Multi-valve engine

[pandaman]

is there realy a point small gains in hp
all lost on restictive intake and exhaust
some times i think it's just braging right's to sell a car

A very good point, like 1991_vn2nv was saying, hp figures are all well and good, but in some new engines, it's all top end, gotta rev the ring outta the poor engine to get any go out of it.

 

[Don Sutton]

For those historically inclined and this is probably not the first OHC engine but MG had a 1000cc yes thats right a 1 litre six cylinder engine that was supercharged and driven by a Major Gardiner held the land speed record at the time (1933) of 186mph.

OHC engines give the designer the freedom to place the valves at the angles they want and reduces inertia on the valve train. Short stroke engines cry out for more valves per cylinder to get the charge into the cylinder quickly with little air flow inertia due to slow piston speeds. An undersquare (long stroke) engine does not lend itself to multiple valves because of reduced cyl head area but does have good cylinder filling at slower speeds because a high air speed can be achieved. Each to ther own if you want a stump puller you go long stroke and if you want a high reving racer you go short stroke. OHC also allows easier implementation of variable independantly adjustable between intake and exhaust valve timing and that coupled with variable intake length can overcome many of the shortcomings that are inherent in piston engines. There are actually a lot more issues that go with this argument and they are very detailed and insufficient room to go into such as the benefits of direct injection etc.

 

[vztrt]

vztrt, the first OHC engine was the late 1920's I think. Still you are correct, not a new technology. First high profile application of it that I can remember is Jaguar's 6 cylinder back in the late 50's/60's/can't remember(kinda drunk), that family of engine lasted a loooooong time.

Could be, but I seem to remeber the first one was about early 1900's.

Either way not new technology.