equation to convert airflow to throttle position?...

[DSteck]

Does anybody happen to know the equation that converts the airflow values defined by startup airflow, final idle airflow, and all the modifiers combined with the defined ETC Area Scalar into a throttle position? I'm interested in this to develop a better way to determine final idle airflow and startup airflow values aside from "try this and see".

[Roger Ramjet]

D -

I did this last year for a LS2.5 powered Blazer. It's too big to post. I'll send it to your gmail. Hope it helps!

Roger

[DSteck]

While interesting, I was hoping to find a relation between airflow values and throttle position.

[redhardsupra]

Roger, can i get the spreadsheet too? sounds interesting... or at least if you could post the main idea/formulas how you went about constructing this spreadsheet, that'd be good too.

[DSteck]

Roger, can i get the spreadsheet too? sounds interesting... or at least if you could post the main idea/formulas how you went about constructing this spreadsheet, that'd be good too.

The spreadsheet he sent me basically lays out the relationship between the angle of the blade and the effective open cross sectional area that you have by calculating the blocked cross section of an ellipse (twist the blade and look head on, and you see an ellipse of which the short dimension is the sine of the blade angle multiplied by the blade radius).

[Roger Ramjet]

Here is a zipped version.
Change the file ext to zip.
Unzip.
Should have a useable xls file.

[DSteck]

Bump. I'm still interested in the math that translates an airflow value into a throttle blade position.

[redhardsupra]

Lemme verify that my 'reverse engineering' of your formulas are correct:
A is a diameter of one dimension of an oval.
B is a diameter the other dimension of an oval.
Area is the 'frontal area' of the TB, which happens to be an oval, thus the two diameters coming in useful.
Rotation is the TB angle in degrees.
Delta is the 'open' area that is the closed throttle minus the 'frontal area'.

So the whole function is just a cosine relationship, with a minimum value, if you assume that the moment 'frontal area' becomes smaller the area covered by the shaft, then the area taken up by the shaft becomes the frontal area.

Please tell me if I'm understanding this model correctly.

[tygerone71]

Hi tis excel sheet seems to be corrupted...could you pls repost it. thanks in advance

Tyrone

[mowton]

Bump. I'm still interested in the math that translates an airflow value into a throttle blade position.

I am interested as well. Is there a better answer to Dave's question other than the TB excel sheet. I have a 2009 CTSV which seems to have a mind of its own and cruise controls at what ever rpm you were at prior to releasing the gas pedal. You can see the log open the throttle blade from the closed throttle value of 18.8% then increase in one frame to say 31% and kind of oscillate back and forth to maintain the speed you were at?

Would like to know what the PCM is "thinking" when it makes the move from the closed throttle to the 31% value.

It is not Min Idle air (almost zeroed and same thing) and occurs in any gear (manual transmission). Looking to see if I can figure out what the PCM is calculating toarrive at the new TB opening.

Thanks,

Ed M