How to - Timing Advance

**Rockrz** · 02-14-2009

So, back in the day GM with carbed engines running HEI ignition,
we would kick the timing up to the point where the engine would
ping under acceleration and then we'd back off the timing until
the ping went away for hotter ignition.

This would typically leave the timing a few degrees above
where the manufacturer said it ought to be, and it resulted
in noticable increase in power, and we'd have to drop the
idle a bit so the engine would idle decently.

it may take me some time researching and studying how to
do this, but eventually I want to run my truck hotter than stock
where the timing is concerned

So, on todays computer controlled vehicles...what is all involved
with increasing your timing aside from the timing increase itself
and resetting your idle speed?

**Another_User** · 02-15-2009

I think the general rule is increase until you get knock retard, then reduce by 2 degrees. I deleted EGR on my car, and was able to add almost all the timing back and then some without knock retard. Much much better.

Do the 2003s still have the restrictor plate on the throttle body? That needs to come out, and you should upgrade to a bigger MAF and tune. The MAF becomes a choke point. Lots of good stuff you can do to that engine....I've had a few S-10s with the 4.3. If you have the factor locking rear that will help you keep the tires stuck, but a lot of S-10s don't have them...and even with them a lot of people say they are POSs.

If you haven't tuned your transmission yet, that will help a ton. I drove one with an auto once and it was a dog.

Originally Posted by Rockrz

So, back in the day GM with carbed engines running HEI ignition,
we would kick the timing up to the point where the engine would
ping under acceleration and then we'd back off the timing until
the ping went away for hotter ignition.

This would typically leave the timing a few degrees above
where the manufacturer said it ought to be, and it resulted
in noticable increase in power, and we'd have to drop the
idle a bit so the engine would idle decently.

it may take me some time researching and studying how to
do this, but eventually I want to run my truck hotter than stock
where the timing is concerned

So, on todays computer controlled vehicles...what is all involved
with increasing your timing aside from the timing increase itself
and resetting your idle speed?

**Rockrz** · 02-15-2009

My truck doesn't even have EGR. Apparently GM was able to build the
engine and it's accessories to be so efficient, it didn't need EGR.

Yes, I've already removed the little restrictor and I've cut out the front
of my stock air box so at least it can get more air

The stock MAF is supposed to be good up to about 350-400hp which
I'm not trying to obtain to so stock should be fine for my purposes.

I haven't done anything with the tranny's shifting but that is something
I need to look into. I'll play with those settings just as soon as I figure
out exactly where they are and what to do with them.

**Rockrz** · 02-17-2009

So, on todays computer controlled vehicles...what is all involved
with increasing your timing aside from the timing increase itself
and resetting your idle speed?

Will it hurt anything to simply bump the timing up a few
degrees as long as doesn't ping under heavy acceleration?

I talkin maybe 4 or 5 degrees of timing advance...

**jimmyblue** · 02-19-2009

That's the way I've done it, drive around histogramming
KR and then pull out a degree anywhere I got hits, and
add one anywhere I didn't, until I was right on the edge
everywhere, then subtract three across the board. Just
going on some stuff I had read, that MBT timing was a
couple of degrees before onset of ping.

However I have seen, later, people saying that relation
is going to vary from motor to motor and I have also found
that a little warmer weather and A/C on, gives you a
different picture (gurgle, gurgle).

There is some region of "flat top" in the torque-vs-spark
curve and you don't need any more than stops helping.
Maybe you want to go with "Plan A" but follow it up by
subtracting additional spark until you feel it's punking
the motor out. Of course something quantitative would
be better than listening to your butt.

**Rockrz** · 02-19-2009

Great! That was what I was looking for was some ideas about how to proceed with
trying to advance the timing a little at a time. I'll make sure I keep good notes about
exactly what I change so I can change it back if it isn't working.

Sounds like I need to learn about histogramming before I do much on this.

So, what is KR?

