9pt to 30 pt MAF conversions

TT331FB · 09-07-2005, 08:32 AM

What math model is used to perform these conversions? My guess would be a polynom curve fit?

Also, I noticed that Tweecers conversion produced seven points below .4 MAFv. Given that my car idles at >.5 MAFV, these lower points are totally useless and result in less curve accuracy where you need it. My hunch is that the EEC interpolates between points and the distance beween these curve points increase error as it reduces resolution in the normal operating area of the MAF curve. Why have points below the min MAFv?

Anyway, my plan is to do a curve fit and check it against what Tweecer does. Once I have the curve solution, I can pick my own MAFv points and they will start a little below my exspected min MAFv.

Input?

Thanks, Eric

Dale McPeters · 09-07-2005, 09:32 AM

Eric,

If you use Jack Hidleys spread sheet from the Yahoo EEC-Tuner list you can make it 5th, 6th or whatever order fit that you require for your application. Clint has also added a maf fitting tool to the EA if you have it.

TT331FB · 09-07-2005, 09:46 AM

Hi Dale,

I was motovated to come up with my own curve fit spreadsheet just to learn.

I used a sixth order with maximum error of 1.3% between calibrated and predicted data. I customized my own MAFv points to get more resolution in the ranges I operate in. Happy to send it to anyone. Just need a e-mail address.

Thanks!

86GT · 09-07-2005, 09:58 AM

Eric
You are correct, the EEC does a linear interpolation between two point on the curve. You said that your car idles at .5 volts. You will need one or two points below that and here is why. When you snap the throttle body closed the velosity of the air moving into the engine hits a brick wall (TB plate) and bounces back. This reverse air flow causes the MAF to read lower values. This may only happen in a split second, but if it happens at the point at which the tweecer loggs then you will see it.

When I first saw this, I thought it was data garbage data being droped by the tweecer. It was sparatic and non I could not duplicate it. When I finally started snapping the throttle, it was repeatable.

The lower MAF voltages may also come into play during decel. In the A9L there is a table set aside for MAF backflow. This table is what got the gears turning in my head.

The EA can also do the conversion for you. It can also do the custom voltages. Send me the flow sheet and I will post what I get.

QWKSNKE · 09-07-2005, 10:03 AM

Quote:

Originally Posted by TT331FB

Hi Dale,

I customized my own MAFv points to get more resolution in the ranges I operate in. Happy to send it to anyone. Just need a e-mail address.

Thanks!

If you would like, you can upload the file in our EEC Archive.

Italian LX · 09-07-2005, 10:05 AM

Quote:

Originally Posted by 86GT

The EA can also do the conversion for you. It can also do the custom voltages.

How come when I save a MAF curve in CalEdit, the curve comes up in EA with some weird numbers? Is there any way around this, or am I doing something wrong?

86GT · 09-07-2005, 10:08 AM

The export feature of the Tweecer is FUBAR. The voltages actually get exported in about half the real values.

86GT · 09-07-2005, 10:24 AM

Eric
Here is what i come up with for you MAF that you posted in the other thread.

Dale McPeters · 09-07-2005, 10:29 AM

Quote:

Originally Posted by 86GT

The export feature of the Tweecer is FUBAR. The voltages actually get exported in about half the real values.

.......

TT331FB · 09-07-2005, 11:02 AM

Quote:

Originally Posted by 86GT

Eric
Here is what i come up with for you MAF that you posted in the other thread.

Clint, Thanks!

I plotted the EECA results against my 6th order fit and got a match at all points except at 5.0 MAFv . My fit says 1802.252, yours says 1914.198. Big difference. I will send you my excell sheet for your review.

