S5 Turbo 2 Ht18-2S and V Band dump

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S5 Turbo 2 Ht18-2S and V Band dump

#1 Post by arran » Mon Feb 04, 2019 10:01 pm

Hi all,

I've got the S5 turbo off my 13B and am wondering about V Band. The turbo does not have the backing plate and my dump pipe has a flange that bolts up where the backing plate used to be, and has a separate pipe for the wastegate. See the pictures. The hot side is from a spare standard turbo I have, I have not messed around pulling apart the turbo I've had on the engine yet.

Problem is that I can't get a gasket and have had some dramas with an exhaust leak. I'm wondering if I can get a V Band on there to connect the dump, allowing much easier removal and a good seal. Has anyone come across a company that makes a weldable backing plate? The Mazda backing plate is cast so I don't think I should be welding this. If I can get a backing plate, I should be able to weld on a V Band for the dump and another for the wastegate.

The pictures show a copper gasket that I made up. This is the second one. While they don't melt, they get so hot that the exhaust gas pushes it out the side of the interface and creates a hole.

Also, does anyone know if there is a T4 footed turbo hotside with V Band that could be substituted? It might be an option to cut off the S5 foot from the manifold, replace with a T4 foot and keep the turbo in the same location. The manifold is a custom job that tweaks the path of the rear rotor runner to give me good clearance to the steering rack. It is based on an SDR S5 manifold so that I didn't need to remake stuff.

I am not that keen on replacing the turbo, it is a TO4E compressor and makes plenty of power. I'd need a new manifold, new intercooler pipe, new intake duct, and probably a new cold air induction setup.


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Re: S5 Turbo 2 Ht18-2S and V Band dump

#2 Post by KYPREO » Tue Feb 05, 2019 7:56 am

V bands leak too. I typed out half a post about how you could try making a copper gasket and then re-read the bit I missed saying you already tried that :lol:

I want to go down the V band route, I'm personally not aware of an off the shelf option. But you could get a custom backplate machined up in stainless steel with provision for the V-band flange to be welded in. AusRotary user xhristofer made up a series of plates to build up a modular, shaped backplate (to help relieve back pressure from the wastegate outlet). See here: viewtopic.php?p=2704090#p2704090

plates (1).jpg

I imagine you could do something similar, although the machining costs would be expensive for a one-off.

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Re: S5 Turbo 2 Ht18-2S and V Band dump

#3 Post by bumpstart » Tue Feb 05, 2019 4:07 pm

weld your current backing plate onto another 16mm steel backing plate and have it and the back of the turbine housing faced/ fit longer studs and bolts in the 5 bolt pattern
mazda used no gasket here and had no issue with leaks between turbo and backing plate

when i was highflow i also ran a very chunky custom backplate and dump .
with much thicker wall pipe than most and so it moved the 1st gasket down under the car and kept a 3.25 ID down to the first flange

i would suggest it could be improved by machining a groove in the backing plate with slight overlap on itself and laying some copper motor winding wire in the groove

my old dump and flange is 16mm on the backing plate around the gate area and 29 mm where the dump is

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Re: S5 Turbo 2 Ht18-2S and V Band dump

#4 Post by Ale » Wed Feb 06, 2019 2:05 pm

I've welded mild steel to cast iron exhaust manifolds and rear turbo housings.
For best chance off success, Pre heat the casting, tig weld using s/steel filler wire or arc weld with cast rods.
Then throw the whole assembly in a empty steel bucket with a lid (or preheated oven) so it cools down slowly.

Success will vary in quality of the cast iron and your welding abilites


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