**Another_User** · 02-21-2009

Originally Posted by Rockrz

Great! That was what I was looking for was some ideas about how to proceed with
trying to advance the timing a little at a time. I'll make sure I keep good notes about
exactly what I change so I can change it back if it isn't working.

Sounds like I need to learn about histogramming before I do much on this.

So, what is KR?

KR = Knock Retard.

**S2H** · 02-21-2009

Something I have found from many many cars is that timing till knock and then back off a few is not always the best answer...
a friends vette made more power at 24* than it did at 27*
and we could go up to 29 without knock...
it also made more torque around 21*

there are so many factors in making power with timing that you cant just guess at it
really the method I like to do is:
2 pulls at a time
start with a flat value for timing(command it in the scanner not in the tune...use the absolute timing button
1st pull add some timing and check Air fuel...2nd pull leave the timing the same but now you have properly corrected Air Fuel
then you up the the timing by 1* and rinse lather repeat

you can then look at your dyno graphs of each one....and compare...and figure out which spark made the best Horsepower and torque every RPM interval...

voila...custom spark table...
you can do the same thing with the fuel...

in general though in a Naturally aspirated car you can shot for 12.8 for most of the run and give it 12.5 around where it makes the best torque and above where the Horsepower peak starts to fall off...
some vehicles will like a little less fuel or a little more...you just have to play with it...
on a loaded dyno you can just crank er down and just work on each cell one at a time and watch where the dyno tells you it takes the most to keep at it the selected RPM....

**S2H** · 02-21-2009

something else that is useful...
there is a max torque table in the tune..I dont know how many have it and how many dont...
but you can do a careful copy and paste(sometime the axis are reversed) and you can put the values in your timing table(dont forget to blend the cells that dont exist in the torque table)
you will actually find that it works incredibly well on a stock motor

obviously a modified car need different timing....
but its an easy pick me up for a stock vehicle

in the next release you will be able to copy and paste and it will automatically put them in the right cells even if they are not the same size and shape of table...
the beta already does this function.....

**Rockrz** · 02-22-2009

I think I need to catch you someday when your in Austin and bring my
laptop with HP Tuners software on it and see if you can tune mine using
my laptop so I can have all the files so I can see what was done.

This may be the best way for me to get started so I can compare
what was changed with my stock file.

Do you ever do that, in addition to whatever fee you charge?

**Another_User** · 02-22-2009

Originally Posted by soundengineer

a friends vette made more power at 24* than it did at 27*
and we could go up to 29 without knock...
it also made more torque around 21*

Ugh. That makes no sense. You can't make more power (horsepower?) at one setting and make more torque at another, at a specific RPM. Horsepower is based off torque. What that means is that the timing was not optimal throughout all RPMs, so the 21* was optimal at one RPM, and 24* at another.

And while I am ranting, I have to make this point...I don't care how many horsepower a MAF is SUPPOSED to support, if your MAF hole is smaller than your TB hole, your MAF is a choke point. If it weren't you would not need a TB that big!

Unless there was a change I missed, GMs special gift to anyone that figured out about the TB restrictor was the smaller MAF that would keep you from using the extra airflow. Everyone, please buy calipers and measure.

*************

**S2H** · 02-22-2009

Originally Posted by Another_User

Ugh. That makes no sense. You can't make more power (horsepower?) at one setting and make more torque at another, at a specific RPM. Horsepower is based off torque. What that means is that the timing was not optimal throughout all RPMs, so the 21* was optimal at one RPM, and 24* at another.

And while I am ranting, I have to make this point...I don't care how many horsepower a MAF is SUPPOSED to support, if your MAF hole is smaller than your TB hole, your MAF is a choke point. If it weren't you would not need a TB that big!

Unless there was a change I missed, GMs special gift to anyone that figured out about the TB restrictor was the smaller MAF that would keep you from using the extra airflow. Everyone, please buy calipers and measure.

