2.8 30V MAF modification in-depth...
09-25-2003, 06:10 AM
#1
AudiWorld Super User
Thread Starter
2.8 30V MAF modification in-depth...
<center><img src="http://pictureposter.audiworld.com/711/30vs3maf.jpg"></center><p>
I was approached by a local Audi owner to offer some mods for his 96 A6 30V Q/T that would allow him to gain a few unclaimed ponies and stay a little closer to my 2.8 12V which he's both driven and ridden in. And while my car is manual transmission it will kill him seven ways to Sunday in ANY dead-stop/rolling start race. And my car is completely stock except for all my bolt-on induction mods and exhaust, fuel/air controller, monitor and injectors.
So last week we swapped cars for a week and I set about seeing what I could find that would give him more HP/TQ, throttle response that would remain bolt-on in nature and able to be done by the average person with minimal hand-tools in his/her own garage. The first area I found is what I'll cover today. Yes, there are several others but none of them have been implemented yet and are still on the flow bench being sorted out or parts are being sourced so we don't risk ruining his as sometimes ya gotta break some eggs when omelette is on the menu.
So here is the first of several to-come items for the 30V:
First thing I found is the MAF housing. Audi part # 078 133 471C. No other 30V's are around for me to look at so I don't know if this MAF is still being used or if it's been replaced/superceeded by Audi. This is the one on the A6 in here for the work so this is the "only" MAF part number that I "know" to work with this modification. The MAF required to do this modification is Audi part # 078 133 471A. It's over $600 from Adui but usually available from salvage yards in the $50-$100 range with sensor. Both sensor and housing are required for conversion.
Next I had to find a MAF that would accomplish several things. First it's had to have the same output voltages as the stock MAF. Second it had to fit the airbox with no or minimal modifications. And lastly it had to work with the existing wiring harness and ECU.
I got lucky on this part and found that the MAF I'm using for my Stage 3 mods on the 12V cars was a perfect fit and all signal outputs were a perfect match.
The stock plastic MAF on the 30V car has a total "net" I.D. of 2.12" when you subtract all of the obstructions and reducers cast into the body along with the mass of the air sampling tube incorporated. It also has a laminar diffuser (screen) at it's entry which is VERY restrictive. When we tested a simple velocity stack MAF inlet over at the 12V Development forum the overwhelming consensus of the poll taken indicated a net 7HP gain with the velocity stack in place and the screen removal. That should translate to a 50% or greater net gain on a car with 2.5 times more valves and a corresponding increase in flow. However with screen removal alone the car is prone to throw CEL's and idle rough. The velocity stack is used as a "non-restrictive" diffuser with the added benefit of increased velocity and volume.
With this knowledge in-hand I set about replacing the stock plastic MAF with one of my Stage 3 units. Essentially a 96/97 2.8 12V MAF cast from aluminum. I then remove the samppling tube from this MAF and bore it to a little over 3" I.D. But rather than a straight bore I incorporate a tapered "velocity stack" wall that increases the air velocity as it enters the MAF which also allows it to pull in greater volumes of air behind the preceeding air. It also smooths the air across the sensing element allowing for good, consistent, code-free readings from the sensor element. Then just aft of the sampling area I machine in another taper of a slightly different degree which allows the air to smoothly expand back to a 3" diameter column as it enters the MAF-to-plenum hose. After all machine work is done on the MAF housing it is then subjected to a 3-stage honing/polishing process to enhance flow. Each MAF is aslo trued and it's bore set on a 90 degree axis to it's flange face so that it is completely true and perpendicular to it's gasket face. So the MAF when machined is far truer and aligned on axis than in it's cast form from Hitachi (MAF manufacturer).
Once the MAF is machined and cleaned it's ready for installation on the airbox which is a straight-forward 4-bolt 10 5 minute swap. The MAF velocity stack is a "push-in" precision interference-fit to the airbox exit hole requiring no adhesives/fasteners. All new ISO 9006 Hollo-Krome stainless steel allen cap screws are used instead of the 10mm hex bolts and button head stainless screws now hold the sensor element to the MAF housing instead of the Torx that originally comes with the MAF.
I'm guessing upwards of 15HP with this mod as its is NOT a subtle modification. I don't even drive one of these cars and I could feel it easily from the 10 minute drive I took before setting to work on it. May likely be more. And as people at the 12V Development forum will tell you I don't pass out HP claims easily or frivolously. And it's all seat of pants but I've been doing this for a long time and I'm no stranger to cars or Audi's as my user account number here at AW clearly shows. I've been around awhile.
The above pic is of Stage 3 MAF installed with standard induction hose.
I was approached by a local Audi owner to offer some mods for his 96 A6 30V Q/T that would allow him to gain a few unclaimed ponies and stay a little closer to my 2.8 12V which he's both driven and ridden in. And while my car is manual transmission it will kill him seven ways to Sunday in ANY dead-stop/rolling start race. And my car is completely stock except for all my bolt-on induction mods and exhaust, fuel/air controller, monitor and injectors.
So last week we swapped cars for a week and I set about seeing what I could find that would give him more HP/TQ, throttle response that would remain bolt-on in nature and able to be done by the average person with minimal hand-tools in his/her own garage. The first area I found is what I'll cover today. Yes, there are several others but none of them have been implemented yet and are still on the flow bench being sorted out or parts are being sourced so we don't risk ruining his as sometimes ya gotta break some eggs when omelette is on the menu.
