The OEM rubber boot connecting the runner to the cylinder head port.
Isolates the runners from thermal and vibrational effects from the engine, which is why CR26I mounted the plenum to the OEM boots rather than making a rigid connection.
No part-specific design process is documented. The Manifolds subsystem design process applies: 1. Build the engine model in GT Suite from measured geometry: silicone-cast and 3D-scanned intake ports, dial-indicator-measured cam lobe profiles, MTS-measured valve spring curves. 2. Use GEM3D to convert manifold CAD into GT Suite flow geometry, which cut manifold setup from several hours to about 30 minutes and let subassemblies be swapped for fast comparison. 3. Sweep plenum volume, runner length and primary length in the model against volumetric efficiency. 4. Confirm on the flow bench. CR26I plenum flowed 2.34% more than CR25 and 11.15% more than CR22 on average across 10-50 in-H2O, with testing extended to 70 in-H2O (17.4 kPa) to reach WOT conditions. 5. Prototype-test the muffler on the previous car before finalising, sweeping length (14 in and 16 in), packing density, tailpipe diameter (2 in and 1.5 in) and a diffuser-style tip against the sound limits.
Laid up on a 3D printed mold, printed directly, or formed from sheet.
OEM rubber. From the cost report drawings and CAD: From the cost report drawings: 6061 Aluminum (CR26i AL Runner Boot); Rubber (OEM Runner Boot).
The OEM boot exists to isolate the runners from engine thermal and vibrational input. That matters because CR22's runners cracked at the base (Fault Vault, 2023-07-27) with high EGTs at idle, and softer rubber isolation was one of the three candidate fixes.
292 g for the set. From the cost report drawings and CAD: CAD mass, CR22 master assembly: 0.176 lb (0.080 kg), 4 instances, 0.704 lb total. CG at X 68.87 in, Y -0.44 in, Z 17.90 in in vehicle coordinates. Dimensions called out on the cost report drawings. These are the figures printed on the drawing, not a labelled specification; open the drawing itself for what each one refers to. Runner Boot (as drawn): 4.88, 5.06, 8.65, 4.63, 2.03, 0.76, 4.33, TRUE 2.22 Runner Boot (as drawn): 4.84, 1.13, 8.60 CR26i AL Runner Boot (as drawn): 53.21, 5.32, 95.25, 9.53, 19.05, 1.91, 40.13, 4.01 OEM Runner Boot (as drawn): 85.96, 8.60, 6.32, 0.63, 22.81, R2.28, 73.29, 7.33, 23.68, 2.37 Source: SolidWorks mass model exports: CR22 (5 May 2024), CR25 (4 Jul 2025), CR26I (30 Jul 2025), CR26E (22 Mar 2026) | Cost report drawings: CR22/Powertrain/Design/X - Cost Report Drawings/Manifolds/Intake/Runner Boot.pdf; CR25/Powertrain/Design/Y - Cost Report Drawings/Manifolds/Intake/Runner Boot.pdf; CR26i/Powertrain - IC/Design/Y - Cost Report Drawings/Manifolds/Intake/CR26i AL Runner Boot.pdf; CR26i/Powertrain - IC/Design/Y - Cost Report Drawings/Manifolds/Intake/OEM Runner Boot.pdf and 4 more Quantity per car, as costed: 4
Nothing in CrimsonStorage covers these yet.