club.liberty.asn.au

Thought I would post this picture so you can see what the stock dump pipe looks like. Its bloody heavy and fairly restrictive as you can imagine. I managed to get rid of it to another member here who has some plans for it and I am happy to be rid of it.

you should show us the opening of the dump pipe to see the restrictor plate

Holy moly

Judging by the pic it looks like the wastegate exit on the back of the turbo basically hits a wall, has to turn 90°, then has to join the main exhaust gas at right angles??

And what's this about a restrictor plate? It sounds like a nice cheap mod if the rest of the dump flows okay? It won't fix the wastegate restriction if the above is correct but it might help a bit.

subnub wrote:Judging by the pic it looks like the wastegate exit on the back of the turbo basically hits a wall, has to turn 90°, then has to join the main exhaust gas at right angles??

Welcome to Subaru ownership Marc, that's their standard design.

subnub wrote:Holy moly
Judging by the pic it looks like the wastegate exit on the back of the turbo basically hits a wall, has to turn 90°, then has to join the main exhaust gas at right angles??

thats one question i was scared to ask due to a lack of mechanical knowledge when that whole argument about splitters and wastegates and messing up gas flow because it had to some how combine with other gas flow was happening.......
serious question for those with the knowhow, could anything be worse than this?

pretty sure pic by jimboliscious

Wow!

I'm no engineer but my understanding is that it's not just that it joins the main flow at right angles, it's also that it does so at an extremely reduced gas velocity. Think about a car trying to merge onto a 100km/h highway at 10km/h. That design would basically kill all gas velocity out of the wastegate port, and cause huge turbulence in the main exhaust flow, and would most likely cause issues with boost control because it may not be able to bleed off excess exhaust gas consistently. While the wastegate is shut it may even work better than having a large common exhaust/wastegate area (thanks to high velocity exhaust gases creating a vacuum in the area behind the closed wastegate, that's my theory anyway) but it's certainly going to hurt it at WOT.

Maybe it's done to control boost spiking, reduce noise, or to keep the emissions cardigans happy I don't know, but in terms of getting the exhaust gases away from the engine, it's hard to imagine a much worse way of doing it short of bolting a flat piece of plate to the back of the turbo.

No wonder the aftermarket dumps give such an enormous improvement to power and driveability!

subnub wrote:No wonder the aftermarket dumps give such an enormous improvement to power and driveability!

But don't the aftermarket ones have to be more or less the same shape to fit?

AndrewCowley wrote:

subnub wrote:No wonder the aftermarket dumps give such an enormous improvement to power and driveability!

But don't the aftermarket ones have to be more or less the same shape to fit?

Nope. There is plenty of room in there for a nice smooth tapered collector.

This dump pipe design is exactly the same as what Subaru have been fitting to WRX/STi/RS since late 1980s. You'd think that by now they would have learned. It's bad enough in cars that have the wastegate flapper directing the gas flow across into the turbine outlet but I'd imagine it would be even worse with turbos like the Liberty where the flapper directs the gas flow directly into the flat plate.

To their credit, Subaru got it right briefly with the collector from the twin-scroll Liberty GT.

Cheers,
Ben

unfortunatly with the Libertys the Bellmouth once again has to be specailly made for the Aussie Spec Libs. Libs run into the same problem as the WRXs.

WRXs and the Libs share the same steering knuckle which is larger then the STi WRX ones. so if u use a cast head like the Invidia or a COBB Tuning down pipe the Dump will fit up no worries at all but soon as load is put on the engine whilst turning a corner the knuckle WILL hit the Dump pipe.

Here is a design that is best suited to the Libertys/WRX



The one on the left is the conventional Down Pipe from USA with CAST head
The one on the Right is the one used for Aus Spec cars .. Toemi Also use a similar design head on their Twin Scrol Down pipe.. I beleive the HKS, SARD and ZEROSPORTS also use this design..

Troy