So you have a 924S or 944, and you want to make it into a part-time track car for autocross or HPDE, but still want to keep it street legal that you can use on weekends. How to proceed?
The problem is simple – an all-out race car isn’t practical for street use, but you want more than stock. While the decisions that you make can be personal and based in a lot of situations, there are some basic things to consider. Here are some things to think about.
This topic is something about which people have very strong opinions. This is not a guide of requirements for your track car/street car, but instead a listing of things to consider. From these you should make a list of upgrades and equipment that will get you to your goal in the smartest, most economical way.
SAFETY
HELMET: Autocross and HPDE require helmets. Proper fit is vital, so getting a helmet that fits comfortably for you is very personal. One brand XL will fit differently than another brand XL. Buying online may not be the best idea. Get properly fitted. - Make sure you get an SA HELMET, not an M (Motorcycle) helmet. Check the rules association with the track and sponsor to ensure that your helmet meets the criteria.
- HANS: We don’t like being in a car on track without a HANS, especially in HPDE. That means the purchase of a piece of equipment. There are stand-alone “Hybrid” HANS that you wear around your body that makes it okay to use with three-point belts, and the original kind that use the shoulder belts.
- BELTS: If you use the stock three-point belts, consider replacing them with new. Old belts can deteriorate and stretch with time, and the tensioner mechanisms can wear out. If you use multi-point belts (5, 6 and 7 point), you will need proper anchoring and seats. Again, for HPDE we prefer multi-point belts with either full cage or four-point roll bar. A good harness bar is okay, especially with autocross, but there are lots of pros and cons about using a harness bar.
- COMPLETE SAFETY SYSTEM: If you are going to use a harness, make sure you go for the “complete safety system” that includes 5-6 point harnesses, the proper seats with properly positioned holes for the shoulder and lap belts, a HANS device and a roll bar, all properly and securely mounted according to the manufacturer’s instructions. If a piece of “safety equipment” carries a disclaimer that it is “not to be used in racing,” then don’t use it in HPDE. It’s not safe. (We see this in a few ads for Miata “show bars” that are chrome roll bar-looking things that are not structurally sound enough to actually act as a roll bar!)
ENGINE
- With any track car, reliability should be the primary focus. You don’t want to get to the track and have the engine get sick after the first session. So PREVENTIVE MAINTENANCE is at the top of the list. Belts, rollers, water pump, fluids, ignition parts, plugs, wires – all should be fresh and new. Remember that trying to eek out that extra four or five horsepower is normally done at the mercy of reliability.
- Upgrades that do not normally effect reliability include using a higher compression stock engine (10.2/1 pistons, 1988), an upgraded cam, and opening up the exhaust a bit. Many tracks have sound level limits and they regularly check levels with a DB meter. Make sure you stay within the limits.
TRANSMISSION
- Finding and installing a LIMITED SLIP DIFFERENTIAL is a great upgrade, but can get pricy. On the track, an open differential will put the power to the wheel with the least amount of grip. So when you are accelerating out of a turn, the inside wheel with the least amount of weight on it will get the power. The LSD will put nearly equal power to both wheels, allowing you to power out of the turn. It is a noticeable difference.
- There is a lot of talk about installing a “short fifth gear” from a 924S gearbox. For most HPDE tracks, you may never get to fifth gear. It is an expensive upgrade that may not be worth it.
- CV AXLES can fail due to inadequate lubrication and just wear. Track and autocross driving put a lot of stress on them. Also retorque the CV bolts as they have been known to loosen and back out on track. (Don’t ask how I know about that one.). Also beware of cheap aftermarket CV axles that may break with track use.
- SHORT SHIFT KITS like the ones available from Only944.com are good. Make sure you get used to it before shifting hard on track so you don’t miss the 2-3 shift and go back to 1st gear. They also have an upgraded shifter that takes the slop out of the stock shift mechanism.
