VADER, what are your reasons again for not modding the MAF??
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I'm glad I got you thinking about it. Yes, there is always an intake restriction, even on a velocity stack intake. The numbers are all theoretical.
For example, your engine is a four-stroke cycle, naturally aspirated overhead valve piston engine. The theoretical displacement of the eight cylinders of the engine totals almost 350 cubic inches, or about one-fifth of a cubic foot (0.2025463 cu. ft., to be exact). Since your engine is a four-stroke cycle design, it can theoretically flow that amount of air on every two revolutions - one complete cycle for every cylinder. If your crankshaft spins at 5,000 RPMs, that would mean 2,500 complete cycles for every cylinder, or 506.365 cu. ft. every minute. If that same engine achieves 6,000 RPM, the theoretical flow would be 607.639 cu. ft. every minute.
Again, these are theoretical numbers. This assumes that the intake valves actually are removed from the ports, and the valve sizes are 4.000" intake and 4.000" exhaust - the same as the bore. The intake and exhaust ports would have to be the same size to assure no restriction and maximum air flow. The throttle body would have to have two 3" bores to accommodate 1.414 (square root of 2) cylinders on an intake cycle at any given time. If all these things were true, the air flow into the engine would be 607.639 cu. ft. per minute at 6,000 RPM. The stock MAF would then be a restriction, since it can only flow 544 SCFM without creating more than 0.1" W.C. static pressure drop.
This would be in a theoretical world. In the real world, the valves are only as large as the combustion chamber design will allow, and the intake and exhaust ports are significantly smaller than the 4" bore of the engine. This means that there is a significant decrease in theoretical flow right at the heads (more on that later).
Next, the only way the cylinder can fill with a fuel/air mixture is if there is a vacuum in the cylinder to draw the mixture in. The air in the manifold can't "wish" its way into the cylinder. To create a vacuum, even a slight one, the piston must travel down in the cylinder while the intake valve is open. This means that some of the theoretical displacement of the cylinder has been "wasted" to create this vacuum. So even though the cylinder volume may be 43+ cubic inches, you'll be really lucky to get 40 cubic inches of air/fuel mixture in to it, even with the theoretical 4.000" intake valve. And since the intake valves are nowhere near that theoretically ideal size, and the ports offer restriction of their own, the volume entering the chamber on even a well-designed engine is more like 75-85% of the theoretical displacement.
Additionally, these theoretically ideal valves would have to completely open the instant that the piston started on its downward stroke, and instantly close when the piston reached the bottom of its stroke (actually, a few degrees after that, but close enough for argument's sake). Since our small valves open and close very slowly in relation to the piston travel, there is additional loss and restriction. To compensate, the valves are opened a little sooner than the theoretical optimum, and close a little later to ram that last little bit of air/fuel mixture into the cylinder.
Farther upstream, the intake passages in the manifold and/or runners are nowhere near the size they would need to be to feed the engine at its theoretical maximum flow. The same holds true for the throttle body and ductwork. All of these passages would have to accommodate the 4.000" size for a zero-restriction system. This would mean that the MAF would have to be somewhere in the range of 4.756" (120.8mm) in diameter. Since it is only 70mm in diameter, it should be restrictive!
Factor in all the losses on a real-world "perfectly designed" engine. This engine would have at least 2.20" valves and the cam timing would have to be at least 50°BTDC intake opening to achieve maximum intake flow at that RPM. The exhaust valves would have to be 1.90" minimum, and the individual matched head pipes would have to be tuned and megaphone-belled at about 28-30" to make the most scavenging action at that RPM. (Is this beginning to sound like a top-fuel engine? - It should.) Intake passages would have to be as short as possible to provide the least possible restriction and tuned length.
With all these things in place, the 350 cubic inch engine would flow around 534.722 cubic feet per minute at 6,000 RPM. Your stock engine is nowhere near that efficient in flow. By that determination, the 544 SCFM of the stock Bosch MAF should provide enough flow for your engine to achieve 7,000 RPM easily.
