Total advance timing
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 397
From: Lakeville MI
Add the main spark table and PE offset and any other offsets that may be present and subtract any knock retard if present. The result is the total advance.
The other way would be to scan it and observe the spark advance relative to tdc and subtract the knock retard, or observe the spark relative to reference pulse and add the base offset and then subtract any knock retard.
This is analagous to base timing plus mechanical advance, plus vacuum advance in a mechanical distibutor.
Usually the maximum value at WOT for high rpm is reported as the total advance.
This one value is an oversimplification, of course, but it gives you an idea of where the advance is relative to others without delving into the details of the tables and offsets, etc.
113 headed cars seem to like around 42 degrees total advance.
The other way would be to scan it and observe the spark advance relative to tdc and subtract the knock retard, or observe the spark relative to reference pulse and add the base offset and then subtract any knock retard.
This is analagous to base timing plus mechanical advance, plus vacuum advance in a mechanical distibutor.
Usually the maximum value at WOT for high rpm is reported as the total advance.
This one value is an oversimplification, of course, but it gives you an idea of where the advance is relative to others without delving into the details of the tables and offsets, etc.
113 headed cars seem to like around 42 degrees total advance.
Drifting
Joined: Sep 2005
Posts: 1,867
Likes: 3
From: Pasadena Maryland
If you have a car that you can use a timing light on? You can buy a timing light with a dial on it, rev the engine turn the dial so the 0 degree timing mark is lined up and read the total advance on the dial.
Melting Slicks
Joined: Mar 2003
Posts: 2,472
Likes: 0
From: Toronto ONTARIO
trying to determine what your total timing is? or trying to figure how to tune your car for maximum timing ??
I guess one way of really seeing what actual timing is get it on a dyno with a timing light.
To determine what the max timing should be for best performance, from what I've gathered is to analyze the combination on paper. Another is to compare to a similar combo and use it to start and go beat on it on the street.
I found the best way was with a G-tech accelerometer. I did the 100 -150 mph in 4th gear with the G-tech recording the time it took and tried different timing. the G-tech allows you to overlay all the graphs so you can see at which timing and at what rpm the car pulled faster. I did this for weeks, and still do it and my car performed better than I expected at the track.
I guess one way of really seeing what actual timing is get it on a dyno with a timing light.
To determine what the max timing should be for best performance, from what I've gathered is to analyze the combination on paper. Another is to compare to a similar combo and use it to start and go beat on it on the street.
I found the best way was with a G-tech accelerometer. I did the 100 -150 mph in 4th gear with the G-tech recording the time it took and tried different timing. the G-tech allows you to overlay all the graphs so you can see at which timing and at what rpm the car pulled faster. I did this for weeks, and still do it and my car performed better than I expected at the track.
Thread Starter
Instructor
Joined: Dec 2005
Posts: 141
Likes: 0
From: SoCal California
I appreciate everyones input. The problem I'm faced with is that my engine builder put higher compression pistons in my short block than I wanted and I'm trying to deal with a DCR of an assumed 9.5 - 9.7. I've been told to try to keep my total advance below 34* but I don't know how to determine this. The car runs fine, w/o detonation, but am I just buying time? I'd really like to know what I'm dealing with. I have aftermarket 56 cc heads and have considered having the chambers ported to 58 cc to lower my cpr.
So can I have my total advance checked on a dyno?
So can I have my total advance checked on a dyno?
Former Vendor
Joined: Sep 2006
Posts: 15
Likes: 0
What year is your vet? Is it a stock chip? What are your cam specs and your static compression ratio? What exh and intake are you running? These all play into what total advance you need. Aftermarket fast burn cyl heads don't need as much advance as a stocker either. It's a lot easier to change the chip calibration than it is to yank heads to grind out 2 cc's. I would't even consider doing that!
I've seen LT1's run good with low 30 degree timing at WOT, L98's need less, in some cases a lot less.
Mark
I've seen LT1's run good with low 30 degree timing at WOT, L98's need less, in some cases a lot less.
Mark
Thread Starter
Instructor
Joined: Dec 2005
Posts: 141
Likes: 0
From: SoCal California
Originally Posted by MSITuner
What year is your vet? Is it a stock chip? What are your cam specs and your static compression ratio? What exh and intake are you running? These all play into what total advance you need. Aftermarket fast burn cyl heads don't need as much advance as a stocker either. It's a lot easier to change the chip calibration than it is to yank heads to grind out 2 cc's. I would't even consider doing that!
I've seen LT1's run good with low 30 degree timing at WOT, L98's need less, in some cases a lot less.
Mark
I've seen LT1's run good with low 30 degree timing at WOT, L98's need less, in some cases a lot less.
Mark
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Verdad Gallardo
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
You need to Datalog and EPROM burn.
There are places in the timing tables where the spark timing is as high as 45*.
That + the base timing = 'A Lot of Spark Advance' at times.
Not at WOT, of course.
You are going to HAVE to get access to the tables in your ECM.
The 'cheeeepppest' way to do it 'IMHO' is a Datamaster cable and a laptop for scanning.... and TunerCat for adjusting the tables.
You'll have 'bout 300 bux in the deal not counting a basic slow laptop and you can use it from now on.
Uh-oh, I forgot, you'll need an EPROM burner too. Used.. bout 50 bux.
You'll spend that much in time and frustration paying somebody else to do it for ya.
PLUS, you will learn a LOT about how the ECM does what it does.
'Most' of the mystery will be gone after you get a handle on it.
You haven't got to know how to do it... there's PLENTY PEEPS here that will be willing to take you by the hand and guide you thru this.
Compression is a GOOD thing. I'd rather deal with too much than too little. LOL, it cost more to GET it than to get RID of it.
That + the base timing = 'A Lot of Spark Advance' at times.
Not at WOT, of course.
You are going to HAVE to get access to the tables in your ECM.
The 'cheeeepppest' way to do it 'IMHO' is a Datamaster cable and a laptop for scanning.... and TunerCat for adjusting the tables.
You'll have 'bout 300 bux in the deal not counting a basic slow laptop and you can use it from now on.
Uh-oh, I forgot, you'll need an EPROM burner too. Used.. bout 50 bux.
You'll spend that much in time and frustration paying somebody else to do it for ya.
PLUS, you will learn a LOT about how the ECM does what it does.
'Most' of the mystery will be gone after you get a handle on it.
You haven't got to know how to do it... there's PLENTY PEEPS here that will be willing to take you by the hand and guide you thru this.
Compression is a GOOD thing. I'd rather deal with too much than too little. LOL, it cost more to GET it than to get RID of it.
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
It won't work quite right on an EFI engine......
The ECM takes into account a few more parameters other than RPM and maniflold vacumm so this time honored traditional technique won't work for our Vettes.
It's a good method for non EFI engines however.
SORRY, I didn't realize how old this thread was.
Last edited by VetNutJim; Feb 20, 2007 at 04:44 PM.
