Vac distributor under boost needHelp!
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Joined: Mar 2009
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From: Jericho, Vermont
Vac distributor under boost needHelp!
So I recently added a turbo to my 12a we are having timing problems and I'm thinking my distributor due to the lack of vacumn under boost can anyone help me?
from your other thread you made a couple days ago on the same timing issue:
Well there's not a whole lot you can do besides lock the distributor or switching to an electronic spark advance/EFI system. Locking the distributor means eliminating vacuum and centrifugal advance so timing is fixed--like a lawn mower or something. That's not exactly ideal for a street car although it is done often enough. On the FC and later engines the timing is completely controlled by a computer instead of by actual vacuum or centrifugal weights. Therefore it works much better on a boosted application because the basic timing calculation is based on rpm & measured airflow (FC) or rpm & manifold pressure (FD).
Joined: Mar 2001
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From: https://www2.mazda.com/en/100th/
the whole point of a turbo is to have lack of vacuum!
um you should do a little reading, the Rx7 distributor works like every other distributor, except that it has 2 pickups, one for leading and one for trailing.
so the distributor has two different methods of advancing the timing.
mechanical advance; the mechanical advance uses a pair of springs and weights, when the rpms go up, the centrifugal force moves the weights and advances the timing. so as rpms go up, advance goes up.
vacuum advance; the vacuum advance is used to advance the timing @cruise, when engine load is low.
mazda was nice enough to print both charts in the shop manual which is @ www.foxed.ca
generally you set the total advance (mechanical) @4500rpms.
um you should do a little reading, the Rx7 distributor works like every other distributor, except that it has 2 pickups, one for leading and one for trailing.
so the distributor has two different methods of advancing the timing.
mechanical advance; the mechanical advance uses a pair of springs and weights, when the rpms go up, the centrifugal force moves the weights and advances the timing. so as rpms go up, advance goes up.
vacuum advance; the vacuum advance is used to advance the timing @cruise, when engine load is low.
mazda was nice enough to print both charts in the shop manual which is @ www.foxed.ca
generally you set the total advance (mechanical) @4500rpms.
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