airfoil experience....and IAC counts.
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Registered User
Joined: Dec 1969
Posts: 41
From: indlps,in
airfoil experience....and IAC counts.
I decided to play with an airfoil for my 52mm ported factory TB. If you ever looked at one, you would see that it is possible that it would restrict idle air flow. So, months ago i "PORTED" my airfoil. i opened up the exsisting opening for idle air flow and added others. even with this "PORTING" my IAC counts went from 24 to 80. Drivability was ok, but as you come to a stop, the engine wanted to stall as it learned to idle at the higher count number. BLM's at idle, surprisingly, were not affected greatly. I removed the airfoil and the IAC counts went back to 24. Just an FYI....in my experience.
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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.
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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.
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Joined: Nov 1998
Posts: 71,110
From: Hell was full so they sent me to NJ
Which airfoil was it?
I had an airfoil that was made for a Corvette.... big black plastic oval that fit entirely over the TB, then had the airfoil down the middle. Was supposed to be held in by fingers that stuck in the pleats of a Corvette bellows. It had two idle air holes in the foil, one on either side of the vertical centerline. I never noticed any changes in IAC counts with and without. Also never noticed any performance diffference.
Seems to me that no matter what you put in front of the two holes in the TB, it is going to mess up air flow as you experienced, but maybe some designs are worse than others.
I have been swapping out 58mm TB's and the IAC changes radically between the Holley (IAC counts too low at times) and the BBK (IAC counts seem too high). I figured with the Holley it was because of the very sloppy fit of the blades, a large gap around the edges. But after a minor nitrous pop bend the blades, like a pretzel, I hammered them straight, which enlarged them sightly, then hand filed them for the correct fit, and the IAC counts didn't seem to get any better.
The shop that tunes my motor wanted to drill small holes in the BBK blades to drop the IAC counts, but it is "borrowed" so I didn't want to drill it.
Fred
I had an airfoil that was made for a Corvette.... big black plastic oval that fit entirely over the TB, then had the airfoil down the middle. Was supposed to be held in by fingers that stuck in the pleats of a Corvette bellows. It had two idle air holes in the foil, one on either side of the vertical centerline. I never noticed any changes in IAC counts with and without. Also never noticed any performance diffference.
Seems to me that no matter what you put in front of the two holes in the TB, it is going to mess up air flow as you experienced, but maybe some designs are worse than others.
I have been swapping out 58mm TB's and the IAC changes radically between the Holley (IAC counts too low at times) and the BBK (IAC counts seem too high). I figured with the Holley it was because of the very sloppy fit of the blades, a large gap around the edges. But after a minor nitrous pop bend the blades, like a pretzel, I hammered them straight, which enlarged them sightly, then hand filed them for the correct fit, and the IAC counts didn't seem to get any better.
The shop that tunes my motor wanted to drill small holes in the BBK blades to drop the IAC counts, but it is "borrowed" so I didn't want to drill it.
Fred
Thread Starter
Registered User
Joined: Dec 1969
Posts: 41
From: indlps,in
hey fred, it was the type that fits in the middle with a allen head screw that attaches the foil into a tapered 1/2 cylinder. the 1/2 cylinder sits under the plate on top of the TB and slips down into the opening. I was very surprised that it affected the IAC counts as much as it did. Especially since i ported the foil. I have another airfoil that is not nearly as ported that i will try tonight for kicks.
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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.
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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.
Thread Starter
Registered User
Joined: Dec 1969
Posts: 41
From: indlps,in
i put in a different manufacture airfoil, still bolts in the same way, and it had no affect on the IAC. i took it out, and put in the other one and IAC counts went to 75. took it out, back to 24-28. in with the other, counts stayed the same. these cars!!
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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.
------------------
'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.
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