typeR

so i was curious about ignition timing...never really understood what was happening and wanted to know what did spark advance mean...advance towards what i thought...well it's really in adavnce of what ...and that is TDC (top dead center ) spark happening before TDC is advanced at TDC is retarded...you can imagine if you spark the A/F too earlier your tring to send the piston back down before it reaches the top and well that just cant happen, so bad things result....so anyway though i have a basic understanding now seeing a video of engine dynamics and thinking at the same time hum...the power stroke of a pistons cycle, this is the stroke down in which a spark has occured but several of its strokes it's just along for the ride counting on the other pistons to keep it spinning...so i started thinking we've heard of active cylinder management this is where say 3 of a 6 cylinders pistons are not engaged during low rpm cruise increasing fuel economy...i say what if we could take off line all pistons except for the one in its power stroke at all speeds all RPMs, reducing the load on the engine dramatically?my thinking might be flawed because perhaps the lack of the other "dead" pistons momentum would hurt performance? and perhaps this is where bigger engines get there torque? someone set me straight...scalbert


next i thought and this one has serious holes but what if esepcially at speed we found away to channel air under the car enough to lift it yet still had adequate down force for stability, thus suspending the car and reducing it's acctual weight ...this would free up fuel economy and performance a 3000 LB car could weigh 1000 lb at 70 mph for example....i often thougt formula one cars would eventually have active wings(like a jet fighter) providing increased down force on turns and lift on the straights...

mclarenf3387

Both ideas are flawed.

Deactivating all cylinders will give you no power.

Lift at high speeds will make the car highly unstable and not safe.

scalbert

FYI, the reason why you trigger the ignition BTDC is because things do not happen instantaneously. It takes time for the spark to ignite the fuel and for the flame front to spread. This is why timing is advanced as the revs increase; there is less time for everything to occur.

Pretty much all of the other cylinders are offline when one is on its power stroke. This is why an engine "putts" as cylinders fire at different times. Cylinder deactivation simply means that fuel and spark are not fired. The piston is still moving and using energy to do so.

Maybe I am not following the questioning?

scalbert

Weight is mainly an issue at lower speeds. Drag is the larger issue at higher speeds. Creating lift would simply create an unstable car on the highway.

The analogy of F1 does not include that the F1 cars have negative lift. The proposed active wings would simply reduce the downforce on the straights, not eliminate it. These cars run so much downforce that the amount is grater than the weight of the car.

typeR

i think your following it i just didnt know how the cylinder diactivation works...so what if you were able to have the pistons that werent working on a paticualr revolution just sit there and only travel up and then down they cylinder wall when it was its turn to fire...i think of it as maybe the way vtec works...i dont know maybe ill to think this through some more...

scalbert

There is no easy way to stop a piston from traveling up the wall as it is connected to the crank.

VTEC just works on the rocker arms in the head. It locks a 3rd one to the main two which causes them to follow a different cam lobe. Two different areas completely.

typeR

thats what i m saying is have there be some kind of selenoid that moves the piston/rod over when it's it turn to fire ..the way vtec works is what i meant

scalbert

Nope, to difficult. The connecting rod is stressed enough. Adding some electro-mechanical engagement would be devastating when trying to endure the applied loads.

However, when technology is developed to control the valves more intelligently, such as solenoids, hydraulic, etc. The valves could be kept closed at all times. This would basically eliminate nearly all of the pumping losses. The only energy used would be to move the piston in dead air; no compression stroke. Moving a piston with a compression stroke would hardly require any power.

RooEng

The engine needs all four strokes to fire and create power. Disconnecting it anytime during it's four strokes results in no power.

As for the F1 Q. They tried it a long time ago '70's?? But they ruled against it. If the mechenism didn't function perfectly from low to high downforce it would cause the driver to think he had a lot of downforce coming into a turn.

ThinJim

iTrader: (3)

This has already been done. Back in the 70's, Cadillac had a 4-6-8 or something like that. More cylnders came on line as the demand increased. It was a flop.

typeR

so in therory my two ideas, though tried and failed must have some merit...atleast thats what im going away with

RooEng

Those are very good theories.

Instantanous ignition of the AF mixture near TDC is already being done in Diesels to extract moer power.

Deactivating cylinders was just reintroduced in GM Chrysler and Honda cars.

F1 movable wings were banned because they worked too good (when they worked).