S5 stock maniold, external dump

[TitaniumTT]

Lemme start off by saying that this is pretty damn cool. Good job on the work so far.

Originally Posted by sen2two

38mm is plenty large enough. My motor is completely factory. Hasn't even been rebuilt yet... Most people port the stock wastegate to 35mm.

I am not a fan of overly large wastegates. Here's why... In theory of course, but I would rather be safe than sorry in this case.

whether you have a large wastegate or small wastegate, they still open at the same speed. And that speed is quick. When you hit your set PSI and your overly large wastegate opens, it releases a large amount of exhaust pressure quickly. Most of the time TOO quickly. Causing exhaust pressure drop and possibly a drop in boost momentarily slamming it shut again only to open quickly again. You might not notice this, but I'm sure the motor does.

Instead of guessing, I would datalog it. MAP and EMAP as well as WG duty. If you're running any sort of ems or electronic boost controler, you sould be able to tune it out.

[need RX7]

very interesting.

[RETed]

You've just destroying the whole reason why Mazda redid the turbo exhaust manifold and turbine section.

Seriously, you guys need to leave alone these "rare" parts and go mess with S4 stuff.


-Ted

[Phoenix7]

Originally Posted by RETed

You've just destroying the whole reason why Mazda redid the turbo exhaust manifold and turbine section.

Seriously, you guys need to leave alone these "rare" parts and go mess with S4 stuff.


-Ted

there is no way to get better flow out of the S5 manifold?

[jerd_hambone]

Originally Posted by RETed

You've just destroying the whole reason why Mazda redid the turbo exhaust manifold and turbine section.

Seriously, you guys need to leave alone these "rare" parts and go mess with S4 stuff.


-Ted

Hey now, just because Mazda spent a million dollars redesigning something, doesn't mean it is working at it's peak. He's not trying to mess with what Mazda did exactly, he's more on the lines of trying to make his car as reliable as possible. One good boost spike can do all sorts of damage.

Relax there ol' buddy!

[RETed]

I'm talking about the "independent twin scroll" function of the whole system...

Anyone who has messed with both the S4 and S5 turbo systems knows the turbos produce power differently.
The S5 has a smoother power delivery, because it spools quicker and more linear due to the independent twin scroll.
The S4 will lag a bit and then punch you in the gut when the boost hits around 4kRPM or a little bit after that.

This has nothing to do with boost creep.
I've ported S4 and S5 turbos before, and I've never had a problem with boost creep after porting the wastegate passages.
In fact, I ported the S5 turbo so well, it ended up producing only 5psi of boost with unmolested wastegate vacuum lines, even with no cats.
(We were able to get the boost to hit 10psi with an A'PEXi AVC-R afterwards.)
Oh, and this wasn't with the stock compressor section - it was running an H-trim compressor side.

The S5 turbo parts are not easy to acquire in the states.
In fact, there's a demand for those parts for those who know about it's advantages.
There's a bazillion S4 turbos parts available, and it's easier to stuff an external wastegate on them a whole lot easier.
In the end, you're doing the same thing - remove the independent twin scroll (well, the S4 never had it to begin with) and run an overpriced and oversized external wastegate which, IMO, is not necessary if you know how to port the stock wastegates efficiently.

In the end, I call this kinda project "showing off" just to document the resources you have on hand.


-Ted