main spark table starting point
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main spark table starting point
This is for a 305 TBI w/ 746 computer. I've been tuning the BLM's now for a while and got them pretty good. Does anyone have or know of a good main spark table to start out with that would have a good basic shape to work with? I have headers and 3.73 gears.
I is amazing how crisp you can get these things with just tuning the AE and BLMs. I was actually surprised at the difference! I can't wait to start on the timing table. I would guess the the ANTT file isn't the best.
I is amazing how crisp you can get these things with just tuning the AE and BLMs. I was actually surprised at the difference! I can't wait to start on the timing table. I would guess the the ANTT file isn't the best.
Joined: Jan 2005
Posts: 10,406
Likes: 492
From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
How could that file be the best? Isn't that the one that gives less fuel @ WOT than part throttle. I seem to remember this one giving less fuel at 90 KPA than 70-80 KPA.
TBI can become very snappy when tuned properly.
I would say to start somewhere around 12* @ 90-100 KPA and idle. Work up to about 28* @ 90-100 KPA and 3,200 RPM. I usually bring in timing a little faster then taper slowly off to the max at higher RPMs. For vacuum advance I start out from 0* @ about 90 KPA and work to about 15* @ 45 KPA. That gives me about 38-42* of timing at cruise and 28* @ WOT. These engine seem to like about 24-27* of timing at idle with vacuum (30-50 KPA). That is in the neighborhood for a swirl port headed engine. Then you can tweak from there.
Timing is a place to IGNORE the BUTT-O-METER. Go to the track and watch the MPH, not the ET.
TBI can become very snappy when tuned properly.
I would say to start somewhere around 12* @ 90-100 KPA and idle. Work up to about 28* @ 90-100 KPA and 3,200 RPM. I usually bring in timing a little faster then taper slowly off to the max at higher RPMs. For vacuum advance I start out from 0* @ about 90 KPA and work to about 15* @ 45 KPA. That gives me about 38-42* of timing at cruise and 28* @ WOT. These engine seem to like about 24-27* of timing at idle with vacuum (30-50 KPA). That is in the neighborhood for a swirl port headed engine. Then you can tweak from there.
Timing is a place to IGNORE the BUTT-O-METER. Go to the track and watch the MPH, not the ET.
Last edited by Fast355; Feb 3, 2006 at 07:03 PM.
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The higher timing at idle seems to make sense with something that I ran into. At idle in gear, I kept seeing rich readings even if I kept lowering the VE. I thought maybe the O2 was cooling down too much. I tried adding some timing in at idle and POW, the BLM's smoothed out at 128. thanks for the reply I will start playing with it.
Have you tried zeroing the Spark Bias value? It raises the Main Spark table by the same 20 degrees that you take out of the Bias. This seems to make the timing table look more like the FAST units where you just have a table of the actual timing values. I'll play with it and see what happens.
Have you tried zeroing the Spark Bias value? It raises the Main Spark table by the same 20 degrees that you take out of the Bias. This seems to make the timing table look more like the FAST units where you just have a table of the actual timing values. I'll play with it and see what happens.
Joined: Jan 2005
Posts: 10,406
Likes: 492
From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
In Tunerpro with my 7747 what you see is what you get with a warmed up engine, no PE, no highway mode and no knock retard.
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