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Old 10-11-2004, 05:20 PM   #26
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Quote:
Originally Posted by ataac_flat04
Someone wanted GM MAF values, can go HERE for frequency : g/sec values. There is a graph at the top of the page, the table is further on down. Looks like they go up to ~443 g/sec de-screened. HTH's -Chuck
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Old 10-11-2004, 10:20 PM   #27
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Quote:
Originally Posted by ataac_flat04
Someone wanted GM MAF values, can go HERE for frequency : g/sec values. There is a graph at the top of the page, the table is further on down. Looks like they go up to ~443 g/sec de-screened. HTH's -Chuck
Which is almost exactly the same as the data I posted a few weeks ago here: http://forums.nasioc.com/forums/show...ght=MAF+Sensor

Their graphs just continue up to several times the mg/s. However, the formulas I used for upper end regression give you exactly the same data.

Thanks guys, for not even noticing I'd posted that data weeks ago! Not one single reply in my thread about it. :P

Adrian~
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Old 10-12-2004, 02:57 AM   #28
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It's all in presentation His graphics were nicer.
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Old 10-12-2004, 08:51 AM   #29
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Well, I didn't mean to make anyone mad. Besides, I thought you wanted this info...since it's the whole scale. I had ran across that website a couple of months ago when this topic was on my mind. Just kinda put it in the favorites and forgot about it, thought it might be handy sometime. -Chuck
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Old 10-12-2004, 10:33 AM   #30
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No worries. Not mad. Just giving you guys a hard time. :P

Adrian~
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Old 10-21-2004, 03:07 AM   #31
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im sorry... so what are the gains from having a large maf again?

on my car i get a max reading of 4.3 volts at 1.25 kpa, im also running pe 650 injectors... so is that reading off? i dont think im on the same page as you all
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Old 11-24-2004, 02:29 AM   #32
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Your knock correction over 300 g/sec is prob bad becuase after you go over 300 g/sec there is no additional fueling and you get knock

Did you sort your problem yet ?
Quote:
Originally Posted by MauroMotorsports
bump...

Good info here...and I see what I might need to fix a slight problem I'm having. Using the Delta Dash I've logged several passes to find out why I am having hp issues after 5500rpm. As far as I can tell it's got to do with the intake not being scaled correctly or a problem with injector scaling.

After reading above I noticed that the USDM STi's MAF readings should max out at 348g/sec. Is this really the case, because all of my logs after 5500rpm have a MAF plateau of 300g/sec all the way to redline. Am I correct in assuming that the intake may not be scaled correctly?

Here's what happening...at 5500-7000rpms the MAF readings peak at 300g/sec, the voltage begins to drop, and my knock correction drops from 5 down to -2.0. This is also keeping me from getting the advanced multiplier up and over .88! If the knock correction is falling on its face, couldn't this mean that the ECU is trying to lower the amount of air traveling into the engine in order to get a MAF reading under its peak of 300g/sec? The reason I say this is because I noticed that before 5500rpm I get a MAF reading of 294g/sec and everything is fine, but as soon as it hits 300g/sec it's all downhill.

Now, I've measured the Apexi Power intake to be larger then the stock ID of 2.60in at nearly 2.75in, so I'm assuming the larger diameter would help the situation. However, I'm thinking a Big MAF intake would be a better solution since the ID is still larger at 3.09in. If indeed this is a problem involving intake calibration, would simply rescaling the intake fix it?

I have the actual logs that I could post if necessary. Tuners what do you recommend?

my mods are as follows:

Ecutek Reflash
FP green 7cm
TXS Turboback (2.5 axleback)
PE 850cc injectors
Spearco TMIC
Walbro Fuel Pump
Apexi Power Intake

Thanks,

Anthony
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Old 11-24-2004, 10:05 AM   #33
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Quote:
Originally Posted by DynoFlash
Your knock correction over 300 g/sec is prob bad becuase after you go over 300 g/sec there is no additional fueling and you get knock

Did you sort your problem yet ?
EDIT: I understand what you mean now.

My knock correction is on a fine line at this time. Running a max of 8 at higher RPM. Our next steps are to put a big maf intake on the car, but we made 370wtq and 340whp rather easily with the Apexi intake. No knock. I'm sure if I wanted to bump up the boost a bit more and advance the timing I'd have to put the big maf intake on, but we're taking it step by step. We've used my current mods to the max, then adding parts as necessary (i.e. big maf, front mount, etc.)

Anthony

Last edited by MauroMotorsports; 11-24-2004 at 10:33 AM.
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Old 11-24-2004, 06:40 PM   #34
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Jeff, just to add some info. I made a 3.25 inch inner diameter MAF housing for some of my setups and it corresponds pretty well to offset an 800-850cc injector. The correction on the UTEC is 0% on the OLF injector scaling and the correction on the fuel map is less than 5 units on the fuel map. At part throttle WOT, I have to take fuel out at most points. I generate a raw 4.6 volts at around 475 WHP but scale it down quite a bit. I would assume you will need a 3.5 inch inner diameter MAF housing for really big HP setups.
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Old 11-25-2004, 02:07 AM   #35
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Quote:
Originally Posted by MauroMotorsports
EDIT: I understand what you mean now.

