My spark tables seem weak
Thread Starter
Racer
Joined: Mar 1999
Posts: 292
Likes: 0
From: Vienna VA
My spark tables seem weak
The spark curve above 4800 in the custom PROM (90’ MAP based system with mods listed below) looks pretty weak.
My initial advance is set to 6 in the ECM constant table and at the distributor, which is is fine. The main spark adv. VS RPM Vs. Load table has the following under MAP = 100Kpa (which is where I assume you spend most of the WOT operation in the 1/4 mile) is:
RPM Advance
2000 24.3
2200 26.4
2400 26.4
2800 28.1
3200 27.8
3600 29.9
4000 30.2
4400 29.9
4800 29.9
5200 29.9
5600 32.0
However, the PE Spark Advance table is all 0s, which I assume means that at WOT the engine is not getting more than 29.9 degrees of total advance between 4400 and 5600. The numbers in the stock table for the TPI are more aggressive:
4800 34.1 (Base 28.1 + 7 deg PE)
4800 31.9 (Extended Base table 23.9 + 7 deg PE)
5200 31.9 (Extended Base 23.9 + 7 deg PE)
5600 31.9 (Extended Base 23.9 + 7 deg PE)
Seems my very modified motor should be running more than a stock motor that is choked at the top end by a TPI manifold. Any thoughts on what would be a good spark curve.
I do not understand why the base and extended table advance numbers are not identical at 4400 rpm.
Carl
My initial advance is set to 6 in the ECM constant table and at the distributor, which is is fine. The main spark adv. VS RPM Vs. Load table has the following under MAP = 100Kpa (which is where I assume you spend most of the WOT operation in the 1/4 mile) is:
RPM Advance
2000 24.3
2200 26.4
2400 26.4
2800 28.1
3200 27.8
3600 29.9
4000 30.2
4400 29.9
4800 29.9
5200 29.9
5600 32.0
However, the PE Spark Advance table is all 0s, which I assume means that at WOT the engine is not getting more than 29.9 degrees of total advance between 4400 and 5600. The numbers in the stock table for the TPI are more aggressive:
4800 34.1 (Base 28.1 + 7 deg PE)
4800 31.9 (Extended Base table 23.9 + 7 deg PE)
5200 31.9 (Extended Base 23.9 + 7 deg PE)
5600 31.9 (Extended Base 23.9 + 7 deg PE)
Seems my very modified motor should be running more than a stock motor that is choked at the top end by a TPI manifold. Any thoughts on what would be a good spark curve.
I do not understand why the base and extended table advance numbers are not identical at 4400 rpm.
Carl
Race Director
Joined: Mar 1999
Posts: 12,597
Likes: 237
From: Bartlett Illinois
Re: My spark tables seem weak (Carl90)
Are all different or just one or 2.
on my 1991 BIN there is only one that is different. It is at 90 kPA and 4800 rpm. one ios 32 and the other is 34.1
on my 1991 BIN there is only one that is different. It is at 90 kPA and 4800 rpm. one ios 32 and the other is 34.1
Thread Starter
Racer
Joined: Mar 1999
Posts: 292
Likes: 0
From: Vienna VA
Re: My spark tables seem weak (-=Jeff=-)
Jeff,
Are you still using the stock advance numbers? If I remember right, our two engines are set up pretty close.
On the stock 90' PROM, there are 4 miss-matches between the 4800 RPM base and 4800 extended base. Do not know why.
Carl
[Modified by Carl90, 4:32 PM 7/25/2002]
[Modified by Carl90, 4:33 PM 7/25/2002]
Are you still using the stock advance numbers? If I remember right, our two engines are set up pretty close.
On the stock 90' PROM, there are 4 miss-matches between the 4800 RPM base and 4800 extended base. Do not know why.
Carl
[Modified by Carl90, 4:32 PM 7/25/2002]
[Modified by Carl90, 4:33 PM 7/25/2002]
Melting Slicks
Joined: Apr 2001
Posts: 2,105
Likes: 220
From: Ca.
Re: My spark tables seem weak (Carl90)
How much knock retard do you get on a wot run? If none then try increasing the timing tables-slowly...
But the tables actually look about right for a "moded" engine.
My tables are as low as 19 deg. in a few places + base of 6deg.....
But the tables actually look about right for a "moded" engine.
My tables are as low as 19 deg. in a few places + base of 6deg.....
Thread Starter
Racer
Joined: Mar 1999
Posts: 292
Likes: 0
From: Vienna VA
Re: My spark tables seem weak (drive it)
Knock is not a problem even before I developed a leaking head gasket problem. I definately plan to start adding more advance slowly. First, I plan to pull the heads this sat to solve a water leak problem.
What surprises me is that peak spark advance for stock is 34.1 deg at 4800 rpm. Mine is set to 29.9 at 4800 and 32 max at 5600. I would have expected 35 or 36 for 4800 an up for a hot rodded engine.
Does Total Spark Advance at WOT (no knock) for a 90', which gives you the capability of setting initial advance via a distributer:
= initial advance + spark table value + PE advance value
or
= spark table value + PE advance value ???
I suspect it is the second equation based on my experience with Datamaster.
When I look at my Datamaster, the engine readings corelate to spark table + PE advance value. I assume that the readings include the 6 degrees of initial advance, so if the Datamaster reading is 30 degrees, I am truly seeing 30 deg of advance not 36 (30 reading + 6 initial). The reason that I believe this to be true is that if you had to add the 6 deg initial to the reading, then the original stock advance would be 34.1 + 6 or 40.1, which seems excessive for WOT.
What surprises me is that peak spark advance for stock is 34.1 deg at 4800 rpm. Mine is set to 29.9 at 4800 and 32 max at 5600. I would have expected 35 or 36 for 4800 an up for a hot rodded engine.
Does Total Spark Advance at WOT (no knock) for a 90', which gives you the capability of setting initial advance via a distributer:
= initial advance + spark table value + PE advance value
or
= spark table value + PE advance value ???
I suspect it is the second equation based on my experience with Datamaster.
When I look at my Datamaster, the engine readings corelate to spark table + PE advance value. I assume that the readings include the 6 degrees of initial advance, so if the Datamaster reading is 30 degrees, I am truly seeing 30 deg of advance not 36 (30 reading + 6 initial). The reason that I believe this to be true is that if you had to add the 6 deg initial to the reading, then the original stock advance would be 34.1 + 6 or 40.1, which seems excessive for WOT.
