Thread: The end of the road for VVL?

Continuously Variable Cam duration.

Introduction

Ironically this cam will work in a DE but not a VE, unless you can modify or retro fit different rocker arms to the VE.

Looks very interesting. Looking forward to seeing the first production bike or car with this system. The only downside I can see is that the lift is always constant, but perhaps with some clever grinding they can achieve variable lift as well.

There are so many different cam phasing and cam lift change designs out there it's hard to weed through them all. This system seems worse in just about every way to Ferrari's continuously variable cam duration and lift system. It looks more complicated, more expensive to produce, more failure prone, and less versatile than Ferrari's current solution. Have you taken a look at Ferrari's current tech (in their road cars currently)? It's not the best system, but it seems pretty damn good.

YouTube - 1 - WHC Introduction

I really LOVE the idea of everything being machanical. It kind of reminds me of a go kart clutch... It's a genius idea... thickening the variable portion wouldn't be a bad idea for an inline four... but I have some concerns with it in the limited space of an SR valve train. Everything moving axially would seem to be tough.

I think its a great idea, and he's doing his own marketing by posting his videos showing how it works... its really cool because I can see how you would be able to mod the duration change by simply changing out the centrifugal weights.

YouTube - 5 - Automatic duration change with RPM by centrifugal controller

The thing is duration is great, but there is no way to change lift... so from a performance standard (which is really all we care about) I don't see it being super useful, especially with interference engines.

He is going with the right approach though. This will definitely increase the potential for greater fuel economy, smooth powerbands, and generally better torque curves... which is what car companies want to market these days.

Pretty innovative... but I agree with Ben, it's a very failure prone piece... mainly because the cams aren't one piece. I like it but if it fails, so does your engine, and the potential is risky.

He discusses everything in detail in all the articles... but the videos are very informative as well... he discusses alterior options. even though its limited he discusses further advancements in the future toward performance
YouTube - 4 - WHC Durability and LIVC

Pretty bright guy.

There isn't much info on the ferrari system on the net it seems. Although I only did a quick search. But from wiki, this guy's invention is truely unique and the only system to address ALL the issues and requirements that the CVCD is supposed to have. I especially like the idea that it can be retro fitted to an ordinary valve train. The ferrari system probably uses special/unique rocker arrangements. Not saying it's bad, but I wonder if their 3D lobes can allow such a drastic increase in duration as this guys system.

Looking at this, I'm still sure that extra lift can be had with this cam as well if it's ground right, but let's not get hung up on that. Lift is just another means of getting air into the chamber. Having this much duration with a fairly good base lift will acomplish the same thing, which = performance.

Helical camshaft - Wikipedia, the free encyclopedia

A helical camshaft is a type of mechanical variable valve actuation (VVA) system. More specifically it is a camshaft that allows the valve opening duration to be varied over a wide, continuous, step-less, range, with all of the added duration being at full valve lift.

In this article a “variable duration camshaft” refers to a camshaft that can essentially replace a conventional camshaft in a cylinder head and operate the valves through conventional followers. Further qualifications are:

that the duration range is step-less and continuous
all the added range is at full valve lift
the range is wide enough to allow full torque/power at even extremely high RPM
the range is wide enough to allow engine load control by late inlet valve closing (LIVC)
the rates of valve opening/closing, acceleration, jerk etc. are within acceptable limits at all duration settings
These qualifications must be made as there have been many claims over the years of purely mechanical variable duration camshafts but none have been able to meet all these requirements.

Despite enormous effort and expense being expended by both large organisations and private individuals, camshaft arrangements like patent 1527456 have never been significantly improved upon and have remained unused by the mainstream automotive community. The opinion of many engineers (and others) on the possibility of a workable variable duration camshaft being developed after so much effort and so many years of unsuccessful attempts was that it was highly unlikely that it ever could be done and would remain an unobtainable “holy grail.”

The Helical Camshaft is notable and significant because it appears to employ a previously unknown mechanical principle[dubious – discuss] in its essential helical movement. .

While we're on the topic, since you seem quite interested, I'll show you some of the tech I've seen years ago that I like.

I've been following Pattakon for about 10 years and he's always had me excited about valve tech. He has desmodromic valve train plans I've always liked (but couldn't find his simpler version on his site anymore). He has tons of ideas for variable lift and duration valve trains. I personally like his rod version of variable lift* the best:

http://www.pattakon.com/pattakonRod.htm

Don't forget to download and watch the animations.

It's also fun to read about the pulling piston engine, and I'll see if I can find the site with the plans for the self supercharged engine (piston on the down-stroke pressurizes the intake charge).




*It has the same issues all poppet valve systems have with using the valves instead of a throttle body. The air intake amount is so hard to control at tiny valve lifts that idle can't be maintained well. BMW solved the issue by machining valves and seats to exact specifications. Other engine makers add an auxiliary port to the cylinder with an idle valve control. You can see on that site he's found that issue as well and working on it.

You're right that the big advantage of the Williams Helical Camshaft is the apparent ability to retrofit some heads with the design, instead of requiring an entirely new head.

Cool. I'll read through those a bit when I have more time.

If these types of cams make it into production we might just see DE prices go through the roof - ha ha.

Someone better start making fixed, DE style rocker arms for the VVL heads soon though


The one thing about these cams that I don't get is what is gonna be used to activate them? Since the movement must be continuous and rpm dependant I can only imagine that it must be some pressure based hydraulic system. I can also imagine that tuning will be a bit complicated. I mean it's one thing to vary the duration in search of power, but at the same time you need to be weary of interference. On a non interference engine this concept would work wonderfully.

There was one video where there was an rpm activated centrifugal weight... I'm not sure if that is the one he created for use with the system, but if its not all he has is a over jacked adjustable cam gear that adds fixed duration

Nice. That would be fairly simple then to upgrade say a DE to use such cams.

Now all we have to do is build bottom ends capable of handling 15,000rpm

(I hope the 2012 GSXR1000 engineers are talking to this oke. Either that or they must build a V4)

Has he run that design in an engine yet? I'm starting to see some issues he might run into. To extend the duration, he extends one part of the cam profile. It makes most sense to extend the highest lift section of the cam profile for a couple reasons, but even when you do it the best way (at max lift) you still are totally changing valve spring dynamics and resonance. Valve springs need to be tuned to the cam profile and 5th (or up to 9th?) order harmonics need to be taken into account especially as rpm rise. Changing the cam profile like that seems like there would be hard problems to solve with valve float. Especially when it looks like you're just adding a flat section to the cam profile, not a nice curved slope.

But I guess just about every other variable duration (and/or lift) cam profile has to deal with the same issue (except desmodromic actuation), so maybe not as big a deal as I'm making it out to be.