PATTAKON
GREECE
Real Thing Specifications
Renault 19 Energy (1390 cc, bore 75.8 mm,
stroke 77 mm, compression ratio 9.5:1).
The engine is a normal one with the addition,
modification or replacement of the following parts:
1. The single camshaft remains in place idle (immovable), only for keeping
the oil into the cylinder head covering its end bearings.
2. The rocker arms, their pivot shaft, and the cylinder head cover are
removed.
3. In the place of the original cylinder-head cover it is secured (by the
eight 6 mm screws previously securing the cover to the cylinder head and the
five 8 mm screws previously securing the rocker arm pivot shaft to the cylinder
head) a base aluminum plate completely covering the cylinder head. This base aluminum
plate serves as the lower bearings framework for the two control shafts. This
base plate has eight holes, one above each valve. Each hole has a diameter of
10 mm, coaxial to the relevant valve. Along each one of these holes slides a
small cylindrical pin (acting as both, push rod and valve clearance adjuster)
being of 10 mm diameter and about 14 mm height, having at its top end a
hemispherical cavity of 6 mm diameter which acts as the bearing of the relevant
valve lever (valve needle).
4. Two intermediate aluminum plates, one for intake and one for exhaust
valves. Each of them acts as the top bearing for the relevant control shaft and
also as the lower bearing for the relevant camshaft.
5. Two top aluminum plates, one for intake valves and one for exhaust
valves. On each one of them the top bearings, for the relevant camshaft, are
cut.
6. On the base aluminum plate it is secured by ten 8 mm screws the
intermediate and the top plate of intake valves, and with another ten screws of
8 mm are secured the intermediate and the top plate for exhaust ones.
7. On the base aluminum plate there are holes for the "oil bath" type
lubrication, of the involved parts. The central screw, for securing the base
plate to the cylinder head, is properly drilled to deliver the pressed and
clean oil. The oil level in the eight chambers formed into the aluminum plates
is kept by a number of drain holes. When the oil exceeds the desired level, it
is drained into the cylinder head through the holes and then into the
crankcase. The aluminum plates form also the top cover and oil sealing means of
the engine (see photos of real thing).
8. A control shaft for the intake valves and a control shaft for the
exhaust valves are added. Each one is rotatably supported between the base
aluminum plate and its relevant intermediate aluminum plate. Both control
shafts exceed for about 15 mm from the aluminum plates, at the flywheel side.
At this end of each control shaft it is secured a lever for its rotation. The
control shaft has pairs of holes of 12 mm diameter for bearing the control
levers at an eccentricity of 25 mm from its base axis. All these holes are as
coaxial as could be managed.
9. For each valve there is a control lever swivelably coupled at the
relevant 12 mm eccentric holes on the control shaft, abovementioned. On the
control lever and at an eccentricity of 25 mm from the swiveling axis is formed
a hemispherical cavity of 6 mm diameter. On the control lever there is also
formed the cam follower, which is a cylindrical surface of 35 mm diameter (at an
angle of about 120 degrees) with axis passing through the center of the
relevant hemispherical cavity.
10. For
each valve, a valve lever is provided. It is a 4 mm diameter needle ending at
both ends in 6 mm diameter spherical surfaces. The centers of the two spherical
surfaces are at 25 mm distance. The upper spherical surface of each valve
needle is swivelably supported on the spherical bearing of the relevant control
lever, while the lower spherical surface of each valve needle is swivelably
supported on the spherical cavity of the relevant cylindrical pushrod.
11. One
camshaft for intake valves and one for exhaust valves, each one having four
cams, are provided. The cams have 30 mm base circle and 10 mm maximum
eccentricity. The duration of the camshaft is significantly longer than the
normal camshaft (diagram below). The intake camshaft drives also, at its
flywheel side, the distributor. Each camshaft is rotatably supported between
its relevant intermediate and top aluminum plates and at its opposite to the flywheel
side has been secured its sprocket (the normal one, having 38 teeth).
