Maf mod - Whatcha think? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-13-2004, 02:36 AM   #11
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the article says "Do NOT reinstall the sampling tube backing plate!" so I'm guessing just pull the backing and hack accordingly
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Old 09-13-2004, 02:44 AM   #12
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I'm not too sure that this is something that I would dork with. I wish I had a torture car around to try this stuff out, but limited on parking as it is. I also don't honestly think that there would really be anything to gain from this?
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Old 09-13-2004, 03:31 AM   #13
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Quote:
Originally Posted by DrJay
Quote:
Originally Posted by PontiacDad
I read the same article a few days ago DrJay. I agree the throttle body is a limiting factor and the Maf is which translates the air flow into an electrical signal. You would need a mini afc to tune the maf as the maf'* air curve is set in the pcm. By boring out the tb you throw the curve out of wack? One of the problems I've noticed here is Bonne'* eat afc calibraters, they work for a while then die? I'm not sure whats going on in the pcm to do this but suspect it maybe has something to do with the map sensor?
The MAF table won't change any and correct me if I'm wrong but the only reasons you'd want a calibrator is if you change the injectors or put a maf adjusted for different injectors in. The only issue I can see at the moment is at idle if there isn't a good flow over the wire it might be a little rough. A a/f calibrator won't change that.
Your right the maf does not change and the table is based on sensor and tb dimensions. So if you put in more air by boring it out the table is out of calibration and the engine runs lean? The pcm will correct for this as best it can via the o2 sensor but an afc will improve the a/f ratio for a quicker responce?
If the flow is strong enough you may also get DTC P0101 'maf sensor performance'
The MAF signal frequency indicates an airflow significantly more or less than a predicted value based upon the barometric pressure, the throttle position and the engine RPM.
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Old 09-13-2004, 04:53 AM   #14
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Quote:
Originally Posted by PontiacDad
Quote:
Originally Posted by DrJay
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Originally Posted by PontiacDad
I read the same article a few days ago DrJay. I agree the throttle body is a limiting factor and the Maf is which translates the air flow into an electrical signal. You would need a mini afc to tune the maf as the maf'* air curve is set in the pcm. By boring out the tb you throw the curve out of wack? One of the problems I've noticed here is Bonne'* eat afc calibraters, they work for a while then die? I'm not sure whats going on in the pcm to do this but suspect it maybe has something to do with the map sensor?
The MAF table won't change any and correct me if I'm wrong but the only reasons you'd want a calibrator is if you change the injectors or put a maf adjusted for different injectors in. The only issue I can see at the moment is at idle if there isn't a good flow over the wire it might be a little rough. A a/f calibrator won't change that.
Your right the maf does not change and the table is based on sensor and tb dimensions. So if you put in more air by boring it out the table is out of calibration and the engine runs lean? The pcm will correct for this as best it can via the o2 sensor but an afc will improve the a/f ratio for a quicker responce?
If the flow is strong enough you may also get DTC P0101 'maf sensor performance'
The MAF signal frequency indicates an airflow significantly more or less than a predicted value based upon the barometric pressure, the throttle position and the engine RPM.
Hmm...I guess this would all depend on how much is getting around the MAF sensor. One of the modifications is to pull the backing off the MAF. While its said that this may produce a rougher idle it also seems that off idle it would get a better sample of the air. How much this may be off is anyones guess but this seems like a fairly common mod in the ford realm. While its a different animal we at least have 3 things in common with the Ford engine, supercharged 3.8 with a hitachi MAF. The abilities of the PCM to adapt are of the most concern though.

Is MAF performance something the OBDI monitors? Aparently OBDII does but I haven't heard anything about it on OBDI so I'm not sure.

I guess this is the whole reason its great Dame agreed to do the experiment
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Old 09-13-2004, 09:29 AM   #15
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Quote:
Originally Posted by DrJay
Quote:
Originally Posted by Damemorder
Quote:
Originally Posted by Twister97
I think I would hold off, until there were some numbers backing this mod up, unless I missed it on his page. Can removing that metal strip actually gain anything at all?
Laminar flow.


I have a spare TB, get me some suspected numbers and I'll cut it, Otherwise We'll just always wonder.
As in flow?

Stock 3800 vin L throttle body w/ screen -- 419.1 cfm
Stock 3800 vin L throttle body w/o screen -- 444.8 cfm
No, not the maf screen, but that metal strip that dude cut away. The one actually inside the TB.
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Old 09-13-2004, 05:55 PM   #16
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Quote:
Originally Posted by Twister97
No, not the maf screen, but that metal strip that dude cut away. The one actually inside the TB.
The one in the middle of the flow from the front? It'* right in the path of the air. Wait til you see my pics, There'* a huge advantage to having that thing out of the way. I'll have to measure my stock TB to get the numbers perfect, But I'm thinking 1.25-1.5 sq. in. of metal from the front will now be gone. That means the air can fly right in, instead of having to weave around the "Lower MAF Support", as I'm now going to call the peice that'* being cut out.

I've got maybe 5-6hrs of careful grinding and polishing left, It'* purty.
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Old 09-13-2004, 07:15 PM   #17
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Wouldn't taking off the plate dramatically change the way the air flows over the MAF filaments? It would increase airflow over them by so much, I think you'd exceed the MAF'* capabilities to read.
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Old 09-13-2004, 07:35 PM   #18
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Quote:
Originally Posted by jwikoff99
Wouldn't taking off the plate dramatically change the way the air flows over the MAF filaments? It would increase airflow over them by so much, I think you'd exceed the MAF'* capabilities to read.
Yup, We'll see if the car can cope.
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Old 09-13-2004, 09:36 PM   #19
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I was heavily considering doing this to my old spare TB (now in dame'* possesion). However the only tool i have that would be feasable to do this on would be my dremel which wasn't happening.

But it'* a relatively smooth piece inside the TB from what i remember, and if you look at it, the throttle plate will sit behind it as well. So the Throttle plate will still occupy that same area you're cutting out, and it'* not as smooth on the perimter either. Your MAF sensor should still see the same air unless you cut the entire section out of the bore, and the MAF sits exposed (common on some cars).

You could be possibly disrupting your airflow more then stock, and further back on stock, which could hurt N/A motors a lot...

I think the best way to increase CFM in the TB is to get a bigger one, and port your SC or manifold accordingly....

Just my .02 thou..

Jason
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Old 09-14-2004, 05:43 PM   #20
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Almost done now, Just need to get the Lower Intake Gaskets replaced and broken in to get my Butt dyno tuned in, Then I can swap the TB and see the results.
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