Straight-8
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 One • Two • Four • Six • | |
| Engine types Gas turbine • Piston • Jet • Rocket engine • Steam engine • Stirling engine • Tschudi• Twingle Rotary • Wankel • Free-piston • Britalus • Coomber • Swing-piston • Orbital • Quasiturbine | |
| Valves Cylinder head porting • D slide • Four-stroke • Manifold • Multi • Piston • Poppet • Sleeve | |
| Piston layouts Single cylinder • Straight • Opposed • Flat • V • W • H • Deltic • Radial • Rocket engine nozzle • Rotary • Stelzer • Controlled Combustion • Bourke | |
| Motion mechanisms Cam • Connecting rod • Coomber rotary • Crank • Crank substitute • Crankshaft • Linkages (Evans • Peaucellier-Lipkin • Sector straight-line • Watt) • Double acting/differential cylinder | |
| Thermodynamic cycle |