acid battery sitting back there.

Try as I might, I cannot get my hand past the battery tray to install the LH side recovery plates.

Craig

[flash]

yeah - i knew the cabs had it back there, but didn't know about the hardtops - was that OEM?

recovery plates?

surprised to hear about the lead acid battery - was that OEM?


i put mine it the right hand pocket area, knowing full well about he left, but i wanted to balance the car - i did use the ground point on the left though - i made a saddle for it, suspended it like the boat anchor was suspended, and then cabled it forward