BRAKES
STOCK CALIPERS. AND ROTORS are normally good enough for track use with the RIGHT PADS. What are the right pads? That is a matter of opinion, including driving style, temperatures, and even the track that you are driving. Just don’t go cheap on the pads – get good ones. Rotors are also a source of controversy – for HPDE, we use normal, inexpensive rotors and replace them when needed.- BRAKE FLUID must be changed often. Brake fluid attracts moisture which lowers its boiling point can causes brake failure. We change brake fluid after every third event – probably excessive, but its a quick, cheap fix that gives us peace of mind. And don’t forget to bleed the clutch at the same time you are changing fluid.
SUSPENSION/STEERING
- Front POLYURETHANE/DELRIN BUSHINGS are a great addition to the suspension, even if you only do the front. When preparing a car for track use, the bushing may be the original rubber bushings that are dead after thirty-plus years. Replacing them with plastic stiffens the front suspension and makes if more positive.
- Rear POLYURETHANE/DELRIN BUSHINGS are also a great addition, but can be a little more difficult to install.
- POLYURETHANE/DELRIN BUSHINGS holding the steering rack in place are also a great addition. Again, old rubber bushings can allow the rack to move around under the torments of a track day.
DE-POWER THE STEERING RACK can get rid of the leaky power steering. Some will change over to an early 944 manual rack, but many like the quicker ratio of the power rack, so de-powering the power rack may be more desirable. Instructions to de-power the rack can be found online.- SWAY BAR replacement with larger adjustable sway bars is a good upgrade for the track. Clarks Garage has a nice chart showing what size sway bars came with what different models.
- FRONT COIL OVERS are an effective and inexpensive upgrade with the proper springs allows you to set ride height – and lower your car. We tend to go softer than most for HPDE/Autocross setups at 250 pound front springs, augmented by larger sway bars.
- A STRUT BAR and SOLID/ADJUSTABLE STRUT MOUNTS keep the tops of the struts in place.
- UPGRADED SHOCKS are a must. Koni Sport adjustable shocks are the choice of many. Adjustments on the rear shocks are a little more difficult, but we set our rears a little stiffer than center. We then make the adjustments on the front shocks to dial it in.
- LOWER THE RIDE HEIGHT: Lowering the car improves handling. The rear can be lowered about 3/4″/20mm by adjusting the trailing arm plates, while the front coil overs will take care of the front.
TIRES AND WHEELS
- Of course, wider tires and wheels are a must. CHOICE OF TIRES is a personal preference thing coupled with the thickness of your wallet. Pay attention to the tire wear rating, which is a number between 0 and as high as 800. (See the article here on how to read your tires.) The higher the number, the harder the compound. A tire with a rating of 600 will not perform on the track as well as a tire rated at 200.
WHEELS are again a personal preference thing. We find, for example, that the addition of 16″ 944 late offset wheels on our 924S cars really improves handling and feel. We have mounted 16″ x 7″ front and 8″ rear on our 924S street cars, with 205/55-16’s on the front and 225/50-16 on the rear. This maintains the same diameter front and rear and also fits them under the fender quite nicely – no modification. We also like to stay with Porsche wheels as some of the aftermarket wheels have not been up to the rigors of track work.- RACE TIRES/SLICKS are not necessary unless you are very experienced. Save the expense and stick with treaded 200-rated tires until you get really good.
Our advice is simple – even the most stock 944 is a better can than most new HPDE students. Suspension is more important than engine, and sticky tires with no suspension upgrades is silly. Safety, including brakes and safety equipment, are at the top of the list. Reliability is also paramount in this discussion.
As you gain seat time, make improvements to the car that match the improvements in the driver. Remember that if you are going to use the car on a daily basis, don’t do things that will “improve” the car for the track to the detriment of daily driving.
Be aware of the rules for the groups with which you will be driving, including things like sound regulations and required safety equipment. Comply with pre-event safety checks by qualified mechanics, and prepare you car well in advance to ensure that you have a fun and productive weekend at the track.
