how to tune timing

[Baldric]

Hi all, pretty new here /havent been around long. Have recently bought efilive V1 7.5+ and im tuning a mates car and its a basically stock VY SV8 and ive worked out after reading information on how to tune the ve table with ltft etc now im not exactly sure where to start with the spark high octane and wondering if someone can point me into the right area /information on how you actually tne the spark in effictivly rather hit and miss. I can't really seem to find any information on this so if anyone could shed some light it would be great

thanks for your help :)

[WeathermanShawn]

Obviously a dyno would be ideal, but there are a few 'street tricks' you can use.

If you are basically stock, I would just load up the stock High-Octane Spark and go from there. Log KR and audibly listen for any rattles or ping. I usually knock down the spark for any cells that show any legitimate spark. If the KR is in the higher load cells, I will decrease the spark advance 2-3 degrees.

I have generally found more power by reducing timing at higher loads, and increasing spark advance at lower loads. For the lower loads, I will watch the Coolant ECT and MAP. If it likes the higher advance at lower loads, the ECT will drop 4-6 degrees and the MAP will lower.

I agree it is hard to find solid information of tuning timing.

[Baldric]

thanks for that. how much do you generally increase a cell by ? whats a good range to increase by

[WeathermanShawn]

I usually work on a block of cells, especially concentrating on specific RPM's while still keeping the basic integrity of the spark curve.

Graphed the spark curve will look like the inverse of your HP/TQ curve. Less spark as your TQ curve peaks. Work on advancing spark ~ 2 degrees at a time.

[joecar]

Timing is good when you get the best peak torque (which means AFR has to be right) without knocking... i.e. if you try to advance further torque does not increase (but combustion chamber temps increase)... it's not easy to do on the street.

[Baldric]

so basically monitor KR and ETC for any slight changes any knock at all or anything more than 1* ?

[WeathermanShawn]

I think what Joecar and others are saying is that spark tuning on the street is quite challenging. I would strongly recommend a dyno. As Joecar alluded to, sometimes you can be increasing timing and not get knock, but in reality you are losing power.

You can basically load up a stock conservative High-Octane Spark Table, then begin logging. My High-Octane looks similar to the 2002 Z06. Log Spark and KR. Construct a MAP using the pre-configured EFILive MAPS. For every cells you have KR, lower the timing 1-2 degrees.

I would try the Spark/KR technique (with a wideband), and then strongly urge you find a reliable dyno.

[Baldric]

thanks mate. appreciate the words of wisdom :) still learning this

[Ryan]

I don't think it's possible to properly tune your spark advance on the street: even if you had some way of accurately measuring torque output, you have no way of eliminating all the variables that go into final timing without an absurd number of trials.

To "properly" create your spark map, you need to use a load dyno in a climate-controlled room with fuel with a high enough octane to allow you to reach MBT (minimum advance for best torque). You set timing to something low, but reasonable, and slowly advance until you reach MBT. The load dyno enables you to hold the vehicle conditions at a specific cell while monitoring torque output. The climate-controlled room allows you to maintain stable IAT to limit variability. You'll want to do this without any of the spark modifiers in place, and then add them back in after finding your base timing.

Combustion isn't a repeatable process, so even MBT is actually an average spark advance that yields best torque most of the time; some events will actually require more/less advance for best torque.

Obviously you aren't driving around on the street with higher octane fuel, but you generally can't find MBT without it. Once you find it, your spark modifiers typically move final timing down (for IAT, ECT, EGR, crappy gas, whatever) depending on conditions. The knock sensors pull timing for the worst case.

[Sid447]

thanks mate. appreciate the words of wisdom :) still learning this

Baldric,

As an option or suggestion, try the timing table for the 2001 ZO6 from Holdencrazy. I had good results with this (no KR).
I started by reducing the timing in the range from 1600 to 3600rpm and only from .68 Gm/C and up by 2 degrees initially. As I thought this part looked pretty drastic. Reasoning that it uses a bigger cam than a VT-VZ and can thus advance can be "quicker."

Then found it ran with no problems with it at minus one to the ZO6 HOT in the 2000 to 3600rpm range and also upped the timing from 22 to 24 (again between 0.68 and up, above 4800 (i.e. from 5200 to the limiter).

It's an option to try that worked for me on a stock cammed VX-2 in a desert climate. :)

SS

[kwhiteside]

Great timing thread. Shawn, you are all over the place dude.

[WeathermanShawn]

Thanks Ken:

That was a compliment, right?

