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Old 03-02-2012, 07:06 PM   #41
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Default Re: Variable Valve timing

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hmmm, the valves look the same but the heads i remember didn't have a mechanical drive on them. they were spun by some sort of electric motor
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Old 03-02-2012, 09:55 PM   #42
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Default Re: Variable Valve timing

Every now and then, when I'm interested in a technology that isn't quite ready for prime time, I search with Google Patents. http://www.google.com/advanced_patent_search

Try searching for phrases of interest such as "camless engine" or "variable valve timing" or the like.
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Old 03-03-2012, 11:26 AM   #43
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Default Re: Variable Valve timing

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Originally Posted by TangoFoxTrot View Post
Put me in the camp of NOT wanting this type of technology. I've never had a traditional cam "fail" on any car I've ever owned, and the advantage of this type of technology would only be at the bleeding edges of performance.
I heard the same thing from people when fuel injection started replacing carbs.
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Old 03-03-2012, 12:49 PM   #44
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Default Re: Variable Valve timing

454 Chevys are known for going through camshafts.My father's friend Tim's 1972 El Camino SS with the 454 did this 3 times and fixed it converting to a roller cam set up.Cummins did test a camless engine,was not perfected yet.
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Old 03-03-2012, 04:44 PM   #45
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Default Re: Variable Valve timing

Well, F1 uses air pressure to open and close the valves. No camshafts.

Also, BMW's valvetronic uses the valves to regulate how much air gooes into the cylinder. So they can eliminate the throttle body bottleneck..
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Old 03-03-2012, 04:50 PM   #46
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Default Re: Variable Valve timing

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Originally Posted by wafrederick View Post
454 Chevys are known for going through camshafts.My father's friend Tim's 1972 El Camino SS with the 454 did this 3 times and fixed it converting to a roller cam set up.
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Old 03-03-2012, 05:04 PM   #47
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Default Re: Variable Valve timing

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OK, so I had a thought the other day, my wife tells me this is dangerous so I try no to do it too often. Why do we use cam shafts in modern engines? Why not just actuate the intake and exhaust valves via some other means, air, hydraulic or most likely electrical? Has this been done?

Even cars that are advertised as having variable valve timing are still just shifting the timing of the can shaft, they cannot effect duration or lift at all just opening time. It would seem the ideal solution would be a completely cam free engine to allow a computer controlled valve to open the right amount and duration to optimize performance. Just imagine, no more trading high end horsepower for low end torque. Just tell the computer what you want and hit the loud pedal?

Am I crazy, has it been done, what say you?

Tom

There is no cost-benefit to doing so. Engines have reached the point of extremely diminishing returns in regards to efficiency. The cost of such systems outweighs the limited fuel economy and power benefit they would provide.

And a puny little engine can only have so much torque no matter how it's cammed.
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Old 03-03-2012, 05:04 PM   #48
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Default Re: Variable Valve timing

Anyone remember the Cadillac "V8-6-4" it was dropped in short order
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Old 03-03-2012, 05:14 PM   #49
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Default Re: Variable Valve timing

ME today had an article about a company a while ago that came up with the appropriate pneumatic valve design to do this.
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Old 03-03-2012, 05:16 PM   #50
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Default Re: Variable Valve timing

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There is no cost-benefit to doing so. Engines have reached the point of extremely diminishing returns in regards to efficiency. The cost of such systems outweighs the limited fuel economy and power benefit they would provide.

And a puny little engine can only have so much torque no matter how it's cammed.
Wow. You're clueless in multiple threads.

Engines are getting more and more efficient all the time. They have to be in order to keep up with CAFE regulations. Probably the biggest thing lately is GDI technology. We're starting to see it even on mainstream engines in low-cost cars now. Pretty soon, port injection will go the way of carburetors and distributors.

And BTW, lots of small engines make fantastic torque with the addition of a small turbocharger. Just ask an Audi owner. Great torque and great efficiency.
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Old 03-03-2012, 05:25 PM   #51
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Default Re: Variable Valve timing

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Anyone remember the Cadillac "V8-6-4" it was dropped in short order
And auto manufacturers are now building similar engines that work just fine - technology has come a long ways since then.
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Old 03-03-2012, 05:46 PM   #52
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Default Re: Variable Valve timing

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Originally Posted by TangoFoxTrot View Post
Yea, if only GM adapted camless engines, I'm sure they'd NEVER have any issues with it.
I never said they wouldn't.

Just pointing out the fact that there have been specific cam issues contrary to your personal experience. And poking a little fun at GM.

Sorry if I was to subtle for you.
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Old 03-05-2012, 02:17 PM   #53
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Default Re: Variable Valve timing

I think this will rapidly become more important as we slowly and dimly figure out that we are using a hell of a lot of oil and selling our souls to unpleasant folks in the middle east to get it.
One way or another oil prices are going to keep going up and most people are going to eventually be heading out of the Suburban and into something with a small engine, and getting a super wide usable range out of a tiny engine is going to require fully variable valve timing...
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Old 03-05-2012, 02:42 PM   #54
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Default Re: Variable Valve timing

Would be interesting to have a 1.8L engine that produces 80hp at 3k rpm for 45-55mpg cruising and 400hp at 13k for when you want to be somewhere in a hurry. You could run a quarter mile in first gear and stop to pick up groceries on the way home.