09-07-2005, 08:32 AM	#1
TT331FB Member Join Date: Aug 2005 Posts: 53	9pt to 30 pt MAF conversions What math model is used to perform these conversions? My guess would be a polynom curve fit? Also, I noticed that Tweecers conversion produced seven points below .4 MAFv. Given that my car idles at >.5 MAFV, these lower points are totally useless and result in less curve accuracy where you need it. My hunch is that the EEC interpolates between points and the distance beween these curve points increase error as it reduces resolution in the normal operating area of the MAF curve. Why have points below the min MAFv? Anyway, my plan is to do a curve fit and check it against what Tweecer does. Once I have the curve solution, I can pick my own MAFv points and they will start a little below my exspected min MAFv. Input? Thanks, Eric __________________ TT331FB - T3/.6/.63 turbos, Spearco intercooler, 302/331 Mexican Block,AFR 185 heads, 80mm MAF, 75mm TB, 50# injectors, Tweecer, Track Heat intake, Comp cams roller blower grind, MSD BTM, DIY-WB, Yokogawa video display,T-56 tranny, 9" 3.5:1 Traclock, 4x disk brakes, TCP most everything, shelby roll bar. First fire up 2/14/2004.

09-07-2005, 09:32 AM	#2
Dale McPeters 5.0 Block/Walnut Cracker Join Date: May 2005 Location: Working.... Posts: 2,409	Re: 9pt to 30 pt MAF conversions Eric, If you use Jack Hidleys spread sheet from the Yahoo EEC-Tuner list you can make it 5th, 6th or whatever order fit that you require for your application. Clint has also added a maf fitting tool to the EA if you have it.

09-07-2005, 09:46 AM	#3
TT331FB Member Join Date: Aug 2005 Posts: 53	Re: 9pt to 30 pt MAF conversions Hi Dale, I was motovated to come up with my own curve fit spreadsheet just to learn. I used a sixth order with maximum error of 1.3% between calibrated and predicted data. I customized my own MAFv points to get more resolution in the ranges I operate in. Happy to send it to anyone. Just need a e-mail address. Thanks! __________________ TT331FB - T3/.6/.63 turbos, Spearco intercooler, 302/331 Mexican Block,AFR 185 heads, 80mm MAF, 75mm TB, 50# injectors, Tweecer, Track Heat intake, Comp cams roller blower grind, MSD BTM, DIY-WB, Yokogawa video display,T-56 tranny, 9" 3.5:1 Traclock, 4x disk brakes, TCP most everything, shelby roll bar. First fire up 2/14/2004.

09-07-2005, 09:58 AM	#4
86GT Member Join Date: Mar 2005 Location: Sacramento California Posts: 449	Re: 9pt to 30 pt MAF conversions Eric You are correct, the EEC does a linear interpolation between two point on the curve. You said that your car idles at .5 volts. You will need one or two points below that and here is why. When you snap the throttle body closed the velosity of the air moving into the engine hits a brick wall (TB plate) and bounces back. This reverse air flow causes the MAF to read lower values. This may only happen in a split second, but if it happens at the point at which the tweecer loggs then you will see it. When I first saw this, I thought it was data garbage data being droped by the tweecer. It was sparatic and non I could not duplicate it. When I finally started snapping the throttle, it was repeatable. The lower MAF voltages may also come into play during decel. In the A9L there is a table set aside for MAF backflow. This table is what got the gears turning in my head. The EA can also do the conversion for you. It can also do the custom voltages. Send me the flow sheet and I will post what I get. __________________ EEC Analyzer A9M, TwEECer, 306ci, 73mm C&L w Tuner Tube, Cobra Intake, 42# inj, Edelbrock 6037, E303 cam, 155 fuel pump, FPR, 70mm TB, E-Fan, 3.55 gears, Powerdyne 9psi actual 5psi...way more.

09-07-2005, 10:08 AM	#7
86GT Member Join Date: Mar 2005 Location: Sacramento California Posts: 449	Re: 9pt to 30 pt MAF conversions The export feature of the Tweecer is FUBAR. The voltages actually get exported in about half the real values. __________________ EEC Analyzer A9M, TwEECer, 306ci, 73mm C&L w Tuner Tube, Cobra Intake, 42# inj, Edelbrock 6037, E303 cam, 155 fuel pump, FPR, 70mm TB, E-Fan, 3.55 gears, Powerdyne 9psi actual 5psi...way more.