Ignition timing range ?

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Scott V
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Re: Ignition timing range ?

Unread post by Scott V » Tue Jan 10, 2017 12:52 am

acarlson wrote:
Scott V wrote:no. the stock setting is 24 is because thats what the engine needs for the correct timing at full throttle & w/boost. vacuum advance has no affect on timing at full throttle & during boost.
Actually the engine gets more then 24 at full throttle w/boost. 24 is what the engine gets until the turbo kicks in. After that the turbo pressure retard starts reducing the timing till you get up to about 4000 rpms. After that the centrifugal advance kicks in and adds more advance timing to the mix. The pressure retard and the centrifugal advance do not cancel each other out so the net timing at full throttle and full boost is a lot more then 24
some confusion here.......we were talking about initial timing........not total timing. i didnt say the total timing is 24 max. the factory dizzy is set @ 24 inital so the engine gets the correct timing at full throttle & w/boost.
acarlson wrote:Actually the engine gets more then 24 at full throttle w/boost.
actually the engine may not get more than 24 @ full throttle w/boost.
maybe this will help as i dont think you understand how the turbo engine works & why the factory timing is the way it is.

heres 1 example....but theres lots more. 4th gear going up a steep hill - full throttle @ 3600 rpm........ & you get 3.7 psi boost.

your total timing would be 24 + centrifugal + boost retard. this example your total timing is 24 + 0 - 8 = 16. if your timing is @ the clarks setting of 18 initial.........you would have 18 + 0 - 8 = 10. 10 maybe is not enough timing. thats why i said you should see if your engine is ok w/the reduced timing from the factory setting.
acarlson wrote:24 is what the engine gets until the turbo kicks in.
the engine could have more than 24 before the turbo kicks in. example: 2nd gear going down a hill - full throttle - 4900 rpm. theres going to be no or very little boost so no pressure retard. your timing is 24 + 18 + 0 = 42

-Scott V.

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Re: Ignition timing range ?

Unread post by acarlson » Tue Jan 10, 2017 5:56 am

Scott V wrote:...misc...
Point taken ! :tu:
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Re: Ignition timing range ?

Unread post by miniman82 » Tue Jan 17, 2017 2:41 pm

Easiest way to think about it: mechanical advance works with engine speed, and is independent of what the manifold pressure/vacuum is doing. Boost retard/vac advance could care less what engine speed is, it takes it's cues from the manifold signal. They both work together to make sure the engine has what it needs at all times, but more or less act independent of each other. It's been my experience that the base timing on these engines is much too high, the mechanical advance comes in far too late, and the stock boost retard function is questionable at best. I never had any luck sorting out the pressure can, if it was right in one respect it was always totally wrong in another. I hope it works out for you but if it doesn't, there are better alternative out there.
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