RockLobster

iTrader: (7)

500$ shipped from japan, i verified it is a factory new part. I kinda ordered it on a whim so i could use my old one to experiment on (rebuilding, porting, etc).

RockLobster

iTrader: (7)

Update.

I fixed a problematic blow off valve and tuned the AFRs and timing. Both were leading to boost spikes at let off.

I have the boost controller bypassed and took the car to the DYNO yesterday.

The car generated 180 RWHP at 7k rpms on a mustang dynomometer. The mustang dyno is a more acurate mesurement of power output than other Dynos, and according to the factory recomended correction factor, i suspect the car generated somewhere between 230 and 240 "crank" HP.

Again as far as I know this is with just racing beat 3" full race exhaust and cone intake filter as power mods. (the engine is a reman of some kind that was put in before I purchased the car)

The dyno also showed that with the boost controller bypassed the car never managed to generate more than 6.5 PSI of boost. The wastegate also stabilized boost at 5.5 PSI as the computer brought the AFRs down into the mid 11s near redline (5500-7000 rpm).

I feel this is more concrete evidence that the primary restriction in the S5 Turbo wastegate system is the gate itself. Not the passages. As I only have that spacer, allowing the gate to open further.

It is also fun to note that the car produced more HP than stock with the RB exhaust, at less than stock boost.

NZConvertible

In my first post I suggested that it was the wastegate actuator that limited flap opening angle, and I've since proven that to be correct. When I did all the porting to my S5 turbo I noticed there was a mark on the pivot arm that indicated it was hitting the backplate. I figured there may well be some benefit to opening the flap further, but when I applied compressed air to the actuator the spring bottomed out with the flap lifting only a very small amount more than it would with the backplate in place, perhaps another 1mm. I can't see than improving flow much at all.

I wonder if the extra volume in the chamber is reducing turbulence. This would reduce the restriction to the wastegate's flow, which would improve boost control. Not sure, just a theory.

SureShot

My J-spec & A-spec turbos were exactly the same also.
I also suspect this is a mod you lucked into.

I'm a cheapskate so I just used a file on the back of the door.

RockLobster

iTrader: (7)

I did a similar test back last fall and found similar results. There was some extra range of motion with the spacer and the housing clearanced to allow the arm to move past it, but not alot.

I also think that the bypass chamber and the point where it remixes with exhaust that has gone through the turbine could be the real problem. You've got two high velocity exhaust gass streams colliding at right angles to each other. As anyone knows in fluid flow that only creates massive back pressure on both incoming streams of gasses, from the mixing turbulence ant the re-entrainment of the two gas streams. The space must give it some more space to work with. Its hard to say what is happening but im happy with the results.

I intend to track the car and I may just let the gate see full boost pressure when at the track because, with the free exhaust it will still have more power than stock but I wont be overworking the turbo and engine sustaininig high RPMS for 20-30 mins at a time.

Now the real test will be my first 30 min session to see if all my cooling upgrades help keep things running nice and cool.

SureShot

Backpressure? not here.. (Modified pre-cat)

When I open this mother, the stock turbo gets way happy with about 2 PSI of creep.
Even with the ported waste gate.

RockLobster

iTrader: (7)

I have full 3" racing beat exhaust. So with a 3" downpipe im in pretty good shape myself. It's not the restrictions creating losses in velocity pressure I am talking about. It is the flow dynamics (and associated turbulence) of having wastegate gasses slaming into post turbine gasses at a 90° angle with little room to do so in. That can cause similar loss of velocity pressure and thus (im guessing) create backpressure on both the gate and the turbine. Im guessing with the small stock chamber downstream of the wastegate this has more of a negative effect on the wastegate than the turbine as the turbine flow is the majority of the flow.

Pressure drop (losses) comes from many forms. Restrictions, turbulence, flow dynamics, friction, restrictions. All interelated...

NZConvertible

That's pretty much what I think. This is the well-known downside of internal wastegates and is the reason I'm currently running a custom divided downpipe on my S4 turbo. For the S5 turbo I have sitting on my workbench I've taken a different approach. This should give you a clue...

RockLobster

iTrader: (7)

So is that just a flat spacer. or a flange for something more?

NZConvertible

It's a custom laser-cut DP flange. The exhasut pipe will be welded onto it, making a so-called "big-mouth" DP. They're be a divider plate in there as well. I posted this pic earlier in the thread; this is the idea I'm aiming for.

http://www.mrtrally.com.au/performan...s/mrtexhus.jpg