What size wastegate pipes do you guys have on your exhaust manifolds. Are you running a pipe off each runner or one pipe?
What is the angle of the pipe/pipes?
What internal diameter is the pipe/pipes?

As some of you know I have just fitted a larger turbo and I am having an overboost problem.This is what my manifold looks like. The i/d of the pipes going to my wastegate are currently 27mm. They are split all the way up to the bottom of the wastegate.

Are these too small?
Is the angle wrong?
Would I be better off just having one larger pipe coming from just under the flange?

Any advice would be appreciated.

 

Moving the wastegate piping to the outside of your first bends, pointing towards the camera, will allow gasses to enter the wastegate more readily, as they do not have to make as tight of turn. Lots of wastegate tubes come out at worse angles and still work, though.

Also, two 27mm tubes have the same cross section as a single 38mm. Depending on the size of that wastegate flange, it looks like you bring the two 27mm tubes together into a diameter of no more than 30mm. It looks quite a bit smaller than your wastegate flange.

Just my two bits, for what it's worth. I even modified your picture a little to show what I mean, but of course the server does not allow me to attach pictures. We need 3000 posts worth of women in the lounge instead

 

Maybe "Y" the WG pipes into the main runners instead of having them like a "T". Or "T" them in a bend instead of along a straight but that may interrupt flow to the turbo a little more than the "Y" method.

 

that angle is not as important as the main runners to the turbo. Wastegates are all about pressure, and less about flow angles.

 

Try to maintain symmetry and runner lengths from each port to the wastegate collector.
I'd say if you can enlargen the diameter of the piping that would help.

What kind of wastegate and spring do you use?
What is the wastegate outlet diameter (ID)?
What is the wastegate inlet diameter (ID)?

J

 

I dont have the room to move the pipes towards the camera. The two pipes run down together until the flange. I cut the back out of the inside of one pipe so they came down split all the way. The flange is 42mm as that is the size of the wastegate.

I think I will use larger diameter pipes and move the wastegate so it points up inbetween the radiator and the timing cover. I think in that position the gas might have more of a chance to escape.

Thanks for the replies, keep them coming.

 

What size is the pipe on your manafold??

Dale

 

i used 1.5 inch steam pipe for the runners as I wanted to keep the gas speed up. I didnt want heaps of lag as it is a 12a. I will use 1.25 inch pipe for the wastegate pipes instead of the 1 inch that I had.

I'll keep you posted.

 

Hope to have pics of my manifold up by the weekend, I am waiting to get the tubo back before I finalize the exact WG placement (worried about clearance! will be going up like the old one) I paid strong attention to the flow angle of the WG tubes (Basically did a Y junction of a shallow angle to give the pipes the best shot of the main header pipes) and the sizes (42mm ID) as I had similar problems to what Dale was describing with my old design even with 2" ID header tube.

Did you vent your to atmoshpere? how loud is it?

 

Yeh I vented it to atmo. My car was very loud before, now it is just plain stupid.
Lucky I live in the country.
It will eventually be plumbed back into the exhaust but not until it is all running properly and I am ready to stop driving it.