12. The
rotation angle for the control shaft from minimum valve lift (at idling) to
maximum valve lift (at max revs and full load) is 65 degrees. The maximum valve
lift available is 10.3 mm (wider than the 10 mm of the cam lobe size).
13. The
timing belt is removed and another one, having 128 teeth, is used to drive the
sprockets of the two camshafts from the existing sprocket on the crankshaft.
The existing timing belt tensioner is kept in charge. As the normal width of
the timing belt is 17 mm and the only available (Renault Laguna 1.8) 128 teeth
timing belt of same form and module has 25 mm width, the last one was sliced in
two belts, one 17 and one 8 mm width.
14. The
distributor is the original one, but it is now mounted in a new aluminum base
secured between the top and intermediate aluminum plates, at flywheel side.
15. The
fuel pump is the normal one. It is moved 10 mm backwards, by the insertion of a
proper gasket, to make room for the base aluminum plate. The fuel pump arm is
driven by an eccentric cylindrical cam, cut on the intake camshaft, by means of
a "J" shaped wire.
16. The
carburetor is the normal one. The butterfly is fixed permanently wide open. The
chock is idle (i.e. not used). The richness of the mixture is not modified and
it seems that at very low revs it becomes too lean, as the carburetor is
designed not for this kind of use (fully opened butterfly at very low air
speed). The accelerating pump is idle too, as there is no butterfly motion, yet
the response in all conditions is immediate, direct and instant. Of course the
last thing that matches such a design is a poor Weber carburetor.
17. The
spark is retarded as many as 7 degrees, by relocating the relevant sensor on
the flywheel cover. The high voltage cables are the original as well as the air
and oil filters.
18. Silicon
gasket glue is used between the aluminum plates for oil sealing.
19. The
same string, previously activating the throttle of the carburetor of the
original engine, is now used to transfer the commands from the accelerator
pedal to both control shafts. The intake and exhaust control shaft rotation
angles needs not be necessarily equal. There is no returning spring, neither
for the control shafts nor for the control levers since valve springs manage to
take care for all of these.
20. The
oil level stick is removed and from its metal pipe the crankcase gases, by
means of an elastic pipe, are forwarded to the carburetor.
As there is no vacuum in the intake manifold,
there is no servo in the braking system. The brakes pedal is too hard, yet it
manages to stop the car, provided driver's foot is sturdy.
Depending on the revs of the engine, more
torque can be obtained with partial valve lift instead of maximum. And this is
exactly the driver's feeling. Only at high revs and full load the maximum valve
lift seems necessary.
The camshafts are made deliberately wild in
order to improve the power output at extreme revs, as the torque at any lower
revs is guaranteed by the correct control of the valve lifts.
The above plot is the valve lift (vertical
axis, mm) of exhaust (red) and intake (blue) valves of the mechanism for 65,
33, 18, 8, 3 and 1 degrees of control shaft rotation. The horizontal axis is
the crankshaft rotation. The bold curves are the relevant lifts of exhaust
(orange) and intake (green) valves of the normal engine.
As shown, the overlap, not the angular but the
effective or actual one, is linearly proportional to the selected valve lift
for intake and exhaust.
The substantially constant pressure at intake
manifold, combined with the variable actual overlap, changes dramatically the
behavior compared to that of ordinary engines. Since there is no vacuum in
intake manifold to pull back (suction) the gases from cylinder and exhaust
manifold, the behavior of the whole system, from intake to exhaust, is quite
different. This explains the surprisingly instant response to the acceleration
pedal in all conditions, despite the elimination of the carburetor's
acceleration pump (due to constantly full open throttle) and the lean mixture.
The immediate constant idling well below 500
rpm with the engine really cold (after a night at 5 degrees centigrade),
without any assistance from chock, is just an indication of the capabilities of
the variable valve lift system at low revs.
The resistance for the rotation of the
camshafts, as compared to that one of the normal engine, is negligible at
idling: the small finger of a child can rotate it, giving another indication of
the smoothness at idling this variable valve lift system provides. This
negligible resistance proves the elimination of the loads and hence the
fatigue, friction and wear of the cam lobes, of the timing belt, of the valve
springs and valve seats etc.
