Will Camshafts Soon Become Extinct?
12-30-2006, 05:40 PM
#41
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Originally Posted by hammertime
I thought it was the amperage that was most dangerous. At least for 12v/24v/48v dc and 110v/220v ac. Your skin shouldn't allow enough conduction, unless the current burns through the outer flesh.
from http://www.cdc.gov/niosh/elecovrv.html
from http://www.cdc.gov/niosh/elecovrv.html
i know, but i couldnt help myself. 
01-01-2007, 08:23 PM
#46
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I believe that electrical valvetrain actuation is not where
it's at. Not directly anyway. Too much power needed in a
small hot space, bad for electricals unless you wanted to
push the art in high temperature magnetics. Electrical has
to supply all the power and that's not the slick way to do
it.
But, solenoid valves gating more serious pulsed power, like
a compressed-air open/closed disc piston on the valvestem,
contactless except for the guide, tolerate a little air blowoff
for not needing a seal and you can have a lighter valvestem
mass than right now, a thin wall cylinder mounted to the head
(or cast and bored) and maybe the air passages cast in with
the solenoid vaves screwed in? How much pulsed air power
can you deliver through a 1/4" pipe and a good air 'noid?
Cheapo belt driven compressor replaces cam drive and
all of the moving parts except the engine valves and the
solenoid valves. And solenoid valve timing can be put to
lead valve event or mess it around to make your wildest
valve event timing dreams, wet ones.
Here is my drawing of one that could be built in any
machine shop to demonstrate. Tubing and sheet stock,
tap and die, compressed air and switches, badda bing.
One thing I see as an issue for air or electrical valve
systems is that of opening against the still substantial
pressure head inside the chamber at BDC. This pressure
adds to the seat pressure and that's a bitch to push over
for a coil or even a decent air pressure (2" apply piston,
100PSI air, about 300lb of force). The hard push camshaft
type valvetrain has a whole lot more capability there.
it's at. Not directly anyway. Too much power needed in a
small hot space, bad for electricals unless you wanted to
push the art in high temperature magnetics. Electrical has
to supply all the power and that's not the slick way to do
it.
But, solenoid valves gating more serious pulsed power, like
a compressed-air open/closed disc piston on the valvestem,
contactless except for the guide, tolerate a little air blowoff
for not needing a seal and you can have a lighter valvestem
mass than right now, a thin wall cylinder mounted to the head
(or cast and bored) and maybe the air passages cast in with
the solenoid vaves screwed in? How much pulsed air power
can you deliver through a 1/4" pipe and a good air 'noid?
Cheapo belt driven compressor replaces cam drive and
all of the moving parts except the engine valves and the
solenoid valves. And solenoid valve timing can be put to
lead valve event or mess it around to make your wildest
valve event timing dreams, wet ones.
Here is my drawing of one that could be built in any
machine shop to demonstrate. Tubing and sheet stock,
tap and die, compressed air and switches, badda bing.
One thing I see as an issue for air or electrical valve
systems is that of opening against the still substantial
pressure head inside the chamber at BDC. This pressure
adds to the seat pressure and that's a bitch to push over
for a coil or even a decent air pressure (2" apply piston,
100PSI air, about 300lb of force). The hard push camshaft
type valvetrain has a whole lot more capability there.
01-01-2007, 09:43 PM
#48
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Originally Posted by jimmyblue
Here is my drawing of one that could be built in any
machine shop to demonstrate. Tubing and sheet stock,
tap and die, compressed air and switches, badda bing.
machine shop to demonstrate. Tubing and sheet stock,
tap and die, compressed air and switches, badda bing.
That looks simple, almost too simple
That is actually a great design; one side of the 'chamber' is to open and the other side is to close.
Can air activated solenoids work as quickly as electric solenoids?
01-01-2007, 09:54 PM
#49
Originally Posted by ProdriveMS
F1 engines still use a camshaft to actuate their valves. They have done away with valve springs and use air to return the valve . The system is called PVRS(pneumatic valve return system). You should be able to find tech articles if you search pvrs. A valve spring stiff enough to close the valves at 20k would never survive an hour and a half, let alone two race weekends. Look at how long Pro Stock springs last. We were working on a pvrs in prostock when the NHRA preemptively banned it.
