Thoughts on variable valve timing...

"BaconSandwich is tasty." (baconsandwich) 09/03/2013 at 17:48 • Filed to: None

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For some odd reason, today I've been thinking a lot about variable valve timing. I did a bunch of reading on Wikipedia about it, and it definitely seems like there are a bunch of different ways to go about implementing it. The one that has really stuck in my brain is by Koenigsegg:

Rather than using a traditional cam setup, it uses some sort of electro-mechanical actuators to move the valves. This got me thinking: why the heck hasn't anyone else done this before, and why isn't it in production (or at least undergoing more testing/prototyping)?

Any engineers (or anyone else) out there have a few thoughts on the matter?

It seems like the more I study, the more joy I find in the simplest of solutions. Having hydraulic systems to move cams around seems a bit pedestrian after thinking about the simplicity of electrically driven valves.

vdub_nut: scooter snob > BaconSandwich is tasty. 09/03/2013 at 17:54

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probably the same reason Desmo valves never took off. Overly complicated for the benefits, not necessarily long lasting.

Paul, Man of Mustangs > BaconSandwich is tasty. 09/03/2013 at 17:54

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I think they're now testing with pneumatic valves. Perhaps the control devices just haven't been perfected enough at this point to be practical, or the actuators haven't been fast enough or reliable enough. Koenigsegg seems to be pretty close to perfecting the system, though.

Mikeado > BaconSandwich is tasty. 09/03/2013 at 18:09

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Their SAAB 9-5 test car suggests they're fine-tuning it and making it reliable before adding it to the Agera 2 or something. They also have a lot of freedom to play with ideas like that, which mainstream companies (usually the best-funded) might not.

But yes, it's the future of the internal combustion engine and needs to become commonplace ASAP! The numbers he mentions are incredible.

hollanddjw 1 > BaconSandwich is tasty. 09/03/2013 at 18:19

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I believe that Fiat has used this technology in the exhaust valves of their MultiAir engines.

Danimalk - Drives a Slow Car Fast > BaconSandwich is tasty. 09/03/2013 at 18:23

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I feel like all I'm talking about is Fiats today, but their Multi-Air system is pretty trick.

No Intake cam. Instead the Exhaust cam primes the (red) actuator with oil, then an electric signal tells valve not only when to open, but how far as well, allowing for the valve to move completely independently from the rest of the engine. The fewer amount of moving parts and smaller head packaging seems to be the biggest benefit so far, until they can develop and perfect the technology. They do get ~170lb-ft out of a 1.4 in the Abarth (180 in the 500L) so these trick valves may have something to do with that.

BaconSandwich is tasty. > hollanddjw 1 09/03/2013 at 18:25

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Interesting - especially considering there are MultiAir engines being used in the Fiat 500. For some reason I thought the MultiAir did it's VVT through another means.

Link for the curious: http://en.wikipedia.org/wiki/MultiAir

BaconSandwich is tasty. > Mikeado 09/03/2013 at 18:27

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Agreed! What I would find interesting is doing at least a few more test mules to try it out. Rather than sticking it just to a single Saab, why not try it out on half a dozen, and make the employees drive them on a daily basis? It'd definitely help get some more numbers on durability, and possibly help identify any weak points.

BaconSandwich is tasty. > Danimalk - Drives a Slow Car Fast 09/03/2013 at 18:29

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That is quite impressive!

hollanddjw 1 > BaconSandwich is tasty. 09/03/2013 at 18:38

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I was partially wrong- it's the intake valves that are electronically controlled. Found a video! It's exciting that this kind of technology is already available in such everyday cars, and also that high-dollar manufacturers such as Koenigsegg are using it.

BaconSandwich is tasty. > hollanddjw 1 09/03/2013 at 18:44

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I just found the same video. It's still an interesting concept. It's like we've gone 90% of the way, and now we just need to do the other 90%....

Chteelers > BaconSandwich is tasty. 09/04/2013 at 08:51

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BMW's Valvetronic is pretty trick. They use an extra shaft which adjusts the intake cam to increase or decrease the valve lift. This eliminates the need for a throttle body.