TOO MUCH VALVE SPRING

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C130 Chief said:
Two drawbacks to running too much spring pressure. First, as others have mentioned is wear and load on the entire valvetrain. Keep in mind that the cam sees the open pressure times the rocker ratio. So 300# open pressure is 450# at the cam lifter interface with a 1.5 rocker, placing greater load on the oil film (insert zinc debate here).

The next is a bit more subtle, but still important especially on a street engine. It simply takes more energy to compress a stiffer spring. This is $4/gal energy that isn't turning the driveshaft. Pure parasitic loss. Worse, it rises exponentially with RPM, and is proportionally greater at lower power settings like cruise.
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Minus heat loss, any power lost compressing one valve spring is gained by an opposing spring when it is closing the valve.
 
Go to comps spring chart and look at the pressures per lift. 1.70=115lbs seat
Open at your lift is not 300 lbs...........

...........you're at .470.. you're looking at less than 300...like 250 or so open.
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This place always makes everything harder than it should be.

The Comp chart shows the spring rate to be 402lbs/in.
I already showed that if you started at 1.700.....115lbs, that at 1.250(.450 lift) the force would be 296lbs.
Guess what the Comp chart shows for the force at 1.250...... amazingly..... it’s 296.

At 402lbs/in the force changes 20.1lbs per .050 of travel.
If you wanted to lower the open force by 40-50lbs, the open height would need to be .100-.125” taller.

I used .450 lift to account for the loss of lift you typically see with the stock rockers.
If you started at 1.700, and actually had .470 lift at the valve, the open force would be 304lbs.
Oh..... they’re [email protected](.500 lift), and [email protected](.550 lift)...... by the chart(and the math).
 
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cojohnso said:
I explored designing/creating an active spring system for engine value trains. The idea was to use a spring material that more easily collapses to open valve. But then becomes ridged under electric field to close value at timing. 20 years ago the materials were available, but not strong enough to stand up to engine valve stress. The idea of course was to greatly reduce valvetrain stress, thus increase engine efficiency and performance.

I thought I would throw the idea around for maybe a younger mind to pickup and maybe follow up on material advancements as well has newer engineering concepts.

We can always use a better spring design for many applications.
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These clever folks are on it...

 
Cuda416 said:
These clever folks are on it...

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I have Schubeck DOHC engine in a '70 Cuda that uses "Actuators" for its value control. Although not from a camless design like that shown in this video. But from a double over head belt driven cams. One of its limitations that was not discussed is its dependent on fluid dynamics just as a hydraulic lifter. Thus it does have max RPM restrictions. Just as hydraulic lifter has. And that begins at 6500 RPM. (Which is the redline of my Schubeck DOHC engine.)

In the case of the Schubeck 904 ci monster marine engine design. The engine is stroked to 6". Thus due to high piston speeds, 6500 RPM is about the max that can be managed anyways with traditional balancer technology. Engine achieves about 1200 HP at 5200 RPM. 1150 ft/torque at 3000. All on pump 91 octane gas at 10.0:1 compression.

So this does solve high spring pressure concerns for typical RPM ranges. But doesn't for high race performance RPM needs. In my opinion.

ZomboDroid 27072020230012.jpg
 
cojohnso said:
I have Schubeck DOHC engine in a '70 Cuda that uses "Actuators" for its value control. Although not from a camless design like that shown in this video. But from a double over head belt driven cams. One of its limitations that was not discussed is its dependent on fluid dynamics just as a hydraulic lifter. Thus it does have max RPM restrictions. Just as hydraulic lifter has. And that begins at 6500 RPM. (Which is the redline of my Schubeck DOHC engine.)

In the case of the Schubeck 904 ci monster marine engine design. The engine is stroked to 6". Thus due to high piston speeds, 6500 RPM is about the max that can be managed anyways with traditional balancer technology. Engine achieves about 1200 HP at 5200 RPM. 1150 ft/torque at 3000. All on pump 91 octane gas at 10.0:1 compression.

So this does solve high spring pressure concerns for typical RPM ranges. But doesn't for high race performance RPM needs. In my opinion.

View attachment 1715912523
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yup, no argument, though there method pretty cool.

We're talking about 600 HP from a three cyl, 2.0L engine... not bad....
 
Cuda416 said:
yup, no argument, though there method pretty cool.

We're talking about 600 HP from a three cyl, 2.0L engine... not bad....
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Certainly better efficiency. Thus lighter package. Thus better performance.

So the balancing act of High end HP vs low end torque continues. Lol.
 
cojohnso said:
Certainly better efficiency. Thus lighter package. Thus better performance.

So the balancing act of High end HP vs low end torque continues. Lol.
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Definitely a different world but I don't see why that tech couldn't work on other platforms. The smaller (lower) engine allows them to get pretty tight to the ground.

Anyway, not trying to hi-jack the thread OP. back to you..
 
Cuda416 said:
Definitely a different world but I don't see why that tech couldn't work on other platforms. The smaller (lower) engine allows them to get pretty tight to the ground.

Anyway, not trying to hi-jack the thread OP. back to you..
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All threads go's sideways a bit. But does illustrate high spring pressures is a topic of discussion. With the simplest of notions. Use the lightest spring thus lowest spring pressure that can still close valve timely for a particular performance application.

I agree with "A little too much" is better than not enough spring. So recommendations should be when in doubt? Go with higher spring strength. With the understanding that unneeded spring strength does mean some loss in performance. And additional valvetrain wear.
 
PRH said:
This place always makes everything harder than it should be.

The Comp chart shows the spring rate to be 402lbs/in.
I already showed that if you started at 1.700.....115lbs, that at 1.250(.450 lift) the force would be 296lbs.
Guess what the Comp chart shows for the force at 1.250...... amazingly..... it’s 296.

At 402lbs/in the force changes 20.1lbs per .050 of travel.
If you wanted to lower the open force by 40-50lbs, the open height would need to be .100-.125” taller.

I used .450 lift to account for the loss of lift you typically see with the stock rockers.
If you started at 1.700, and actually had .470 lift at the valve, the open force would be 304lbs.
Oh..... they’re [email protected](.500 lift), and [email protected](.550 lift)...... by the chart(and the math).
Click to expand...
Feel better?
 
@PRH yeah and the rough actual lift was already figured in too ...and it's not just from the rocker arm being a 1.45 instead of a 1.5 ...it's also cuz the lifter angle at 59.
 
For the open force to be 250lbs from a spring that has a rate of 402lbs/in, with a closed force of 115lbs....... the open height(lift) would be .335”.

Even if the net lift at the valve were only .425”(which would be an overall effective rocker ratio of 1.35) the open force would still end up at 286lbs
 
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