[joecar]

lol... best way to learn is to jump right in.

[Baldric]

indeed :) but my wb02 is broken :(

[dfe1]

The problem with tuning in a climate controlled environment is that it's very difficult to take that environment with you when you need to go out for a drive. Although such test facilities are great for learning and experimenting, in my experience they are primarily devices that allow you to pick the fly shit out of the pepper. The fact that you achieved optimal torque in a controlled environment is no guaranty that you'll also achieve it in the real world. As an extreme example, how does testing in 60-degree air with 10% humidity relate to driving in 85% air with 75% humidity? Certainly, what you learn in one environment can be applied to another, but settings that are optimal in one environment may not be optimal in another.

I don't mean to imply that controlled-environment experiments are without merit. The point is that such experimentation shouldn't be considered mandatory. It's surprising how close you can get to optimum performance with street tuning, some logic and patience.

[N0DIH]

Just remember when tuning the high octane table that the low octane isn't too close in value to the high. The combination of the low and high and octane scaler % makes a 3D table that the PCM uses. The PCM needs room to go lower on spark if it deems the need with the octane learning.

Watch your octane scaler % pid and see where it is, it should be somewhere in between 0 and 100%, if 100%, that might indicate a cell that can add some timing, 0%, your low octane table isn't low enough.

[Ryan]

The problem with tuning in a climate controlled environment is that it's very difficult to take that environment with you when you need to go out for a drive. Although such test facilities are great for learning and experimenting, in my experience they are primarily devices that allow you to pick the fly shit out of the pepper. The fact that you achieved optimal torque in a controlled environment is no guaranty that you'll also achieve it in the real world. As an extreme example, how does testing in 60-degree air with 10% humidity relate to driving in 85% air with 75% humidity? Certainly, what you learn in one environment can be applied to another, but settings that are optimal in one environment may not be optimal in another.

I don't mean to imply that controlled-environment experiments are without merit. The point is that such experimentation shouldn't be considered mandatory. It's surprising how close you can get to optimum performance with street tuning, some logic and patience.

What you are suggesting is akin to trying to solve an nth-order differential equation with no boundary conditions. Even if you do all of your tuning in one day, you can't account for the variation in temperature, pressure, etc. which happen locally around your environment. The values you find for one cell of the VE table will be relevant for only that cell at that temperature and pressure; the variables will not be uniform across the entire table, making your one cell relatively useless (except for at precisely those conditions).

The reason you tune in a controlled environment is to provide the PCM with a base temperature from which it can derive airflow values (using the VE tables) relevant to the current IAT. You find optimum torque in an ideal environment with controlled variables: using gas with a high enough octane rating to allow you to find MBT timing, no humidity, and constant temperature. The PCM accounts for variations from the ideal; i.e. when you run pump gas instead of certification gas and when the density of the air charge varies due to temperature/pressure.

It's certainly not mandatory to tune this way, but you will almost certainly not find optimal BSFC without it unless you are very, very lucky. Even then, you might be able to create a VE table that is close, but you will not be able to verify your timing changes.

Something to think about: the variation in air density due to humidity is substantially lower than the variation due to temperature and pressure and is generally neglected.


Watch your octane scaler % pid and see where it is, it should be somewhere in between 0 and 100%, if 100%, that might indicate a cell that can add some timing, 0%, your low octane table isn't low enough.

You should absolutely not continue advancing timing until the engine knocks. At some point you could be so far advanced that you will be generating peak pressure well before TDC and will lose power. Perhaps this was not your intended meaning, and if so, I apologize, but that is how what you wrote appeared to me.

[OLS108]

indeed :) but my wb02 is broken :(

John, Why not drive over to HDT and speak to Jez, he might be able to give you a few hints etc. If not have a chat to Geoff at NTAE about the dyno he hires ( one we used when i was up in Mackay).

good luck Hammer.


Dave

[dfe1]

What you are suggesting is akin to trying to solve an nth-order differential equation with no boundary conditions.......
True enough, but it is either difficult or impossible for many people to find and/or afford a facility with a controlled environment. So the choice is often to either do the best you can with what you have available, or do nothing. And while tuning in a non-controlled environment may not produce technically optimal results, my bet is that the difference in actual performance is minimal at best. What you're implying is that everyone on this forum (or anywhere else for that matter) who has not tuned in a controlled environment has pretty much just been wasting time.

[joecar]

If your budget is small, you do what you can (i.e. tune on the street/track, with precautions/safety of course)... it becomes a choice: parts or dyno time.