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Description: The main point is that there is no iteration involved, unlike traditional alignment methods which depend on measuring, adjusting, and measuring again. This approach can be problematic for DIYers, as it often requires expensive tools or necessitates re-adjusting the suspension after each change. The goal is to bypass this iterative process by modeling all significant geometric aspects of the suspension and measurement process, allowing for calculated adjustments that account for their interactions. A spreadsheet has been created that contains key suspension geometry factors for the Porsche 996 and addresses various issues encountered during measurement. For instance, when measuring toe, the laser beam should ideally be perfectly horizontal, but it was instead directed slightly downward to hit a tape measure on the ground, which significantly affects the measurement. Caution is advised when using this method, as accurate suspension setup and measurement adherence are crucial. The spreadsheet is a Google Docs resource available for non-commercial use under a Creative Commons license, with plans for updates based on user experiences. Geometry adjustments should only be made with a thorough understanding of the spreadsheet and suspension geometry. The process involves entering measurements in centimeters, with conversion from inches as needed, and adjustments for camber and toe angles are calculated automatically. The alignment setup requires minimal input, and once measurements are entered, the required adjustments are displayed. The process is detailed for both front and rear wheels, ensuring accurate alignment for each.

Measuring toe is critical in alignment, especially for finely tuned vehicles like Porsches, where precise specifications are essential for tire wear and handling. The alignment specifications for the 996 model indicate a toe-in of 5 minutes, which translates to a very small angular measurement. Achieving this precision requires careful setup and measurement techniques, including the use of lasers for accuracy. The methodology involves determining the car's centerline and ensuring each wheel is measured individually against it, rather than comparing one wheel to another. To ensure the required accuracy, a tape measure is used in conjunction with a laser to gauge the distances accurately. The spreadsheet aids in calculating adjustments needed, simplifying the alignment process while maintaining precision. The adjustments for camber and toe are detailed, with clear instructions on how to interpret the results and make the necessary changes. This systematic approach allows for effective alignment without the need for iterative measuring and adjusting, streamlining the process for DIY enthusiasts.The key point is that there is no iteration as is usually done. All alignment methods I have seen rely on measuring, tweaking, measuring, tweaking, etc. There are many problems with this: for the DIYer it means expensive tools or settling the suspension after each adjustment. My thought was to completely short circuit all of that and find a way to do this procedure without any iteration. The only way to achieve this is to model all the important geometric details of the suspension and the measurement process, and then calculate the adjustments including all the interactions between them. This is what I have tried to do in the spreadsheet which I`ll provide a link to in a moment. The spreadsheet contains all the key suspension geometry factors for the Porsche 996, and compensates for a number of other issues.

For example, when measuring the toe in Part 4, we should have measured it with the laser beam perfectly horizontal. But we didn`t, we measured it with the beam pointing down a bit to hit a tape measure lying on the ground.

Is this is a big factor YES! When dealing with toe of a few minutes of arc (5 minutes for Porsche specs), and a camber angle in the 1-2 degree range (12-24 times the toe angle), even a small deviation from horizontal affects the measured toe angle by much more than the toe angle itself. I must warn anyone using this method that although I have spent a considerable amount of time testing and improving the spreadsheet on my own 996, and it seems to work well, but only if the suspension setup and measurements in earlier parts are rigorously followed!

I was having trouble getting my toe to come in where it should be (the steering wheel was pointed just slightly off center when going straight). Finally I discovered ” after not following my own advice ” a loose bolt holding one side of the rear diagonal suspension brace, probably from the mechanic not having torqued it after dropping the transmission for the IMS bearing replacement 6 months ago (this is when I bought the car and the IMS issue was found in the pre-purchase inspection).

Here is the 996 alignment spreadsheet. It is a Google Docs spreadsheet. It is free for anyone to use for non-commercial purposes, licensed under a straightforward Creative Commons license. You are free to view the original and copy it and modify it as long as its origin is appropriately attributed by maintaining the license notice.

