VAF to MAF Conversion??

[wytbishop]

Thanks, I have spent more hours in a post secondary classroom than anyone should in a lifetime.

My head is filled with so many cool ideas every time I get a new idea an old one is forced out. Mostly I think about manufacturing techniques these days. My focus is almost exclusively on a design project I've been working on for about 15 months now.

http://www.mx-3.com/phpBB3/viewtopic.php?f=7&t=78902

I have just started doing FEA on the rear subframe.

[Josh]

Since it is related.. I thought I would put this right here

http://max.pilotpowersupply.com/2011/06 ... v_version/

[wytbishop]

That is a very good idea. This is one of the things that always made me want to run the Megasquirt. I just want to use the Barro sensor and do away with the VAF altogether.

In thinking about this over the long years since it occured to me that the whole "Mass of air hitting the cone...blah blah blah" is obviously not true. In a rudimentary way the VAF is actually measuring the volume of air passing the cone. X opening = X CFM = X volts to the ECU. The ECU must be estimating intake air mass using the IAT input and some sort of assumption about pressure. As far as I know though, there is no pressure sensing device in the control system...so I'm not sure how it knows the difference between an engine running at sea level and one at 4000ft.

Someone smarter than me should put their two cents in.

[Josh]

I am not an Electrical Engineer by any means. But this system it pretty sweet. Looking around the web several BMW guys are running this with great success. There are several systems out there like this, I will be picking mine up soon, I just haven't gotten around to doing it yet. When I do I will report my findings.

On the OP (even though its from 08') the VAF to MAF conversions takes place on the OBII cars. It can be done on ours but it is an elegant dance between resistors and other electrical type things I have very little knowledge of to make the swap work. There was something I read on PT or MX-6 club on it I will try and find it again.

[_-Night-Shade-_]

Just to add to this, since I saw earlier in the thread that it was mentioned - there actually is a barometric pressure sensor. It's built into our ECUs.

Besides, the ECU is designed to calculate based on volume, not mass (this being the difference between VAF and MAF).

Actually Mike that's not correct. The air entering the engine must be measure by mass or else a barometric pressure sensor must be used to compensate for altitude and temperature (Ideal Gas Law). Our cars do not have any sort of pressure sensing device. The cone in the VAF is acted on my a calibrated spring to hold it closed. The mass of the air entering the engine opens the VAF. Two cars running at the same RPM but at different altitudes would have different air/fuel ratios because the denser air at lower altitude has greater mass for the same volume and imparts a greater force on the cone of the VAF.

Unless I'm wrong and the MX-3 has a baro sensor that I don't know about. That would make me sound pretty stupid.

[MrMazda92]

MegaSquirt, VAF delete is full of win.

Still waiting on an external IAT sensor for mine. ;(

[_-Night-Shade-_]

MegaSquirt, VAF delete is full of win.

Still waiting on an external IAT sensor for mine. ;(

Yeah that's nice; we're all waiting for lots of things. I'm waiting for some people on this board to stop spamming. This is a technical discussion thread, not your diary. If you feel the need to update whomever you think is interested in what you're waiting on, please do so in your worklog.

[MrMazda92]

Yeah that's nice; we're all waiting for lots of things. I'm waiting for some people on this board to stop spamming. This is a technical discussion thread, not your diary. If you feel the need to update whomever you think is interested in what you're waiting on, please do so in your worklog.

While I understand the point you are trying to make, I do post plenty of technical information in this section, as well as others.