Quattro 88 80

I've been reading about boring and polishing the MAF and adding a velocity stack to it to improve performance. Does anyone know for sure if this is the correct P/N for a 98 A8 4.2l Quattro? And has anyone tried modding one before?<ul><li><a href="http://cgi.ebay.com/ebaymotors/VOLKSWAGEN-AUDI-A8-A6-BOSCH-MAF-METER-NEW_W0QQcmdZViewItemQQcategoryZ6763QQitemZ79963631 63QQrdZ1">http://cgi.ebay.com/ebaymotors/VOLKSWAGEN-AUDI-A8-A6-BOSCH-MAF-METER-NEW_W0QQcmdZViewItemQQcategoryZ6763

PaulW

It has something like a 1/4" wall thickness, don't think that would help. Polishing isn't really gonna help either IMO, it's plastic.

If you start modifying the intake, make sure you know the stock ECU map can handle any changes that you induce.

I believe that is the correct MAF for a ABZ motor.

Quattro 88 80

That thing is plastic? Sure looks like cast something to me. I haven't looked at the one installed in my car but from what I understand they have a screen in them. I was going to remove the screen, possibly bore it out, and polish it. Add a velocity stack to smooth out the air flow and give it a try. If that Auction goes off sub $50 it's a worthwhile gamble at a test situation.

Do you really think it's a waste of time? You are the 4.2 god as I understand it. Right now I have a stock air filter and stock set up. I'd like to slowly and at bargain prices start to get more power out of this motor.

In reading the 12 forum I've seen that they add a cold air induction system, velocity stack, port and polish the maf, silicone tube to throttle body, P&amp;P throttle body, Intake man, heads and use a bigger exhaust.

I'm trying to follow the same basic priciples knowing the differences in the motors we can't do it all, but there has got to be power to be had from a 4.2. My guess is it's just a matter of finding it.

PaulW

An exhaust will gain you a lot more HP......I have a cold air intake, it makes no difference, the exhaust increased gas mileage almost 1 MPG, so it does free up HP.

I personally think you could easily do more harm than good by messing with it.

--------------From a Previous Post-----------

I bought JayS8's cold air intake from him, came the other day so I had to put it in. It's made to be installed in the 97-99 A8 airbox, he had his installed in his S8 with a custom configuration because of the secondary air pump is in there.

So I had to do a little monster garage work yesterday to get it to fit. First of all, the MAF sensor is mounted in the top half of the air filter cover, take it off and turn it upside down and this is what you see.

<img src="http://www.audipages.com/upgrades/coldair1.JPG">

<img src="http://www.audipages.com/upgrades/coldair2.JPG">

So take the two screws out that hold the inlet air straightner in place and remove it and the MAF sensor.

The cold air intake is a 3.5" metal pipe that is mandrel bent and has the two side support welded on. Just use a hose clamp to attach the air filter to it.

I had to drill the mounting holes to a larger diameter to get some additional movement so it lined up correctly and I had to bend the arms a little.

I did not have a 3.5" piece of rubber tubing and clamps to attach the cold air intake to the MAF sensor, so I just used some high tech duct tape....maybe I'll go back in someday and change it out.

<img src="http://www.audipages.com/upgrades/coldair3.JPG">

<img src="http://www.audipages.com/upgrades/coldair4.JPG">

You remove the stock airfilter and this whole thing sits in the air box.

It works! Is the car any more responsive? Heck, I don't know. But I can tell you that with the exhaust and now this, it sure seems a little more responsive, maybe it's just the exhaust note. It's really hard not to put my foot into now!

Quattro 88 80

<center><img src="http://pictureposter.audiworld.com/69854/figure_12-27.jpg"></center><p>Wow I'm dumb - that thing has a velocity stack on it anyway. It's just not in the optimal flow path. It also has restriction with the cross in it and the screen but who knows how much. Attached are some pics of the loss coefficient for turbulent flow. The lower the number the better the flow. As you can see in the pic the sharp edge has a ton of flow restriction (.50) compared to the rounded edged (.03). The larger the radius the better the flow. Now in the set up that we have where the tube actually enters the air box we have an "enormous" .8 loss coefficient. So it looks like I'm going to have to design an elbow and new air box top to succed in reducing the flow coefficent to anything less than it already is.

I don't think a cone filter gives any better flow than it's rectanglar brother if the filter media is the same, but I have't researched that yet.

Zap

Boring / polishing: If you are going to make the MAF inside diameter bigger, at the same time velocity of the air inside will be smaller - which can result in worse performance actually.
Removing screen / cross: of course that parts are restrictive. But at the same time they make the flow of the air more laminar, so the readings from MAF are more accurate. If you are going to remove them, then the straight part of the intake (which means no elbows nor design like we have in the original box) in front of MAF shall be at least something like 3 times dia. Still remains question about changes in velocity .

Both of the problems can be solved by adjusting the map, but I have no experience with that.

Quattro 88 80

Since this part is obviously plastic I'm not going to fool with any of it. It's just too easy to screw up. I am going to look into redesigning the top half of the air box to make it more of a "funnel" feeding the maf. Who knows what I'll come up with but I'll certainly post it when i get it done.

THANKS