Al
Al
01-02-2007, 08:33 AM
#50
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The Coates rotary valve system shows a lot of promise for a purely mechanical setup.
http://www.coatesengine.com/engine_of_the_future.html
While not offering the degree of control possible with computer controlled direct actuation, it is a huge leap forward over the current poppet valve technology. A 5.0L stock engine from a Lincoln which produced 260/249 went to 475/454 when equipped with their head and valve system.
http://www.coatesengine.com/engine_of_the_future.html
While not offering the degree of control possible with computer controlled direct actuation, it is a huge leap forward over the current poppet valve technology. A 5.0L stock engine from a Lincoln which produced 260/249 went to 475/454 when equipped with their head and valve system.
01-02-2007, 09:38 AM
#51
I've actually looked into this before, and the two things holding the technology back are:
1. improving reliability
2. getting fast enough solenoids
As far as I know, there are no solenoids capable of acting continuously fast enough for a car engine at high rpms. The examples I saw were for low revving diesels.
1. improving reliability
2. getting fast enough solenoids
As far as I know, there are no solenoids capable of acting continuously fast enough for a car engine at high rpms. The examples I saw were for low revving diesels.
01-03-2007, 11:26 PM
#55
TECH Fanatic
Thread Starter
I will attempt to get back on topic with something that I was thinking about on the ******* today:
Would the cam profile necessarily need to be dependent / controlled by the position of the throttle and / or engine sensors, or would it also make sense to allow for optional driver input? For example: Let's say that you have a pickup that you use for a variety of functions, including some towing and some off-roading. Certainly, we can all agree that there are different optimal cam profiles for low-RPM towing and higher-RPM mudding. I would think that at high-RPM's you would want the most aggressive horsepower making profile. At low RPM's, the answer get's a little more grey. Do you want to drive at 2000 RPM's with the best fuel economy or at the highest obtainable torque value? Are these two conditions one in the same? What if I want to tow at 2000 RPM's with a very aggressive cam profile for the sheer joy of it and don't care about fuel efficiency? Would the computer use throttle position as well as the other usual sensors (MAF, MAP, IAT, Temp, O2, Ect) to determine and adjust the cam profile on the fly for both driving conditions, or would it make more sense for the driver to inform the computer ahead of time that he intends to tow at low RPMs or Off-Road at high RPM's? This was touched upon earlier, but I think it is worth a second look. I guess I am just trying to imagine how much control, if any, that the driver would have or even need to have.
Would the cam profile necessarily need to be dependent / controlled by the position of the throttle and / or engine sensors, or would it also make sense to allow for optional driver input? For example: Let's say that you have a pickup that you use for a variety of functions, including some towing and some off-roading. Certainly, we can all agree that there are different optimal cam profiles for low-RPM towing and higher-RPM mudding. I would think that at high-RPM's you would want the most aggressive horsepower making profile. At low RPM's, the answer get's a little more grey. Do you want to drive at 2000 RPM's with the best fuel economy or at the highest obtainable torque value? Are these two conditions one in the same? What if I want to tow at 2000 RPM's with a very aggressive cam profile for the sheer joy of it and don't care about fuel efficiency? Would the computer use throttle position as well as the other usual sensors (MAF, MAP, IAT, Temp, O2, Ect) to determine and adjust the cam profile on the fly for both driving conditions, or would it make more sense for the driver to inform the computer ahead of time that he intends to tow at low RPMs or Off-Road at high RPM's? This was touched upon earlier, but I think it is worth a second look. I guess I am just trying to imagine how much control, if any, that the driver would have or even need to have.
01-04-2007, 08:25 AM
#57
Guys, this isn't a high school debate forum. Please keep the threads on topic and spare us of your "I'm a genius" book smart chest-thumping. All this does is provide a bunch of garbage that the rest of us aren't impressed by, or care to read about.
I just deleted about 15 replies of bullshit. If I have to do this again, some of you will be getting a vacation from this site.
I just deleted about 15 replies of bullshit. If I have to do this again, some of you will be getting a vacation from this site.
01-04-2007, 10:40 AM
#58
TECH Fanatic
Re: Electro-magnetic valve actuation in F1 engines, which was banned a few years ago, here's a recent quote form Mario Illien, the chief architect for Mercedes-Benz F1 engines:
Question: Has electro-magnetic valve actuation ever been seriously considered?
MI: "No chance, not at the speed we are running. You cannot generate enough energy to do the job. If you worked out how much energy it takes to open and close the valves you would be surprised!"
"An air spring is stored energy which is helping you a great deal"
Thoughts:
Are we sure we want "square wave" valve motion? I'm not sure the air can start flowing smoothly thru an "instant open" valve. Of course, as we approach a "square wave" lift profile, the aceleration and therefore the force needed increases proportionally which requires more electro-magnetic (EM) energy. It's a viscous circle!
