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Straight-8

1933 Bugatti DOHC straight-8 in a Type 59 Grand Prix racer


A Straight-8 is a straight engine with eight cylinders.

Unfortunately, a straight-8 is a very long engine and requires more main bearings to support the crankshaft adequately. In addition, the change in design of cars from a long engine compartment between separate fenders to the modern configuration beginning with the Chrysler Airflow and its shorter engine compartment led to straight-8 engines being phased out of automobile design. Moreover, the quest for higher revs and higher compression ratios showed another weakness of the design: there were slight torsions of the long crank and the long camshafts, limiting the development of such engines. ALFA Romeo were the first to react: in their racing car engines for the P2 and P3 and in their 8 C 2300/2600/2900 sports cars of Mille Miglia and Le Mans fame the camshaft drive had been moved to the engine center between cylinders # 4 and 5, thus reducing the aforementioned limitations.

Most straight-8 engines were used pre-World War II in expensive luxury and performance vehicles. Bugattis commonly used DOHC straight-8 engines. Postwar, the main users of the straight-8 were American luxury cars belonging to Chrysler (flathead configuration) and General Motors owned marques (flathead and OHV configuration), but the straight-8 lost favor by the 1950s, almost universally replaced by the V8. Ford never adopted the straight-8, using V8 or V12 engines from the 1930s on. The legendary Mercedes-Benz 300 SLR, winner of the 1955 Mille Miglia with Stirling Moss behind the wheel and Denis Jenkinson as his navigator used a 3 liter Straight-8 outputting 290hp. This was the final consequence of the ALFA design of the early 1930: essentially a combination of two in-line fours, as not only the camshaft, but now also the prop shaft was driven from the engine's center.


Piston engine configurations
Straight Single, 2, 3, 4, 5, 6, 8, 9, 10, 12, 14
V 2, 4, 5, 6, 8, 10, 12, 16, 20, 24
Flat 2, 4, 6, 8, 10, 12, 16, H
W 8, 9, 12, 16, 18
Other inline H, VR, Opposed, U (Square), X
Other Hemi, Radial, Rotary, Pistonless, Deltic, (Wankel)



Heat engines
Stroke cycles
OneTwoFourSix
Engine types
Gas turbinePistonJetRocket engineSteam engineStirling engineTschudiTwingle
RotaryWankelFree-pistonBritalusCoomberSwing-pistonOrbitalQuasiturbine
Valves
Cylinder head portingD slideFour-strokeManifoldMultiPistonPoppetSleeve
Piston layouts
Single cylinderStraightOpposedFlatVWHDelticRadialRocket engine nozzleRotaryStelzerControlled CombustionBourke
Motion mechanisms
CamConnecting rodCoomber rotaryCrankCrank substituteCrankshaftLinkages (EvansPeaucellier-LipkinSector straight-lineWatt) • Double acting/differential cylinder
Thermodynamic cycle