Thoughts on whether or not the 5252 cross over would still exist?
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Old 03-05-2012, 02:42 PM   #55
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Default Re: Variable Valve timing

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Originally Posted by Even Steven View Post

Engines are getting more and more efficient all the time. They have to be in order to keep up with CAFE regulations. Probably the biggest thing lately is GDI technology. We're starting to see it even on mainstream engines in low-cost cars now. Pretty soon, port injection will go the way of carburetors and distributors.

And BTW, lots of small engines make fantastic torque with the addition of a small turbocharger. Just ask an Audi owner. Great torque and great efficiency.
The engines aren't getting more efficient, the chassis are becoming more efficient along with more efficient transmission/driveline/accessory operation.

Engines have actually seen a reduction in efficiency due to increased reductions in Nox. That's why manufacturers have to result to all sorts of "tricks" (like cylinder cancellation) in order to make the engines more efficient.

(cylinder cancellation essentially makes the engine smaller)

Turbochargers, variable valve timing etc all add considerable cost to the engine for very little efficiency benefit to the end user.

Last edited by checkthisout; 03-05-2012 at 02:45 PM.
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Old 03-05-2012, 02:45 PM   #56
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Default Re: Variable Valve timing

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I think this will rapidly become more important as we slowly and dimly figure out that we are using a hell of a lot of oil and selling our souls to unpleasant folks in the middle east to get it.
One way or another oil prices are going to keep going up and most people are going to eventually be heading out of the Suburban and into something with a small engine, and getting a super wide usable range out of a tiny engine is going to require fully variable valve timing...
It's more beneficial to go to a hybrid type setup which allows you to both recover braking energy, and run the engine at a more constant and thus more efficient speed and load.
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Old 03-05-2012, 02:46 PM   #57
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Default Re: Variable Valve timing

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Turbochargers, variable valve timing etc all add considerable cost to the engine for very little efficiency benefit to the end user.

I agree with a lot of what you've written but I do not think this is a true statement.


For instance, a turbocharger can increase the volumetric efficiency of an engine by over 100 percent without much hassle at all.

edit - rude not to give real world examples:
GM's ecotec engine (the good one), is a 2L 4 cylinder engine that produces 260ft/lbs of torque from 2500rpm (more than 200ft/lbs from 2k) all the way to 5300rpm. It routinely gets 35mpg when not being horsed. That's a pretty significant increase in efficiency from a 2L n/a motor without direct injection and VVT cam phasing unless you were driving at some other meaning for the word.

Last edited by Dickey; 03-05-2012 at 02:55 PM.
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Old 03-05-2012, 03:17 PM   #58
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Default Re: Variable Valve timing

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I agree with a lot of what you've written but I do not think this is a true statement.


For instance, a turbocharger can increase the volumetric efficiency of an engine by over 100 percent without much hassle at all.

edit - rude not to give real world examples:
GM's ecotec engine (the good one), is a 2L 4 cylinder engine that produces 260ft/lbs of torque from 2500rpm (more than 200ft/lbs from 2k) all the way to 5300rpm. It routinely gets 35mpg when not being horsed. That's a pretty significant increase in efficiency from a 2L n/a motor without direct injection and VVT cam phasing unless you were driving at some other meaning for the word.
I was leaning more towards fuel economy rather than horspower.

What other engines are available in the car and what sort of fuel economy do they get and how much do they cost?
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Old 03-05-2012, 03:32 PM   #59
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Default Re: Variable Valve timing

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I was leaning more towards fuel economy rather than horspower.

What other engines are available in the car and what sort of fuel economy do they get and how much do they cost?

10 years ago there were no 260hp engines that managed 35mpg. Certainly not with a 100 thousand mile warranty as well.

//also I was mistaken somewhat, the aforementioned engine also came from the dealership with a 290hp "dealer update" option - not surprising considering that owners were able to dial that motor well past 300hp/350tq with little more than a cat back exhaust and some computer updates.


The only other engine that I'm aware of for the Solstice and Sky was a 2.4L ecotec that managed 28-31mpg and produced 177hp and 170tq. It was not a direct injection motor nor did it possess a turbocharger.

edit - that 2.4 motor was only rated at 25mpg, though I recall some friends of mine reporting closer to 30 - my bad for any confusion this might have caused. The Saturn Sky's msrp was between 27.5k and 33k. The Redline came with a lot of other options in addition to the engine that the base trim package did not offer. I think it would be safe to argue that there was a 15-17 percent increase in cost (5k) for the hot motor. Not only did it enjoy a 20 percent increase in fuel economy, it also made 46% more power with an engine package that was physically identical save for the added turbo charger and requisite plumbing that entails.

Last edited by Dickey; 03-05-2012 at 03:48 PM. Reason: left out information
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Old 03-05-2012, 03:52 PM   #60
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Default Re: Variable Valve timing

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Thoughts on whether or not the 5252 cross over would still exist?
By definition, torque in ft-lbs = (Hp x 5250)/RPM, so the two values will always equal each other at that speed.
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