How do you gauge your timing?

[johnsZ06]

I have my tune pretty much down but I'm always curious if I can tweek the timing so as to get better mileage and drivability. Do you guys have any methods or secrets to help optimize timing (besides WOT on the dyno) so you know it's the best it can be? Basically, how do you adjust timing for cruise/mid range power if you don't mind sharing.

[joecar]

JimmyBlue on ls1tech posted a response: http://www.ls1tech.com/forums/showthread.php?t=729403

Determining best timing without a dyno is like a black art...
advancing till onset of ping and backing off may or may not be good, but is the easist running on the street without a dyno.

[johnsZ06]

That was me that asked the question on LS1tech. :D

I had a couple of ideas in mind as well, such as monotoring the calculated power Pid for a specific RPM vs. VSS or monitoring injector pulse width for given loads, etc.

I was just curious if anyone did something different and what seemed to work the best. Granted, the ideal way would be to drive on a load bearing dyno but how many people have access to one of those.

Thanks for your reply! :cheers:

[cmitchell17]

Is there any benifit to adding timing at part throttle for a stock motor? Seems like you could get a little more power and torque with more timing at low/mid grams/cyl areas.

I also heard that for WOT timing you should take out 3-4 degrees of timing at your peak torque. But on GMs timing table timing is always increased at peak torque?

[Redline Motorsports]

Running timing to hit KR is the only way to find the threshold of too much timing. It is not recommended that setting timing to the edge of KR is the bottom line either. You can make X amount of power with 24 degrees of timing, add 2 degrees and make the same power. My recommendation would be to stay at 24 degrees. With a load controled dyno which can report real time torque changes you can really find the point of peak cylinder pressure which is where timing is optimized. This of course would need to be done in a realtime control.

As far as down low; most setups can tolerate a healthy increase in timing in the lower cyl/air points. There is less load and the timing can really help accelerate the motor. You do need to be careful going to far as once you are past peak cylinder pressure, the additional timing advance will actually raise cylinder temperatures which will promote detonation.

Timing is where most of the power comes from in a tune.

Howard

[johnsZ06]

Running timing to hit KR is the only way to find the threshold of too much timing. It is not recommended that setting timing to the edge of KR is the bottom line either. You can make X amount of power with 24 degrees of timing, add 2 degrees and make the same power. My recommendation would be to stay at 24 degrees. With a load controled dyno which can report real time torque changes you can really find the point of peak cylinder pressure which is where timing is optimized. This of course would need to be done in a realtime control.

As far as down low; most setups can tolerate a healthy increase in timing in the lower cyl/air points. There is less load and the timing can really help accelerate the motor. You do need to be careful going to far as once you are past peak cylinder pressure, the additional timing advance will actually raise cylinder temperatures which will promote detonation.

Timing is where most of the power comes from in a tune.

Howard

Nice explanation Howard. That's one reason I wish I had a Road Runner so I could change timing on the fly.

On my own tune I've tweaked the timing table every which way looking for optimum results but as you know, without a way to measure and quantify the results it more or less an exercise in futility! And what's even more daunting is the fact that just about every LS version of a timing table seems to be way different than the next, almost as though the deisgn enginners couldn't make up their minds on which way to go. I know that's not the case though.

The bright side of all this is, it gives me something to do when I get bored! :)

[mistermike]

Using detcans or reading NOx on a 5 gas analyzer will allow you to detect the early onset of detonation before the knock sensors read it, or possible engine damage occurs with F/I motors.

[cmitchell17]

Im going to try this by using the a KR histogram. I have already switched my 2000 truck to a 2005 timing table which looked a little better. (The 5.3hp went from 285 in 2004 to 295 in 2005 I think)

Would the optimal timing table be close to follow? It seems like it has pretty normal timing but once it gets to the high g/cyl like .50+ the timing really climbs like 30+.

Is there any way in efilive to take the optimal timing table which only has about half the cells of rpms and g/cyl in it and move it to the high octane timing table? would there just be a way to paste it and it only paste the cells that where in the optimal timing table? Then you could just smooth the table out to where you would get a blend of mostly the optimal timing?

[Redline Motorsports]

One other factor to consider is the proper blending and "ramp rate" of timing. I have seen many tables where guys take a huge section of the table and flat line the values. There is something to be said about the enertia that a motor produces and timing has a big effect on this. Making sure the table looks smooth is beneficial to smooth acceleration.

