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MAF Transfer Points Won't Fit - Solved

Unread postPosted: Tue Jul 31, 2018 9:44 pm
by yeastieBoB
New MAF came with a transfer curve that has 30 points. Since I have to leave the max/min values the same, I have 28 points I can put into the curve.

Do I just leave off the lowest two voltage points, or how do I adjust the transfer curve down to 28 points? Thanks

Re: MAF Transfer Points Won't Fit

Unread postPosted: Tue Jul 31, 2018 10:39 pm
by gamh44
I have been messing with my MAF curve recently and I reckon I would keep the top and bottom points and dispense with some others. I don't see much happening below 175IMAF so at least one below that could go. Then maybe another one closer to the top. ECU will interpolate between the data points anyway. decipha's dumbed down starting curve only has 14 points in it.

What are you like with spreadsheets? I used XL to do a polynomial regression to get an equation. Then used the equation to generate flow data for evenly spaced IMAF points (every 50 ad counts). Gives a smooth place to start from and dial it in from there as required.

If you think this would be useful for you, you can shoot me the points you have and I will do the XL for you.

Should admit that I don't know much about this whole tuning thing (just getting started) but I am pretty comfortable with XL.

Re: MAF Transfer Points Won't Fit

Unread postPosted: Tue Jul 31, 2018 11:03 pm
by decipha
lately i have been using the latest mafv points for all my tunes

max
5.000
4.750
4.500
4.250
4.000
3.750
3.500
3.250
3.000
2.750
2.500
2.375
2.250
2.125
2.000
1.875
1.750
1.625
1.500
1.375
1.250
1.125
1.000
0.875
0.750
0.625
0.500
0.250
0.000

which comes out to in ad counts

max
1000
950
900
850
800
750
700
650
600
550
500
475
450
425
400
375
350
325
300
275
250
225
200
175
150
125
100
50
0

just interpolate you flow at those points and plug it in, then just dial it in

Re: MAF Transfer Points Won't Fit

Unread postPosted: Wed Aug 01, 2018 10:48 am
by yeastieBoB
Thanks folks. I'm decent with spreadsheets, so I'll give it a shot.

Re: MAF Transfer Points Won't Fit

Unread postPosted: Fri Aug 03, 2018 8:24 pm
by yeastieBoB
Thanks again for the tips. I found a YouTube video with basics on polynomial regression and was able to use the resulting formula to generate kg/hr values at the mafv points provided. I used polynomial regression with an order of 4.

Side note: My wife walked up while I was doing my calculations. I explained how MAFs work and what I was doing with the regression. She said she was surprised by the complex things I can figure out. Then added "if only you'd put that effort into things around the house." :lol:

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Fri Aug 03, 2018 10:21 pm
by gamh44
Good work! The regression is probably overkill but it worked well for me too! And I'll bet the house can't do 12s 1/4s.

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Sat Aug 04, 2018 4:08 am
by decipha
sounds like a bunch of wasted time to me, just simply interpolate the value and done

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Sat Aug 04, 2018 6:11 am
by gamh44
decipha wrote:sounds like a bunch of wasted time to me, just simply interpolate the value and done


decipha

Yep, probably. But for someone (viz: me) just trying to get their head around all this, it was just a way to get a job done and see how things all fit together. Estimating airflow between IMAF points using a linear model will introduce small errors. With my (lack of) understanding, I have no idea if these would be significant to the tuning process. As such the regression. A lot less errors and given I use excel all day long, took me about 2 minutes. I understand now that the errors wouldn't be a problem anyway so wins all round.

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Sat Aug 04, 2018 10:21 am
by yeastieBoB
gamh44 wrote:And I'll bet the house can't do 12s 1/4s.


Huh?

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Sat Aug 04, 2018 9:05 pm
by gamh44
Yeah, sorry - poor attempt at humour. I'll stick to my day job, I think.

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Sun Aug 05, 2018 9:34 am
by yeastieBoB
decipha wrote:sounds like a bunch of wasted time to me, just simply interpolate the value and done


Decipha, can you elaborate on how you interpolate maf values? I searched, but couldn't find any methods.

Re: MAF Transfer Points Won't Fit

Unread postPosted: Sun Aug 05, 2018 11:00 am
by red5.0fogger
On the homepage under write ups go to fuel. There is a generic maf flow to give a visual as to how they interpolate. You just increase each notch to give a smooth progression to each subsequent notch.

Re: MAF Transfer Points Won't Fit

Unread postPosted: Sun Aug 05, 2018 5:49 pm
by decipha
you can very easily just cross calculate the interpolate values, 99% of the time i do it in my head

its very simple

=((YUpper-YLower)/(Xupper-XLower)*(XInput-XLower))+YLower

I put a little spreadsheet together for you to make it simple

Re: MAF Transfer Points Won't Fit

Unread postPosted: Sun Aug 05, 2018 9:29 pm
by yeastieBoB
Thanks for that. Now that I see the formula it makes sense.

I compared the curves generated with interpolation vs regression (order of 4). For the most part the curves on average were within .15% of each other. One exception of an 80% variance at .250V (2.26 interpolation vs .45 regression). 3% overall average variance.

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Sun Aug 05, 2018 10:02 pm
by decipha
honestly it doesn't make any difference, your going to be adjusting it any who, when i get lazy i just plug in any number that pops up in my head to start with and then just dial it in from there

one time on I just started plugging in random numbers and 10 of the 30 were within 1%, fucking insanity, now if only i had that kind of luck with lotto i'd be in good shape

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Mon Aug 06, 2018 6:04 pm
by yeastieBoB
Yeah I hear you. I'm just hoping I'll get lucky with an accurate MAF curve and can just adjust the inj. high slope.

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Mon Aug 06, 2018 8:31 pm
by decipha
with siemens deka 80s the injector data is perfect just dial in the maf

Re: MAF Transfer Points Won't Fit - Solved

Unread postPosted: Thu Aug 09, 2018 8:13 pm
by yeastieBoB
Will do, thanks