Following WT's recommendation and a lack of response confirming permission from author of K&N thread, have decided to start this thread.
Quoting Rodney bud...
Piston kinematics is interesting. It is counter-intuitive, but rod motion is not sinusoidal. If one were to run the trig. (in say single or tens of degrees) for any reciprocating piston engine from diesel forklift to F1 engine, he'd find that piston movement around top of stroke [top dead center (TDC)] is quicker compared to around the bottom of stroke [bottom dead center (BDC)]. Rod ratios augment or diminish the differences in motion around the TDC and BDC to some degree, but the only way the relation between piston motion and crankshaft rotation will be purely harmonic / sinusoidal, is if the rod is of infinite length. This is impossible, so there are no exceptions to the curve being flattened around BDC.
The lower acceleration off BDC is further encouragment for the use of efficient higher velocity higher inertia tracts that allow cylinder charging past BDC.
The problem with high velocity tracts and late closing valves is that below the operating range velocity can't be built and compression is reduced. Street cars require a wide range of operating RPM, so the bias is always towards low-mid range power (earlier intake valve closing [IVC]) which is where 95% of day to day driving takes place. Variable cam phasing helps but in current form is limited in degree.
Totally agree, but don't forget the port! The closer one gets to the cylinder, the more important the design of that part of the tract. It should be no surprise that the intake port design is critical.
Where we design the velocity into a tract is important. It does no good to have a long column high velocity area early on in the tract only to have it feed into a larger area before entering the cylinder.
Agree, but there are some exceptions in high velocity turns or anti reversion ledges where either poor port, cam, selection/design, or just rules, lead to limited optimization.
The larger the number of cylinders, the smaller the pressure changes within an intake tract. Everything down to a 4 cyl has 1 cylinder on intake stroke at any time though, so is it not a matter of having cylinders all seamlessly drawing air, but having the draws closer together for the least change. The only way to do this is with more cylinders.
Resonance is seperate from inertia cylinder charging.
In fact F1 engines DO have runners drawing from a large volume plenum which is fed by the intake above the driver's head. The throttles are individual barrel throttles and location is in the runners. Attached are 2 pictures I took at a recent convention in Indy. They are of the Cosworth 2003 Jordan engine - after the plenum has been opened and filter removed. The barrel throttles are shown at ~20% open. At WOT they present pure orifice with zero flow restriction unlike with standard butterflies.
Totally agree. I see little advantage to messing around with a street driven non-tracked small-med displacement NA it if the stock balance is found good.
There are some fringe components that one can look at and immediately tell that they will make things worse or provide zero improvement, but with the large majority, testing is needed. Plug and test, plug and test, may sound backward but it is not. Even at levels where industry standard 15K USD fluid simulation software is used, plug and test is still prevalent. There are teams, shops, with rows and rows of shelves just stacked with things like manifolds, all money spent in the effort to find the peak performing one that works in combination with the rest of the tract.
Testing with the right tools. Test process control is another big area of concern.
Quoting Rodney bud...
Piston kinematics is interesting. It is counter-intuitive, but rod motion is not sinusoidal. If one were to run the trig. (in say single or tens of degrees) for any reciprocating piston engine from diesel forklift to F1 engine, he'd find that piston movement around top of stroke [top dead center (TDC)] is quicker compared to around the bottom of stroke [bottom dead center (BDC)]. Rod ratios augment or diminish the differences in motion around the TDC and BDC to some degree, but the only way the relation between piston motion and crankshaft rotation will be purely harmonic / sinusoidal, is if the rod is of infinite length. This is impossible, so there are no exceptions to the curve being flattened around BDC.
The lower acceleration off BDC is further encouragment for the use of efficient higher velocity higher inertia tracts that allow cylinder charging past BDC.
The problem with high velocity tracts and late closing valves is that below the operating range velocity can't be built and compression is reduced. Street cars require a wide range of operating RPM, so the bias is always towards low-mid range power (earlier intake valve closing [IVC]) which is where 95% of day to day driving takes place. Variable cam phasing helps but in current form is limited in degree.
Totally agree, but don't forget the port! The closer one gets to the cylinder, the more important the design of that part of the tract. It should be no surprise that the intake port design is critical.
Where we design the velocity into a tract is important. It does no good to have a long column high velocity area early on in the tract only to have it feed into a larger area before entering the cylinder.
Agree, but there are some exceptions in high velocity turns or anti reversion ledges where either poor port, cam, selection/design, or just rules, lead to limited optimization.
The larger the number of cylinders, the smaller the pressure changes within an intake tract. Everything down to a 4 cyl has 1 cylinder on intake stroke at any time though, so is it not a matter of having cylinders all seamlessly drawing air, but having the draws closer together for the least change. The only way to do this is with more cylinders.
Resonance is seperate from inertia cylinder charging.
In fact F1 engines DO have runners drawing from a large volume plenum which is fed by the intake above the driver's head. The throttles are individual barrel throttles and location is in the runners. Attached are 2 pictures I took at a recent convention in Indy. They are of the Cosworth 2003 Jordan engine - after the plenum has been opened and filter removed. The barrel throttles are shown at ~20% open. At WOT they present pure orifice with zero flow restriction unlike with standard butterflies.
Totally agree. I see little advantage to messing around with a street driven non-tracked small-med displacement NA it if the stock balance is found good.
There are some fringe components that one can look at and immediately tell that they will make things worse or provide zero improvement, but with the large majority, testing is needed. Plug and test, plug and test, may sound backward but it is not. Even at levels where industry standard 15K USD fluid simulation software is used, plug and test is still prevalent. There are teams, shops, with rows and rows of shelves just stacked with things like manifolds, all money spent in the effort to find the peak performing one that works in combination with the rest of the tract.
Testing with the right tools. Test process control is another big area of concern.
The microsystems are all pretty much figured out, but the interaction of all of them as a whole is less known and a matter of finding balance since they compromise one another.