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volkswagner

Freebird: SR20VE+T 510 Wagon

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On 12/22/2018 at 10:57 PM, ol' 320 said:

does Sam have a thread somewhere on his 521?

I do but it's accidentally in the >trucks>521 section, whoops

 

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Next up was mounting the turbo. The idea was to use a DET manifold and cut off the T28 flange and weld on a T3 flange at the appropriate angle. 
I had thought the stock manifolds were an open "log" design. As it turns out that is very wrong. They actually have separately cast runners that twist past each other and combine at the turbo housing. In fact cylinders 4+1 and 2+3 only combine in the manifold and there are two exiting orifices that then merge in the housing. This meant that as I cut back the angle, the separating walls caused  choke points. I was able to get satisfactory results by grinding out all of the walls just before the outlet which creates a 4>1 manifold that dumps into the turbo rather than the 4>2 that it originally was. Not Ideal but it will do for now and I'll want to do a tube header whenever I upgrade turbos in the future anyway.

The fitment process was a bit tedious, any small change in the flange  position was magnified once the turbo was bolted up.
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This meant the setup went in and out and regrinded/welded and back in at least a dozen times. Eventually I got it where I wanted.

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To fully weld the flange I had to do some research since, I've never welded cast before. Turns out pre-heat and a controlled cool are the key to prevent cracking.
I rolled the BBQ into the shed and brought it up to full grille temp, 600F or so. Once the manifold was heat soaked it seemed to weld quite nice.

Then I let it sit under the cover while I stepped down the temp over a few hours. No cracks! but we'll see how it holds up to engine cycles.

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After grinding and welding it seemed best to touch up the flange surface. The inlets were off by more than I expected. I'm sure they would still have sealed u when bolted tight but it's nice to keep that stress out of it.

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Least step was to grind off some flashing just for good looks and coated with black VHT.

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New studs for the turbo, M10 ratehr than the M8's used on T28. I hear chatter on the webs that the T28's lose their seal alot easier due to the smaller M8's stretching whereas the M10 T3 flanges seem much less leak prone, not sure as to the truth in that.
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I was tempted to tack the nuts in place once torqued but decided to try a nut locking tabs first. 
I made some up from a spare stainless gasket. 

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With the manifold / turbo installed I focused on the plumbing. In retrospect, I should have installed the lines on the turbo first. Some of the fittings were VERY hard to get on in situ.
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All in place and happy with the fitment so far.

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Right about now is when I came across a post on RB turbos that I hadn't up to this point (somehow, thought I had read it all) This particular post identified casting marks and which car they came from. To my dismay, in the same day as buttoning up the turbo I find out, its from an RB20 NOT an RB25 as advertised... 😫
This brings it's efficient power range from about 300 down to 250. They can still be pushed up towards 280 with a little added heat. 
Oh well, lets me develop a solid tune at lower risk power levels and gives more motivation to upgrade later.

 

Moved on to the cold side plumbing. I was able to find a jog pipe that was the perfect shape (couple inches of length trimmed off) to line up with the air outlet with intercooler inlet. 

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It also left enough room underneath to slip the air filter up behind the headlights using a 45 elbow.

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Tucked the boost control solenoid next to the brake bias valve.

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Still have to weld in the BOV and tackle the exhaust.

 

I spent a bit of time trying to figure out what to do with the intake manifold. The VE manifold could possibly be cut/welded again until it fit but in the end it would just be more work to get a terrible looking poorly performing solution.
I have an S13 and S14 manifold around. The S14 doesn't line up at all. The S13 intake actually is pretty close but the runner outlets are spaced differntly and te throttle body angle would have to be modified. This brings it right back to the same issues as the VE manifold.

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Instead, I'm going to try and fab one. I'll make a custom manifold that welds on to the stock runners/injector bosses.

I like to think Greddy does it's research to make their parts perform well so I looked to them for geometry.

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Then using sheet metal and stock mandrel bent pipes I approximated it as closely as I could. This gives me about 3 liters of volume which is well above the "equal to engine cpacity" rule of thumb for manifold volume.

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This is  45 degree pipe instead of the 30 degree pipe I will use but it shows the idea.

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Then as Jeff mentioned, I bought a Pusar GTIR and have been spending most of my free time on that the last few weeks. 
That's nearly driveable now though so, back to this soon!


 

 

Edited by volkswagner
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14 minutes ago, volkswagner said:

Next up was mounting the turbo. The idea was to use a DET manifold and cut off the T28 flange and weld on a T3 flange at the appropriate angle. 
I had thought the stock manifolds were an open "log" design. As it turns out that is very wrong. They actually have separately cast runners that twist past each other and combine at the turbo housing. In fact cylinders 4+1 and 2+3 only combine in the manifold and there are two exiting orifices that then merge in the housing. 😫

 

 

According to Corky Bell this is the correct way for a 4 cylinder to feed into a turbo as there is only one pulse per 180 degrees. Every effort should be made to keep each pulse strong and undiluted from spilling back onto other empty pipes. 👍

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As well as pulse overlap, I believe it's best to keep them separate as long as possible to maintain exhaust velocity which is quite critical for driving the exhaust wheel.

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