A new Continuously Variable Valve Actuation system

[Anonymous]

xctasy wrote: "The key here is that when owners of cars change camshft timing and the ammount of lift at the valve, they do it by getting an aftermarket camshaft, which incorporates about 100 years of developement."

xctasy, when you install a racing camshaft into your car and comes the moment to drive the car into city traffic, the fact that "it incorporates 100 years of development" isn't enough to make your life easy.

Think now that if the EXACT valve lift profile your "racing" engine uses is "copied" to the VVA cylinerd head (i.e. with the gas pedal pressed 95% the intake and exhaust valves of your engine with the VVA system move exactly as the valves in your "racing" car), there is no reason to take less power or less torque or worse economy than the original "racing" car. When the gass pedal is compressed at 100% then the valve lift is a little higher as well as the overlap, so the VVA engine could provide a little more power and torque than your "racing". On the other hand, when the gas pedal is only slightly pressed, the valve lift profile is anything but "wild" or "racing", making the driving into city traffic easy.
So, think once more what you can gain with a VVA and what you loose.


jamyers,
a carburator cannot control correctly the quality of the mixture in a VVA application, especially when the throttle valve is open and the speed of the air is slow or very slow (idling). The easy and cheap way is the fuel injection with lambda sensor (for feedback and adjustmnet) at exhaust.

Thanks
Manolis Pattakos
, the

 

[jamyers]

Manolis,

I'm reading your page "How VVA works", and thinking of the usefulness of your VVA system in 'my world': Older cars/engines with a carburetor, owned by guys who like to tinker on them and get the best out of them. And I'm liking it so far!

Keep the carb for idling and mixture - a good carb is as good a flow meter as fuel injection, and the fact that most aftermarket-type guys and their cars are going to use a carb, at least around here. Converting to EFI is too expensive or involved for the benefits.

Don't worry so much about idling down around 300rpm, it's not that big a deal (to me, anyway), and it opens up other issues to overcome: alternator charging, air conditioner compressor speed, and engine-driven cooling fan operation. Idling smoothly at 600-650rpm, that'd be fine. Since you're not worrying about zero or near-zero valve lift, you don't have to worry about the idle valve (which makes it WAY simpler to install).

Since any engine has an optimum VVA setting for a particular rpm, how about a simple rpm-based method of controlling the VVA, so that the valve actuation very closely follows rpm? Use an electronic tachometer input, some sort of electronic controller, and your electric shaft-controlling motor. All I as a user would have to do is to find the optimum VVA settings for several rpm points (like every 500 rpm from idle to 6000rpm on my 455-inch V8), and adjust the control mechanism accordingly.

Then, as I drive the car with the throttle, the VVA continuously matches the camshaft profile to the engine rpm. I floor the pedal, and as the rpm's climb the cam 'gets bigger' to match the increased rpm.

While the low-rpm idle is a neat thing, I don't think it's your main selling point.

I'd present your idea from the other end - "Hey, you can use a really, really wild camshaft, and my VVA tames it down so that you can drive it on the street to go get groceries. Instead of camshaft selection being a compromise, you can now get the best of all worlds."

Now the BIG question: What would it take to put a VVA system like I'd described on an american V8 - specifically a Buick V8 with shaft-mounted rocker arms?

 

[Anonymous]

Jamyers,

I also prefer the “upper end “ of VVA. But if you start with it, the next question is “how it behaves at partial loads and low revsâ€￾ because there is where the problem really is (everybody can use racing cam(s) to get more and more power but then the engine becomes a nightmare at light loads and low revs).

The application of the Pattakon VVA in side cam engines is simpler than in OHC or DOHC engines.

Open the animation
http://www.pattakon.com/vva/SideCam.exe
This version of VVA can be applied on the American V-8 (and V-6 and V-2) and can control either the intake valve lift or all valves lift.
A unique control shaft – per cylinder bank – can control valve lift.

What it takes?
As regards HW : the replacement of each rocker arm with a “double oneâ€￾ and the installation of the two control shafts. The existing pivot shafts remain as they are. It may be needed a “servoâ€￾ to assist the gas pedal because it will be heavy (in Honda VVA prototype the gas pedal is heavy because they are used hard valve springs and because the VVA controls all valves, intake and exhaust. In the light version for Honda Civic VVA, now on road tests, the VVA controls exclusively the intake valves making the gas pedal “softâ€￾).

Lately a guy asked if the Pattakon VVA can control the valves of a Diesel engine. The Pattakon VVA is adequately strong and light to run at more than 9000 rpm and is adequately accurate to keep the 0.2 mm of valve lift at idling. As Diesels “endâ€￾ at only 4500 rpm and never need less than 1.5 mm intake valve lift to operate, there is no question: the Pattakon VVA can control the vales of any diesel. (yes, VVA offers a lot on Diesel engines too, because it optimises volumetric efficiency, turbulence and swirl at all revs).

