Spark Advance Graph (any thoughts?)
Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
Spark Advance Graph (any thoughts?)
Everyone...
I've been concerned that my spark advance was messed up when I put the new MSD distributor on... just doesn't seem to have the same hole shot and acceleration power.
I checked the advance at multiple RPMs this afternoon from idle until full advance was in... The graph below is the result. Shows idle(700 RPM) at 13 degrees with a full advance of 38 degrees in at 2,800 RPM. Does this seem right? Is 25 degrees of advance (idle to full advance) correct? Is it coming in too soon?
Ignore the bumps in the line as it was just my trying to get readings at the various RPMs... the advance was smooth...bottom line is that idle and full advance are accurate and the rate of advance is accurate.
Thanks in advance...no pun intended...
I've been concerned that my spark advance was messed up when I put the new MSD distributor on... just doesn't seem to have the same hole shot and acceleration power.
I checked the advance at multiple RPMs this afternoon from idle until full advance was in... The graph below is the result. Shows idle(700 RPM) at 13 degrees with a full advance of 38 degrees in at 2,800 RPM. Does this seem right? Is 25 degrees of advance (idle to full advance) correct? Is it coming in too soon?
Ignore the bumps in the line as it was just my trying to get readings at the various RPMs... the advance was smooth...bottom line is that idle and full advance are accurate and the rate of advance is accurate.
Thanks in advance...no pun intended...
Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
you want more initial advance. I have mine at 24 degrees at idle and 35 by 3000I also feel that ALL cars should have vacuum advance. I feel the vacuum advance keeps the motor cleaner and crisper at idle and doesn't affect anything else.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
The engine has ran well without the vacume advance and it was the way the speed shop built it. So, I just replaced the distributor in the past 500 miles when the old one was damaged... not really interested in spending another $300. Unless the vacum is really needed and I can add it to the current one.
With that said, unless the lack of a vacum advance is keeping me from doing this...I would like to get some input on my original question on the curve and when max advance should be in.
Thanks in advance and respecfully....
With that said, unless the lack of a vacum advance is keeping me from doing this...I would like to get some input on my original question on the curve and when max advance should be in.
Thanks in advance and respecfully....
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Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Your Edl heads probably use fast burn technology. Which would mean that max power is attained at some lower max advance number like 32 degrees.
recurve the dist for something like 16 initial + 16 mech. all in by 3000 rpm
Then if you think that you need more timing you could try 18 initial + 16 = 34. Without a dyno you are never going to really know the best advance curve for your motor. I personally have not seen gains with max timing coming in early. I have always used 3000 - 3200 rpm with higher initial settings
recurve the dist for something like 16 initial + 16 mech. all in by 3000 rpm
Then if you think that you need more timing you could try 18 initial + 16 = 34. Without a dyno you are never going to really know the best advance curve for your motor. I personally have not seen gains with max timing coming in early. I have always used 3000 - 3200 rpm with higher initial settings
Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
thanks... and am taking the advice...
reducing the mechanical advance from 25... Additional question...
If I go with 21 total mechanical advance (and assume 36 is my total advance target)... I will get an initial advance of about 15.
or
If I go with 18 total mechanical advance (Assume 36 is my total advance target)... I will get an initial advance of about 18.
What would be a better initial target? 15 or 18????
reducing the mechanical advance from 25... Additional question...
If I go with 21 total mechanical advance (and assume 36 is my total advance target)... I will get an initial advance of about 15.
or
If I go with 18 total mechanical advance (Assume 36 is my total advance target)... I will get an initial advance of about 18.
What would be a better initial target? 15 or 18????
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
The best power and fuel efficiency is to run as much initial timing as your engine will allow (allowing easy cranking). Then add whatever mechanical advance you need to achieve your target max. timing.