I did a MAF mod I think it’s worth sharing.

We all know the stock Throttle body and MAF are very restrictive. The stock TB diameter is 50mm and the stock MAF housing diameter is 45mm.
My stock TB is bored out to 50mm. But my MAF housing is stock.
Around 2 years ago a got a spare MAF sensor housing rebored to 48.5mm. I remember I installed it but it didn’t work well. I installed the stock one back and that was it.

A few weeks ago I remember that MAF housing and I also remember that once on the old TS forum, there was a topic about enlarged MAF housing but I don’t think they had succes with them. I also remembered someone posted that if the MAF housing was to be enlarged, the air velocity through that opening will go down. This is where the problem starts because the air velocity through the sample hole in the MAF housing will also go down, Which will make the engine run rough. You cannot make the sample hole larger because it will make it even worse.

So, how do I increase the air velocity through the sample hole? according to physics, I should decrease the diameter of the sample hole to increase the volume flow rate. The length doesn’t matter.

The stock sample hole has a diameter of 8mm and a depth of around 33mm.
I went to the hardware store and looked for a bushing I can fit into the hole.
I managed to get a nylon spacer with an O.D. of ⅜″ and I.D. of .171″ (4.4mm).
I took my MAF housing to a friend who had a bench drill press and I drilled the sample hole to ⅜″. After that I cleaned it pretty good and the nylon spacer went in tight.

Now where the sensor hot wires goes into the housing, I used a dremel to open up that area. It got pretty messy with a nylon bits everywhere. But I got the sensor to fit back into the housing without a problem.

Also before inserting the nylon spacer into the maf housing, I grinded / drilled the ends of the nylon spacer with the dremel to make it form like a “V shape” or like a velocity stack. This for the air to flow in smoothly.

Today I decided to test the maf mod. I took off the sensor from the stock housing I had on the car and screwed it on the modded housing. Connect everything and started the engine.

It started right up (which surprised me) and remained idling. Idle was around 150-200rpm lower than normal. I loosened the idle air screw at the side of the throttle body and it got to idle better. I think I can also adjust the throttle stop a little to make it idle a bit higher.
Keep in mind I do have Sandros chip in the ECU and 3tech 222/365 cams (aggressive) installed.
Overall I’m VERY satisfied with the mod. The engine revs instantly to 8600 with NO hesitation. It really is very good.

If anyone wants to do this mod, I advise you to do it on a spare maf housing for obvious reasons.
Also I have a friend who I tried to get him to 3d print the spacer so I can insert it into the sample hole without drilling it out. But he’s didn’t have material to do it.

It got late I stopped testing the mod. In the upcoming week I’ll try again. I also plan to install a potentiometer inline with the WTS to see if I can richen up the AFR a bit. I do have a wideband ready for the car but it has yet to be installed.

hey this mod could work on my gti! i already have mikes most aggressive cams and its chipped to 8800 (cant remember the tune, its on team swift somwhere.....!..

i was just thinking yesterday about taking the gti out for a spring run....😏
If you're gonna do it, do it on a spare maf housing. ;-)

Also you should have a rebored stock TB because otherwise, the stock size TB will be the restricor.
Yeah we did do larger ones from like some Ford 3.8 V6's. We even adjusted the amount of air bleed to make the measure right for Idle and stuff. It works. But it much easier to go stand alone without one. I even looked at using just the sensor in the tube alone.