So here is the first of several to-come items for the 30V:
First thing I found is the MAF housing. Audi part # 078 133 471C. No other 30V's are around for me to look at so I don't know if this MAF is still being used or if it's been replaced/superceeded by Audi. This is the one on the A6 in here for the work so this is the "only" MAF part number that I "know" to work with this modification. The MAF required to do this modification is Audi part # 078 133 471A. It's over $600 from Adui but usually available from salvage yards in the $50-$100 range with sensor. Both sensor and housing are required for conversion.
Next I had to find a MAF that would accomplish several things. First it's had to have the same output voltages as the stock MAF. Second it had to fit the airbox with no or minimal modifications. And lastly it had to work with the existing wiring harness and ECU.
I got lucky on this part and found that the MAF I'm using for my Stage 3 mods on the 12V cars was a perfect fit and all signal outputs were a perfect match.
The stock plastic MAF on the 30V car has a total "net" I.D. of 2.12" when you subtract all of the obstructions and reducers cast into the body along with the mass of the air sampling tube incorporated. It also has a laminar diffuser (screen) at it's entry which is VERY restrictive. When we tested a simple velocity stack MAF inlet over at the 12V Development forum the overwhelming consensus of the poll taken indicated a net 7HP gain with the velocity stack in place and the screen removal. That should translate to a 50% or greater net gain on a car with 2.5 times more valves and a corresponding increase in flow. However with screen removal alone the car is prone to throw CEL's and idle rough. The velocity stack is used as a "non-restrictive" diffuser with the added benefit of increased velocity and volume.
With this knowledge in-hand I set about replacing the stock plastic MAF with one of my Stage 3 units. Essentially a 96/97 2.8 12V MAF cast from aluminum. I then remove the samppling tube from this MAF and bore it to a little over 3" I.D. But rather than a straight bore I incorporate a tapered "velocity stack" wall that increases the air velocity as it enters the MAF which also allows it to pull in greater volumes of air behind the preceeding air. It also smooths the air across the sensing element allowing for good, consistent, code-free readings from the sensor element. Then just aft of the sampling area I machine in another taper of a slightly different degree which allows the air to smoothly expand back to a 3" diameter column as it enters the MAF-to-plenum hose. After all machine work is done on the MAF housing it is then subjected to a 3-stage honing/polishing process to enhance flow. Each MAF is aslo trued and it's bore set on a 90 degree axis to it's flange face so that it is completely true and perpendicular to it's gasket face. So the MAF when machined is far truer and aligned on axis than in it's cast form from Hitachi (MAF manufacturer).
Once the MAF is machined and cleaned it's ready for installation on the airbox which is a straight-forward 4-bolt 10 5 minute swap. The MAF velocity stack is a "push-in" precision interference-fit to the airbox exit hole requiring no adhesives/fasteners. All new ISO 9006 Hollo-Krome stainless steel allen cap screws are used instead of the 10mm hex bolts and button head stainless screws now hold the sensor element to the MAF housing instead of the Torx that originally comes with the MAF.
I'm guessing upwards of 15HP with this mod as its is NOT a subtle modification. I don't even drive one of these cars and I could feel it easily from the 10 minute drive I took before setting to work on it. May likely be more. And as people at the 12V Development forum will tell you I don't pass out HP claims easily or frivolously. And it's all seat of pants but I've been doing this for a long time and I'm no stranger to cars or Audi's as my user account number here at AW clearly shows. I've been around awhile.
The above pic is of Stage 3 MAF installed with standard induction hose.
09-25-2003, 06:13 AM
#2
AudiWorld Super User
Thread Starter
Pic 2:
<center><img src="http://pictureposter.audiworld.com/711/30vs3maf2.jpg"></center><p>Installation with silicone hose kit and pic of velocity stack in spare airbox lid. MAF inlet is deriectly behind velocity stack once mounted. You can view other angles and more pics of the Stage 3 setup at my picture poster.
09-25-2003, 06:20 AM
#4
AudiWorld Super User
Thread Starter
Pic 4:
<center><img src="http://pictureposter.audiworld.com/711/30vs3maf4.jpg"></center><p>MAF outlet end bore shot. Sorry about the quality of this one as I had to shoot the pic blind. I couldn't see into the viewfinder while taking pic. There's a better shot of this in my picture poster on a 2.8 12V thats more focused. The aluminum ridge at the lower end of the MAF in this pic is the MAF velocity stack outlet entering the MAF housing.
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09-25-2003, 07:00 AM
#10
AudiWorld Super User
Thread Starter
S'funny you should mention that and at first-glance that would seem to be the case...
but in having over 50 of these out there and in-use it doesn't happen. Our sensors are actually identical as far as voltage outputs go and the MAF adapts to it's new found air as does the ECU and the injector pulse and it's duty cycles. You can do a VAG on it and see nothing ever gets dangerously out of whack and certainly never leans itself out. Further use of a fuel-air ratio montitor long-term bears this out further.
But maybe, just maybe it's more mis-callibrated from the factory than it is once this is done. Thats seems to be how it's working out for over 4 dozen others on a car with only 12 vlaves. If there was going to be an issue or a problem with a larger bore MAF I think it'd have manifested itself sooner on a car that flows half of what a 30V engine is capable of. In terms of comparison you guys should be able to adapt a 4.5" MAF.
But maybe, just maybe it's more mis-callibrated from the factory than it is once this is done. Thats seems to be how it's working out for over 4 dozen others on a car with only 12 vlaves. If there was going to be an issue or a problem with a larger bore MAF I think it'd have manifested itself sooner on a car that flows half of what a 30V engine is capable of. In terms of comparison you guys should be able to adapt a 4.5" MAF.