The Manifold

With a compact collector done, the next step was to run pipes from it to the head flange. I used the same 38mm bends because they fit in the head flange. Or so I thought. Woops, actually the parts store supplied 42mm bends with the ends crimped to 38mm. That's not what I call a 38mm bend. Actually these bends may be a bit too large for a 1600cc engine. In retrospect, I might have been better off getting smaller pipes. Making them smooth would have been more critical, but easier because the bends would be smaller radius as well! Oh well, live and learn.

So I ended up using (effectively) 42mm pipe (1.6"). Applying a few exhaust rules of thumb, even 32mm (1.25") might have been sufficient for each cylinder and much easier to route.

Where?

We bolted the collector to the turbo, removed the stock exhaust manifold and hung the turbo in its tight future place between radiator and engine. Because the 4A-GE sits upright even in FWD applications, there is NOT much room there. In fact, I had to relocate the oil filter to make it clear comfortably. Nice side effect: this also gives me something to tap into for the turbo oil feed.

The only way the turbo would fit was with the turbine side to the battery. Turbo was positioned as high as possible while still clearing the PS pump with the compressor inlet.

How?

I chose to do an approximately equal length design. Starting with the above collector, one way to achieve "equal" length and still clear the distributor would be to run the engine side runners to the furthest cylinders (1 & 4) and have the opposite runners bend back to cylinders 2 and 3 (over the other two runners).

In such a cramped space there was no avoiding some slightly slant cuts (to artificially shorten bend radius) and even one *very* tight bend. But with runner #4 in place, we no longer needed the turbo. Trust me, that's a heavy item to hold in place while test-fitting the manifold !! Also note that we made all the other runners off the manifold and _then_ welded them onto the manifold. This way, building the runner itself is easier. Also minimizes the amount of welding you do on the manifold itself, which helps prevent stress.

The #1 runner was fairly straightforward, and also the only one that I am really happy about since it would fit without sharp angles.

Runners 2 and 3 posed a problem. There was not enough room to go up and make a full U-turn down into the collector. A compromise was made. A few cuts in the bend sharpened its radius relatively smoothly but still not enough. The bend from the flange up over the #1/#4 runner just wouldn't meet it. It might have been possible to extend the sharpened bend further down and sharpen it slightly more to eliminate that nasty angle that now emerges but that would have made the inner radius of the "modified" bend really rough.

Done!

So this is it. Finally got a turbo manifold. It has some restrictions, but it's still a sort-of-equal length turbo header! Not the best but it'll do the job.

The flanges needed resurfacing (of course they warped during welding, but not too badly.) but otherwise it's done, although I might have it ceramic coated after it proves itself for a while, and iron out some of the hairy details. For now, seeing the stress and warpage introduced by welding, I assume that even though we're bracing the turbine to the engine, the manifold will crack after a while so it's not worth coating yet.

Pipe lengths (relative to one full 90 degree bend) are probably approx 0.8, 1.1, 1.2, 1.0. Not equal length but closer than I thought I'd get.