VOES Switch Explained
3rd Gear
Joined: May 2017
Posts: 7
Likes: 0
From: Garland, TX
What a VEOS switch does is advance the timing when there is enough vacum is pulled as the rpm go up. Yes if the VEOS switch is bad can keep it from reveing up and can mess up your motor from running retarded all the time. A quick test to see if it is work at all is disconnected both wires to the VEOS and sucking on the tube and with a ohm meter see if it gets continuity while sucking on it. Now to see if you is kicking in at the right suction you have to have a vacuum pump with a gauge. If the suction is off you and adjust it if you dig all the goop out of the end as there is an adjustment screw under it. Most time the problem is the diaphragm has gone bad in it.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,900
Likes: 8,006
From: poway
Well with the WOES disconnected, doesn't it run the slow curve? Doesn't that mean the ignition advances with the VOES connected and low manifold pressure?
I'll agree that running the slow curve isn't going to keep the motor from reving.. It might make partial throttle response feel a little sluggish and kill the mileage. If broke and the switch is closed all the time, you could get detonation.
I'll agree that running the slow curve isn't going to keep the motor from reving.. It might make partial throttle response feel a little sluggish and kill the mileage. If broke and the switch is closed all the time, you could get detonation.
HDF Community Team
Joined: Dec 2005
Posts: 5,404
Likes: 2,605
From: NC USA
Well with the WOES disconnected, doesn't it run the slow curve? Doesn't that mean the ignition advances with the VOES connected and low manifold pressure?
I'll agree that running the slow curve isn't going to keep the motor from reving.. It might make partial throttle response feel a little sluggish and kill the mileage. If broke and the switch is closed all the time, you could get detonation.
I'll agree that running the slow curve isn't going to keep the motor from reving.. It might make partial throttle response feel a little sluggish and kill the mileage. If broke and the switch is closed all the time, you could get detonation.
Opposite of that.
The voes is simply an on/off switch connected to ground. That ground signal is sent to the ignition module when the switch is closed (vacuum above pre-set value). The ignition module changes the timing, based on engine rpm and that ground signal.
With vacuum and closed switch, the timing is advanced to a value based on rpms as read by the module. With switch open (low vacuum), timing retards to a value programmed into the module and also based on rpm.
The voes is "closed" most of the time with the engine running. A blip of the throttle will drop it out maybe 1/2 to 1 second. On a long pull, uphill or WOT at lower speeds, it'll be open longer.
Depending on the module (stock or aftermarket) above a certain rpm, the timing is fully advanced by the module, regardless or voes signal or rpms.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,900
Likes: 8,006
From: poway
Correct.
Opposite of that.
The voes is simply an on/off switch connected to ground. That ground signal is sent to the ignition module when the switch is closed (vacuum above pre-set value). The ignition module changes the timing, based on engine rpm and that ground signal.
With vacuum and closed switch, the timing is advanced to a value based on rpms as read by the module. With switch open (low vacuum), timing retards to a value programmed into the module and also based on rpm.
The voes is "closed" most of the time with the engine running. A blip of the throttle will drop it out maybe 1/2 to 1 second. On a long pull, uphill or WOT at lower speeds, it'll be open longer.
Depending on the module (stock or aftermarket) above a certain rpm, the timing is fully advanced by the module, regardless or voes signal or rpms.
Opposite of that.
The voes is simply an on/off switch connected to ground. That ground signal is sent to the ignition module when the switch is closed (vacuum above pre-set value). The ignition module changes the timing, based on engine rpm and that ground signal.
With vacuum and closed switch, the timing is advanced to a value based on rpms as read by the module. With switch open (low vacuum), timing retards to a value programmed into the module and also based on rpm.
The voes is "closed" most of the time with the engine running. A blip of the throttle will drop it out maybe 1/2 to 1 second. On a long pull, uphill or WOT at lower speeds, it'll be open longer.
Depending on the module (stock or aftermarket) above a certain rpm, the timing is fully advanced by the module, regardless or voes signal or rpms.
ignition advances with the VOES connected and low manifold pressure?
Last edited by Max Headflow; Apr 4, 2022 at 12:19 PM.
Grand HDF Member
Joined: Apr 2007
Posts: 3,725
Likes: 3,070
From: Brighton, MI
Yes, Max and t150 are both correct.
It's just a play on words with how vacuum is described, but agree when vacuum reaches a certain point it activates the advance curve. There! Added another word to the mix to help confuse thing more.
Good movie, 'shakin the bush boss", shakin the bush".
It's just a play on words with how vacuum is described, but agree when vacuum reaches a certain point it activates the advance curve. There! Added another word to the mix to help confuse thing more.
Good movie, 'shakin the bush boss", shakin the bush".
Grand HDF Member
Joined: Apr 2007
Posts: 3,725
Likes: 3,070
From: Brighton, MI
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