Removing the screens and heat sink fins will undoubtedly reduce the restriction and decrease the static pressure drop across the sensor. But the difference will be so minimal that the little gain would probably be overshadowed by the nuisance problems you might experience with a modified MAF. Among these problems is the overhating of the electronics package in the MAF, potentially causing erroneous readings at the EM of MAF failure. Removal of the screens can also affect air flow through the MAF at part throttle. There have been at least two distinct cases on this board in the past year where a gutted MAF caused erroneous MAF readings at part throttle. The only explanation is that the air was not turbulent enough through the MAF body to cause a proportional amount of air to pass through the sampling tube in the MAF, instead taking the easiest path through the sensor and causing a low-flow error (Code 34). Within 600 mS, the SES light is on and you are in "limp-home" mode, bad performance and bad economy. The other potential problem is that the MAF hot wire is no longer protected from sonic shock by the now absent screens. The screens also deflect the sonic shock waves created by lean backfire and pulsation from intake valve "howl" at WOT (that growling noise from the intake when you nail the throttle). These same shock waves are strong enough to force extra air into the cylinders (Tuned Port Injection - duh!) and also to crack the hot wire sensor in the MAF. Once it's toast, you'll be shopping.
All of this is in regard to a 350 CID engine. If you're considering the modification on a 305, you'll never even get close to needing more flow through the MAF. Obviously, some people with 4" bore strokers would be closer to needing more flow if they ever got near 6,500 RPM, or 400+CID engines might be hampered by the stock MAF as well. But if you're going to sink a few thousand bucks into the large-displacement engine, why would you take the cheap route on the fuel system? You'd probably go out and get a larger MAF. Incidentally, the GMPP RJ502 BBC engine makes 510 HP/550Lb/ft torque with a 48mm throttle body, less cross-sectional area than that of a stock Bosch MAF. So where are all the MAF-gutters getting their "required" flow numbers from to substantiate hacking up a MAF to make more power? Did I miss something here? Maybe the engineers at GM don't know the MAF trick yet. Next year they'll offer the same engine at 600HP? Maybe, but don't hold your breath.
------------------
Later,
Vader
------------------
"Make Me Bad"
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For example, your engine is a four-stroke cycle, naturally aspirated overhead valve piston engine. The theoretical displacement of the eight cylinders of the engine totals almost 350 cubic inches, or about one-fifth of a cubic foot (0.2025463 cu. ft., to be exact). Since your engine is a four-stroke cycle design, it can theoretically flow that amount of air on every two revolutions - one complete cycle for every cylinder. If your crankshaft spins at 5,000 RPMs, that would mean 2,500 complete cycles for every cylinder, or 506.365 cu. ft. every minute. If that same engine achieves 6,000 RPM, the theoretical flow would be 607.639 cu. ft. every minute.
Again, these are theoretical numbers. This assumes that the intake valves actually are removed from the ports, and the valve sizes are 4.000" intake and 4.000" exhaust - the same as the bore. The intake and exhaust ports would have to be the same size to assure no restriction and maximum air flow. The throttle body would have to have two 3" bores to accommodate 1.414 (square root of 2) cylinders on an intake cycle at any given time. If all these things were true, the air flow into the engine would be 607.639 cu. ft. per minute at 6,000 RPM. The stock MAF would then be a restriction, since it can only flow 544 SCFM without creating more than 0.1" W.C. static pressure drop.
This would be in a theoretical world. In the real world, the valves are only as large as the combustion chamber design will allow, and the intake and exhaust ports are significantly smaller than the 4" bore of the engine. This means that there is a significant decrease in theoretical flow right at the heads (more on that later).
Next, the only way the cylinder can fill with a fuel/air mixture is if there is a vacuum in the cylinder to draw the mixture in. The air in the manifold can't "wish" its way into the cylinder. To create a vacuum, even a slight one, the piston must travel down in the cylinder while the intake valve is open. This means that some of the theoretical displacement of the cylinder has been "wasted" to create this vacuum. So even though the cylinder volume may be 43+ cubic inches, you'll be really lucky to get 40 cubic inches of air/fuel mixture in to it, even with the theoretical 4.000" intake valve. And since the intake valves are nowhere near that theoretically ideal size, and the ports offer restriction of their own, the volume entering the chamber on even a well-designed engine is more like 75-85% of the theoretical displacement.
Additionally, these theoretically ideal valves would have to completely open the instant that the piston started on its downward stroke, and instantly close when the piston reached the bottom of its stroke (actually, a few degrees after that, but close enough for argument's sake). Since our small valves open and close very slowly in relation to the piston travel, there is additional loss and restriction. To compensate, the valves are opened a little sooner than the theoretical optimum, and close a little later to ram that last little bit of air/fuel mixture into the cylinder.
Farther upstream, the intake passages in the manifold and/or runners are nowhere near the size they would need to be to feed the engine at its theoretical maximum flow. The same holds true for the throttle body and ductwork. All of these passages would have to accommodate the 4.000" size for a zero-restriction system. This would mean that the MAF would have to be somewhere in the range of 4.756" (120.8mm) in diameter. Since it is only 70mm in diameter, it should be restrictive!
