Renault - and EM valves.

[wheelnut]

Sorry if this question's been asked and answered before, but there's been speculation about whether Renault's new V10 uses an EM-valve system.

I was wondering, if the weight of this system negates any gains made by having an engine with a lowered COG, is it possible that the whole reason for Renault going down this road was to accommodate the heavier valve-system!
The advantages of EM-valves must be considerable, whereas the advantages of just lowering the COG, must be compromised by the problems this engine configuration creates.

Is it possible that Renault are actually much smarter than some people give them credit for?

[Jozo]

According to Mario Ilien, the power consumption (for accelerating valves and hardware) would be too great for EM-valves to work. The required precision needed for valve positioning would also be a problem. And, as you mention, the heavy electromagnetic coils and magnets would raise the centre of gravity of the engine.

[RWC]

What JOZO said + Most of these valve control systems(incl the ones on production cars)generally only help to give an engine more drivability, NOT more maximum horsepower(they're allready at the present limit of valve optimization)so it's not worth it
-yet

[dctifosi]

If Renault gets E-M valves working right, it could open the doors to more rev's. There will also be less internal friction.

[Dino IV]

Latest gossip I caught was about Honda working on a wide angled (110-120 degrees) V10 with EM valves only for the inlet valves. Exhaust valves are operated by a regular cam.

Question is ... why?
Because power consumption or weight addendum is indeed that disadvantageous that a full EM head isn't attractive yet, but with EM valves possibilities favourable for the inlet valves they decided to opt for a split set-up?
Or just because of packaging trouble on the exhaust side combined with the wide angle?

[Arneal]

On some of their production car engines Honda puts the VTEC variable valve lift and timing gear on only the intake side; the exhaust side is left fixed. Why I don't know, but the analogy to the rumor Dino IV discussed is clear.

Presumably you gain more advantage with precise control of the intake than you do with the exhaust, so sometimes it is worthwhile to just do the intake side. I doubt it has anything to do with packaging.

[koenda]

If you can achieve variable valve-lift to maximise the intake-air velocity you will have some advantage. The fuel gets atomised better with a high air-velocity. Smaller fuel-droplets will burn faster than larger ones. So at half-throttle you will have a better combustion, which may result in a better torque or fuel-consumption.

That's why BMW also adapted the mechanical operated variable lift only on the intake-valves. (Which reminds me... doesn't it work at 18 krpm yet??)

[RWC]

I think i can help with the 'why variable intake only?'
It's the exaust suction effect that is the main benifit they're trying to optimise with VVT.Thats the moment when both inlet & exaust valves are open at once,the effect being that the high inertia exaust gases help pull the intake charge into the cyl.

Also ,the intake,as i recall is very sensitve to time/revs variations where you can get the intake charge leaking back out of the (still open ) intake valve at low revs or not letting enough in at high revs.
Exaust timing by itself is not so sensitive.

Most of these problems can be addressed by using variable intake timing only