Collect exhaust from all four cylinders and tune the exhaust pressure wave to the target engine speed.
Four primary runners of equal length feeding a collector. Primary length is set by pressure wave tuning: L = (ECD x C) / (2 x RV x 6 x RPM), with C the speed of sound at exhaust temperature. Achieving a reflective value of 4 at the target peak rpm is the design objective.
CR26I shortened the primaries from 14 in (356 mm) to 12.44 in (316 mm) to align the tuned point with the engine's targeted operating range. 1.25 in diameter tubing maintains cross-sectional area between the exhaust port and the primaries. Individual mounting flanges rather than a single flange gave a 19% total weight reduction and eliminated 16 hours of manufacturing time by removing the need to sand the primaries flush with the engine.
Maximum deviation of 0.118 in (3 mm) from designed length between runners. Packaging around the frame, undertray and driver. Heat: 187 C measured in the exhaust bay at the end of a half endurance, with average exhaust gas temperature 760.49 C (1401 F) at a 1.00 lambda target. From the design reports and one-pagers: From the CR22 Exhaust Design Report: 103 dB at idle and 110 dB at three quarter mean piston speed (11,000 rpm); integrate with the undertray in limited space; and withstand a thermal environment up to 1700 F. Rules: IC.7.1.1 the exhaust must be separated from flammable materials including fuel and oil systems, and from thermally sensitive components including brake lines, composites and batteries. IC.7.2.1 routing must prevent driver fumes at any speed. IC.7.2.2 the outlet must be no more than 45 cm behind the rear axle centreline and no more than 60 cm above the ground. IC.7.2.3 components protruding from the side of the body ahead of the main hoop must be shielded. IC.7.2.4 fibrous or absorbent material such as header wrap must not be used on the outside of the manifold or system.
GT Suite simulated VE against exhaust primary length. Effective cam duration measured experimentally with a dial indicator on the cam lobe. From the design reports and one-pagers: Primary length is set by pressure wave tuning, with the required optimal length increasing across the rpm range considered; 14 in gave peaks at 8,000 and 10,500 rpm on CR22. GT Suite compared 11 in primaries (CR21) against 14 in (CR22) and showed higher volumetric efficiency between 8,000 and 11,000 rpm at the same intake runner lengths, which reduces pumping losses. Material selection was a three-way comparison: low-carbon steel is marginally lighter than stainless by density but corrodes at high temperature; aluminium is much lighter but will not survive exhaust temperatures around 1300 F; titanium is half the weight of stainless but twice the price and difficult to manufacture properly. CR22 stayed stainless; CR25 and CR26I moved to CP1 titanium downstream of the collector once the Ticon sponsorship made it viable.
Pie-cut and welded tube with individual mounting flanges. From the design reports and one-pagers: Primaries: print the jigging, outsource tube bending to BMRS, cut tubing to fit the jig, tack weld the seams on the jig taking care the jig does not melt, then remove and weld the seams. Thermocouple bungs: cut the NPT thread off (10 min), weld the bung to the primary (15 min) making sure the bolt-on flange is mated against the port flange so the bung does not block the primary bolting to the head, drill a through hole for the thermocouple, then position the thermocouple with its tip in the middle of the flow path and tighten the collar. Port mating flanges: CNC lathe (1.5 hr), assemble primaries into the jig with the flanges, weld to the primary (30 min, only after the primaries are welded in their jigs). Primary bolt-on flanges: waterjet (1 hr). Collector: weld the V-band flange to the end (30 min), fit bolt-on flanges to every primary first, weld the inner star onto the primaries in the jig (2 hr), weld the collector to the primaries in the jig (2 hr).
Stainless steel primaries with individual flanges. CP1 titanium from the secondary onward.
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.
Primary length 12.44 in, 1.25 in diameter. CR25 primaries 2044 g without nuts, flanges 192 g, clamp 167.26 g. From the design reports and one-pagers: CR22 primaries: 1.25 in OD with 0.049 in walls, the thinnest available tubing, 14 in length across all cylinders to minimise cylinder-to-cylinder variation, K-type thermocouples mounted directly after each port to measure individual cylinder EGTs, packaged behind the firewall and inside the frame so the engine can be dropped without removing the primaries. Roughly 4 lb. CR22 collector: 2 in outlet, purchased, welded in rather than slip-on to ease manufacturing and guarantee no leaks, with a star in the middle to reduce minor losses through the transition and a V-band to the secondary. 0.6 lb with the V-band flange. From the cost report drawings and CAD: 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. Exhaust Manifold (as drawn): TRUE 5.08, 4.61, 4.21, 15.39, 3.81, 5.46, 55.53, TRUE 4.32 TRUE 3.68, TRUE 4.90 Source: Cost report drawings: CR22/Powertrain/Design/X - Cost Report Drawings/Manifolds/Exhaust/Exhaust Manifold.pdf Quantity per car, as costed: 1
Nothing in CrimsonStorage covers these yet.