Vac distributor under boost needHelp!
06-05-11, 10:41 AM
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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?
06-05-11, 11:13 AM
#2
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).
06-05-11, 12:47 PM
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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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