I had ported my wastegat to the stock flapper, and I cannot see that as being enough...What is good to use other than an exhaust valve? I thought about finding a big washer, and grinding the sides down so it will fit and then weld it on, or port out the whole in a washer so that it fits tightly around the stock flapper then weld it on.... Does that sound like it would work?

Or how do you weld the exhaust valve, or other part on?

 

You need to understand (fluid) dynamics...
For laminar flow, I think the fomula is for ever n increase in diameter, there is a n^4 increase in flow potential.

i.e. - 2x diameter and you get a 16x increase in flow potential

It only takes a little to increase flow potential significantly.



-Ted

 

Do your best to smooth out the path dowsnteam form the wastegate as well- eliminating turbulance reduces backpressure, resulting in more flow.
I overported mine slightly- there is about 1/8th of an inch around the flapper.
I noticed no difference in turbo response, though I'm sure there may be a few rpm's difference, just not noticable.
I couldn't keep boost below 12psi on my old setup, with a moderately ported wastegate, but I have NO PROBLEMS at all keeping it down to 6 psi in most gears and 8 psi in 4rth and fifth with the overporting. I bet you'll find it works just fine.

ReTed's right, flow potential is proportianal to cross-sectional size minus all instances of surface friction (boundry layer) I don't think it's to the 4rth power though... I could be wrong of course.

 

Sorry I am dumb, well I sorta understand. I just really would like to have complete control over my boost, that is why i would like the flapper bigger. Like say run 7psi in all gears or something like that....

What I gather from you guys is just porting the wastegate is sufficent enhough? What size? What do you mean smooth out the path down stream? Like insde the runners where the wastgate is?

Back to what I posted about with the washer would that work?

 

Oops, it's radius not diameter.
It's called Poiseulle’s Law.

"According to Poiseulle’s Law – the volume of discharge is inversely proportional to the length of the tube and directly proportional to the fourth power of the radius of the tube. Thus, is the length of tube is doubled, the volume of fluid discharged is halved (if all other factors are constant).

If the radius is reduced by half the force or pressure propelling the fluid through the tube must be atleast doubled to maintain constant volume.

Ex. How much do we decrease resistance to flow if we double radius? 16x

Triple radius? 81x"

Reference URL:  http://www.hodsonhome.com/mna2001/ch...snotes7.28.htm

Thus, if we apply the formula, a 10% increase in diameter comes out to a 46.41% increase in flow potential.  Now I realize that this is ideal conditions, and most people will approximate double the radius increase to flow potential when factoring all the friction stuff; thus, 10% increase in radius is approximate 20% increase in flow potential.


-Ted

 

For wastegates bigger is still better. The bigger the wastegate the more it can flow, and the more it can flow the better boost control will be. People who've ported to the edge of the stock flap still complain of boost creep.

Getting a turbo shop to replace the flapper with a bigger one is relatively cheap, then you can port it to the edge of the new flap (or just get them to).

 

Has anybody with an s5 turbo ported and used an enlarged flapper door? I always thought it was an s4 only thing to change to a larger flapper.

 

If you've seen the S5 flap, you'll know why nobody's tried to change it.

 

Don't need to...
See bottom of this page...
http://fc3spro.com/TECH/HOWTO/KWG/kwg.html


-Ted

 

The problem is I do not have any turbo shops around here. My father and Uncle both can weld damn well, its just we coming up witht he best solution to do it...

 

Is your car an S5 or S4? On my S4 wastegate I had a stainless steel washer welded on and I ported as big as I could go. I still get boost creep on cold nights, but other than that it works great!
http://24.175.236.46/fc/wastegate.html

 

Its a S4, how did ou weld the washer to it? did you grind doen the existing flapper and the grind down the washer?

 

S4 WG



S5 WG

 

i think it is pretty safe to guess that exhaust flow (especially in the turbo) is NOT laminar flow. laminar flow conditions are waaayyyy to slow compare to exhaust gases.
try using turbulent flow.

howi

 

I just had them weld the washer to the face of the stock flapper. The welder filled in the center of the washer and then ground it flat with a grinder.
-John