Thread: Ignition Timing
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fredmeister fredmeister is offline
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Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Originally Posted by e170drvr View Post
Ok whats confusing is I see you have a 79 I have an 87 US I guess those dizzys are different. Do you have vacuum advance, or is it just mechanical? Mine is tapped from both sides of the TB. The top port will advance timing on vacuum and retard on boost pressure. Also I thought I was reading that you set your timing further advanced than the factory specs by the number of degrees of retard that you get at full boost. I have always set mine dead nuts on 26 degrees btdc 4000 rpm top hose disconnected and plugged. I personally don't have the guts to advance it more than factory spec especially with the **** gas we get around here. Did you ever get the turbo bracket mounted?
I thought my post was pretty clear. I have a vacuum retard on one side of the dizzy, boost retard on the other side via another can. They both function independently of each other and seem to only move in response to either boost or vacuum respectively.
Teeing off a common connector hose to one point on the throttle body below the throttle plate since this port will see vacuum at idle (closed throttle) conditions
as well as boost under open throttle.
I set the timing at 4000rpm which is under vacuum at this point with the retard hose connected. Knowing the value in degrees of boost retard that I will see I set the timing value so that under boost it reaches 26-29 degrees max. This means doing a little math depending on the boost retard for your particular dizzy. That winds up to be about 4 degrees BTDC at idle for me from memory.
I don't see the car running worth a hill of beans at factory spec of 5-10 degree ATDC. I tried it at only 0 degrees and it ran like crap so badly it was dangerous. Plus the car exhaust runs extremely hot at retarded timing like that. Since we don't have emissions testing in MI all my emissions crap is gone and no inspection to worry about.
I am running a big intercooler and 0.8 boost to be conservative, but think this may be ok for 1.0 bar as long as I run super premium gas (91-93octane). The final value of 29 degrees is what worries me as I don't have consensus from others if this is dangerous under the above stated condition (1.0bar).
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 02-13-2009 at 04:54 AM..
Old 02-13-2009, 04:48 AM
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