Home Made 4 inch MAF Tube

rushhour · 03-12-2006, 12:56 PM

For any of you 04's interested in making your own tube to replace the stock one - I just up loaded some pictures of the one I completed yesterday in the 04 mechanicals gallery.

I had a 4 inch HSV tube on it for about 2 years now and it constantly worked it self loose at the MAF. Nothing worse then pulluing up to the line and all of a sudden hearing the gentle whistle of unwanted air getting in.

Being a former plumber - I figured this can't be to hard to make and it wasn't

I bought the following parts from Airflo.com

1) 4 inch Rubber Elbow
2) 4 inch 22 degree Rubber fitting
3) 1 foot of aluminum pipe

Total cost with shipping about $70. Out of that the biggest cost was the 22 - which was $33. You could probably go with out the 22 and just use a 4 X 3.5 hump adapter - but I felt the 22 worked/looked better.

You also need to find or make a 4 x 3.5 insert to mate the 22 to the MAF. I used a 4 inch thick rubber coupling that I had and cut of an inch of it.

I cut about 1 inch off of the elbow on the TB side to bring it in closer. Then just cut the aluminum tube to the size needed between the elbow & 22. I left the IAT in the tube - so just drilled a 3/4 hole - put a rubber gromet in (had an extra from another tube) and the IAT.

Also knife edged the aluminum tube to keep turbulence down.

Whole project - start to finish probably only took about 2 hours (and a few beers).

I will be insulating the exposed aluminum pipe - figure that 4 inch rubber sleeve properly cut to size will work perfect and match the rest of the unit.

The other benifit besides sealing better - is that the elbow has a large sweep to it - which should help on the airflow/velocity versus the short turn radius on the stock & HSV tubes.

Interestingly - the ECM had to do some adjusting to figure out the A/F. Like I said above - I am sure the HSV tube was allowing some un-mettered air in after the MAF.

The rest of the set up is: 2nd hole added to airbox - like they do in Australia & Shanner 1 PP TB. Rest is stock.

We will see how it runs at ETown on 4/8. The best time run prior was 13.364 @ 104.77 nd best trap was 105.25

Steve