Yes Another VOES Question...
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From: la la land jerzey
i dont understand the question - But the port on the mikuni is directly behind the throttle blade so it has manifold vacume full time -
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From: Poolville
Because the voes switch does not have a gradual retarding of the ignition timing based on manifold vacuum, as in the way Chevy used to do it before electronic ignition. I think I'm going to eliminate the voes and load a custom curve on my D2Ki based on engine rpm. This way 2400 rpm tip in cruising wont ping because the voes still has ignition curve at full advance. Remember as load goes up timing should retard gradually but with the voes there is no graduated retarding of the timing. It's a one time setting based on a 3.5-7" of vacuum. I will let you all know how it works once on the road again. It'll resemble the older style centrifugal advance systems. I will also monitor the difference in fuel mileage..
It's still winter or has it just begun????
It's still winter or has it just begun????
Last edited by 98hotrodfatboy; Jan 7, 2016 at 06:22 AM.
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From: la la land jerzey
we set syn dizzys chevys at 3000 or even 3500 before total advance is achieved with no vacume
harleys is 1800 for shovels and alike as its all the same with a mechanical advance
voes -- sportys in stock form have a 3.5 inches of vacume setting / big twin can be a high as 7.5 inches - what that is all about is that is the total drop in inches that the voes switch sees, will then kick the timing back a fixed 10 degrees of reduced timing - stock twin is 35 degrees so it becomes 25 degrees when engaged as the motor is loaded going up a hill of opening the throttle for max power - THEN as the engine speed catches up to the speed of air going in and out of the carb body, and that air speed increases the vacume signal the timing goes back to 35 degrees - this all happens rather quickly and is not really noticed as you are driving, and that is the reason most have no idea what it does as they have not seen any difference in the way the bike performs driving it around
harleys is 1800 for shovels and alike as its all the same with a mechanical advance
voes -- sportys in stock form have a 3.5 inches of vacume setting / big twin can be a high as 7.5 inches - what that is all about is that is the total drop in inches that the voes switch sees, will then kick the timing back a fixed 10 degrees of reduced timing - stock twin is 35 degrees so it becomes 25 degrees when engaged as the motor is loaded going up a hill of opening the throttle for max power - THEN as the engine speed catches up to the speed of air going in and out of the carb body, and that air speed increases the vacume signal the timing goes back to 35 degrees - this all happens rather quickly and is not really noticed as you are driving, and that is the reason most have no idea what it does as they have not seen any difference in the way the bike performs driving it around
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From: Poolville
That would be correct John. I would set my total advance to come in by 3200 rpm. Depending on ambient temp i would even go as high as total 42* total advance. Base + centrifugal. And of coarse that was when you could get 98 octane leaded pump fuel..... Or 106 at the track.
Question John..... I know it's possible but is it feasible to run 40* advance by 4000 rpm? Have you done that and was there a noticeable increase when run on a dyno?
I mean these evo's do carry some of the same characteristics of an sbc. Except for air cooled to water cooled...
Question John..... I know it's possible but is it feasible to run 40* advance by 4000 rpm? Have you done that and was there a noticeable increase when run on a dyno?
I mean these evo's do carry some of the same characteristics of an sbc. Except for air cooled to water cooled...
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From: la la land jerzey
its a flame front speed and everything is in play no answer that has Merit - at the track the adding / subtracting of ignition timing is also in play that a dyno does not see or can - real life movement - so when we test and tune our super gas car we have moved all kinds of things just to see what does what, and how maybe at a track for a gamblers race we can get it to hook better, or pull on the top at the traps NHRA super gas is 9.90 - my car with the small BBC will run if fair air 9.30 off the stop @ 148
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From: la la land jerzey
had an iron head sporty pro gas bike that ran 48 degrees timing
its the flame front speed that dictates the timing
its the flame front speed that dictates the timing
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From: Poolville
I don' quite understand what you mean by "Flame front speed" would you mind elaborating on that for me, Thanx John...
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From: la la land jerzey
when a sparkplug fires the combustion charge at what ever the distance ( BTDC ) the piston is at - the degree of timing the motor is set at has a play, in the overall speed of the burn, because of the movement of the piston and at that exact point the combustion charge starts to burn - the speed at which it does it - dictates the amount of timing you can use and factoring in the fuels octane / the piston location as it relates to timing < the burn speed the octane you are using burns under those conditions - the combustion cycle burn rate in the amount of time it takes >>>> becomes the ->>>> flame front speed
the most timing you can use under what ever the conditions are before it detonates is a trial and error thing for the most part
the most timing you can use under what ever the conditions are before it detonates is a trial and error thing for the most part