On my new project car it came with a s5 turbo. Now I know the s5 came with a superior exhaust manifold/turbine/wastegate, but I have heard a ported and new flapper s4 wastegate will flow MORE than a ported s5 wastegate. Can anyone put some truth to this? Porting begins this week. I've ported a s4 without a new flapper and it held any amount of boost I threw at it with TID mod, and full 2.25 catless exhaust. But on the new car it's a s5 motor and has a full 3" single exhaust system. I just need to know which wastegate will be able to hold what I throw at it. Thanks fellas.

 

Personally I don't believe that. The combined area of the S5 wastegate ports I've recently finished porting is quite a bit more than the hugely ported wastegate in the S4 turbo I'm currently running. Plus with the S5 turbo you get the adavantage of a divided manifold.

 

Thanks, I was secretly waiting for your reply after reading your s4 wg porting thread.

 

There are some other tweaks you can do also:
File the back side of the door, so it can open wider.
Open up the narrow spot in the exit passage.

 

more surface area does not always mean more flow, there is plenty of variables involved, mainly it is how you port it not simply the size. don't get me wrong though, larger diameter makes it much easier to get more flow.

 

Although the wastegate arm does hit the backplate (it leaves a mark on both), if you remove the backplate and open the flap by applying compressed air to the wastegate actuator you'll see that the flap's travel is limited by the the spring in the actuator reaching full compression. You can only get ~1mm extra travel by grinding either the arm or the backplate, which would have neglibible effect on wastegate flow.

True, but a lot more cross-sectional area (not surface area) usually does.

Even if a ported S4 wastegate can be made to flow as much as a ported S5 one, because of the manifold design the S5 turbo is still the better of the two and should definitely be used if you have the choice.

 

The S4 turbine housing has a .4 AR primary scroll! This restriction is enough that it WILL help stop boost creep by chocking the motor on the exhaust side decreasing its volumetric efficiency.

But, that is a poor way to combat boost creep.

That may be why some people are saying the S4 WG port works better than S5. You can port the S5 WG passages huge too if you need to.

I can fit all five of my fingers in EACH wastegate passages of my S5 housing- though this requires ditching the stock WG flappers for an external WG on the turbo backplate.

You definitely want to ditch the S4 turbo in favor of the S5 turbo if given the oportunity.

 

Great info guys. Started grinding on the s5 today. I'll get pics when I'm all finished up.

 

I port-matched the manifold to the turbine housing and also widened the two passages a little bit. Since the die grinder was out, it seemed silly not to...

 

how about an external setup if you really want to get crazy?

I ran this setup last summer...loud as FAWK with the dump tube...

But I never had any creep issues baby...the gate is a VW (probably audi) and is 34mm......

 

WORD TO THAT!!! haha, I get a little port crazy....

Finished the smaller hole, took it from 18mm to 26mm. Going for the big hole today and finish up port matching.

My little dremel hates me now, I'm in desperate need of a air compressor/die grinder.

Oh and a word of advice to newbies, don't do port work with a carbide bit with flip flops, you WILL get metal slivers in your feet. haha. Sanding stones and flip flops are a ok though.

Any advice for the big hole? Kinda looks hard to get at.

 

A tip with a Dremmel.
Work in 30 to 60 second sessions.
Then turn off the Dremmel & cool the burr in a small cup of water.
That keeps the heat from getting to the Dremmel's bearings, and keeps your fingers from cramping.

 

Dual waste gates - why not..

 

well, the factory internal was welded shut, so only the external was functional

 

My S5 wastegate ports- still had boost creep with clipped P trim exhaust wheel...



But what finally solved the boost creep was porting the turbo manifold and runners to reduce velocity before the wastegate holes as seen in this pick. Spool was still full 15 psi by 3,500rpm on my little 3" exhaust.

 

can i buy that turbo