Factor in all the losses on a real-world "perfectly designed" engine. This engine would have at least 2.20" valves and the cam timing would have to be at least 50°BTDC intake opening to achieve maximum intake flow at that RPM. The exhaust valves would have to be 1.90" minimum, and the individual matched head pipes would have to be tuned and megaphone-belled at about 28-30" to make the most scavenging action at that RPM. (Is this beginning to sound like a top-fuel engine? - It should.) Intake passages would have to be as short as possible to provide the least possible restriction and tuned length.
With all these things in place, the 350 cubic inch engine would flow around 534.722 cubic feet per minute at 6,000 RPM. Your stock engine is nowhere near that efficient in flow. By that determination, the 544 SCFM of the stock Bosch MAF should provide enough flow for your engine to achieve 7,000 RPM easily.
Removing the screens and heat sink fins will undoubtedly reduce the restriction and decrease the static pressure drop across the sensor. But the difference will be so minimal that the little gain would probably be overshadowed by the nuisance problems you might experience with a modified MAF. Among these problems is the overhating of the electronics package in the MAF, potentially causing erroneous readings at the EM of MAF failure. Removal of the screens can also affect air flow through the MAF at part throttle. There have been at least two distinct cases on this board in the past year where a gutted MAF caused erroneous MAF readings at part throttle. The only explanation is that the air was not turbulent enough through the MAF body to cause a proportional amount of air to pass through the sampling tube in the MAF, instead taking the easiest path through the sensor and causing a low-flow error (Code 34). Within 600 mS, the SES light is on and you are in "limp-home" mode, bad performance and bad economy. The other potential problem is that the MAF hot wire is no longer protected from sonic shock by the now absent screens. The screens also deflect the sonic shock waves created by lean backfire and pulsation from intake valve "howl" at WOT (that growling noise from the intake when you nail the throttle). These same shock waves are strong enough to force extra air into the cylinders (Tuned Port Injection - duh!) and also to crack the hot wire sensor in the MAF. Once it's toast, you'll be shopping.
All of this is in regard to a 350 CID engine. If you're considering the modification on a 305, you'll never even get close to needing more flow through the MAF. Obviously, some people with 4" bore strokers would be closer to needing more flow if they ever got near 6,500 RPM, or 400+CID engines might be hampered by the stock MAF as well. But if you're going to sink a few thousand bucks into the large-displacement engine, why would you take the cheap route on the fuel system? You'd probably go out and get a larger MAF. Incidentally, the GMPP RJ502 BBC engine makes 510 HP/550Lb/ft torque with a 48mm throttle body, less cross-sectional area than that of a stock Bosch MAF. So where are all the MAF-gutters getting their "required" flow numbers from to substantiate hacking up a MAF to make more power? Did I miss something here? Maybe the engineers at GM don't know the MAF trick yet. Next year they'll offer the same engine at 600HP? Maybe, but don't hold your breath.
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Later,
Vader
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"Make Me Bad"
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Joined: Mar 2000
Posts: 1,468
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From: Orland Park, IL, USA
Car: 88 IROC-Z
Engine: L98
Transmission: TH350
Axle/Gears: 3.45
Um anyone have some screen to fit a MAF opening??? Vader made me cry. i spent almost 2 hours making sure my maf was totally clean and free of restriction and you have to go and make me feel bad. THANKS A LOT 
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1988 IROC-Z 350 TPI
(its an original 350 car)
License Plate: STG KLR 1
Engine Mods:
Edlebrock TES Headers, Hypertech Chip, Flowmaster Muffler, Intake Airfoil, Removed MAF Screens, bored .030 over, Other minor mods
Trans Mods:
2,500 stall converter, Redline clutches,Heavy Duty Steels, Trans-Go reprograming kit
, Heavy Duty 2-4 band, Corvette Servo, B&M Mega Shifter w/ Carbon Fiber Handle (looks sweet in a black car!)
Best Time So far: 14.104@99.66 Told you id go faster
"If you can put it on your car, its fair" Quote By Guido
Foundering Member of the Illinois Overkill Crew (IOC) http://www.suempresaenlinea.com/drowned/images/iroc-black.gif[/img]
[This message has been edited by 88blkiroc (edited September 28, 2000).]
