07-22-2016, 10:39 PM
It be real hard to make the wrong part work correctly.
It is ported vacuum and the following features (factory tuning)
1: the Carb ported vacuum, is tuned for location and hole sizes. (in or near the venturi)
2: the vac, advance spring force is tuned (or in some cars this spring is in the distrib on the advancing plate)
3: the Vac diaphragm size.
4: and limiters. the stroking rod , has limits that can be changed, many limits stops are located on the advancing plate.
5: all the above tuned for transmission type. (many ATs or MT , usually this is by smog laws)
6: tuned for a working EGR or not. (many G16's ping with no EGR active)
7: and last, suzuki used different distribs in different markets, not sure why but did, and the VAC is diff, fit. "physical fit" making parts very hard to locate.
some brands of cars have 50 different vacuum devices, for engine sizes, 1 to 2+ liters. and different body weights(loads). some done for forced factory carb changes, (the seller stops making a carb, is one cause)
that is where EFI wins best, it tunes by simple table.
many guys with old cars , very old cars, that cant get the Vacuum advance to work correctly, due to gross head millings, (CR way too high and no high octane to match it)
They modify the advancing weights /springs, (lighter weights, or stronger springs or lil of both) Spark timing is a very very complex topic !
This is common on old race cars, where they only need advance at one speed around a loop track. (the methods and ways and means)
The advancing springs can not work very good, at all for engine load. as vacuum does.
so is a gross compromise, the centrifugal is RPM only, simple and effective for speed.
you can run all day with no vacuum advance, all you give up is that instant torque off the line. the VAC advance is LOAD sensing device.
no vac, no load, can be sensed, and there for no power off the line, no power when you need engine torque now, leaving you with one choice
that is to down shift and make the distributor spin faster, .
if you advance static timing ,that makes the engine almost impossible to start. after all it tries to start backwards.
think about that , the piston rises, an at say 15 to 20 Deg. BTC it fires way too early, and that fires backwards, see?
Ask old real HARLEY riders how that sends you over the handle bars,skipping step one,(retard lever)
your pinch vac tube, cause the Vac advance to work as an accumulator. (like battery or electronics capacitor holds a charge)
It is ported vacuum and the following features (factory tuning)
1: the Carb ported vacuum, is tuned for location and hole sizes. (in or near the venturi)
2: the vac, advance spring force is tuned (or in some cars this spring is in the distrib on the advancing plate)
3: the Vac diaphragm size.
4: and limiters. the stroking rod , has limits that can be changed, many limits stops are located on the advancing plate.
5: all the above tuned for transmission type. (many ATs or MT , usually this is by smog laws)
6: tuned for a working EGR or not. (many G16's ping with no EGR active)
7: and last, suzuki used different distribs in different markets, not sure why but did, and the VAC is diff, fit. "physical fit" making parts very hard to locate.
some brands of cars have 50 different vacuum devices, for engine sizes, 1 to 2+ liters. and different body weights(loads). some done for forced factory carb changes, (the seller stops making a carb, is one cause)
that is where EFI wins best, it tunes by simple table.
many guys with old cars , very old cars, that cant get the Vacuum advance to work correctly, due to gross head millings, (CR way too high and no high octane to match it)
They modify the advancing weights /springs, (lighter weights, or stronger springs or lil of both) Spark timing is a very very complex topic !
This is common on old race cars, where they only need advance at one speed around a loop track. (the methods and ways and means)
The advancing springs can not work very good, at all for engine load. as vacuum does.
so is a gross compromise, the centrifugal is RPM only, simple and effective for speed.
you can run all day with no vacuum advance, all you give up is that instant torque off the line. the VAC advance is LOAD sensing device.
no vac, no load, can be sensed, and there for no power off the line, no power when you need engine torque now, leaving you with one choice
that is to down shift and make the distributor spin faster, .
if you advance static timing ,that makes the engine almost impossible to start. after all it tries to start backwards.
think about that , the piston rises, an at say 15 to 20 Deg. BTC it fires way too early, and that fires backwards, see?
Ask old real HARLEY riders how that sends you over the handle bars,skipping step one,(retard lever)
your pinch vac tube, cause the Vac advance to work as an accumulator. (like battery or electronics capacitor holds a charge)
(07-22-2016, 08:12 PM)Swiftdoog Wrote: Back again with one detail...the delay is so big that letting off the throttle causes the timing to back down so slowly that on certain situations pushing the throttle will cause ping "again" :S (sometimes, not all the time). I grabbed the timing light and saw the damper indicator move so slowly back to 6 degress that it was amusing. Could I just unplug the vac advance until I find the right vac advance pot? Maybe advance the timing to compensate a little, all this with the vacuum advance disconnected. sure many have, power will lack.
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