VVT concept
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,816
Likes: 3
From: River Valley AR
VVT concept
I have had an idea in my head for a long time now about how to set uo variable valve timing on an older engine. Since I haven't done anything but think about it I thought I might share it in the hopes that someone with the resources to do it could give it a shot.
Picture a conventional timing chain and gears. Add a couple of links to the chain so it's too long.
Install two idler sprockets side by side on the inside of the timing chain, and mount both idlers on a bracket that can slide right and left.
Use a vacuum signal going to a vacuum-powered actuator to slide the idlers left or right.
As the idlers move from one side to the other, the excess length of chain moves from one side of the setup to the other. Just using random numbers say that one side of the crank sprocket has 15 links of chain going over an idler to the cam sprocket. The other side of chain is 18 links long between the sprockets. When the actuator moves to the other side the excess chain moves also, thereby advancing or retarding the cam.
If anyone tries it let me know if it works or not........
Picture a conventional timing chain and gears. Add a couple of links to the chain so it's too long.
Install two idler sprockets side by side on the inside of the timing chain, and mount both idlers on a bracket that can slide right and left.
Use a vacuum signal going to a vacuum-powered actuator to slide the idlers left or right.
As the idlers move from one side to the other, the excess length of chain moves from one side of the setup to the other. Just using random numbers say that one side of the crank sprocket has 15 links of chain going over an idler to the cam sprocket. The other side of chain is 18 links long between the sprockets. When the actuator moves to the other side the excess chain moves also, thereby advancing or retarding the cam.
If anyone tries it let me know if it works or not........
Post Fiend
Joined: Jan 2003
Posts: 8,600
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From: Iowa
It's still on the first page even!
https://www.ford-trucks.com/forums/s...d.php?t=488254
Great minds think alike.
https://www.ford-trucks.com/forums/s...d.php?t=488254
Great minds think alike.
!["Beemer Nut"'s Avatar](data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 50 50'><circle class='avatar-circle-default' fill='%23bc5285' cx='25px' cy='25px' r='20px'></circle><text class='avatar-text-default' x='49%' y='53%' fill='white' text-anchor='middle' alignment-baseline='middle'>"</text></svg>)
Post Fiend
Joined: Dec 2003
Posts: 6,658
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From: "Islander"
I'll bite, use a centrifugal governor running off the timing chain to direct motor oil to both sides of a small ram that push / pull a bar with two idler gears. Use adjustable bolt stops for each side of the case to limit amount of bar travel for cam advance / retard. Have replaceable governor weights in different weights to control when advance begins.
Cap off the distributor hole but retail gear for the oil pump drive and go to a crank triggered ignition.
Remember "KISS"?
Cap off the distributor hole but retail gear for the oil pump drive and go to a crank triggered ignition.
Remember "KISS"?
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,816
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From: River Valley AR
Beemer your idea would also work, but my thinking says that RPM would have to change before tha system would move. I would guess that a vacuum operated system would change the cam timing as the load changes, and help you accelerate more quickly.
I also believe that a vacuum signal could be strong enough to directly actuate the system. It may have to be large in diameter to be strong enough, but it could be done.
I also believe that a vacuum signal could be strong enough to directly actuate the system. It may have to be large in diameter to be strong enough, but it could be done.
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
Optimal cam timing is more rpm based than throttle based, right? Most all of the variable timing systems used by OEM's are rpm based (VTEC comes to mind).
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,816
Likes: 3
From: River Valley AR
On second thought you could use the vacuum signal to operate a small valve that would in turn deliver the oil or even power steering fluid to actuate the device.
I guess all we need now is someone to donate a couple of engines, a machine shop, a dyno, and some beer and some beer. Volunteers???
I guess all we need now is someone to donate a couple of engines, a machine shop, a dyno, and some beer and some beer. Volunteers???
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Fleet Mechanic
Joined: Feb 2004
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Likes: 3
From: River Valley AR
Originally Posted by EPNCSU2006
Optimal cam timing is more rpm based than throttle based, right? Most all of the variable timing systems used by OEM's are rpm based (VTEC comes to mind).
Post Fiend
Joined: Dec 2003
Posts: 6,658
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From: "Islander"
Fuel mixture in / hot gases out vary by rpms hence VVT.
The best of both worlds with strong low end TQ and high rpm HP.
Now the dyno with beer sounds good but a keg tastes better.
.....=o&o>.....
The best of both worlds with strong low end TQ and high rpm HP.
Now the dyno with beer sounds good but a keg tastes better.
.....=o&o>.....
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
Maybe the OEM's compare the TPS to other parameters to tell what the load is?
Post Fiend
Joined: Dec 2003
Posts: 6,658
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From: "Islander"
BMW's have opened valves electronicly with coils and use variable lift to control engine idle to full throttle, the intake tract is like a diesel without throttle plate restrictions.
Honda did a great job with the dual intake tract back in the mid 80's, long for low end then the throttle plates opened un another shorter tract for top end.
.....=o&o>.....
Honda did a great job with the dual intake tract back in the mid 80's, long for low end then the throttle plates opened un another shorter tract for top end.
.....=o&o>.....
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
The electronic valve actuation wasn't what I was referring to, although it is quite a neat setup. The VANOS (or a similar acronym) system was what I was talking about where the cam phasing is altered at the cam drive gear, much like what was suggested in the first post.
Honda used a variable runner length intake on the integra, probably up until they dropped it in favor of the rsx. It was a clever system as well. Ford uses a similar concept in the SVT contour which uses butterflies to close off one port of each cylinder's two intake ports at low rpm.
Honda used a variable runner length intake on the integra, probably up until they dropped it in favor of the rsx. It was a clever system as well. Ford uses a similar concept in the SVT contour which uses butterflies to close off one port of each cylinder's two intake ports at low rpm.
Last edited by EPNCSU2006; Jul 12, 2006 at 11:59 AM.
Thread Starter
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,816
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From: River Valley AR
Ford uses a similar concept in the SVT contour which uses butterflies to close off one port of each cylinder's two intake ports at low rpm.
Beemer-
If lift and duration are controlled electronically with a solenoid operated valvetrain, then is a cam even necessary?
Another assumption of mine- VVT would allow you to change the intake centerline of the cam to make a stronger motor (torquey) on the bottom end and a stronger ( scavenging) motor on the top end. What do the OEM's claimthe advantage of VVT is?