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[Marks DTM Calib]

If the engineers wanted to be really clever, the could incorporate the cam lobes onto the crank with four pushrods, 2 inlet and 2 exhaust, with one of each either side of the conrods. Alternatively you could have two gear driven cams, one either side of the crank

That would be a miracle on a four stroke

[Field Marshal Dr. Opti]

I seem to recall that the  Honda VF 750 from the eighties came with gear driven cams.

.....so why are we still using belts and chains today?

[05omegav6]

If the engineers wanted to be really clever, the could incorporate the cam lobes onto the crank with four pushrods, 2 inlet and 2 exhaust, with one of each either side of the conrods. Alternatively you could have two gear driven cams, one either side of the crank

That would be a miracle on a four stroke

Ok do away with cam timing altogether...

A sensor either side of the crank for each cylinder, one exhaust and one intake, each sending a pulse to the ECU. In turn the ECU fires the appropriate solenoid to open or close the valves as required. Infinite valve timing based on fuel/air demands, four valves per cylinder - a solenoid for each one... if a solenoid fails engine can still run at a reduced level. If the engine is designed 'safe' then a total electrical melt down won't destroy it.

Exhaust sensor timing could act as a cross reference for the intake timing and vice versa, so again, if a sensor fails, the engine still runs...

Obviously only as good as the person programming it... but should be alot lighter and alot more efficient 

[Webby the Bear]

My teacher was ex Audi and VW so in our lessons we get a lot of Audi material including this stuff. As peeps have pointed out..... all the way at the back of the engine with 3 or 4 chains. I have no idea, from an engineering point of view whether it's good or bad, but I know I wouldn't like to be the technician having to replace them 

[05omegav6]

Or the person paying for it

[Marks DTM Calib]

Its this issue currently causing issues with the 4 pot beemer diesels.

As for the electronic actuated valve train, its not so far off, already being done by Sulzer on large marine diesels.

Only needs a crank sensor to do this (remember that cam runs at half crank speed on a 4 stroke  )

[05omegav6]

A pair of sensors for each cylinder might complicate things but will give more precise control and add in a degree of redundancy just in case

[Kevin Wood]

A pair of sensors for each cylinder might complicate things but will give more precise control and add in a degree of redundancy just in case

The GM crank sensor has 60 teeth, so the ECU gets an update every 6 degrees of rotation as it is ( potentially 3 degrees if it triggers on both edges). You can happily do a linear interpolation between crank sensor events because the speed won't change much in 6 degrees of rotation, so I'd say there's no need for more sensors.

[chrisgixer]

Its this issue currently causing issues with the 4 pot beemer diesels.

As for the electronic actuated valve train, its not so far off, already being done by Sulzer on large marine diesels.

Only needs a crank sensor to do this (remember that cam runs at half crank speed on a 4 stroke  )

I was amazed how slow the cams actually turned, when we where struggling with TB's gravel chomping rusty bullit engine. Cranking the engine with the cam covers off I was expecting oil to be flung everywhere. But no, they turn surprisingly slowly.

[05omegav6]

A pair of sensors for each cylinder might complicate things but will give more precise control and add in a degree of redundancy just in case

The GM crank sensor has 60 teeth, so the ECU gets an update every 6 degrees of rotation as it is ( potentially 3 degrees if it triggers on both edges). You can happily do a linear interpolation between crank sensor events because the speed won't change much in 6 degrees of rotation, so I'd say there's no need for more sensors.

Well that's the bottom end sorted Would a 3mm headgasket be enough to ensure top end clearance? I know this would drop the compression ratio, but that rather conveniently opens up the avenue of forced induction...

[omega3000]

Engine out jobby, no problemo . Now how would you like to pay for that sir 

[Andy H]

I seem to recall that the  Honda VF 750 from the eighties came with gear driven cams.

.....so why are we still using belts and chains today?

The Honda VF750 had a cam chain, was moderately unreliable (it used to eat cams) and had a reputation for being a bit of a slug. Honda were so embarrassed that they went all out to rebuild their reputation by developing (at great expense) the VF750R racer and VFR750 road bike.

I had a VFR750, I used to commute 18,000 miles a year on it. Almost indestructible (a lorry reversed over mine  ).

The gears were an engineering marvel and reputably cost a fortune to make. They made a very distinctive whine which I found quite adictive

[andyc]

What make me laugh is in the V8 Supercars you now have Merc & Nissan who have spent thousands on quad cam, multi valve all singing all dancing engines and the old pushrod motors from Ford & GM are still beating them

Had i better no say that the new engines from GM are also rear chained

Andy

[Rods2]

What is wrong with using hi-vo chains like many motorbikes do and that are designed to last the life of the engine. They are much, much stronger than conventional chains. 

[chrisgixer]

I seem to recall that the  Honda VF 750 from the eighties came with gear driven cams.

.....so why are we still using belts and chains today?

The Honda VF750 had a cam chain, was moderately unreliable (it used to eat cams) and had a reputation for being a bit of a slug. Honda were so embarrassed that they went all out to rebuild their reputation by developing (at great expense) the VF750R racer and VFR750 road bike.

I had a VFR750, I used to commute 18,000 miles a year on it. Almost indestructible (a lorry reversed over mine  ).

The gears were an engineering marvel and reputably cost a fortune to make. They made a very distinctive whine which I found quite adictive

The rc45. Very expensive.
http://en.wikipedia.org/wiki/Honda_RVF750_RC45