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Old 05-02-2019, 03:03 PM   #1
Matilda Car
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Default 90 degree bend before AMM - needed or not?

Hi,

Used the search but can't find a consensus. Have a 1990 240 Wagon with B230FT, 016 AMM. Been reading some posts suggesting that a 90 degree bend before the AMM is needed as this is the Volvo set up. Some seem to have noticed no real difference after doing it.

So the question is will it make that much of a difference or not?

Thanks
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Old 05-02-2019, 04:15 PM   #2
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I recently read some posts here that mention including the bend prior to the MAF. I have also read, from reputable sources, that you want a straight entry to the MAF at least twice as long as the diameter of the MAF. I've tested neither, but the straight entry makes more sense to me. It also seems the difference, at least on a car that isn't tuned with precision to the moon and back, would be negligible.
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Old 05-02-2019, 09:03 PM   #3
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You want as much straight pipe in front of and in back of the AMM as possible. ^ his statement about the entry to the AMM is correct in an ideal situation, in real life we do the best we can. That being said, I attached a S&B cone filter directly to the AMM (it was 012 3") and had a 45 degree bend a few inches behind it to attach to the turbo, see pic. This worked well, no issues.

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Old 05-02-2019, 09:25 PM   #4
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Quote:
Originally Posted by shoestring View Post
I recently read some posts here that mention including the bend prior to the MAF. I have also read, from reputable sources, that you want a straight entry to the MAF at least twice as long as the diameter of the MAF.
The factory 7/9 turbo airbox sweeping plastic 90* has approximately 2 AMM diameters of "equivalent length" at the centreline...... for what it's worth. I also understand the wire mesh in front of the AMM instrument is necessary as well.
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Old 05-02-2019, 09:30 PM   #5
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You don't really need the mesh, the front and rear mesh are to straighten airflow, so it has some value for that if you have a bend, It can also stop a bit of dirt. I used the front mesh and left the rear off.

If you look at newer cars with a AMM or MAF, many have thick versions of the mesh, my L33 has a mesh that is about 1/4" thick to better straighten the airflow, and if you have a bend directly in front of or behind the MAF, it can cause a lot of performance issues.

That being said, the B230 is not as sensitive.
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Old 05-02-2019, 11:12 PM   #6
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Cool, great info thanks! I have been running a filter off the AMM like 2turbotoys pic with no issues either...that I know of anyways. I was looking to get a smaller coolant tank and re route a smaller washer bottle as I am on a mission to reduce heat and free up the inlet a little more. I worked with what I had on hand and just sorta jammed it in there with the stock tank and end of the world size washer bottle.
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Old 05-03-2019, 02:06 AM   #7
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I added the bend before the MAF and AFRs in boost went from 10:1 to 11:1. That’s a significant change.
While having straight sections and mesh to create laminar flow are good ideas, it all comes down to how the factory tuned the ECU with the MAF setup. Anything different than stock can change the tune.
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Old 05-03-2019, 02:41 AM   #8
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The bend before the AMM is to make the air flow into the AMM swirly instead of just sucking straight in if you didn't have a bend. This helps the AMM read the amount of air flowing past the hot wire more correctly. If you look inside the AMM the hot wire is in the middle of it. The mesh thing is to protect the hot wire from getting something sucked into it and breaking it. Best to have the one on the intake side at least.
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Old 05-03-2019, 09:34 AM   #9
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Quote:
Originally Posted by culberro View Post
I added the bend before the MAF and AFRs in boost went from 10:1 to 11:1. Thatís a significant change.
While having straight sections and mesh to create laminar flow are good ideas, it all comes down to how the factory tuned the ECU with the MAF setup. Anything different than stock can change the tune.
Interesting. I've seen this discussed over the years, but nobody has ever mentioned something like this. I think I need to try and do the same.
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Old 05-03-2019, 09:44 AM   #10
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Quote:
Originally Posted by culberro View Post
I added the bend before the MAF and AFRs in boost went from 10:1 to 11:1. Thatís a significant change.
I am going to try it when I free things up, that is a significant change for sure.
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Old 05-03-2019, 02:53 PM   #11
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Quote:
Originally Posted by culberro View Post
I added the bend before the MAF and AFRs in boost went from 10:1 to 11:1. Thatís a significant change.
While having straight sections and mesh to create laminar flow are good ideas, it all comes down to how the factory tuned the ECU with the MAF setup. Anything different than stock can change the tune.
Actual tests beat my suppositions every time.
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Old 05-03-2019, 05:34 PM   #12
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We'll volvo actually said that is why there is a 45 degree bend before the AMM.
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Old 05-06-2019, 02:26 PM   #13
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I have run multiple inlet arrangements to the AMM and have not had any differences with the AFR (data logged), straight was fine.
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Old 05-06-2019, 02:38 PM   #14
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Kool you know more then volvo then. What is your ET and trap speed then hot rod?
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