*************

sorry...let me rephrase...

at the rpm where the torque hump was we saw the best improvement from the 21* of timing
at the RPM where the HP topped off we saw the best at 24*

and sometimes a bigger hole is not always better...sometimes you need velocity...same size hole...longer tunnel
and yes the MAF is a restriction....but the stock TB size ad shape is more of a restriction than the MAF is in most cases and the 90 mm TB just happens to be bigger and makes it no longer the restriction point

**S2H** · 02-22-2009

Originally Posted by Rockrz

I think I need to catch you someday when your in Austin and bring my
laptop with HP Tuners software on it and see if you can tune mine using
my laptop so I can have all the files so I can see what was done.

This may be the best way for me to get started so I can compare
what was changed with my stock file.

Do you ever do that, in addition to whatever fee you charge?

I'll send you a PM

**Another_User** · 02-22-2009

Originally Posted by soundengineer

sorry...let me rephrase...

at the rpm where the torque hump was we saw the best improvement from the 21* of timing
at the RPM where the HP topped off we saw the best at 24*

and sometimes a bigger hole is not always better...sometimes you need velocity...same size hole...longer tunnel
and yes the MAF is a restriction....but the stock TB size ad shape is more of a restriction than the MAF is in most cases and the 90 mm TB just happens to be bigger and makes it no longer the restriction point

Sorry to come off so hard on the issue...I figured as much, but I wanted to get up on a soap box for a minute. It doesn't help that I am still getting over the wonderful stomach bug that is going around.

**gmtech16450yz** · 02-22-2009

and sometimes a bigger hole is not always better...sometimes you need velocity...

AIN'T THAT THE TRUTH!!! (Sorry I had to yell, but I've been trying to tell people that for years.)

Best example I ever saw of that was many many years ago in college auto shop. One of the not so bright kids brought in his pride and joy one night, it was a '65 mustang with a tunnel ram and two massive 4bbl Holleys sitting on top. Only problem was the bottom end, cam and valve train on the 289 was all stock! The teacher, a really good, common sense type of mechanic pulled out a chart that showed optimum cfm vs. cubic inch vs. rpm. If I remember right those dual quads would have worked fine between about 15k to 20k rpm! I'm thinking it might be a little hard to get a 289 to turn that high.

I've seen plenty of the older (70's) V8's that had tons better throttle response and low end torque with 2bbl's instead of the old Quadraflush's. A big part of making speed is getting the motor to spin up fast, not just make big HP at wide open throttle at a set rpm. Big HP at high rpm is fine as long as it doesn't take forever for it to get up there.

**Another_User** · 02-22-2009

I would imagine there are gains in larger TBs, MAFs, etc, until you start to see almost no vacuum at WOT. As long as you don't have some sort of losses or flat spots due to intake turbulence or just a big flat spot where sucking more air does no good.

However, I think it is fairly safe to say with the 4.3L, the MAF should match the ported TB.

**Chris@HPTuners** · 02-22-2009

if you have access to a dyno, then you set the spark at each load point to whatever gives you maximum torque without knock (pinging) - keeping your AFR in a reasonable range around 12.5-13.0 for a NA engine is typical. Try to do this on an average or colder temperature day for your area.

You should then do a dyno run or scan on a hot day to fine tune the IAT retard table. You can achieve quite good teperature increases by creative shrouding of the intake on the dyno. You will find that in some cases you will need to make the IAT retard more aggressive that the OEM calibration, and in other case you can make it less aggressive. Either way make sure you have no knock under high load on the hottest air temperature days. IAT can rise quite high sitting in traffic on a hot day just when you want to nail it to break free of the traffic

Chris...

**JimMueller** · 04-27-2009

Chris,

1) So on a load bearing dyno, with OLSD, you complete the VE table(s), then tune spark using the method above and as long as the AFR is in that range don't even play with optimizing fuel any further?
2) Where is this IAT Retard table you speak of in the 98 F-body calibration? I can't seem to locate it.

Thanks!

**HawkZ28** · 04-29-2009

Under Engine/Spark Control/Burst Knock Retard/Mult vs IAT?

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How to - Timing Advance