I finally installed the TB! It was a pain in the butt, as countless modifications had to be made in order to make it work. The TB is from a '91 240sx (KA24DE engine) and although it has the same bolt-pattern as the one from the SR20, I don't think it's same one... or people have been lying all the time about how easy it is to fit it to a Gti.
My carbide bits couldn't take the manifolds material for some reason, so I had to do file down the intake by hand
. As I didn't had the time or the energy I could only get it to 55mm, but I'll continue with this process later to get it to 60mm so a nice air-flow can be achieved.
The GTi's TPS can NOT be used with this TB, because of it's shape. So I used the Nissan one. That was the intention anyway, as it is really cheap compared to the Suzuki one. The butterfly-shaft from this TB doesn't have a lever at the end, it goes IN the TPS... see that hole in the middle?
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I set the TPS to 0.3V at idle and it works great, although I had to file down the edges of the manifold in order to let it turn. There are no flat-spots in the rpm-range and the ECU is not throwing any codes.
For the throttle wheel I used the smaller one (the one used for cruise-control), as the bigger one hit the fuel rail-lines and the Gti-one doesn't fit. I had to modify the throttle cable-bracket, other wise the cable would have been too short.
The coolant lines were connected with no mayor issues.
As this TB doesn't have an idle-screw, I had to bypass the butterfly so I could accurately adjust idle-speed. I didn't used the throttle lever stop-screw to adjust, as it was modified to simulate the idle-switch (the Nissan TPS is a 3-wire type). So I bored the TB after the butterfly...
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and plugged a hose from there to a T-fitting in the stock air-lines.
Tomorrow I'll have pics of how it all looks like... count the catch can in and that's a lot of hoses
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Performance wise: There was definitely an improvement in the top-end with no real loss in the low/mid-range, however the car is kind of sensitive in traffic. Maybe that can be solved by using a bigger throttle-wheel or even an eccentric one. I'll work on that first, before enlarging the intake completely to 60mm.
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I personally think those flat spots are more related to air-flow vs throttle-body size, which causes poor flow at lower rpm's if the TB is too big. There's no way to know this though, unless the ECM and sensors are live-monitored. Maybe with Rhinoman's software?
Hope I can find some throttle-bodies at the junk-yard.
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. Pics as promised...