Constructing a turbo kit for a specific vehicle involves carefully selecting the right combination of custom and off-the-shelf components and combining them together in a way that balances performance, cost, and packaging. One-off turbocharger conversions are relatively easy, however designing a turbocharger kit that must be consistently replicated many times over in an economic fashion, is much more challenging. Luckily, that is what Radium Engineering excels at.
Here at Radium Engineering, our Lotus Elise/Exige turbocharger kit has been in development for over 1 year. Why so long? We have had our protoype turbocharger kit up and running since July 2010, however, moving parts into production takes a long time. This article outlines an example of the development that went into a single component of the turbocharger kit, the downpipe elbow. Now multiply that procedure many times over for all different custom designed components in the turbocharger kit and you can see the amount of time adds up quickly.
The downpipe elbow attaches to the exhaust outlet of the turbine side of the turbocharger. It is the piece that channels exhaust gasses exiting the turbocharger into the exhaust/muffler system. This part sees extremely high temperatures and must be designed to withstand them without warping, cracking, or degrading in any way.
We decided very early on that this piece would best be cast out of stainless steel due to its anticipated complex shape.
However, tooling required to produce a casting is very expensive and we were not going to make that investment without positive testing to back up the concept. Additionally, if we were going to make this large investment, we wanted this part to work on several different turbochargers without modification.
This is a behind the scenes look into what went into designing and producing the Radium Engineering downpipe elbow:
The first step in the process is to hand fabricate a pipe from stainless steel tube using off the shelf flanges and mandrel bends. This part is used to verify the performance and serve as a jig for measuring fitment of the elbow. The part shown here is ceramic coated. Notice how it transitions from bell mouth to 3" round.
Once the performance is verified, the hand fabricated part is measured with our FARO arm. This device accurately measures the part to within 0.005 inches in 3D space and creates exact data in Solidworks which serves as the foundation for the CAD model.
Based on the 3D data from the FARO arm, a 3D CAD model is created with Solidworks. With investment casting chosen as the maunfacturing process, much freedom in the shape of the part was allowed. Investment casting does not require draft or a parting line like other less expensive casting methods such as sand casting. The CAD model is fine tuned and all detail is added to ensure the best fitment possible.
After the CAD model is approved, we have a 3D print made. While there are many technologies for producing rapid prototypes, we choose FDM (fused deposition modeling) because of it's low cost and high level of accuracy. We simply export a CAD file and a few hours later, we have a plastic prototype in our hands.
The plastic prototype is used to test fit components and ensure all geometry is correct.
The plastic prototype is also bolted in place and everything is checked. We pay close attention to fitment as well as clearance from adjacent components and tool access to fasteners for servicing.
Most of the time, we find details to change on the prototype, so we go back to the CAD model and make adjustments and have another rapid prototype made. This iterative process can cycle many times until we have achieved the best design possible.
Once the design is locked down, manufacturing drawings are created. These drawings must clearly communicate to the vendor exactly what we want. The 3D CAD model and 2D prints are then sent to our casting company. Over the years of working in the industry we have been fortunate to find some of the very best in the business to work with.
We often request feedback from our vendors on new designs. This is useful for finding ways to reduce cost without sacrificing the form or function of the part. Once the design and drawings are locked, the PO is sent. Then we wait....
Months and months later, we finally receive the first article sample parts we have been anticipating.
The cast downpipe elbow is investment cast out of 347 stainless steel.
The first thing to do is to check the final part and make sure it matches the CAD model within the tolerances specified. This is done with the FARO arm.
Using a process like this, while tedious and time consuming up front, pays dividends when the final part is test fit. Perfect fitment is achieved on the first part revision. If there were any fitment or design issues, changes to casting tools can be very expensive and they add weeks and/or months to the project.
The downpipe elbow is an integral part in the turbocharger/manifold system.
These components are all standard in our Lotus Elise/Exige turbo kit.
Here the progression from prototype to production piece is clearly shown.
WIth the recent arrival of our cast downpipe elbows, we are now in the final phases of releasing our Lotus Elise/Exige turbocharger kit for sale. Please check back for pricing updates.