Also remember how much time you actually spend in each cell. By looking at cell counts, especially at WOT, its not long. I wouldn't micro manage this too much. It's all about the sweeping motion!:)

Howard

[cmitchell17]

So this can actually be done? I have heard a lot of people say that they have had good luck using the optimal timing table, but it also creates knock. It dosent matter what octane I run to me.

[johnsZ06]

It was so simple in the old days. Disconnect the vacuum advance on your distributor, crank in 40 degrees total advance and select a set of springs to tailor your advance curve.

[shallow bay]

Is there any way in efilive to take the optimal timing table which only has about half the cells of rpms and g/cyl in it and move it to the high octane timing table? would there just be a way to paste it and it only paste the cells that where in the optimal timing table?
Yes there is. Open the Optimal Timing Table, select all of the cells, right click and chose Copy with labels (Shift+Ctrl+C). Next open the Spark High-Octane Table, select all of the cells, right click, chose Paste and then Paste with labels (Shift+Ctrl+V).

[KAZ MotorSports]

I have a really hard time with some tuners who swear by a knock sensor as the guide to maximum allowable timing. I know you have been in the game for a while as well Howard and do not know if you have experienced this or not, but I have seen max power at 25*...knock is finally sensed by the PCM at 42*...yet the power difference between 25* and 42* has fallen off by 12-15HP on some setups.

One of my competing shops in Colorado Springs tells his customers that unless maximum timing is used up and until knock is sensed...that the power will never be at it's highest. I always chuckle when I hear people talking at events or where ever that have been mis-educated by this person. Of course I try to lead them down the path of experience, but to tune around a knock sensor is awfully scarey to me.

-Kenny

[johnsZ06]

Kenny, yes, I know what you are referring to. I have seen max power at 24* and advanced up to 28* with no change in power output but after 28* the power and torque begin to gradually decline. Of course, there was no KR noted and probably would not have seen any until way into the 30s.

When I'm fortuante enough to tune on a dyno, after I set AFR, I advance the timing until I see max power and torque. I might advance a few more degrees and if I don't make any more I back off to where I saw peak and lock it down. The LS based engines don't need much timing like in the old days which is due to efficient cylinder head design.

[Redline Motorsports]

Ken,

Your example of 42 degrees vs 25 was on an LSX based engine?? I have never experience anywhere near 42 degrees under load on these engines!:Eyecrazy: Personally I have found the stock knock sensors (post 98!) to be fairly decent for the most part. If a motor doesn't knock at 23 degrees but knocks at 25 degrees its most likely that the sensors are working and that you have reached the limit. Obviously going back to 23 is the logical move.

Not for nothing but having been tuning systems like FAST and GEN7 on a load control dyno; we continue to add timing until the peak torque has been established and additional 2-3 degrees don't make any difference. Even at that point we still have not hit knock but we back it off the 2-3 degrees for a margin of cush.

Since there was no more increase in power why be on the edge of activating the knock system and playing the whole decay game.



HT

[KAZ MotorSports]

Howard,

I agree 100% and this is exactly what I am talking about. The car (2000 LS1 equipped) came in with driveability issues that the competing shop could not "figure out". I ran a baseline and saw loads of knock in the scan. When I downloaded and opened the tuning file I found that the mid to upper RPM map was filled with 38-42* of timing.

When my final tune was completed he was up 36HP and 29ft/lbs over what the other shop had done. The driveability issues were easily found and corrected along with some other significant problems in the "tune" they completed for him.

Lower to mid 20's was the max timing used where 38-42* was present. Up here in the thin air (less dense) we can get away with a touch more timing to increase cylinder pressure on the N/A cars, but not that much timing! :Eyecrazy:

-Kenny

[Redline Motorsports]

Howard,

I agree 100% and this is exactly what I am talking about. The car (2000 LS1 equipped) came in with driveability issues that the competing shop could not "figure out". I ran a baseline and saw loads of knock in the scan. When I downloaded and opened the tuning file I found that the mid to upper RPM map was filled with 38-42* of timing.

When my final tune was completed he was up 36HP and 29ft/lbs over what the other shop had done. The driveability issues were easily found and corrected along with some other significant problems in the "tune" they completed for him.

Lower to mid 20's was the max timing used where 38-42* was present. Up here in the thin air (less dense) we can get away with a touch more timing to increase cylinder pressure on the N/A cars, but not that much timing! :Eyecrazy:

-Kenny

I'll buy that explaination! Sounds like you need to be installing more superchargers!

HT