I will be updating the spreadsheet based on my own and others` experiences with it. There are still a few minor geometry effects I want to do a little bit better, so it will be changing. I will track the version number on the spreadsheet. Geometry, both of the suspension and the unchanging parts of the measurement setup. This section should not be changed without thorough understanding of how the spreadsheet and the suspension geometry works.

Proceed through the spreadsheet from top to bottom as you work through the steps in the process. Adjustment calculations are always immediate, but will not be correct until you have filled in the blue cells with the correct data from the previous steps. The front and rear wheel alignments are independent of each other so the spreadsheet will be gone through once for the front wheels and once for the rear wheels.

For the first set of wheels, half of the entries will be meaningless, but they will be filled in later. Please note that all distances are entered in cm (centimeters). This was very convenient for me just because my tape measure had an easily read cm scale on it. I`m sorry but you will have to enter all your measurements in cm also. To convert from inches to cm, just multiply your measurements by 2. 54. You can enter different values than I have in the Target section. My Targets are for a slightly aggressive street alignment for a normal 996 (not GT3) with the X74 suspension.

Refer to the alignment specs appropriate to your car and modify the target values as needed. Distance from the laser level`s laser hole to the tape measure lying on the ground either in front of or behind the wheel when you made the toe measurements We will first enter the distance to the tape measure in the Alignment Setup section, then enter the other four measurements in the Measurements and Adjustments section. Once the measurements for a wheel are entered, all the adjustments required for that wheel are calculated and displayed.

We will then take out the wrenches and get to work, described in Part 7 (rear wheels) and Part 6 (front wheels). The Alignment Setup section has only two numbers to fill in. These are the distances from the laser level`s laser hole to the tape measure when it was lying on the ground with its end at the car`s centerline and the laser dot shining on it.

One number is for the front wheel measurement, and the other for the rear. I assume that the distances are the same for right and left; if not you may need to enter values separately for the left and right. But the precise value of this distance is not so critical; if you are within 1-2% it is totally fine.

Notice that I measured this distance by putting the tape measure behind the wheels, with the laser shining backwards. For me the rear wheels got in the way of the laser beam from the front wheels so the furthest back I could go was the rear wheel itself.

The Target section lets you fill in what you want the alignment angles (camber and toe) to be when you are done. Refer to the alignment specifications, a copy of which is here: Laser Spot on Tape Measure, from Part 4.

Remember that there were two separate measurements made, flipping the laser level over between them. The average of those two measurements must be entered here. Once the three measurements are entered for each front wheel, all the red cells for that wheel show the adjustments that must be made to bring the wheel into alignment. Even though there are four red cells per front wheel, there are only two adjustments ” don`t panic! The three adjustments in the Toe  row are actually all the same thing, just different ways of looking at it.

The camber adjustment is done by moving the top of the strut either in or out. The red cell for camber adjustment tells how far the top of the strut needs to move. Again, a positive movement is toward the outside of the car, and a negative adjustment is toward the inside of the car. The toe adjustment is done by rotating the steering tie rod against the tie rod end that connects to the front wheel.

The leftmost red toe cell labeled Adjust, mm  tells how much the tie rod end needs to move; again positive is toward the outside of the car (resulting in more negative toe, an unfortunate confusion in signs) and negative is toward the inside of the car (resulting in more positive toe). But an adjustment in mm is hard to judge in this case. Much easier is using the thread of the tie rod and tie rod end themselves to help us measure the adjustment.

This thread is a 1. 5 mm thread, in other words for one full turn of the tie rod, it moves 1. 5 mm against the tie rod end. That is what the second red toe cell labeled Adjust, turns  says. If it says 0. 5, then the tie rod end must be pushed out by 0. 5 turns of the tie rod thread. In my experience, since these adjustments are generally quite small, an even more convenient way to measure the adjustment is in 1/6s of a turn. This is how much the tie rod turns when it is turned so that one of its adjustment faces that you place the wrench on goes around enough so the next face takes its place.

This is very easy to judge when working underneath the car and have only a limited range of movement of the wrench. It is easy to know when you have turned the tie rod 1/6 of a turn. That is what the last red toe cell labeled Adjust, 1/6 turns  says. After entering measurements in the three cells for each rear wheel, two red cells are calculated with camber and toe adjustments required to bring the wheel into alignment.

