Octane/Timing relationships

[ice445]

Now the next question is how much timing is too much? Did Ford actually test MBT and fill the tables or did they just guess?

Oh they did a great job with timing tables on this engine. I doubt he's on stock tune though

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[WildHorse]

Now the next question is how much timing is too much? Did Ford actually test MBT and fill the tables or did they just guess?

I suppose when the KS keep removing timing.

I doubt he's on stock tune though

Correctomundo.

 

[K4fxd]

I doubt he's on stock tune though

MBT is a function of the fuel being used and the design of the combustion chamber, tune has nothing to do with it.

 

[Pistol_91]

There comes a point where adding more timing doesn't change anything but a number being higher.

 

[K4fxd]

I suppose when the KS keep removing timing.

I don't know. I think it is true MBT but I haven't been able to test.
If we remove the limits the ECU will over advance the timing as long as there is no knock.

 

[ice445]

MBT is a function of the fuel being used and the design of the combustion chamber, tune has nothing to do with it.

I mean it's defined in the tune pretty clearly. You'll rarely hit it on any sort of pump gas so it seems correctly mapped to me

 

[K4fxd]

I mean it's defined in the tune pretty clearly. You'll rarely hit it on any sort of pump gas so it seems correctly mapped to me

MBT is minimum timing for max brake torque. If the engine makes 400 Lb/feet at 4500 with 28 degrees and makes the same 400 with 32 degrees, 28 would be MBT timing.

The only way to change this would be to use a different fuel, E85 VS pump or to physically change the engine, more or less quench, combustion chamber shape, piston top.

Some tuners will use 32 and claim their tune is better than another tuner who knows engines and tuning, and uses 28.

 

[engineermike]

I suppose when the KS keep removing timing.

Knock sensors removing timing doesn’t tell you much of anything about what timing achieves MBT.

 

[engineermike]

According to Ford, Wot mbt is somewhere around 26-27 on pump gas, and less on e85. Most tuners run 28-30 on e85. So who is right?

 

[K4fxd]

So who is right?

Have you been able to test on a dyno?

 

[engineermike]

Have you been able to test on a dyno?

Nah, all my dyno time was supercharged.

 

[WildHorse]

So who is right?

Dunno. With good fuel, who runs into more knock ? Ford, or the tooners ?

 

[engineermike]

Dunno. With good fuel, who runs into more knock ? Ford, or the tooners ?

Knock does not tell you where MBT is.

 

[WildHorse]

Knock does not tell you where MBT is.

Minimum timing for best torque ... A good starting point for optimizing ignition timing in such an engine would be to set the initial spark advance to around 8 to 10 degrees BTDC. From there, you can fine-tune the ignition timing based on engine performance, and the absence of engine knock or detonation. Which, Ford graciously did, albeit conservatively.

Some tooners are just adding to WOT. Others like LUND for example, claim to do the entire ignition curve with little adjustments here and there . Frankly, I've never seen a LUND tune dyno make more low to mid range power than Ford. Ford did a very good job at that.

 

[Pistol_91]

MBT is minimum timing for max brake torque. If the engine makes 400 Lb/feet at 4500 with 28 degrees and makes the same 400 with 32 degrees, 28 would be MBT timing.

The only way to change this would be to use a different fuel, E85 VS pump or to physically change the engine, more or less quench, combustion chamber shape, piston top.

Some tuners will use 32 and claim their tune is better than another tuner who knows engines and tuning, and uses 28.

Off topic a little bit speaking of engine brake torque... Is this derived from just the MBT tables?

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