So I'm in the planning stages of a new build, and am planning on using a HE351VGT. I already own a couple and am really drawn to the technology. They use a 60mm cold side and I think it's going to be a great fit for my power goals on a boosted 3.0. For those not familiar with this turbo it has a 60mm compressor and the hotside uses a sliding ring that makes it adjustable from 4 to 25cm. So it has the potential to spool instantly yet flow well up top if a guy can take advantage of its adjustable hotside.
I picked up these turbos back when they were new and have read everything I can about controlling them. There are some electronic controllers on the market but they are for diesels and are very expensive. The first mechanical one I saw a guy used a 8psi WG can that changed the hotside from like 8 to 14 when it hit 8psi. The new one I am seeing guys doing are limiting how small it can get, say 10cm and then are using drive pressure to open it up with a spring to control/restrict how fast it opens. Neither are bad setups, but I'm wanting to get a little fancier.
Aries_Turbo really got my gears turning when he suggested somehow, maybe electronically using a setup that maintained a 1:1 drive pressure. We have all seen how getting that "perfect" 1:1 ratio effects HP. So I quickly got to thinking... and think I may have found a mechanical solution. Weld a arm onto the gear that currently moves the sliding ring. Then hook a dual diaphragm WG can to it. Like the ones the 84 turbo used. Feed one side with boost pressure and the other with the drive pressure. Since the drive pressure is typically higher, it should overcome the boost pressure and open the hotside up until it equalized. Then theoretically it should maintain a 1:1 ratio as the RPM and drive pressure goes up. The problem is without boost pressure it's just going to go wide open to 25cm and never build any boost. So I think a pressure switch and solenoid would be needed so the can doesn't get any drive pressure until you reach the desired boost level. I am sure a external WG would still be needed to control boost. Not sure how the WG opening would effect this contraption, as it is bleeding off drive pressure too. But I think the dual diaphragm setup would still open up the sliding ring. With the turbo limited to say 7cm and 20psi of boost its still going to have a drive pressure above 1:1.
Am I making sense? I can try to draw out a diagram if that helps. Just wanted some second opinions if I am on the right track here. I think if this works I could get instantaneous boost and not be choking the motor at 8000 rpms.