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Knock Table Load Axis - TPS vs MAP

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Hi all,

To begin this topic discussion I would say is an expansion on selecting load axis for tuning fuel, ign, etc. I started looking at different tunes done by different people and noticed that the knock tables generally are setup either with TPS or MAP as the load axis.

For me it would make sense that the load axis for knock would be the exact same as your load axis for your fuel and ign maps. With my Vipec V88 I have the options of selecting either TPS or MAP.

Although on my current tune, I've noticed that the last person to touch the tune set this axis using TPS while all other load axes are using MAP. This got me to question - why is it setup this way?

I'm curious if there is a preference to each selection for the load axis in the knock table, is there a control strategy that I'm missing? The engine in my car is on the noisier side with hydraulic lifters, I'm curious if this was used as a knock tuning strategy that I don't quite understand just yet.

Thoughts?

What are your preferred load axis' for tuning knock?

I'm just guessing here , but TPS should work equally if not better than MAP for the load axis on an NA engine.

The risk of damage is greatly reduce when you don't "ask" (open the throttle) for power no matter of the intake pressure (or vacuum to be precise).

But on an supercharged engine, I would definitely choose MAP over TPS since you want to take into account the boost pressure (more prone to induce knock)

The background noise profile of an engine will depend on how much power it is producing. For this reason adding a load axis can be beneficial. For a naturally aspirated engine TPS makes sense as the load axis but for a forced induction application I would definitely recommend MAP. This is even more critical if you are running multiple boost levels as the noise profile at 10 psi for instance is likely to be quite different to 20 psi.

Thanks for the replies all,

I would certainly agree with most on the argument of TPS vs MAP based load axis with respect to N/A and forced induction applications. I will definitely be changing my load axis' and retuning the knock tables in my ECU :)