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- #21
another photos
Divided Intake and Swirl Flap Installation on a 1HD-FT
- Thread starter VADUS
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- #22
Now for the electrics. We installed a ready‑made solution for RPM control – the BK08 onboard computer. For this, we had to remove the alternator and bring out its W terminal. While at it, we fitted new brushes and belts. For controlling the flaps, we plan to use a large vacuum valve – it's normally closed. Accordingly, we'll need to use a normally closed relay to control this valve in our setup. This automation hasn't been implemented yet – we still need to buy the appropriate relay and hoses.
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- #23
And now the most interesting part: road tests……
With flap automation not yet configured, I went out last evening with the flaps open on an empty highway to evaluate the pure effect of the split manifold. To my surprise, the effect was VERY significant and noticeable: the car responds much more sharply to the pedal at any speed, acceleration is more dynamic, the engine sound became quieter, and the timbre lowered. So all my expectations were met, and the theory works… The twin‑scroll now has a logical complement; the cylinder groups have become almost completely decoupled, and the engine breathes much more cheerfully.
There's clearly more torque.
This morning I drove around town with the flaps closed. The effect is also present – the very bottom end up to 1400 rpm is definitely and noticeably better, at 1600‑1800 it's also better than without flaps. However, from 1800 to 2000 there's a trade‑off: if you drive with light throttle, the flaps are better than without, but if you go full throttle, they are worse. So I'll set the flap switching point somewhere in this range – 1800‑2000 rpm. It's no coincidence that Serega's Mercedes manual mentioned 1850 rpm – it seems very plausible. What's most pleasing is that accelerating to 2000 with the flaps engaged requires much less pedal input compared to the open position, yet the car accelerates more quickly. So fuel economy should be noticeable. As I suspected earlier, for automatic transmission owners the flaps may be rather useless, but the split manifold itself will work very well, especially with a twin‑scroll turbo.
Now a small curiosity in the Toyota technical manual. The employees (apparently marketers) who were responsible for the final document got the photos of the cylinder head orientation mixed up. What they label as "front" is actually the rear. Therefore, the curved swirl port remains open, while the straight port is closed. Below is the incorrect picture – it's reversed.
With flap automation not yet configured, I went out last evening with the flaps open on an empty highway to evaluate the pure effect of the split manifold. To my surprise, the effect was VERY significant and noticeable: the car responds much more sharply to the pedal at any speed, acceleration is more dynamic, the engine sound became quieter, and the timbre lowered. So all my expectations were met, and the theory works… The twin‑scroll now has a logical complement; the cylinder groups have become almost completely decoupled, and the engine breathes much more cheerfully.
There's clearly more torque.This morning I drove around town with the flaps closed. The effect is also present – the very bottom end up to 1400 rpm is definitely and noticeably better, at 1600‑1800 it's also better than without flaps. However, from 1800 to 2000 there's a trade‑off: if you drive with light throttle, the flaps are better than without, but if you go full throttle, they are worse. So I'll set the flap switching point somewhere in this range – 1800‑2000 rpm. It's no coincidence that Serega's Mercedes manual mentioned 1850 rpm – it seems very plausible. What's most pleasing is that accelerating to 2000 with the flaps engaged requires much less pedal input compared to the open position, yet the car accelerates more quickly. So fuel economy should be noticeable. As I suspected earlier, for automatic transmission owners the flaps may be rather useless, but the split manifold itself will work very well, especially with a twin‑scroll turbo.
Now a small curiosity in the Toyota technical manual. The employees (apparently marketers) who were responsible for the final document got the photos of the cylinder head orientation mixed up. What they label as "front" is actually the rear. Therefore, the curved swirl port remains open, while the straight port is closed. Below is the incorrect picture – it's reversed.