View Full Version : Here's why the latest MAF mod works so well...
<center><img src="http://pictureposter.audiworld.com/711/mafscreen2.jpg"></center><p>As you'll be able to see from the pics the MAF bore opens up a TON of room for more air to flow. More air= more torque and there seems to be zero apparent draw-back associated with the modification. I tested my MAF on my sons 90S with auto/front wheel drive this morning and took 2.12 seconds off his previous low 0-60 (my method) time. No codes and no CEL.
Fist pic is what MAF inlet bore looks like before modification (disregard the screen as it and the entire center section have been eliminated in the current revision).
<center><img src="http://pictureposter.audiworld.com/711/bleedport1.jpg"></center><p>this combined with above pic provides a ton of visual proof why this thing can now flow more air. Note: Before boring the MAF can only flow air equivalent to a 1.98" I.D. housing due to the center post sampling tube. After boring MAF flows air at the full 73mm (2.874") housing I.D. A net flow increase of just over 48.5%.
<center><img src="http://pictureposter.audiworld.com/711/mafbore1.jpg"></center><p>with integrated velocity stack MAF inlet. This VS protrudes thru the airbox and into the MAF where past the screen retainer ring to eliminate any/all potential groove disturbances. The smaller outlet size going into and compared with the MAF inlet size is offset by a factor of over 2000% when taking into account the inlet flair and tapered walls. The opening on the velocity stack is 33% larger than the opening in the top of the airbox. This thing breathes LARGE!
<center><img src="http://pictureposter.audiworld.com/711/mafbore2.jpg"></center><p>This pic is what it all looks like from the business-end of the MAF housing. From here it hits the next obstruction I'll be workking on. The smaller intake plenum hose and inlet. The inlet, hose and plenum will soon be replaced by Samco Sport 3" I.D. hose and elbows from the MAF outlet all the way to the throttle body.
Later today I'm going to mill a flat on the end of the black wire sampling tube then turn a radiused aluminum button cap to epoxy on the end of the MAF sampling orifice tube. It'll flow better than the square-cut sharp end that's on there now and allow that piece to create a lot less disturbance and turbulence to the air flowing past it. Hey, if you're gonna be a dog, why be a chihuahua!?!
Mr.D-'97 A4q 12v
04-18-2003, 10:01 AM
with the stock paper element?
Until you approach that tubing diameter running without a filter you can't outflow whats there with a filter, no matter which filter you use. But a brand new K&N panel filter only flows 1%-1.5% more air new than a new stock paper element. I've checked it. Thats why on this car I've opted to remain stock, filter-wise.
And at speeds over the 35mph the stock airbox starts to transition to positive pressure rather than negative pressure before 35mph due to intake inlet behind the grill. At 75mph the stock airbox is running 4+ psi positive pressure even with the engine pulling air out of it for combustion. At 100mph it's 7psi positive pressure. This is not a poorly designed or under-engineered airbox!
04-18-2003, 12:31 PM
In this pic I've epoxied the polished aluminum dome. This will allow the air to flow smoother and with less disturbance and turbulence over the rounded dome than over the previous square cut end with light bevel. Should facilitate a smoother, cleaner, more stable passage of air thru the sensor wire orifice by smoothing the small vortexs, turbulences and boundary layer disturbances on the inlet/outlet side.
I've also dressed up the sensors calibrated intake orifice on the the other side. Just a mild, tapered chamfer thats more precise than the stock sharp-edged, cast black plastic inlet bore.
04-18-2003, 02:44 PM
So do you have any tricks left for the intake track? Or is it time to start work on the fuel system now?
Also, if you need any web space to store your pictures, I have more space than I ever need and can give you your own storage area and FTP access if you want it.
tho I'm only going with 10% higher flow and will rely on the blueprinting and higher efficiency Lucas disc injectors efficiency over the pintle injectors we use now. But the injectors won't be used for my original goal which I'll touch on below. They'll be used as "icing on the cake" to further enhance this kit and only as an option for further gain if someone wants more. And who doesnt... but that is for later when my goal has been met or surpassed. There's also the possibility of using the injectors in place of an exhaust system. Injectors will cost less than the exhaust I'm planning. Time will tell as I can't do both and stay under budget. Once my goal is met people can supplement whatever mods they choose with the knowledge it'll only get better. And I'll probably continue the research here as well tho not as ardently or the with the same dogma as I am right now. Spring is nigh and other enticements beckon.
I still have to finish the work on the Samco 3" MAF-back induction hose to the throttle body as that should almost nearly double the efficiency of the MAF modification. And there's a catch can and associated hoses with vac return line to be sorted out during the induction hose adaptation.
Beyond that will come exhaust and I've just barely scratched the surface on that one. But it will consist of manifold-back with high-flow cats if necessary, and all stainless construction.
