Supercharging BMW, production with casting process modeling.

As the demand for shorter lead-times grows, the pressure is on metalcasting facilities to find ways to cut production startup times. Casting process modeling software is becoming a necessity for metalcasters who want to stay competitive, and Alphacast Software Ltd., Northampton, England, is meeting that demand with its Mavisflow software.

Crossroads Product Development, Salt Lake City, an engineering firm with a specialty in designing cast components, recently used Mavisflow casting process modeling in designing automotive castings for Eurosport High Performance, Salt Lake City, and its BMW supercharger project. The customer needed to install a 1.7-L displacement Opcon twin screw compressor and a Laminova three-core air-to-liquid intercooler into the same space currently inhabited by the naturally aspirated manifold of a BMW S50B30 3.0-L engine, meet or exceed the performance of the prototype, and minimize the number of components.

On the pressure side of the compressor, a manifold casting and intercooler mount casting had to be produced that met the space limitations of the design. On the suction side of the compressor, a casting had to be produced that positioned the throttle with respect to the compressor without compromising the traction control system or the position to an existing cold air inlet system.

Crossroads took 13 prototyped parts from Eurosport and redesigned them as seven castings: the inlet manifold, intercooler, intercooler end cap, intercooler outlet, throttle body adapter, nose support bracket and tail support bracket. Using airflow simulation software, the firm was able to model air flow through the throttle body to benchmark and compare different designs against the prototype design without having the physical prototype available for calibration. Mold flow and solidification simulation available through Mavisflow also allowed Crossroads to evaluate every mold design by looking at flow patterns and solidification progression.

In one step of the design process, Crossroads found isolated late freezing regions in the throttle body adapter. The firm changed the part to remove material from late freezing regions and added material to open up feed paths to remote regions (Fig. 1 and 2). Air flow simulations were re-run on the adapter to ensure the modifications to the geometry did not degrade the performance of the part below the benchmark level.

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Early simulations of the inlet manifold casting showed solidification issues in the areas of the part close to the gates and at the junction of the risers. Changes to the gate areas and risers moved the shrinkage problems out of the part.

Dies for all seven parts was constructed from February through October 2004. Three of the dies produced useable parts on the first shot. The manifold tooling was the only one that required additional work to fix a feeding problem, which the software had predicted but Crossroads had misinterpreted. Two other dies were modified to deal with air venting issues. Without casting process modeling, the procedure of proving the dies would have taken three times as long.

After the design was finished and produced, the customer tested the engine in a production car. On a 3.2-L engine, the production version gained an additional 17 hp over the prototype for a total of 365 rear wheel hp.

Select No. 001 at www.moderncasting.com/info

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