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1988 IROC-Z 350 TPI
(its an original 350 car)
License Plate: STG KLR 1
Engine Mods:
Edlebrock TES Headers, Hypertech Chip, Flowmaster Muffler, Intake Airfoil, Removed MAF Screens, bored .030 over, Other minor mods
Trans Mods:
2,500 stall converter, Redline clutches,Heavy Duty Steels, Trans-Go reprograming kit
, Heavy Duty 2-4 band, Corvette Servo, B&M Mega Shifter w/ Carbon Fiber Handle (looks sweet in a black car!)Best Time So far: 14.104@99.66 Told you id go faster
"If you can put it on your car, its fair" Quote By Guido
Foundering Member of the Illinois Overkill Crew (IOC) http://www.suempresaenlinea.com/drowned/images/iroc-black.gif[/img]
[This message has been edited by 88blkiroc (edited September 28, 2000).]
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88,
If you're lucky, you shouldn't have any problems with a gutted MAF. A very small percentage of people have the false lean code problem, and lots of MAFs are out there with no screns and are surviving. If you've already done it, I wouldn't sweat it. I also wouldn't risk damaging the MAF again by trying to reinstall screens.
I only wanted to point out the potential problems, and risk of damage to a fairly expensive component for something that may or may not provide any real performance gains.
Some people swear by their gutted MAFs. I swore at mine when it failed, then at myself after doing the homework and determining that I really gained nothing by doing it in the first place. I did get forced into hunting down a better MAF sensor, and I now have no hot wire to break and 700+ SCFM (like I'll ever need it). I guess it might have been worth a couple hundred bucks to learn a lesson, but the lesson is not beneficial if it doesn't benefit anyone, so here I am.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
If you're lucky, you shouldn't have any problems with a gutted MAF. A very small percentage of people have the false lean code problem, and lots of MAFs are out there with no screns and are surviving. If you've already done it, I wouldn't sweat it. I also wouldn't risk damaging the MAF again by trying to reinstall screens.
I only wanted to point out the potential problems, and risk of damage to a fairly expensive component for something that may or may not provide any real performance gains.
Some people swear by their gutted MAFs. I swore at mine when it failed, then at myself after doing the homework and determining that I really gained nothing by doing it in the first place. I did get forced into hunting down a better MAF sensor, and I now have no hot wire to break and 700+ SCFM (like I'll ever need it). I guess it might have been worth a couple hundred bucks to learn a lesson, but the lesson is not beneficial if it doesn't benefit anyone, so here I am.
------------------
Later,
Vader
------------------
"Make Me Bad"
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iTrader: (8)
Joined: Jan 2000
Posts: 3,968
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From: Macedonia ,OH
Car: Formula
Engine: 6.0 LSX
Transmission: 4L60E
Axle/Gears: 9 Bolt 3:27
I was thinking about doing it at the beginning of the year then I read vaders article in like febuary and havent touched the maf yet
Supreme Member
Joined: Mar 2000
Posts: 13,414
Likes: 6
From: Central NJ, USA
Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
My GM service book states that the screen is there to "smooth airflow over the sensor". When I removed it, I was lucky enough to keep the clip intact! My car instantly got an error code for low air flow. I had the stock intake on there, and on my Firebird, there's a 45 degree bend between the MAF and airbox. I think the air was hugging the outer wall of the MAF (due to the bend, think of a car's path as it heads into a turn), and skipping over the v6's "frequency film". I don't think my MAF was sensing any air at all.
Camaros with the dual-snorkel intake might not notice this because their MAF is straight-on with the rest of the tubing.
Thought I'd throw my 2 cents of experience in there... good article, Vader!
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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
Camaros with the dual-snorkel intake might not notice this because their MAF is straight-on with the rest of the tubing.
Thought I'd throw my 2 cents of experience in there... good article, Vader!
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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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Supreme Member
Joined: Jul 1999
Posts: 2,844
Likes: 4
From: Maryland
Car: 2005 Subaru STI
Engine: 153ci of Turbo Power!
Transmission: 6-Speed
I'll swing to the other side of the spectrum and say removing the screens does provide a benefit on 350s.
1) Also take into account air velocity and the pressure drop when you first open the throttle blades. Good example - *theoretically* a 48mm TB is all you need for a 350. But, installing a 52mm on a lightly modified engine will increase horsepower without hurting lowend torque. Even installing a 58mm TB on a heavily modified engine (read good sized cam and big heads will produce horsepower in the upper RPMs). Performance gains are seen by installing a 52mm TB that flows over 700cfm. The stock MAF flows what?
