Toymods Car Club Inc: Tech & Conversions => New stepless throttless valvetrain

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oldcorollas
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Kita-Ku, Sapporo, Japan
Registered:
January 2003

Re: New stepless throttless valvetrain

Thu, 03 July 2003 05:05

manolis wrote on Wed, 02 July 2003 19:33

The flattening of the valve opening graph at max lift is only because the cam lobe profile was selected to have a specific simple form, for demo reasons.

ohh oki.

manolis wrote on Wed, 02 July 2003 19:33

The expected longevity of the mechanism in “real” driving conditions is better than the conventional valve train system.
The normal car operates most of its “life” in low revs and partial loads, where the new system operates actually unloaded, as the valve springs are only partially compressed. Compare this case to the idling (or low revs) operation of the conventional engine having the 80lbs/240lbs valve seat pressure you mentioned. The cam lobe has to compress completely the strong springs, while the timing belt or chain has to provide the necessary “impact” torque.
No matter how strong the valve springs are, you can rotate at idling (which means 0.15 to 0.2 mm valve lift) the camshaft of the new system (with the timing belt removed) easily, just by your small finger. Try the same in a conventional head.
The new system is loaded as the conventional system only at its maximum valve lift operation. And this maximum valve lift is necessary only at “high revs with full load”. Anywhere else the new system operates with lower loads than conventional.

thats a very good point, would reduce the valve train loading quite a lot.

manolis wrote on Wed, 02 July 2003 19:33

By the way, what is the percentage of time that a racing engine operates at its maximum revs with full load?
The small ‘push rods’ with the spherical ends, do seem weak.
But their 4 mm diameter, their 25 mm length form center to center and the 6 mm diameter of their spherical ends could easily change to 8 mm, 25 mm and 12 mm without changing the basic design.

i don't actually know, but they would be at high revs for about 1/2 the time...
if the exposure to high rpm and load will not cause significant wear, then it might last...
as an example, in my road car (1.3L) cruising is at about 4500rpm, and when driving hard the rpm stay between 5000 and 8000rpm... although i don;t always drive hard, it is this time that will cause the most damage.

as far as the pushrod size, i think the OHV pushrods in my motor are about 5mm diamter, but hollow, so i guess your dimension may not be too bad. i would be concerned with the wear of the contact points at the ends tho... what happens when maybe 0.5-1.0mm of wear has occurred? are the parts rebuildable?

a couple more questions. how do you turn the lever part to achieve the different lifts? electric motor wuth screw thread? how loaded are these parts?

anbd finally, do think this sort of system could be retrofitted to an OHV type design? ie replacing conventional rocker arms with something similar to this?
Cya, Stewart

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