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Old 01-27-2019, 06:45 PM   #1
pcampbell
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Default Practical limit for MAF with larger housings?

How high could you go on a MAF tune with 76, 82, 89mm maf housing?

I have read low end becomes an issue with big housing - does honeycomb air straightener help this? Is it that big of a deal that a slightly higher idle won’t be fine?
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Old 01-27-2019, 08:26 PM   #2
CarmelValleyWRX
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by widening the range of measurement you loose resolution through the whole range, especially at low air flow. think about how slow the air is moving though a tube a idle. now make the tube bigger and the same amount of air is going even slower. its hard for the sensor to read air that is barely moving.
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Old 01-28-2019, 06:44 AM   #3
pcampbell
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Default Practical limit for MAF with larger housings?

Makes sense. When does it become difficult to tune? For example is 400g/s on a MAF reasonable?
This may be what I’m looking for.

https://forums.nasioc.com/forums/sho...6&postcount=29

That poster is in the low 400s going for an 83mm., was on 73mm.

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Old 01-28-2019, 10:57 AM   #4
Homemade WRX
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It's not a matter of 'when it becomes difficult' so much as it's a gradient of less resolution as you go larger.

When does low speed control become detrimental might be a better question.
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Old 01-28-2019, 12:37 PM   #5
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if you don't care about idle quality and ease of driving in the town you could go to a huge maf. if you do care then you need to find the perfect balance to not run out of range on the high or low end of the maf scale. the other option is full SD or a hybrid of MAF at low loads and SD on high load and boost.
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Old 01-28-2019, 12:49 PM   #6
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I don't know that SD is an easy option on a 32 bit NA ECU which is why I'm looking at big MAFs. Seems like the smallest one that'll measure the max airflow would be best.

Currently have a 70mm (pipe ID) straightener, which is obviously not very large but I get the feeling that the straightener helps resolution a bit. I figure it's worth trying this route.
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Old 01-30-2019, 11:48 AM   #7
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is it NA still or boosted? a WRX maf would probably be plenty for an NA setup with extra flow.
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Old 01-30-2019, 03:11 PM   #8
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It’s supercharged. Not hitting MAF limit yet , but interested in really pushing it at some point.
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Old 01-31-2019, 10:41 AM   #9
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I’m pushing well over 400g/s on a 3” maf tube. Resolution is fine at idle. Clearly it’s impossible for it to be accurate as an OEM plastic tube, but it’s not hard to get the LTFT in an acceptable range.
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Old 01-31-2019, 11:47 AM   #10
pcampbell
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Nice thanks. MRP manufacturing sells Subaru maf housings of all sizes with air straighteners (or not) I will probably try it when I need that.
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