MAF bug in latest release

[ashford]

my registered version does not show up either, it is v 2.5 though if that matters. that would of saved me a massive headache of hand inputting a flow curve.

[vw_chuck]

Yea the whole strategy seems very buggy to me. Sometimes it loads right but it never gives you the full scale that you select. I don't think you need a selectable scale for the y axis anyways. Just make it huge like 3000g/s and then let the y axis auto scale once you load in the curve you want.

[jsmcortina]

Sometimes it loads right but it never gives you the full scale that you select.

That is intentional. 12.5% of the scale is reserved for negative flow that some advanced Bosch MAFs support.

I don't think you need a selectable scale for the y axis anyways. Just make it huge like 3000g/s and then let the y axis auto scale once you load in the curve you want.

This is the nature of the way microcontrollers work, if you had a massive range then you would lose precision on low flow MAFs.

James

[vw_chuck]

James the resolution is based on the curve of the flow meter you are using. When I select the range I want it just scales the y axis to that range and makes an upper limit for me. Can you explain how this has an affect on the resolution?

[jsmcortina]

James the resolution is based on the curve of the flow meter you are using. When I select the range I want it just scales the y axis to that range and makes an upper limit for me. Can you explain how this has an affect on the resolution?

The firmware stores flow in a 16bit number. If you make the maximum flow larger, then each small step becomes larger and coarser.

James

[LT401Vette]

You can right click the graph and select "Auto Scale Y Axis"

[vw_chuck]

James yes agreed.
This is the resolution of the sensor you are speaking of. No matter what max value you have the y axis set to it will not change the resolution of said sensor.
I just don't understand the need to select a range which basically only adjusts the limits of the y axis.

[jsmcortina]

No, I'm not talking about the resolution of the sensor. I'm talking about the resolution of the MAF flow curve. The larger the flow range the coarser the steps.

James

[vw_chuck]

Ah the downfall of digital. A to D conversion. Whoever sold digital off as superior to analog was one great salesman.

[Sam280Z]

I don't think you'd be doing anything remotely like this at all without digital processing - which requires A to D conversion.

[vw_chuck]

Yea I know the pluses far outweigh the minuses.

[subwoofer]

Ah the downfall of digital. A to D conversion. Whoever sold digital off as superior to analog was one great salesman.

Really has nothing to do with ADC, since that coincides with sensor resolution and range. Microcontrollers (MCU for short) do not in general provide floating point arithmetic, everything has to be done with fixed point calculations. That means that every time you double the range, you double the size of the smallest step that can be calculated. You sacrifice resolution for range, simple as that.

Without ADCs you would still be running an old K-Jetronic at best.

[vw_chuck]

"That means that every time you double the range, you double the size of the smallest step that can be calculated. You sacrifice resolution for range, simple as that" Definition of an ADC.

[subwoofer]

"That means that every time you double the range, you double the size of the smallest step that can be calculated. You sacrifice resolution for range, simple as that" Definition of an ADC.

Also applies to ADCs - but is not anywhere even close to a definition of one, but AFAICT you were wondering why there was a setting for MAF range in the firmware. The ADC range is 0-5V no matter what, and the raw MAF resolution is determined by the transfer function of the MAF. That value then goes through a series of calculations and corrections, where the MAF range variable applies.