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02-09-2008, 02:21 AM | #1 |
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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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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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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 |
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. |
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. |
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. |
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 |
02-14-2008, 10:59 PM | #8 |
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Great information guys
Thankyou |
02-14-2008, 11:16 PM | #9 | |
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Quote:
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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02-14-2008, 11:53 PM | #10 |
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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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02-15-2008, 09:29 AM | #12 |
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thanx!
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02-15-2008, 06:08 PM | #13 | |
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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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02-17-2008, 11:15 PM | #14 | |
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Quote:
I simply asked him why the tables need scaling. Last edited by fujiillin; 02-17-2008 at 11:25 PM. |
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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. |
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 |
02-18-2008, 01:05 AM | #17 | |||
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Quote:
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:
Quote:
And of course 'tuning' the tables for any changes in VE. |
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02-18-2008, 07:52 AM | #18 |
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02-18-2008, 08:33 AM | #19 | |
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Quote:
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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02-18-2008, 10:09 AM | #20 | |
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Quote:
Last edited by Jon [in CT]; 02-18-2008 at 10:17 AM. |
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02-18-2008, 02:27 PM | #21 |
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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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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 |
02-18-2008, 02:58 PM | #23 | ||
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Quote:
Quote:
Last edited by fujiillin; 02-18-2008 at 03:30 PM. |
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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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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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