Mike TexaSS

iTrader: (2)

Since most of the tables are fairly the same between the LT1 Edit and the LS1 Edit i thought i post some of the things i learned from others and my self kind of a basic guide to the first fuel spark changes you should make really basic stuff thats fairly easy. And is worth anywhere from 20-40 HP compared to stock programs. This is basic info for tuning on the dyno but some of these will work right off the bat with out need for a dyno.

It takes a lot of change to make a difference of just 1/2 a point AFR ( like 6-7 % PEvsRpm in my experience.)



To use the charts, I set my PEvsCool to 16 in all operating temps, this takes out the variable there.

Run the car on the dyno with a wideband and examine each of the data points at the rpm for the PEvsRPM table.



i.e.. at 3600 rpm you have a value of 1.0 (wild example) and the dyno wideband said your real world afr is 14:1, so you're running a bit lean.

Find 1.0 in the leftmost column and go over to the 14.0 column, the value to use is 18, this should give you the change needed to have a 13:1 AFR.



If running dual widebands and you see a disparity between the two sides I recommend looking at the average of the two banks.



Now the guts:

I saw very little power difference between 12.5:1 and 13.5:1, so naturally I was disappointed. In higher power cars it makes more of a difference, and in supercharged cars it naturally makes a huge difference. I expected to see something, but I only saw 1 ft-lb of torque between the two. I rather run 12.5:1 on the dyno for two reasons:

1.) Since the dyno is 3000 lbs and my car is 3800 lbs, the car will be leaner on the street, maybe 13.1:1

2.) Since I'm running 11.4:1 compression I prefer to keep the combustion chambers cool, so I don't see knock.



What does make a big difference on the dyno is timing, and don't assume more timing is better.

If you're running a higher compression motor, you in fact may need less timing, since the charge is more dense and the flame spreads quicker.



On the other side, if you're running a higher overlap cam, with longer duration, then it may take more timing to get the best performance.

This is again because the charge is not as dense, so the flame speed spreads slower. The whole idea is to get the charge to ignite at about 15 degrees After Top Dead Center, it take different amounts of lead time for the flame to spread throughout the chamber, so finding the optimum timing is the trick.



For a naturally aspirated car (non-supercharged):

You'll adjust the timing by modifying the 95 and 100 Kpa rows in the Load vs. Adv. 400-4000 and Rpm over 4000 tables.



Note:

The F-body stock tables max at what I like to call "total timing" at 2,800 rpm with 33 degrees advance.

The Y-body and most tuner programs for slightly larger cams max "total timing" at 3,200 rpm with 33 degrees advance.

Below total timing the stock advance decreases at a rate of 3 degrees per 200 rpm, so you may want to follow the same format.

Several tuner programs decrease the advance at 2 degrees per 200, some even 1 degree. Most dyno runs don't have data below 2,000 rpm because people usually aren't WOT that low.

You may want to run less timing at low there to retard the WOT so you don't have major traction problems when you floor it on street tires, then again you may want to leave the traction control up to your right foot.



Here’s the stock y- body for example:



400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2800 3200 3600 4000

90 KPA 7.0 9.0 12.0 15.0 19.0 22.0 24.0 27.0 32.0 34.0 35.0 35.0 35.0 35.0 35.0

95 KPA 5.0 6.0 9.0 14.0 17.0 20.0 22.0 25.0 30.0 32.0 33.0 34.0 35.0 35.0 35.0

100 KPA 2.0 3.0 6.0 12.0 15.0 18.0 21.0 24.0 28.0 30.0 31.0 32.0 33.0 33.0 33.0



How to experiment (after the Air to Fuel is calibrated):

1. Make two base runs with just the stock total timing, realizing the second run on a dyno is always higher, since the carbon gets blown out of the ports and chambers. Keep an eye on knock, you don't want any detonation, since the knock sensors pull major timing and gives it back very slowly. You should be able to make max power without being within 2 degrees of knock, otherwise the sensor is getting "false knock"



2. Try a run with 1-2 degrees more total timing, see if horsepower increases/ decreases.

Try it also with 1-2 degrees less timing, see what areas like a certain timing- again - avoid knock, your power should start to decrease before the knock occurs, if not it may be false knock.

If false knock, set the knock vs. rpm table to 0, and tune 1 degree at a time, again watching for where the torque starts to decrease- and it will decrease (since premature ignition causes increased pressure in the head of the chamber, which makes it harder for the piston to rise on the combustion stroke.) Knock sensors do go bad, so take that into account, but don’t assume all knock retard is false, verify it by seeing if the torque increases with 1 degree less timing, it should. There is a window, like Ed said.



3. You may find the stock timing is perfect for your car, many have. Others have had to add or decrease timing depending on charge quality. If you end up with stock total timing is dead on, then do what I do - nod your head and say "Damn those GM engineers are good."

