I fully understand the operation and protection features of the voes switch. The stock one for my 98 softail is rated @ 3.5-4.5" of mercury. Which for a stock motor would be adequate but for a performance motor would it be better to run a voes that kicks in at 6" of mercury? With higher compression and motor heat a performance motor would be more prone to detonation so I would think a sooner cut in and higher cut out would protect the motor even better. What say ye all.....?

 

Not looking to hijack your thread but I also have a VOES question that's been in the back of my mind for a long time. On my bike, I have an older Dynatek Dyna 2000-HD1 programmable digital ignition module. This ignition module does not use the VOES. The instructions for the ignition module include the following verbiage:


Most Harley-Davidsons engines are equipped with a V.O.E.S. switch in the intake manifold. The normal function of this switch is to sense light load part throttle conditions during vehicle operation. When this condition exists, the V.O.E.S. switch sends a signal to the stock ignition module which causes the ignition to go to full advance instead of following the normal advance curve.

When everything works properly this is an acceptable action. But, if the V.O.E.S. switch is faulty or the manifold vacuum is different because of a change in carb or manifold (or even exhaust pipe) the V.O.E.S. switch can falsely force the engine to full ignition advance at the wrong time. This can cause catastrophic results, like holes in pistons due to detonation.

For this reason, the V.O.E.S. switch function is not implemented in the Dyna 2000-HD1 ignition. Your Dyna 2000-HD1 will always produce the preset advance curve regardless of the state of the V.O.E.S. switch. This means you can leave the V.O.E.S. wired up and installed, or you can remove it and plug the hole in the manifold. Either way it will not affect the operation of the Dyna 2000-HD1. This will insure your engine always performs at its best.



The newer version of the Dyna 2000 (DD2000-HD1E & DD2000-HD1E8) make use of the VOES. The following is the verbiage from their instruction sheet:

All late model Harley-Davidson engines incorporate a Vacuum Operated Electric Switch (VOES) in the intake manifold. This switch is connected to the ignition system through a purple wire. The purpose of this switch is to sense high manifold vacuum conditions during part throttle operation. When the manifold vacuum is high, the VOES switch grounds the purple wire and jams the stock ignition module to full advance regardless of what the engine RPM is. As it turns out, the VOES switch is almost always closed, causing the stock ignition to be at full advance nearly all the time except under wide open throttle conditions.

The Dyna 2000 module uses the VOES in a slightly different manner. When the VOES is active (grounded), the Dyna 2000 module follows a "quick" advance curve that reaches full advance by 1500 rpm. The total advance generated by the Dyna 2000 is determined by which curve you select. Using this advance scheme, the Dyna 2000 always provides a smooth continuous advance curve function that is optimized for both part and full throttle operation.


I've never noticed a problem with my older Dynatek module that doesn't use the VOES, but should I be concerned? Obviously a later/newer version of the module does now implement the VOES.

 

You can dig the potting out of the end and get to the adjustment, caution to not screw it in to far and damage the diaphragm.

http://www.wildwestcycle.com/f_voes.html

 

This is pretty neat.

http://www.wildwestcycle.com/f_voestelltale.html

 

I checked out the thread you linked Schex and yes It explains very well the designed operation of the voes switch but here's my problem with it.

For years I have been tuning advance systems, both vacuum and centrifugal. When setting the base timing on a small block Chevy , one is to disconnect the vacuum hose from the advance to retard the timing completely. After setting reconnect vacuum line and idle goes up. However when throttle plate begins to open the vacuum begins to decrease which in turn decreases the amount of advance being supplied to the ignition curve, to decrease the posibility of detonation.
So if that has always been common practice why does the Voes switch work the exact opposite. Adding advance to the timing curve at low vacuum? It doesn't make sense to me. Adding timing at low vacuum, high load would to me only add to the possibility of detonation.

As I once read in one of theses threads the only real reason was to clean up the burn under load. More EPA crap.

Does this make sense to Anyone?????

 

dyna and other ignition companys did not under stand how they work - really yep

and you put a SBC in the mix if you think about how a SBC works its the same way a voes works

SBC at idle has hi vacume and the timing mark is not in align at the balancer / remove the vacume line and the idle drops and the timing retards and the balancer mark then is visible, a SBC driving along on a flat ground the timing is hi and vacume is hi as its only part throttle - come to a hill and the motor is loaded your foot presses down and the hi vacume goes away the dash pot on the dizzy retards the timing -

voes - sbc comparison - only thing different is in a sbc its done mechanically as the chevy dizzys plate to vacume dash pot is a mechanical movement and NOT a electronic movement - they do the same thing in a different way

when the engine is loaded ( you step on or turn the throttle ) and it has a hi vacume signal ( driving along at any steady speed ) it retards the timing so as not to cause detonation when you look to add more speed to the motor vehicle .. thats it nothing more simple then that

i have had many many discussions about this and as stupid as it seams it took dyna years and years to re think, the stupid way they designed the ignition they sell and when they woke up, they did not highlight the earlier mistake in the directions soooo it becomes a thing to answer the question correctly because you are up against the directions from dyna hope that helps

 

On the SBC, it also depends on what vacuum source was used, manifold (full)or ported vacuum, for different reasons and results,
man that can open a can of worms.

Damn I miss my '68 Camaro, and my '66 step side, and a few more that would be worth a fortune today, stupid me.

 

any sbc or bbc ran full manifold vacume point condenser and hei dizzys - ford and dodge runs throttle vacume off the top of the carb chevys are always bottom of the carb direct intake vacume

 

Yea I miss my hotrods too. Always use manifold readings.

On another note when I get the itch to hodrod I'll go upstate to my brothers house. he lets me take out his 533tq/511hp 70 corvette (naturally aspirated). The only thing that sucks about that car is no power steering.... yeehaa....

**** it's winter, time for a road trip....

 

My voes vacuum hose goes to the back of the mikuni, looks original to me and hopefully it is because I plan on replacing it with an Oem one, unless someone thinks it could be different.