In the following GM LS1 forum thread:
“LS1TECH - Why hasn't VTEC been adapted to pushrod enginesâ€￾
there were explained the benefits of the SideCam version of VVA, take a look.
Also see the threads:
“LS1TECH - Extending Valve Spring Lifeâ€￾
“LS1TECH - Nice intake manifold___ - The ITB threadâ€￾

If you are interested, make a search to see if people are interested in this modification of big V8.
If yes, a prototype (for the most common V8 ) could be made for road tests. Are you in?

Thanks
Manolis Pattakos

 

[jamyers]

Does your system need shaft-mounted rocker arms, or how about the Ford and Chevrolet V8 stud-mounted rockers? Seems like a shaft-mounted setup would be way easier.

Buick engines aren't all that common, but they do have shaft-mounted rocker arms.

I'm trying to get some feedback over on www.v8buick.com. I don't know if or how many would be interested, but I certainly am. What info would you need to develop plans for a particular engine - detailed drawings, or an actual head?

 

[Anonymous]

Jamyers,

You know better than me the details of V-8.
So, what do you think about the need of pivot shaft?
I think, based on photos, that pivot shaft is not necessary.

Thanks
Manolis Pattakos

 

[jamyers]

I'd think that a V-8 with shaft-mounted rockers would be the same type setup as on a Ford Inline 6, also with shaft-mounted rockers. The differences would lie in the engine-specific rocker arm dimensions (shaft diameter, length of each side's arm, etc). I'd think you could develop one basic size, and make versions for other engines based on it. Most US engines use close to the same rocker arm ratio (1.5 - 1.7), so it shouldn't be too difficult to go from say, a Ford 6 to a Buick 8 or any other shaft-mounted rocker arm. (While Ford and Chevy V8's are stud-mounted rockers, lots of top-end racers are converting to shaft-mounted rockers on their engines.)

Here's a pic of a pair of shaft-mount Buick rockers (couldn't find a Ford pic quickly). These are early aluminum rockers, '72 and later are steel.

Here's a pic of the end view of shaft-mounted rockers (again Buick, sorry)

 

[jamyers]

I'm not sure what you mean by "pivot shaft"...as I'm looking at your drawings and animations for the side-valve engines...here, I've labeled some parts for clarification.

As I'm seeing it;

* the Rocker Arm Roller is riding on a small shaft through the Rocker Arm,

* the Lost-Motion Roller is riding on a small shaft held in place by two arms (not shown) going down to the Rocker Arm Roller's shaft, since that's the movement arc it follows.

* The Control Bucket is actually two similar parts, one on each side of the Lost-Motion Roller itself, and the Bucket(s) bear on the shaft of the Lost-Motion Roller. (Wouldn't it be better for them to bear on another roller, and could it even be the same size as the Lost-Motion Roller?)

* The Control Bucket is also actually a shaft running the length of the cylinder head, so all cylinders are controlled the same.

What's needed is a way to mount the Control Bucket(s) Shaft to the head so it doesn't move - which should be easy to do, since there are already rocker-arm shaft mounting pedestals available. Might need another mounting point for stability/strength, you could go over to the edge of the cylinder head itself if need be.

 

[jamyers]

One more thing - looking at the animations, if you rotated the Control Bucket even more in the High-Lift direction, wouldn't you get even more lift/duration out of a given cam? That might make it easier, since a user wouldn't have to install a really wild cam - but could use the VVA to 'grow' their cam into a bigger one at higher rpms.

 

[Anonymous]

Jamyers,

the free roller does not need any arms to keep it in place.
The free roller is actually ‘trapped’ among the valve-rocker-roller, the pushrod-rocker and the control (or Bucket) shaft. If you see at the Pattakon Civic prototype pictures at Pattakon web site you can see the free roller and its pin. That simple and robust.
Look also at the specific form of the control shaft in the animation of the Rod-Roller version (Peugeot Vts cylinder head). The control shaft has a cylindrical surface along which the pin of the free roller rolls (look the “stopâ€￾ at the end of this surface). See also the pictures of the control (Bucket) shaft of VTS. The control shaft for the V-8 is not far from this design.

Yes the existing camshafts can be used. The resulting valve lift can be more than present valve lift, depending on the design of the VVA. With higher valve lift the actual overlap is increased too.

I like the replies you gathered in V-8 Buick forum.
It is good to see how people react on new ideas.
You are talking for things already on the road and they refuse to take just a look.

Thanks
Manolis Pattakos

 

[Anonymous]

Jamyers,

I hope you got everything I wrote (otherwise ask me).

Thanks
Manolis Pattakos

 

[jamyers]

Yes, been mulling ot all over and emailing some fellow gearheads.

I'll be out of town for a couple of days.