After looking at some throttle bodies for our cars I saw on ebay a 55mm with half shaft mod so I found out all common options we have for how much of an area we have and % increase over stock. I did it with the 49 being our stock size because of the taper on it. First number is area in mm. second is % increase.

7078.54 Stock
7235.34 2.22% stock with shaft mod
8001.76 13.04% 52mm
8173.36 15.47% 52mm with shaft mod
8981.50 26.88% 55mm
9157.50 29.37% 55mm with shaft mod
10740 51.73 60mm
10932 54.44% 60mm with shaft mod

Holy shit I have a 51% increase. AND my Intake is bored to 60 and ported and polished. AIRFLOW!!!11!

Cut the shaft down and you will get a little more. I was amazed at how much more it was. I knew circles grow exponentially but DANG!

Whats the max the stock TB can be bored to? I know there are a lot of 55mm out there but maybe it can be bored to 60mm

Originally posted by SilvrEclips
Whats the max the stock TB can be bored to? I know there are a lot of 55mm out there but maybe it can be bored to 60mm

57mm.

And exactly what is the shaft mod? Is it already done on the MPx?

You just cut the upper part of the shaft off.

The wall thickness of ours at 57 must be like paper! But yea you cut the top half of the shaft that doesn't have threads and the head of the bolts will sit on the throttle plate. Nothing noticeable but a little increase.

ahh. http://mbworld.org/forums/w211-amg/366071-all-throttle-body-shaft-grind-talk.html pictures in this thread make it easier to understand if anyone else does not or is thinking of doing this.

Originally posted by 740 turbo brick
Holy shit I have a 51% increase. AND my Intake is bored to 60 and ported and polished. AIRFLOW!!!11!

Did you bore your runners to?

All this shaft modding talk and no one has brought up knife edging the butterfly plate?

Talked to my boss for about 10 minutes on this (one of the benefits on working for a performance company) And for aerodynamics, you don't want a sharp edge on the leading edge, you want it smooth and circular circular on the leading edge, and on the knife on the trailing edge. I'll be giving this a shot while attempting my half shaft mod.

They knife edge the back? In my head I sorta under stand but not sure how to say it haha.

Almost think of looking at a comet or you got the smooth circular head, and the trailing edge that falls to a point.

Originally posted by Dstach
After looking at some throttle bodies for our cars I saw on ebay a 55mm with half shaft mod so I found out all common options we have for how much of an area we have and % increase over stock. I did it with the 49 being our stock size because of the taper on it. First number is area in mm. second is % increase. 7078.54 Stock 7235.34 2.22% stock with shaft mod 8001.76 13.04% 52mm 8173.36 15.47% 52mm with shaft mod 8981.50 26.88% 55mm 9157.50 29.37% 55mm with shaft mod 10740 51.73 60mm 10932 54.44% 60mm with shaft mod

Next time just throw this in your existing thread.

Oh sorry I forgot I posted the other one. I was just thinking today that I didn't see you post in any threads I recently viewed.