My knock correction is on a fine line at this time. Running a max of 8 at higher RPM. Our next steps are to put a big maf intake on the car, but we made 370wtq and 340whp rather easily with the Apexi intake. No knock. I'm sure if I wanted to bump up the boost a bit more and advance the timing I'd have to put the big maf intake on, but we're taking it step by step. We've used my current mods to the max, then adding parts as necessary (i.e. big maf, front mount, etc.)

Anthony
Sounds like a wise and ordered plan of attack - keep us posted on your progress - good luck
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Old 05-29-2007, 07:26 AM   #36
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i'm curious--has anyone ever worked out an accurate mafv to g/s table for the perrin bigmaf?

and, if so, are you willing to share?

-ken
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Old 05-29-2007, 08:55 AM   #37
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Interresting topic !

Can I make a simple comment. My buggedeye STi (hybrid engine with Crawford 2.5L shortblock and 2L STi heads, stock ECU) is sucking 370 gr/s, but still using the stock airbox and stock MAF tube. The way to carry out that is very simple : As you said, the stock MAF is ECU limited to 300gr/s which coresponds to 4,69 V reading. But the MAF itself is capable of an accurate 4.95 to 4.98 V. So, you only have to apply a reduction coeff. to the MAF scaling (0.81 in my case for 370gr/s max : 370x0.81 = 299) and extend MAF scaling curve up to 300gr/s (or 5V, the first apply). Once done, the ECU will then see less air-flow than actually sucked by the engine. Compensation must then be done to each reference to the "load" in the ECU maps by multiplying the load by the same coeff. for every load occurence. And finally, apply the same coeff. to the injector scaling so that it compensates for fueling. At the end, some adjustments needs to be done to guaranty a 0% fuel learning parameter whatever the RPM is. It proved to be very accurate at least on my car.
Last comment, this can be done up to 380gr/s. Passed this limit, the stock MAF tube will give a 5V MAF voltage reading which can only be overcomed using a bigMAF tube.
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Old 05-29-2007, 09:17 AM   #38
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Quote:
Originally Posted by FRWRX View Post
Interresting topic !
But the MAF itself is capable of an accurate 4.95 to 4.98 V. So, you only have to apply a reduction coeff. to the MAF scaling (0.81 in my case for 370gr/s max : 370x0.81 = 299) and extend MAF scaling curve up to 300gr/s (or 5V, the first apply).
Where does this reduction coefficient get applied? Mucking around with ECU programming? An external circuit that takes the 0-5V from the MAF sensor and reduces it to the 0-4.69V that the ECU can deal with?

Last edited by The Deliverator; 05-29-2007 at 09:24 AM. Reason: bad spelling
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Old 05-29-2007, 10:14 AM   #39
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Originally Posted by The Deliverator View Post
Where does this reduction coefficient get applied? Mucking around with ECU programming? An external circuit that takes the 0-5V from the MAF sensor and reduces it to the 0-4.69V that the ECU can deal with?
Sorry, it has to be done by reflashing the ECU. Applying an external hardware to reduce MAF voltage won't do as it won't be able to deal with load and injector scaling compensations.
AFAIK, there is one or two parameters in ECU code which will do the same job, but don't know their adresses and the way they are encodded.
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Old 05-29-2007, 10:57 AM   #40
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Quote:
Originally Posted by FRWRX View Post
Sorry, it has to be done by reflashing the ECU. Applying an external hardware to reduce MAF voltage won't do as it won't be able to deal with load and injector scaling compensations.
AFAIK, there is one or two parameters in ECU code which will do the same job, but don't know their adresses and the way they are encodded.
I still don't quite follow- unless you're talking about just mapping the tables right up to 300g/s @ 4.69V.

Because making the ECU work with values > 4.69V isn't just a matter of altering the tables to accomodate higher maf V's. If we did that the ecu would know what to do with air flow > 300 g/s, but it wouldn't ever 'see' it.
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Old 05-29-2007, 11:24 AM   #41
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No, it's a matter of scaling MAF so that 5V = 300gr/s. This is my MAF (in purple) vs. stock MAF scaling (blue).



Doing so, the ECU will read 300gr/s whilst effective air flow is 370gr/s. This is why injector scaling and "load" references have to be reduced by the same factor

But sorry I don't want to polute sponaugle's post which is quite interresting and shows that going to bigmaf is not a linear operation and needs some adjusments (which can be done to the MAF scaling).

