Trying to Understand some Hondata Tables.

[dgboyle]

I am new to tuning the FK8 but have experience tuning other cars that are not torque table based ie. standard Honda ECUs. I am looking further into the below tables after reading all of the tuning guides:

If I raise my torque table limits but if timing isn't advanced and the turbo max ratio tables and air charge limit are not touched the demand will not be met.

QUESTION /STATEMENT 1 : I can understand the 'air charge limit' because that's a percentage of total cylinder filling. Considering this is absolute pressure the cylinder take 14.5psi / 1 bar then at 230% filling of the cylinder will be 130% of additional air or, my interpretation, 1.3bar / 18.85 psi. Am I correct?

QUESTION / STATEMENT 2 : I think I understand 'turbo max ratio (temp)'. As the temperature in IAT2 (basically the outside temperature coming into the air box) increases and the RPM increases the absolute pressure (as I understand it above) will be limited more and more. What I don't understand is why the values are so high: at 90 degrees F at 7000 rpm the limit for cylinder pressure is 2.23 of absolute pressure or 1.23bar/17.8psi. Is my understanding correct?

QUESTION / STATEMENT 3 : If I am understanding thus far then the 'turbo max ratio (PA)' should be easier. Depending on how far you are from sea level the PA will change. Depending on the pressure measured in the engine (ranging from 0.7 up to 1.0) and what rpm you are at there are limits for the over all cylinder pressure. At 0.9 PA and 6500rpm the value 3.47 means 1 bar of pressure in the cylinder and 2.47 additional bar of pressure?

Timing is easy to understand but the above are the key to unlocking the bigger picture for me.

Can someone please help get me going on this with some concepts

Much appreciated

Sponsored

 

[kefi]

Air charge is a representation of mass, not pressure. You can have more physical air in the cylinder with less pressure if the air is cooler. This is the magic of the Bosch ECU - it targets an actual physical mass of air that it knows is theoretically capable of producing that much torque so it can properly mix a mass of fuel and adjust the ignition to meet that torque.

The turbo ratio limit tables are a multiplier of inlet pressure to outlet pressure. 2.23 ratio would be 2.23 times the pressure at the turbo inlet. Due to pressure drops at the intake and intercooler it’s not exactly atmospheric at the inlet and the pressure in the manifold won’t be exactly what you expect either.

Most of this is answered in my guide at https://fk8.wiki/Hondata_Tuning_Guide

 

[FK8_K20c1]

Air charge is a representation of mass, not pressure. You can have more physical air in the cylinder with less pressure if the air is cooler. This is the magic of the Bosch ECU - it targets an actual physical mass of air that it knows is theoretically capable of producing that much torque so it can properly mix a mass of fuel and adjust the ignition to meet that torque.

The turbo ratio limit tables are a multiplier of inlet pressure to outlet pressure. 2.23 ratio would be 2.23 times the pressure at the turbo inlet. Due to pressure drops at the intake and intercooler it’s not exactly atmospheric at the inlet and the pressure in the manifold won’t be exactly what you expect either.

Most of this is answered in my guide at https://fk8.wiki/Hondata_Tuning_Guide

I was going to tag you

 

[dgboyle]

That guide is incredibly helpful and I have been through it once but a few more times may help to grasp concepts better.

This statement will be key to making more sense of things for me:
" The turbo ratio limit tables are a multiplier of inlet pressure to outlet pressure. 2.23 ratio would be 2.23 times the pressure at the turbo inlet. Due to pressure drops at the intake and intercooler it’s not exactly atmospheric at the inlet and the pressure in the manifold won’t be exactly what you expect either. "


I am struggling to then understand the areas of change to increase boost as this statement is in the tuning guide:
" While these tables (the turbo ratio limit tables) can technically be used to target a certain amount of boost pressure, that is not their intended purpose and you should not be attempting to directly tune boost pressure on this platform "

The AirC table is a percentage and has been expressed as a percentage associated with atmosphere by countless threads here. Therefore my understanding is that 200% AirC value is 100% over atmosphere measured in bar so 1bar or 14.5psi.
Taking into consideration this:
" This table is a normally deactivated Bosch feature that is not used in the factory calibration, but is used in all of the basemaps and almost every custom tune. "

BUT when I increased my torque table and increased the AirC table I didn't make any additional boost. That lead me to believe that the values in the turbo ratio limit tables was most likely holding me back.

I am starting with the 93 octane basemap with PRL everything but running 94 octane 10% ethanol.
I understand that tuning the fk8 we don't directly tune for a set psi but that it the goal here; increase boost and increase timing to the limits of the fuel pump and the limits of the fuel.

I must be missing something.

 

[kefi]

The turbo ratio limit tables are likely holding you back then, yes.

200% aircharge just means that the cylinders have twice as much physical air as it would at atmospheric pressure and temperature. It makes it so that the temperature is taken into account. Hotter air takes up more space and puts out more pressure, but it does not increase air charge. You can’t convert air charge into pressure. Pressure is only one part of the equation, you have to consider flow and temperature as well, which is what air charge does.

 

[kefi]

To add on, the turbo ratio limit tables are really meant for protecting the turbocharger and preventing over speed, not for tuning power. That’s why it’s in terms of the pressure ratio itself instead of a particular PSI.

 

[dgboyle]

Found the cuprite.

Be careful when you put things together. Dont rush.