2) Most often you see the MAF error when installing a cam. This is easily fixed by modifying the PROM. Remember, if you change any part of the engine or a sensor then you could be throwing the calibration in the PROM off. This is easily fixed by adjusting the minimum airflow table in the PROM. Takes all of 2 minutes to do.
Tim
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TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
1) Also take into account air velocity and the pressure drop when you first open the throttle blades. Good example - *theoretically* a 48mm TB is all you need for a 350. But, installing a 52mm on a lightly modified engine will increase horsepower without hurting lowend torque. Even installing a 58mm TB on a heavily modified engine (read good sized cam and big heads will produce horsepower in the upper RPMs). Performance gains are seen by installing a 52mm TB that flows over 700cfm. The stock MAF flows what?
2) Most often you see the MAF error when installing a cam. This is easily fixed by modifying the PROM. Remember, if you change any part of the engine or a sensor then you could be throwing the calibration in the PROM off. This is easily fixed by adjusting the minimum airflow table in the PROM. Takes all of 2 minutes to do.
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Member
Joined: Apr 2000
Posts: 307
Likes: 0
From: Frederick, MD USA
HOLY MOTHER OF GOD!!! Some on in the 12's that lives in the same city as me!?!?!?!? And you are a prom moderator? Are you gay? Me neither..please marry me though..seriosuly..can we be friends?? I can not beleive you live in Frederick!! How come you never run that in Frederick!! I've never ever in my life seen you on 40, 40 in Hagerstown, or at the infamous Lilypons. I work at your ISP too if that makes you wanna be friends with me more. Please write back..It would really mean alot to me to know someone that knows something aside from Larry at TrakAuto.
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-Red '88 IROC 5 Speed TPI
-Dual Friction Centerforce Clutch
-Accel 300+ Racing Ignition
-Accel 300+ Pro Sleeve Plug Wires
-Accel U-Grove Plugs
-Flowmaster Force II 3 Chamber Cat Back Exhaust
-Hypertech Chip
-Hypertech Airfoil
-Removed MAF Screens
-Gutted Air Box
-Best E/T 14.90, 60 ft. 2.17, 1/8th mile 9.61(bald tires, SES light on)
-Best MPH 92.7(bald tires)
------------------
-Red '88 IROC 5 Speed TPI
-Dual Friction Centerforce Clutch
-Accel 300+ Racing Ignition
-Accel 300+ Pro Sleeve Plug Wires
-Accel U-Grove Plugs
-Flowmaster Force II 3 Chamber Cat Back Exhaust
-Hypertech Chip
-Hypertech Airfoil
-Removed MAF Screens
-Gutted Air Box
-Best E/T 14.90, 60 ft. 2.17, 1/8th mile 9.61(bald tires, SES light on)
-Best MPH 92.7(bald tires)
Supreme Member
Joined: Jul 1999
Posts: 2,844
Likes: 4
From: Maryland
Car: 2005 Subaru STI
Engine: 153ci of Turbo Power!
Transmission: 6-Speed
Yarnster - You have mail.
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Supreme Member
Joined: Jul 1999
Posts: 2,844
Likes: 4
From: Maryland
Car: 2005 Subaru STI
Engine: 153ci of Turbo Power!
Transmission: 6-Speed
Yarnster - You have mail.
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Moderator
Joined: Jan 2000
Posts: 19,684
Likes: 317
Originally posted by IROC-ZTWENTYGR8:
Thanks Vader, so even if u have a heavily modded 350, u shouldn't mod the MAF or get a 52mm or 58mm TB, just stay with 48mm??
Thanks Vader, so even if u have a heavily modded 350, u shouldn't mod the MAF or get a 52mm or 58mm TB, just stay with 48mm??
If you took the last several years of your life to read the post (sorry, I got "happy-fingers"), I said that STOCK 350's would never need more air flow. You can build a well-flowing 350 that may eventually need more air than the stock MAF can flow without serious restriction. For most casual street cars, the MAF will support a lot of modification before it becomes a big problem. Even a 327 or 302 can suck a stock MAF dry at high RPMs.
But as I also stated, if you go to the trouble to build to that point, your system design should have included the calculations for the necessary fuel and air intake to support the engine at the desired power output. If that means you want to make 600 HP at 7,500 RPM, you should have known that before you turned the first bolt and planned accordingly. In those cases, you'd already know that the MAF would be restrictive, and would have a different fuel system. You certainly wouldn't be using a TPI, even a modified one, at that RPM and power level on a normally aspirated engine. If you decided to boost the engine, the MAF would no longer be an issue, since the MAF restriction is meaningless when you are running a blower.
