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Old 02-09-2008, 02:21 AM   #1
Kastley85891
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Default Changing MAF - what it entails

How much alteration to a map is needed when going to a big MAF say from 66mm to 70mm?

Im interested.

Thanks

Also can any one remember the name of the two good tuning books out there?
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Old 02-09-2008, 02:47 AM   #2
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Big MAF is the damn devil. I've been struggling trying to get this thing tuned. I almost have it but not quite.
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Old 02-13-2008, 02:00 AM   #3
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the two books are called

engine management advanced tuning by greg banish (IMO this is best)

and

how to tune and modify engine management systems by jeff hartman

Ive been reading both extensively for the past week and having NO experience with cars let alone tuning these books have brought me into a realm of understanding. Check em out, they're more than worth it
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Old 02-13-2008, 02:02 AM   #4
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I have changed to a "big MAF" on an older ECU, so this is my take.

It takes ALOT of driving around with a wideband. Tune, tune, tune. unless you can get a premade map. Then drive around some, just a bit less.
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Old 02-13-2008, 12:29 PM   #5
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The Perrin short ram and Perrin Big MAF on the LGT takes a lot of patience to tune.

The diameter of the intake is a big factor in MAF scaling, but the overall geometry of the short ram intake has a big impact on MAF scaling.
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Old 02-13-2008, 01:01 PM   #6
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If the design is identical, just on a larger scale, tuning is easy.

Simple fluid mechanics, just calculate the cross sectional area of each intake at the maf, the maf scaling multiplier becomes:

m = Anew / Aold. Then simply multiply the entire map by m.

I just went from a 65mm to 70mm (Both APS CAI), and after applying the multiplier to my old tuned maf table, it is nearly spot on.

It will likely need a little tweaking, there are spreadsheets available to help out in addition to the maf tool in RomRaider.

If the intakes are designed differently, add a few percent to the multiplier to keep it rich, and tune from there.

Last edited by fujiillin; 02-13-2008 at 01:08 PM.
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Old 02-13-2008, 06:48 PM   #7
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Nothing could be easier. Just calculate the increased area of the MAF pipe, Addt his to your MAF table. Set your injectors to where they are supposed to be. Then fine tune the MAF table 10 to 30 minutes tops. Oh and dont forget to rescale the Timing and fuel tables.

CLark
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Old 02-14-2008, 10:59 PM   #8
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Great information guys
Thankyou
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Old 02-14-2008, 11:16 PM   #9
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Quote:
Originally Posted by AZScoobie View Post
Nothing could be easier. Just calculate the increased area of the MAF pipe, Addt his to your MAF table. Set your injectors to where they are supposed to be. Then fine tune the MAF table 10 to 30 minutes tops. Oh and dont forget to rescale the Timing and fuel tables.

CLark
Why would the timing and fuel need to be scaled? Tuned, yes, but scaled? Perhaps you're referring to the load axis?

All necessary scaling for those load based tables is accounted for when the ecu calculates load from the scaled maf table.

Last edited by fujiillin; 02-14-2008 at 11:22 PM.
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Old 02-14-2008, 11:53 PM   #10
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Quote:
Originally Posted by fujiillin View Post
It will likely need a little tweaking, there are spreadsheets available to help out in addition to the maf tool in RomRaider.
where does one find this maf tool within romraider?
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Old 02-15-2008, 01:42 AM   #11
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You'll need to download the newest test release from the links in this forum, then launch the logger and the maf tool is one of the tabs.
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Old 02-15-2008, 09:29 AM   #12
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thanx!
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Old 02-15-2008, 06:08 PM   #13
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Quote:
Originally Posted by fujiillin View Post
Why would the timing and fuel need to be scaled? Tuned, yes, but scaled? Perhaps you're referring to the load axis?

All necessary scaling for those load based tables is accounted for when the ecu calculates load from the scaled maf table.
yeah, that guy azscooby is always giving misinformation about tuning subarus, the jackass.

it sure is lucky we have a guy like you around here to tell him the right way to do it.

way to go!
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Old 02-17-2008, 11:15 PM   #14
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Originally Posted by ride5000 View Post
yeah, that guy azscooby is always giving misinformation about tuning subarus, the jackass.

it sure is lucky we have a guy like you around here to tell him the right way to do it.

way to go!
Is there really a need for this attitude?

I simply asked him why the tables need scaling.

Last edited by fujiillin; 02-17-2008 at 11:25 PM.
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Old 02-18-2008, 12:22 AM   #15
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the tables need scaling because a bigger MAF housing is not 1:1 with the stock housing. if the heated wire of the MAF is the same on both setups, the big MAF will be moving more air. Consider that the MAF sensor wire is exposed to a percentage of laminar airflow, and when you increase the area of flow, the MAF sensor's percentage of exposure drops.