PVRS ("air springs") have some interesting possibilities which have been explored. Spring force can be controlled to the shape of the valve acceleration (force required) curve, whici is far different from the nearly linear force/valve lift curve we get from mechanical springs. Valve bounce on the seat, a power killer, can more easily be controlled with PVRS rather than cramming more seated pressure onto the valves.
Some high end race engines have tiny piston-valve clearances, on the order of a few thousandths, so some sort of a mechanical limit of valve lift at a closely controlled degree of rotation is essential. Mechanical camshafts and PVRS are the elegant solution. EM actuated valves might have a problem here, and we wouldn't want them to bang into a hard stop.
On the other hand, perhaps room temperature super conductors (RTSC) would solve all the problems associated with EM actuated valves. Of course that holy grail has yet to be found.
Question: Has electro-magnetic valve actuation ever been seriously considered?
MI: "No chance, not at the speed we are running. You cannot generate enough energy to do the job. If you worked out how much energy it takes to open and close the valves you would be surprised!"
"An air spring is stored energy which is helping you a great deal"
Thoughts:
Are we sure we want "square wave" valve motion? I'm not sure the air can start flowing smoothly thru an "instant open" valve. Of course, as we approach a "square wave" lift profile, the aceleration and therefore the force needed increases proportionally which requires more electro-magnetic (EM) energy. It's a viscous circle!
PVRS ("air springs") have some interesting possibilities which have been explored. Spring force can be controlled to the shape of the valve acceleration (force required) curve, whici is far different from the nearly linear force/valve lift curve we get from mechanical springs. Valve bounce on the seat, a power killer, can more easily be controlled with PVRS rather than cramming more seated pressure onto the valves.
Some high end race engines have tiny piston-valve clearances, on the order of a few thousandths, so some sort of a mechanical limit of valve lift at a closely controlled degree of rotation is essential. Mechanical camshafts and PVRS are the elegant solution. EM actuated valves might have a problem here, and we wouldn't want them to bang into a hard stop.
On the other hand, perhaps room temperature super conductors (RTSC) would solve all the problems associated with EM actuated valves. Of course that holy grail has yet to be found.
01-04-2007, 09:01 PM
#60
Originally Posted by JohnnyC
I will attempt to get back on topic with something that I was thinking about on the ******* today:
Would the cam profile necessarily need to be dependent / controlled by the position of the throttle and / or engine sensors, or would it also make sense to allow for optional driver input? For example: Let's say that you have a pickup that you use for a variety of functions, including some towing and some off-roading. Certainly, we can all agree that there are different optimal cam profiles for low-RPM towing and higher-RPM mudding. I would think that at high-RPM's you would want the most aggressive horsepower making profile. At low RPM's, the answer get's a little more grey. Do you want to drive at 2000 RPM's with the best fuel economy or at the highest obtainable torque value? Are these two conditions one in the same? What if I want to tow at 2000 RPM's with a very aggressive cam profile for the sheer joy of it and don't care about fuel efficiency? Would the computer use throttle position as well as the other usual sensors (MAF, MAP, IAT, Temp, O2, Ect) to determine and adjust the cam profile on the fly for both driving conditions, or would it make more sense for the driver to inform the computer ahead of time that he intends to tow at low RPMs or Off-Road at high RPM's? This was touched upon earlier, but I think it is worth a second look. I guess I am just trying to imagine how much control, if any, that the driver would have or even need to have.
Would the cam profile necessarily need to be dependent / controlled by the position of the throttle and / or engine sensors, or would it also make sense to allow for optional driver input? For example: Let's say that you have a pickup that you use for a variety of functions, including some towing and some off-roading. Certainly, we can all agree that there are different optimal cam profiles for low-RPM towing and higher-RPM mudding. I would think that at high-RPM's you would want the most aggressive horsepower making profile. At low RPM's, the answer get's a little more grey. Do you want to drive at 2000 RPM's with the best fuel economy or at the highest obtainable torque value? Are these two conditions one in the same? What if I want to tow at 2000 RPM's with a very aggressive cam profile for the sheer joy of it and don't care about fuel efficiency? Would the computer use throttle position as well as the other usual sensors (MAF, MAP, IAT, Temp, O2, Ect) to determine and adjust the cam profile on the fly for both driving conditions, or would it make more sense for the driver to inform the computer ahead of time that he intends to tow at low RPMs or Off-Road at high RPM's? This was touched upon earlier, but I think it is worth a second look. I guess I am just trying to imagine how much control, if any, that the driver would have or even need to have.
In the Variable position the engine sensors gather information and the pcm adjusts valve events for optimum torque vs. fuel economy at any rpm.