how to tune timing

[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.