This is why we use big MAFs in the first place, to give us more headroom with the physical MAF sensor and OEM ECU strategy.

but dont take my word for it, I'm just a shadetree like you. Clark (AZScooby) is one of the most knowledgeable and skilled Subaru tuners in North America. You will do well by listening to him.
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Old 02-18-2008, 12:27 AM   #16
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Missed this thread for some reason. BenW is right. You need to scale the maps out to match the airflow of the newly calibrated sensor. You must also change the values in those maps(tune) to complete the job. What good is a larger MAF housing if you run dont use the increased headroom?


Clark
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Old 02-18-2008, 01:05 AM   #17
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Quote:
Originally Posted by benw View Post
the tables need scaling because a bigger MAF housing is not 1:1 with the stock housing. if the heated wire of the MAF is the same on both setups, the big MAF will be moving more air. Consider that the MAF sensor wire is exposed to a percentage of laminar airflow, and when you increase the area of flow, the MAF sensor's percentage of exposure drops.

This is why we use big MAFs in the first place, to give us more headroom with the physical MAF sensor and OEM ECU strategy.
Right, I understand that, the change in size leads to a new velocity profile for the airflow, which maf scaling compensates for.

What I'm getting at, is that the fuel and ignition tables don't reference maf voltage, they reference the load values which are calculated with maf g/s and rpm. So any changes from the maf table simply trickle down to any table that references load.

Quote:
but dont take my word for it, I'm just a shadetree like you. Clark (AZScooby) is one of the most knowledgeable and skilled Subaru tuners in North America. You will do well by listening to him.
Absolutely.

Quote:
Originally Posted by AZScoobie View Post
Missed this thread for some reason. BenW is right. You need to scale the maps out to match the airflow of the newly calibrated sensor. You must also change the values in those maps(tune) to complete the job. What good is a larger MAF housing if you run dont use the increased headroom?


Clark
I suppose it could just be semantics here, by scaling you meant extending the upper limit and re-interpolating the load axis of the fuel and ignition tables? As to not run static values once your load exceeds the highest column, as anyone running a big maf should need to do?

And of course 'tuning' the tables for any changes in VE.
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Old 02-18-2008, 07:52 AM   #18
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Quote:
Originally Posted by fujiillin View Post
Is there really a need for this attitude?
you tell me.

Quote:
I simply asked him why the tables need scaling.
looks to me like you TOLD him why they DIDN'T.

have a nice day.
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Old 02-18-2008, 08:33 AM   #19
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Quote:
Originally Posted by ride5000 View Post
you tell me.



looks to me like you TOLD him why they DIDN'T.

have a nice day.
Seeing how it provides zero contribution whatsoever and only serves as an attempt to derail things into a personal squabble, no.

Sorry I didn't put a question mark at the end of my second statement, my apologies.

Last edited by fujiillin; 02-18-2008 at 08:42 AM.
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Old 02-18-2008, 10:09 AM   #20
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Quote:
Originally Posted by AZScoobie View Post
Missed this thread for some reason. BenW is right. You need to scale the maps out to match the airflow of the newly calibrated sensor. You must also change the values in those maps(tune) to complete the job. What good is a larger MAF housing if you run dont use the increased headroom?


Clark
This is nonsense. Switching to a bigger MAF housing will have little or no effect on peak load (g/rev). If the MAF voltage vs. mass table is set up correctly, there shouldn't be any need to do anything to the load values in the ignition and fuel tables.

Last edited by Jon [in CT]; 02-18-2008 at 10:17 AM.
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Old 02-18-2008, 02:27 PM   #21
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Quote:
Originally Posted by Jon [in CT] View Post
This is nonsense. Switching to a bigger MAF housing will have little or no effect on peak load (g/rev). If the MAF voltage vs. mass table is set up correctly, there shouldn't be any need to do anything to the load values in the ignition and fuel tables.
that of course begs the question: if you weren't maxing out your original maf sensor housing, then why did you switch to a larger one?
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Old 02-18-2008, 02:37 PM   #22
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You must retune the load reference in the fuel, ignition and Cam timing maps if you alter the size of the MAF tube. IF you dont you will not be using the entire maps load width and the values that will be read will be incorrect. If you are going to install and tune a larger MAF pipe, my advice is to listen to a tuner and to someone who has been working hands on with this system since 2001.

CLark
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Old 02-18-2008, 02:58 PM   #23
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Quote:
Originally Posted by fujiillin
Perhaps you're referring to the load axis?
Quote:
Originally Posted by AZScoobie View Post
You must retune the load reference in the fuel, ignition and Cam timing maps if you alter the size of the MAF tube. IF you dont you will not be using the entire maps load width and the values that will be read will be incorrect. If you are going to install and tune a larger MAF pipe, my advice is to listen to a tuner and to someone who has been working hands on with this system since 2001.

CLark
As I suspected, thanks for clearing that up.

Last edited by fujiillin; 02-18-2008 at 03:30 PM.
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Old 02-18-2008, 03:35 PM   #24
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Clark and Ken are just saying to rescale your load columns to take advantage of your newfound headroom. Of course, this kind of goes without saying.
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Old 02-18-2008, 04:35 PM   #25
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OK...Enough....I will shut this down if outbreaks continue..

...now knock it off

Bill
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