Another thing to bear in mind is that even with a monster MAF and throttle body. the old ECM can only meter air up to 255g/S. After that, any additional flow means that the mixture just gets leaner, and power falls off.
I'll stick top what I said originally. The MAF is not a restriction for most stock 350s, and should be one of the last changes made, not he first. Most 350s with headers, cat-back, MSD, and an air foil will never get close enough top risk it. Even a cam profile improvement would not cause a serious restriction. You would experience restriction near 6,500 RPM, but I wouldn't feel comfortable driving a stock 350 with a cam at 6,500 RPM for very long. Your heavily-modded 350 may be the exception, and you very well may benefit from a larger MAF. Most of what I see on this board doesn't fall into that category. And if you've spent the time and cash to do a serious build, why wouldn't you spend a few more bucks on a larger MAF instead of trying to get flow out of a stock unit? You'd be happier in the long run.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
Supreme Member
Joined: Jul 1999
Posts: 2,844
Likes: 4
From: Maryland
Car: 2005 Subaru STI
Engine: 153ci of Turbo Power!
Transmission: 6-Speed
Just FYI - although the stock MAF only measures up to 255g/sec you can modify the WOT %Change to AFR vs. RPM ... and the Open loop %change to AFR in order to compensate for engines that require fueling above the 255 MAF max.
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Tim
------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org
Member
Joined: Jun 2000
Posts: 293
Likes: 1
From: United States of America
Car: 1987 Chevrolet Camaro Z28 IROC-Z
Engine: L98
Transmission: TeamTripp Performance
Wow, this is good info, tech article stuff. But now I'm thinking, how does this apply to other popular mods intended to increase intake flow? Things like home made ram-air, cut out air boxes, K&N, and throttle body, plenum, and runner porting.
Since these mods are cheaper and easier to do (than getting a new set of heads) they are often the first things done to try to increase stock performance. Given what has been posted here about the limited benefit and decreased reliability of removing MAF screens, can the same thing be said about these mods?
Since these mods are cheaper and easier to do (than getting a new set of heads) they are often the first things done to try to increase stock performance. Given what has been posted here about the limited benefit and decreased reliability of removing MAF screens, can the same thing be said about these mods?
Senior Member
Joined: Mar 2000
Posts: 669
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From: Red Bud, Illinois
Car: 1989 IROC-Z
Engine: 383
Transmission: Pro-Built 700R4 2400 ACT Stall
Axle/Gears: 2.77 Borg Warner 9-Bolt
lol, there's your MAF car to test PROM's on Trax.
I am gonna side with Vader here, i removed the screens and removed the fins, etc all it did was tick me off. I got no hp (from what i could tell) and i got stuck with a bill.
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89 IROC-Z 350 TPI
-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
I am gonna side with Vader here, i removed the screens and removed the fins, etc all it did was tick me off. I got no hp (from what i could tell) and i got stuck with a bill.
------------------
89 IROC-Z 350 TPI
-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
Junior Member
Joined: Feb 2000
Posts: 75
Likes: 0
From: sarasota, fl
Car: FORMULA 350
Engine: ZZ4
Transmission: 700R4
ahhh,,,the screen removal debate rages on. I have removed mine(1991) with no problems. Allthough I have heard of instances when removal has led to replacement of the sensor. Personally, I think some cars are jinxed(spelling) from the get go. Being a Gm dealership employee for 16 years, I have seen jinxed cars. These cars have problems from day one. They are in for repairs every month or so. Others, once they leave the lot, you never see them again until the happy owner trades it in. So, in a nutshell,,,, if you have a good running car without any mysterious problems,,remove the screens. If you have a car that throws you engine lights everytime you start it,,,don't mess with anything that isn't broke. Just my skewed opinion.
Moderator
Joined: Jan 2000
Posts: 19,684
Likes: 317
Originally posted by TRAXION:
Just FYI - although the stock MAF only measures up to 255g/sec you can modify the WOT %Change to AFR vs. RPM ... and the Open loop %change to AFR in order to compensate for engines that require fueling above the 255 MAF max.
Tim
Just FYI - although the stock MAF only measures up to 255g/sec you can modify the WOT %Change to AFR vs. RPM ... and the Open loop %change to AFR in order to compensate for engines that require fueling above the 255 MAF max.
Tim
There is even a pretty cool way to completely eliminate the MAF at WOT, so there is no restriction. The problem is in the transition between closed loop and WOT open loop - it can be less than smooth.
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Later,
Vader
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"Make Me Bad"
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