These adjustments are in mm that the appropriate control rod needs to move. Part 7 shows how to do this with high accuracy. This schematic is (obviously) hand drawn based on reverse engineering the circuit board. It shows only the key parts (active signal path) of the right channel, but it`s most of the components of the channel. Input switching and RC network is not shown, and most supply bypass caps are not shown (there aren`t many).

All elements of the signal path are shown. While a few sources found in web searches indicate that the SE240 ²s circuit is similar to the DH220 kit, which has schematics easily available, it is only partly so. There are quite a few important differences, such as an all-FET input stage with cascode isolation, thermal sensing, input stage switching to support bridged mode operation, and no speaker fuse.

I drew this schematic to diagnose a massive overheating problem which appeared to be due to uncontrolled oscillations (the 10 ohm 5 watt resistor in the speaker output path was smoked). I thought the cause would be a cap in the feedback loop having gone bad, causing loop gain at 180 degree phase to be above 1.

In the end, it wasn`t any such cause; it appears that simply having disconnected the power connector and the fuses restored the amp to perfect working order, and it sounds fabulous again. All FET input stage: MOSFET to drive the positive rail, JFET to drive the negative rail. Unfortunately specs for the MOSFETs (2SK163) appear to be impossible to find. Adjust the bias pot so the ammeter reads 200 mA (I am guessing at this value; I`ve seen people describe settings between 150 and nearly 300 mA).

At 200 mA the amp dissipates 26 watts in quiescent mode, which gets it nice and warm but not hot. I also ordered a set of replacement capacitors for the signal path and bypass caps from Mouser Electronics where I was pleasantly surprised to find all items in stock and at quite good prices, even including Nichicon capacitors. Note the original capacitors are polycarbonate film which is for all practical purposes no longer available (discontinued in 2000), and a good replacement for audio applications is polypropylene film.

The complete set cost under $30 including shipping. Measuring toe is one of the critical steps of an alignment method. Especially with Porsche or other cars that are finely tuned and have wide tires, toe measurement and alignment have big impacts on tire wear as well as handling. 996 alignment toe specs are 5 minutes toe in, +/- 5 minutes. A minute is 1/60 of a degree, so 5 minutes is 1/12 of a degree. Across an 18 ³ wheel rim, 5 minutes is 0. 7 mm, or about 1/32 of an inch. And that is the total allowed variation; we`d like to get closer than that. Imagine placing two tennis balls on the ground at the fence at one end of a tennis court. Now walk all the way to the fence at the other end of the court and look back at the two balls. Place a Porsche wheel at your feet and line it up so that it points right between the two balls. Now you must also confirm that it is not pointing any further away from this angle than the width of one of the balls.

The two balls together is the total range of angle we need to get our toe within, and we should try to hit the center between the balls as best we can. And we have to do this for all four wheels. This is a difficult task whether using strings, lasers, or other tools. It is certainly not possible to do this with the unaided eye. How can we possibly do this with the simple tools available to us We will break the problem down into two parts and use some math (which the spreadsheet does).

First, we are going to spend some time accurately finding the center line of the car. This is one of the key steps in the procedure. Then we will use a laser in line mode  to mark the center line so that it is very easy and accurate to find wherever we are working. Second, we will work on each wheel one at a time and make measurements against the car`s center line.

We will not be comparing one wheel to another, because if we do a good job with each wheel against the car`s center line, then accurate alignment wheel to wheel is a natural result. It`s always good to do a little sanity check. Can we really achieve a 5 minute accuracy We will place a tape measure with its end at the car center line.

We are going to shine a thin pencil of laser light onto the tape measure and read the distance. How much measurement slop can we tolerate and still be well within the 5 minute requirement If we are able to place the tape measure 2 meters away from the wheel we are measuring, 5 minutes of arc shows up at the tape measure as a distance of 2. 9 mm. This is not a lot but it is fairly easy to read on a tape measure. If possible it would be good to place the tape measure further away. If w the adjustment.