My goal is to get Audi's advertised crank HP numbers (172/174) at the wheels for sub $2k at sea level. I'd be very surprised if I werent fast-approaching that number once the induction hose is installed. I'm objectively putting the wheel HP figure with Stage 2+ TB, MAF mod, EFK, airbox velocity stack/MAF inlet and 3" induction hose from MAF-to-throttle body at +or- 155-160 wheel HP. I'm saving a K&N panel filter as my trump card. If I'm 3 or 4 ponies off I'll toss it on the pile. These modifications come to a total of just under $1k.
And if those figures are close I can still come in with exhaust just at or slightly under/over budget. I may have to do some quantity buying to make budget if I see it going into the 'red.'
Thats the plan as it exists today. Stay tuned!
How about making the MAF post into tear drop shape?
hard to make a tear-drop shape when there's a hole running thru the center of it and the exit tail must be at least as large as it's inlet. And the plastic post is hollow so there goes spherical too.
You could do it.
If there is a dyno,why not make some pulls ?
Some nice dyno plots with your mods and you could have a nice little side business.
conducting their own dyno runs. I'd rather have my customers do them without my influence. Additionally no matter how hard you try to explain to people it's still hard overcoming the 18% elevation hit and it's perception. That after a dyno run I can still only produce stock 2.8 12v HP munbers at sea level results. No matter how much you espouse that phenomenon the fact remains people just don't see it as credible or without a jaded opinion.
I want to see the before and afters,I almost never believe the max HP numbers. Too many things can alter those.
What about the tear drop thing. I've no idea but it's a very efficient shape.
impartial and unbiased opinions. You'll see before/after results soon enough on the Stage 2+ TB and the MAF inlet velocity stack and several more innovations next month. All done at sea level and by an owner who stands to gain nothing compared to the manufacturer/designer who stands to gain financially. This is not only better for me but also for you guys... anyone who is now or might become a candidate for any or all of this stuff down the road.
The tear-drop idea is valid but complicated as it involves compound internal/external radii, best suited for a follow-up down the road. Besides I don't even think the polished dome benefits, if any, would show on a dyno. But it was only a 5 minute project I could do simultaneously while polishing the MAF internals. Right now I've got several other fish to fry and need to button up the airbox and MAF and move downstrean a few inches.
All in due time...
If I had a Front Trak or a AWD dyno,I'd offer myself up. Drag strip numbers would be a plus as well. Stock vs MODs. Sure it would take a bit to get use to running at the track but it can show things a dyno will not. It would be nice if you could make some $ off of all this and those kind of numbers will help.
Price: Deposit check of $100 included with MAF housing to be bored. Within one week of installing new one you send me your original MAF housing as payment in full for the machine work and I return or tear your deposit check up when I receive it. I pay all ground shipping charges to you, you pay all shipping charges to me.
I'll do 3 or 4 this way as I need cores to have made up so I can offer an exchange program.
This only applies to 100% stock MAF housings that have NOT been previously modified/altered in any way.
04-19-2003, 01:15 PM
Want anything for the trouble? I can't hardly expect your services to be free of charge.
Let me know.
but at that point I'll be able to offer an exchange. Helps me out, helps you out. Thats good enough for me.
04-19-2003, 03:38 PM
04-20-2003, 02:57 AM
I can adapt, become a little more flexible. My salvage yard is on to me. I used to buy TB's from them for $35 ea, now since they found out what I'm doing with them they want $100ea.
How do you want the housing you're sending me bored to eliminate the screen retainer groove? Tapered? Straight? And what do you do if anything to eliminate such a HUGE flange face inlet once the groove is removed? It looks like if taper it from the back side of ring groove all the way to the flange I'll break thru the housing walls or close and that a taper would end up in or very near the flange bolt holes. Got a pic or drawing of what you have in mind?
04-20-2003, 08:52 AM
I've removed the groove by hand porting the housing. This method takes a considerable amount of time. Its tapered, which leaves about 1/8 of material remaining. The flange face is then given a small radius Only reason I'm asking for the groove's removal, is because I don't run the inlet funnel that you fabricate. I don't think I can, given the configuration of my current cone filter & MAF adapter.
Boring out the MAF via machine looks to be cleaner, and take less time.
Easier without so much hogging out of material that's not going to match up to an inlet face anyway.
I'm thinking boring a straight .049" relief straight inside the gasket flange to the back of the screen retaining ring then turning a small thin wall aluminum sleeve that is pressed in & epoxied flush up against the I.D. inlet walls of the MAF and seated against the rear groove retainer wall (when viewed from the front). Once cured bore the I.D of the pressed-in sleeve flush with the rear "stepped" retaining wall. Then mill the flange face/sleeve flat, then a small bit of "gasket-matching" at your end to mate it up perfectly to your cone/MAF adapter. Or send along an adapter and I'll do it here.
Way nicer than just hogging/tapering out a lot of aluminum that's never gonna mate to anything.