Turbo Downpipe

[Gregsyb 4]

I'm now at the stage in my conversion, where i'm looking at the downpipe

My set up is slightly different to the one in the DIY turbo thread and the wastegate will be coming almost straight on to where the downpipe starts, will this be a problem? I have attached a photo, to get an idea,

The two lambda sensors, will these be best as far down the downpipe as possible, just before a flexi?

Thanks all!

[Gregsyb 4]

[Daverse 175]

It depends on how tight you make the angle I suppose, from the photo it looks like it could make it, but on the hand you want as smooth a curve as possible. What manifold are you using?

[legvw 0]

The wastegate wants rotating 90* so it dumps away from the turbo. As it is it will disrupt the turbine gases exiting the turbo. The output flange of the wastegate wants to point down rather than at the turbo.

[Gregsyb 4]

Cheers lads!

I'm using an ATP clone manifold Daverse

If i make up a pipe from them manifold to the wastegate and then have another flange directly onto the downpipe? What diameter should this pipework be?

[Gregsyb 4]

Anyone?

What diameter of pipework do people run for there wastegates?

[legvw 0]

I think I used 38mm or 1 1/2" tube.

[Gregsyb 4]

Thanks Paul!

[russj249 2]

Give me a short while and I'll post you a pic of my turbo downpipe I made.. I think it might be kind of what you need (but my wastegate is slightly lower down and turbo higher)

[russj249 2]

This is a rather bad picture of my turbo setup (i know its not the same but gives you an idea)

Note im using a cheap Chinese turbo for mark-up in case it got dropped! Then after fabrication, all that was needed was to chop the end off and fit a 3" V-Band fitting for a Garrett GT35.

Anyway, you can see my wastegate which is like yours, very close to the exit.

So with mine, I had enough room to do this...

So... main bit of the downpipe is done

On the turbo it looks like this. NOW... look at my wastegate exit, its going straight into the turbo exit. This will be terrible for exhaust gasses, so as Paul said, you need to turn yours 90 degrees so its facing towards the floor! I obviously had to turn mine 180 degree's to get it to point to the floor.

You'll want to end up with something like this. Which solves the problem, and it the best way to get the gasses to merge and flow properly. (and yes it is 38mm pipe)

This is it finished. No need to worry about grinding welds off as the heat wrap hides all of that, but gives you extra strength.

Finished downpipe with the 3 inch V Band fitting added, wrapped up, and as you can see the gasses flow nice and smooth into each other, but also have a very tight turn just out of the turbo.

Now, you're other problem with O2 sensors is an easy one too. I made my own exhaust and in the front flexy section, I made 2 O2 sensor holes, 1 for the original sensor, 1 for my wideband gauge. If it would be easy to add more, or one further down the system after a CAT or something.

Anyway, I hope this gives you some idea of what to do with the wastegate pipework, you want the smoothest flow possible for the waste gasses. Keeping flow angles nice and tight like this is much better than putting it in at 90 degrees to the flow of the air in the downpipe, but you must not put the waste gasses into the downpipe the way that yours is set up in the picture.

Hope this helps!

[VR6Pete 1,455]

some awesome looking fabrication there mate really impressive!

[russj249 2]

Thanks Pete. It's a shame its all covered in heat wrap and you can't see the exhaust lol.

If you click on one of the pictures they should be hyperlinked to my Flickr account and there's loads of pics of the rest of the build (although not all as I haven't got round to sorting the pics out)

[VR6Pete 1,455]

hah, this is true mate perfect excuse to update your build thread though!!! you making it the rolling road day see what its pushing out?

[vr6guy 29]

how did you get on with your downpipe?

i need mine redone one day!

post some pics of your vr as well