Posted By: Sponge
Distributer Advance - 06/13/09 03:29 AM
Could someone explain the differences (pros and cons) of a distributer with vaccum advance and one that is mechanical. Or when you would chose one over the other.
Thanks
Thanks
Distributer Advance
Posted By: mark7171
Re: Distributer Advance - 06/13/09 06:18 AM
racing has one need, WOT. a mechanical advance with no vac can will provide this. set it and forget it. Off you go.
If you cruise around an drive it distance and varied, the vacuum is almost esential for a smmoth nice ride. with no load a performance engine may love 30-50total timming cruising part throttle. As load inscreases hills/weight/restisitance/foot the advance goes away, and the flame front hits the piston harder, with the reduced timming.
On hi performance, compresssion engines, hard to turn over hot. a electronic retard device is great for this. crank easkno stress on components.
22 inital have your cake an eat it too.
If you cruise around an drive it distance and varied, the vacuum is almost esential for a smmoth nice ride. with no load a performance engine may love 30-50total timming cruising part throttle. As load inscreases hills/weight/restisitance/foot the advance goes away, and the flame front hits the piston harder, with the reduced timming.
On hi performance, compresssion engines, hard to turn over hot. a electronic retard device is great for this. crank easkno stress on components.
22 inital have your cake an eat it too.
Posted By: Sponge
Re: Distributer Advance - 06/14/09 01:19 AM
Quote:
racing has one need, WOT. a mechanical advance with no vac can will provide this. set it and forget it. Off you go.
If you cruise around an drive it distance and varied, the vacuum is almost esential for a smmoth nice ride. with no load a performance engine may love 30-50total timming cruising part throttle. As load inscreases hills/weight/restisitance/foot the advance goes away, and the flame front hits the piston harder, with the reduced timming.
Hence the reason production vehicles have a vaccum advance. But would a MSD Pro-billet distributer,with its spring style set-up, not work the same as a vaccum advance?
Posted By: 2RT'S
Re: Distributer Advance - 06/14/09 02:22 AM
Stock distributers have mechanical and vacuum, the mechanical helps you when you accelerate and the vacuum helps fuel economy when youn are not on the foot feed as much.
Posted By: mark7171
Re: Distributer Advance - 06/14/09 02:35 AM
Quote:Quote:
racing has one need, WOT. a mechanical advance with no vac can will provide this. set it and forget it. Off you go.
If you cruise around an drive it distance and varied, the vacuum is almost esential for a smmoth nice ride. with no load a performance engine may love 30-50total timming cruising part throttle. As load inscreases hills/weight/restisitance/foot the advance goes away, and the flame front hits the piston harder, with the reduced timming.
Hence the reason production vehicles have a vaccum advance. But would a MSD Pro-billet distributer,with its spring style set-up, not work the same as a vaccum advance?
The weights and springs alone are the mechanical advance curve. No correspondance to load at variable throttle. Not anything like the benefit of a vacuum can.
Posted By: dave571
Re: Distributer Advance - 06/14/09 02:44 AM
Quote:
Could someone explain the differences (pros and cons) of a distributer with vaccum advance and one that is mechanical. Or when you would chose one over the other.
Thanks
Stock has both
mechanical timing's main purpose is to compensate for timing needs, at different engine speeds. The amount you have , and when you need it will vary with application.
Vacuum advance is for improved economy at cruise.
Properly set up, a vehicle should not run or perform any different without vacuum advance. It's main purpose is economy.
As for not running vacuum....
Wilder combo's see virtually no improvement in economy with Vacuum advance(hard to imporve on 5mpg in cammed up car), and the vacuum advance can be a bit of a hinderent on wilder 4 gear cars, as it will try to ad some timing between shifts. Can cause the plate to get hung up etc...
I delete vacuum advance when curving more radical builds, but leave it on for most street cars.
FWIW, I do street drive my own, and have no vacuum advance. It has never had a drivability problem, or overheat etc..
The vacuum advance debate can get ugly. Reality is, having a good initial timing value, and a curve to match your combo is what's most important
Posted By: dave571
Re: Distributer Advance - 06/14/09 02:45 AM
Quote:
The weights and springs alone are the mechanical advance curve. No correspondance to load at variable throttle. Not anything like the benefit of a vacuum can.
