Technical Aspects

In an effort to lead the industry in standards of excellence for aftermarket components, APR has chosen to use some of the most cutting edge technologies available. These technologies are used in the design, testing, and production phases for many of their products. These processes in many cases give the products a distinctive edge over the competition.

Computer Aided Design, or CAD, is used extensively in the design process of many APR products. CAD allows APR to model parts in three dimensions and to optimize the model before the first part is made. It also makes it possible for APR to send model files to prototype manufacturers and production foundries via email. This greatly speeds up the time to market for complex parts and insures that the part is dimensionally accurate. Stress and strain analysis, as well as information such as part weight, center of mass, etc. can all be calculated using the three-dimensional CAD models before even a single prototype is made.

Laser scanning is another technology that APR uses to insure that products integrate perfectly with stock components. For example, the stock A4 1.8T exhaust manifold cylinder-head flange was scanned and converted into a CAD file. This CAD file served as the building block for the exhaust manifold incorporated in the Stage 3 & 3+ packages. Another item that was laser scanned for the Stage 3 kits was the turbine housing outlet flange surface.

Rapid prototyping is one of the most useful product development tools. Rapid prototyping is still a relatively new technology and has yet to see mainstream use in the aftermarket performance parts industry. This is sure to change in the future. When using rapid prototyping in conjunction with CAD, APR is able to convert a three-dimensional screen image into an actual part in a very short amount of time. These parts can be prototyped in a variety of plastics, urethanes, or metals. The typical timeframe from CAD file to prototype part in hand is three days. By working with rapid prototypes, APR is able to insure exact part alignment and a quicker time to market.

Rapid tooling is a close relative to rapid prototyping and uses many of the same technologies. Tooling is required for the production runs of all cast metal components and plastics. Conventional tooling usually involves machining the negative image of a part into aluminum or for sand cast parts, carving the actual part geometry out of wood to use as a pattern. This can be a very time consuming and expensive process. Rapid tooling uses more efficient methods to quickly produce the required tooling for production. Sand cast parts can be made by using part models produced with rapid prototyping, substituting the rapid prototyping piece for the wooden model. Epoxy tooling can be produced using rapid tooling for investment cast metals and for plastics and urethanes. For the aftermarket, rapid tooling is ideal: moderate cost, quick time to market, and exact dimensioning are just a few of the benefits.

Computational fluid dynamics, or CFD, is another technology APR uses in the product development process. With the Stage 3 and Stage 3+ 1.8T engine package, APR was faced with the difficult problem of combating the increased turbo lag that usually accompanies the transition from a smaller turbo to a larger one. By carefully studying the problem and with the use of CFD, APR was able to conquer this problem.

Tubular equal-length runners on exhaust can be excellent on high-RPM motors and race applications. In race applications, the RPM is high enough that turbo lag is not much of an issue because there is always enough exhaust gas energy to spin the turbine to make full boost. Also, because of the higher RPM operating range, the positive resonance effects of the equal-length runners will be realized (if properly designed).

APR's keys to a good street-performance oriented exhaust manifold for the 1.8T are twofold: 1) Keep the manifold volume as small as possible without constricting flow; and 2) Keep as much of the exhaust gas energy in the charge as possible (limit heat losses through the manifold walls). To perform 1), APR used smooth bend radii and DID NOT incorporate equal-length runners. For 2) they used a cast manifold with thick walls and used a high-quality alloy, Inconel 625, which has a heat conduction rate 1/4th that of conventional cast iron.

By using CFD analysis, APR was able to further optimize the design of the exhaust manifold. When a single turbocharger is fed the exhaust gases from more than three cylinders, the turbocharger will begin to experience pulse interference difficulties. This interference will affect low-end performance and increase turbo lag. For this reason, some turbochargers use dual-entry turbines that split the exhaust pulses between cylinders. The stock K03 turbocharger used on the 1.8T is small enough that turbo lag is not an issue. Turbo lag was a concern for the Stage III kit due to the larger turbocharger. Although APR did not have the option of using a dual-entry turbine for the 1.8T, they were able to reduce the pulse interference effect using the same basic principles.

The firing order of the 1.8T motor is 1-3-4-2. By interfacing the 1st and the 4th cylinder runners together and doing the same with the 3rd and the 2nd cylinder runners, APR was able to even out the pulses seen by the turbine wheel and improve turbo response. Using computational fluid dynamics, they were able to prove this theory. CFD demonstrated that the resulting runner pressures in the next-to-fire cylinders when one cylinder was exhausted were lower when using the paired runner design.

Although these technologies are not always the cheapest way to bring a product to market, it allows APR to produce products of the highest quality and with top performance. Next in line in terms of major engine performance kits will be the adaptation of the Stage 3 and Stage 3+ kits for the other 1.8T cars (TT, Turbo Beetle, Golf, Jetta, etc.) APR just took delivery of a 2000 1.8T Golf GTI GLS and the 1.8T New Beetle owned by AudiWorld's Neil McGarry is in Auburn getting the treatment. Stages 4 and beyond are being developed as well. APR is working on an RS4 killer kit for the 2.7T cars. This kit will push upwards of 450 horsepower through two dual-ball bearing turbochargers and will use many of the technologies described.

Special thanks go out to Brett Augsburger and the whole APR team for explaining and sharing their technology with AudiWorld readers.

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APR Tuned Pearl White 1997 A4

  • Stage III+: 305hp/310ft-lbs, Tuned ECU, APR Inconel exhaust manifold, GT25 twin ball bearing turbo charger, injectors, 2 1/2" mandrel bent Cat-Back stainless exhaust

  • APR lightweight flywheel and clutch

  • MOMO 1000 lakes race seats with TRW 6 point harnesses

  • MOMO aluminum pedal set and shifter

  • K&N filter

  • Front brakes: Alcon B-Type 4-piston calipers on 13"x 1.25" Coleman rotors, Pagid brake pads, braided stainless steel lines

  • Rear brakes: Alcon R-Type dual opposed-piston calipers on OEM 11" A4(front) rotors, Pagid brake pads, braided stainless steel lines

  • OZ F1 17x8 Wheels with Toyo Proxies RA1 225/45 17

  • Synthetic fluids for differentials and brakes

  • Vortrag coil-over suspension Spring rates 600 fonts / 650 rears

  • Vortrag vented fiberglass hood

  • APR claimed 0-60: under 5 seconds








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