Last edited by FRWRX; 05-29-2007 at 11:47 AM.
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Old 05-29-2007, 11:58 AM   #42
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here is a little something i worked out a few minutes ago...

first, i took the oem translation table from a a4tc400l image (as is used on my car):



next i took jeff's listed equation for the % of maf voltage offset for a bigmaf vs. an oem maf. that equation, in excel, comes out to:

Code:
= -.4335*b2^6 + 8.2988*b2^5 - 64.001*b2^4 + 253.19*b2^3 - 538.74*b2^2 + 581.74*b2 - 240.35
where b2 is the original mafv cell.

i applied the equation to all mafvs between 1.2v and 4.7v to get a delta v.

i applied the delta v to all original mafv to get an effective bigmaf output voltage for each mafg.

however, this cannot be applied to those points outside the range of the original mafg. to get those points we must extrapolate.

to do so, i plotted those known points and let excel solve for a 3rd order polynomial equation. that equation is:

Code:
=5.1405*b2^3 - 6.3011*b2^2 + 3.1401*b2 + 0.0836
again, where b2 is the original mafv cell.



the output of this equation gives us a bigmaf-scaled effective mafg for a given input mafv.

i applied that equation to all of the original mafv points in the oem ecu rom table, and came out with:

Code:
1.74
1.95
2.19
2.38
2.68
3.00
3.37
3.76
4.20
4.68
5.21
5.78
6.39
7.59
9.16
10.96
13.00
15.30
17.87
20.36
23.49
26.95
30.73
34.87
38.79
43.63
51.64
60.60
69.69
80.61
92.63
105.81
118.95
134.49
151.34
167.99
187.50
208.48
230.98
252.99
278.55
305.78
332.27
352.46
373.47
384.27
395.29
406.51
pasted back into the rom 2d map and you get this:



according to my estimations this means a bigmaf should be able to resolve sufficient air to net you around 400whp.

[warning mode]

DO NOT JUST CUT AND PASTE THIS TABLE AND CALL IT DONE.

there were a LOT of assumptions made and it should be considered a very rough starting point for a bigmaf translation table scale.

as a result you MUST verify not only fuel trims but also actual tailpipe afrs after it is applied.
i have never tried this map and it is a PURELY theoretical exercise at this point.

[/warning mode]

a copy of the excel spreadsheet can be found here.

hth
ken
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Old 05-29-2007, 12:11 PM   #43
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I've posted my BigMAF calibration a few times recently. It runs good, but there are some other variables that might throw it off a tad... I'm running PE850cc injectors (using the recommended latency/scaler from cobb) and the Perrin rotated mount intake. It would be a nice test to try the BigMAF on an otherwise stock/stage 2 setup... to eliminate other variables.
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Old 05-29-2007, 12:22 PM   #44
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i just took jays05's data from here and plotted it on the same chart:

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Old 06-06-2007, 10:46 PM   #45
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How come enginuity won't allow you to enter a value of over 300g/s?
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Old 06-06-2007, 10:54 PM   #46
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Quote:
Originally Posted by VideoGameWrx View Post
How come enginuity won't allow you to enter a value of over 300g/s?
Because 0xFFFF is the largest value the ecu can store for that parameter, and 0xFFFF * 0.00457763671875 = 299.995422
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Old 06-06-2007, 11:02 PM   #47
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I just searched a lil and found out, thanks. This is strange to me, how are there so many people running openECU and big turbos if the MAF cannot be scaled passed 300?

For example, I am running a 3inch intake and FP Green
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Old 06-06-2007, 11:15 PM   #48
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Quote:
Originally Posted by VideoGameWrx View Post
I just searched a lil and found out, thanks. This is strange to me, how are there so many people running openECU and big turbos if the MAF cannot be scaled passed 300?

For example, I am running a 3inch intake and FP Green
If we're talking about 02-05 WRX's, two ways:
1) Using a BigMAF as described above
2) Playing mind games with the ECU as FRWRX explains in this thread. Don't feel bad if it doesn't make sense right away....
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Old 06-06-2007, 11:19 PM   #49
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Thanks, I'll read into it. I must be retarded because I was under the impression that scaling the MAF is to compensate for the big MAF, and have to be done simultaneously. The same amount of air to move through a larger pipe would just move slower, but the actual g/s reading would be less?

I am just extremely frustrated because I feel like I have never had my car tuned properly (except when my only mods were vf22, sti pinks, fuelpump, and exhuast, thousands of dollars later and im slower!)

So many different people are telling me completely different things...I would just like to know exactly whats going on for myself so I can trust whether a tuner is just bsing me to have me buy more parts or what

For example, i was told that my modded stock injectors are my problem, yet there are 1000 people using them with no problem. I understand the spray pattern is not the same and the gas is not "mystified." What do you think? Is FP green, 850cc modded stockers, 3inch CAI too much for a stock 05 ECU?

Last edited by VideoGameWrx; 06-07-2007 at 12:01 AM.
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Old 06-06-2007, 11:58 PM   #50
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Dammit don't go to bed people!
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