Meet the mandatory 20 mm intake restriction while recovering as much pressure as possible downstream of the throat.
A converging-diverging duct. The throat chokes at 20 mm, capping mass flow; the diffuser downstream recovers static pressure so the plenum sees as high a pressure as possible. Diffuser length and half angle set how much of the dynamic pressure is recovered before the flow separates.
Analysis is required on diffuser length and its effect on pressure recovery, and on varying throat geometry and location along the duct, with results comparing hand calculations, CFD and flow bench. CR26I: 9.61 in long, 4.356 degree half angle, expansion ratio 0.362 in^2/in, expansion rate 2.315, with a modified inlet for a smoother transition from the electronic throttle body.
The 20 mm throat is a rule and cannot be changed. Packaging length between the throttle body and the plenum.
Theoretical choked mass flow 0.0769 kg/s. CFD run conditions: energy equation, k-epsilon turbulence, density based, axisymmetric, pressure inlet at 101,300 Pa and 300 K, pressure outlet at 12.5 kPa gauge and 300 K, ideal gas. Parameter sensitivity study shows mass flow is most sensitive to throat diameter (a 0.0002 m reduction costs 2.04%), then inlet pressure, then inlet temperature. Evaluated in GT Suite to maintain pressure recovery.
Machined mold (3 hours on CR25, 2 hours on CR26I), layup prep, layup, pull and post-process. While the transient CFD models were in development the flow bench became the primary analysis method, and 3D printed restrictors were used to produce many iterations quickly. From the design reports and one-pagers: Machine the restrictor mould (3 hr on CR25, 2 hr on CR26I), prepare the layup (3 hr CR25, 1 hr CR26I), lay up (2 hr CR25, 1 hr CR26I), pull (5 hr CR25, 1 hr CR26I) and post-process (1 hr). While the transient CFD models were still being developed the flow bench became the primary analysis method, and 3D printed restrictors were used to produce many iterations quickly.
CFRP. From the cost report drawings and CAD: From the cost report drawings: Carbon Fiber (CR26i Restrictor).
None recorded. This part has no entry in Knowledge_Transfer/Issue Logging/Fault Vault.xlsx, in either Issue Log.xlsx, in CR22/Issue Tracking/Shakedown 7-15-23.xlsx, or in any design review issue list found in CrimsonStorage or Box.
110.17 g on CR26I against 134.11 g on CR25 and 138 g on CR22. From the cost report drawings and CAD: CAD mass, CR22 master assembly: 0.219 lb (0.099 kg). CG at X 65.23 in, Y -0.45 in, Z 33.27 in in vehicle coordinates. (CAD component: CR22B Restrictor) CAD mass, CR26I master assembly: 0.111 lb (0.050 kg). CG at X 65.21 in, Y -0.38 in, Z 34.08 in in vehicle coordinates. (CAD component: CR25 Restrictor) CAD mass, CR25 master assembly: 0.111 lb (0.050 kg). CG at X 65.21 in, Y -0.38 in, Z 34.08 in in vehicle coordinates. (CAD component: CR25 Restrictor) 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. Restrictor (as drawn): 0.06, 2.25, 0.20, 1.35, 7.98, 0.04, 2.78, 2.78 0.31, 1.57 CR25 Restrictor (as drawn): 222.45, 22.24, 57.10, 5.71, 20.00, 2.00, 6.35, 0.64, 42.60, 4.26 CR26i Restrictor (as drawn): 57.11, 5.71, 244.13, 24.41, 43.99, 4.40, 20.00, 2.00, 6.35, 0.64 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/Restrictor.pdf; CR25/Powertrain/Design/Manifolds/Intake/3 ~ Documentation/Cost Report Drawings/CR25 Restrictor.pdf; CR25/Powertrain/Design/Y - Cost Report Drawings/Manifolds/Intake/CR25 Restrictor.pdf; CR26i/Powertrain - IC/Design/Manifolds/Intake/3 ~ Documentation/Cost Report Drawings/CR25 Restrictor.pdf and 4 more Quantity per car, as costed: 1
Nothing in CrimsonStorage covers these yet.