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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
Originally Posted by Rodsrsr View Post
Most of the MAF kits are easily over $1500,00 so its really a cost effective solution. Plus the MAF kits usually just come with a chip so there's no adjustability. You can use the barn door, it will work fine, you just need to go push thru. I've heard some people say that the AFM's dont last too long under boost, but I ran mine like that for years without any problem. I would just go BEGI with the MSD and stock AFM to get it going for now. There are dozens of threads detailing the 3.2 on boost.
I've had those old Bosch barn door air flow meters apart many times when modifying and tuning old single cam 3.5 liter six cylinder BMW's with L-Jetronic injection.
They used the same air flow meter housing early Motronic used with a different circuit board inside and the wound up clock spring tension on the barn door is adjustable. So is the position of the barn door stylus on the circuit boards resistance trace.

Boost would have no wear effect on the air flow meter. It's very solidly made and I've never heard of the bearings for the barn door wearing out.

There is a better one though... Toyota made a nice copy of it on the old Toyota Supra.
The Toyota one is a much lighter alloy that weighs a lot less and it flows more CFM of air than the Bosch housing. I remember reading it flows more from a BMW tuner that tested them on a flow bench.
Also the aluminum top cover of the Toyota AFM is screwed on with philips head screws so it can be removed and the inside can then be ported to flow more air while the barn door is in the full open position. The Bosch top cover is riveted and glued on and you'd destroy it trying to remove it.

Use a bead of clear silicone sealant to seal the cast aluminum cover when reinstalling it on the Toyota housing if you remove it to port the inside of it.
The black plastic cover over the circuit boards in both of them can be carefully pried off and then the circuit board is held in place with small screws and it can be removed from the Bosch housing and installed into the Toyota housing.

After doing all that you readjust the clock spring preload tension on the barn door and then adjust the idle air bypass screw for the CO adjustment.

Very few people know about this old barn door AFM upgrade and the old Toyota Supra Bosch copy AFM housings are in salvage yards... If I remember correctly they were made by Nippondenso for Toyota.
Old 01-05-2015, 10:39 AM
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