As always lets post some results from you guys and what changes are made so people will stop being so scared to tune it your self. 1 year ago i had no clue how to even begin. Now ive done many changes that have saved me major dough!

Just recently i deleted my cats on my impala ss and 89.95 for 02 sims yea right just program it out for free BAM just saved 89.95. Ive done TB swap 30lb injector swap MAF meter swap and tuned it all myself sorry for ranting but i can wait to get LS1 edit for my camaro SS and our LS1 Impala too.

Mike TexaSS

iTrader: (2)

And i didnt write all of this im not trying to get credit for all of this or anything just trying to help you guys out!

Blackbird

I noticed as did others that stock programming from 60-100kpa the timing numbers are pretty much identical.

Thus I assumed I would need to change all those cells. You just mention 95-100.

Can you shed any light on this?

thanks!

Mike TexaSS

iTrader: (2)

90-100 KPa is the only time you car is at WOT those are the only place you should change the timing because you want the most power only at WOT so it wont effect part throttle driveability.

KPa is a measurement of air i belive.

Black LS1 T/A

[quote]Originally posted by Mike TexaSS:
<strong>And i didnt write all of this im not trying to get credit for all of this or anything just trying to help you guys out!</strong><hr></blockquote>

Se APPRECIATE your input! <img src="graemlins/gr_chug.gif" border="0" alt="[chug]" />

Blackbird

ok wanna be sure I am not misunderstanding here.

[quote]You'll adjust the timing by modifying the 95 and 100 Kpa rows in the Load vs. Adv. 400-4000 and Rpm over 4000 tables.<hr></blockquote>

where I have been adjusting timing is the advance vs rpm and load table. it's measurements are in gm/cyl vs rpm. same thing? or completely different?

thanks.

Mike TexaSS

iTrader: (2)

Its not measured in kpa in LS1 Edit?? Then i would just change timing in 0-4000 and 4000-7000 only in the WOT range most likely the tables closest to the bottom of whatever timing chart your looking at.


Man that sounded bad! <img src="images/icons/rolleyes.gif" border="0"> <img src="images/icons/rolleyes.gif" border="0">

Blackbird

ok now your making me nervous <img src="gr_tounge.gif" border="0">

well I will give it a try anyhow.

all I gotta do is lift if I hear ping.

nothing ventured, nothing gained.

Chris Jones

I think you'll need to adjust it at 0.6 g/cyl up to 1.0 or 1.2 g/cyl (whatever the highest is). Do you think g/cyl peaks at peak torque or peak hp? Hmm.....

sross

iTrader: (1)

Let me try to clear this up without making things worse. Someone please correct me if I'm wrong...

The LT1 has two separate spark tables, one for 0-4000 and one for 4000-7000 (and above) RPM. Also, the LT1 spark tables are based on pressure (Kpa) which I assume is a MAP derived measurement. That means that LT1 spark is directly related to load (as measured by the MAP) and RPM.

The LS1 has a single table (for high octane) that uses a calculated value based on load measured at the MAP and airflow measured at the MAF. If that's the case then the LS1 spark is also directly related to load (albeit a calculated, not measured value) and RPM.

What's that mean? Basically that the same "bottom of the table" concept applies. Now the question is if the LT1 is WOT at 95-100 Kpa (as measured at the MAP), then what calculated value (in grams/cylinder) represents WOT with the LS1? I've heard anything from .6 and up to .75 and above. With my stock table, .68 and higher is identical. This would probably be a good place to start -- carefully of course.

Here's a formula from Harlan (y2khawk) for calculating grams/cylinder:

g/cyl = 15 * MAF/RPM (where MAF is measured in g/sec)

I haven't tried it yet but I'll certainly take his word for it. I hope that helps...

Team ZR-1

I'm not sure in what your saying ?
for MAP (in Kpa) is related to amount of RPMs (load).

As this graph of a testrun I just did show MAP in Kpa is above 80 Kpa when TPS is less then 80% ( part throttle. )



[quote]Originally posted by Mike TexaSS:
<strong>90-100 KPa is the only time you car is at WOT those are the only place you should change the timing because you want the most power only at WOT so it wont effect part throttle driveability.

KPa is a measurement of air i belive.</strong><hr></blockquote>

Blackbird

the tuning I have done to this point has been modifying from .60 to 1.0 based on I believe your post a while back noticing that from .60 to 1.0 gm pretty much made the tables identical.

maybe I will just start putting them back one by one starting with .60 and see what happens.

I will let anybody know thats interested what I find out.

Blackbird

interesting.

guess it's time for a little testing

pontiaddict

TTT
This is too good to let die! Keep up the good info guys <img src="gr_stretch.gif" border="0"> <img src="graemlins/gr_angel.gif" border="0" alt="[angel]" />

Ben99Z28

this is good sheeiitt, TTT