The valve lift which at idling is a couple of
tenths of a mm makes the turbulence of the mixture suctioned in the cylinder as
optimum as full lift makes it at optimum load and revs and its homogeny too,
making the idling quiet, constant, with clean exhaust gasses and very low
consumption. The engine needs long time to warm up at idling, with less than
500 rpm. Yet, why to wait for the warming of the engine, since the driver can
lock the throttle at wide open and start immediately without any response
problem?
An interesting matter is the low noise from the
exhaust valves at very short lifts. At idling and after removing the exhaust
manifold, the noise from the exhaust ports on cylinder head reminds more a calm
whistling than the unaffordable tab, tab, tab, tab of the conventional engine.
At idling the exhaust gas was checked. The
official result was 0.05 % in volume with normally warmed up engine. The CO was
checked with completely cold engine at less than 0.1% in volume. The CO was
also metered at full load in the region from 1000 to 6500 rpm and the result
was about zero. When the original (without variable valve lift) engine was
metered at idling, the reading for CO was 1.8 %, which makes for more than 30
times higher. And this 1.8 % value for the conventional engine was achieved
only after the warming up period.
Starting even with cold engine the response is
immediate, direct, 1:1, in all conditions. As the throttle is kept constantly
open there is no richness of the mixture at transient conditions. But strange
as it appears the response is as crisp as if the acceleration pump were in full
operation.
The engine is currently running at 7000 rpm
with full load. The red line starts at 5500 rpm, and the dark red at 6000 rpm.
More revs may damage the basic parts of the engine (connecting rods, pistons,
valves and crankshaft).
The top red and top blue curves, in the diagram
above, compared to the normal ones, explain why the engine can rev higher. The
lift is more (about 15%), the duration is wider and the overlap is about
double. At high revs the engine's behavior (response, power output and sound)
reminds motorcycle.
At low and medium revs the most torque is taken
with intermediate lifts, not the maximum. If the power pedal is pressed more
than necessary the torque decreases, as more lift decreases the entry speed and
the turb. Drive by wire could help. Drive by wire could also help in rotating
the two control shafts at proper angles, according existing conditions. The
selected relation of intake and exhaust control shaft angles in the prototype
is very simple, as a string pulls both of them.
The proposed mechanism can achieve constant
valve clearance in all valve lifts. It can also achieve slightly variable valve
clearance, if it is desirable. For instance, if at very low lifts (idling,
partial loads and low revs) a valve clearance of 0.1 mm is selected and at high
valve lifts a clearance of 0.4 mm seems better selection, then by means of a
small modification of the actual lengths of the constituent parts (valve lever,
control lever etc) or by a small relocation of the swiveling point between
control lever and valve lever, or by a slight modification of the cam follower,
or . . . the desirable slightly variable valve clearance can be achieved.
The material of the aluminum plates is of
"aviation" quality and cost, and was selected as the only available. The steel
parts (control shafts, camshafts, control levers, valve levers, cylindrical
push rods/adjusters) were made from cheap low carbon steel and a double nitride
surface hardening was applied. The accuracy in dimensions and the quality of
the surfaces of the various parts are in "tenths" of a millimeter, as most of
them were finished by hand.
The
system can be applied to engines having all valves in a single row. In so far
as a proportional lift is selected for exhaust valves relative to the intake
ones, the application of the method becomes easier, as it takes only one
control shaft and only one camshaft.
The
system fits to the Diesel engines too. The operation of the Diesel engine can
be improved using the Variable Valve Lift System by increasing the turbulence
of the air at all revs and by increasing the amount of air entered and trapped
into the cylinder.
The
system matches also to turbo engines, as the exhaust valve lift can effectively
smooth out pulses, which otherwise impact turbine fins at low revs.
The system can easily be applied to engines having
pushrods for transferring the cam lobe action to the valves.
The
simplicity of the system makes it proper for motorcycle engines too.
Thank you for your time
PATTAKON
Fax and Tel No: +30 210 4934402
Post address : Lampraki 356, 18452 GR
Nikea Piraeus