DaX

iTrader: (1)

Just doing a little free thinking...why wouldn't it work? I can't think right off how you could use boost [besides some kind of electronic control] to control the size of the opening of the aperture to control boost levels, but it would provide a straight through path for the dumped exhaust gasses, compared to all current wastegates that require the gasses to make a 90 degree turn to go through the gate. Designing an aperture that could handle the heat and pressure, yet still be thin and small may be a little challenging, but again...just a little free thinking.

BROOD

So similar to a variable vane turbo (variable geometry) or a sliding sleeve turbo (variable area)?

mos

From my limited experience with rebuilding vintage cameras, doesn't seem like a good match to the application. Doesn't take much soot to jam them. Also, I think by the time you beef everything up to where it will stand up to the pressure, it will be five times as large as a typical wg. Interesting idea though, I could be wrong.

DaX

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BROOD &raquo;</TD></TR><TR><TD CLASS="quote">So similar to a variable vane turbo (variable geometry) or a sliding sleeve turbo (variable area)?</TD></TR></TABLE>

Whoa...variable vane turbo? That's cool...I bet it's huge though.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mos &raquo;</TD></TR><TR><TD CLASS="quote">From my limited experience with rebuilding vintage cameras, doesn't seem like a good match to the application. Doesn't take much soot to jam them. Also, I think by the time you beef everything up to where it will stand up to the pressure, it will be five times as large as a typical wg. Interesting idea though, I could be wrong. </TD></TR></TABLE>

Oh well, it was worth the thought.

BROOD

VGT and VAT turbos are not new by any means......older versions had issues with sticking (early VGT Datonas). Newer technology has changed how they survive in exhaust environments. Look to most of the current turbo diesel engines...many use variable turbos.
I;ve worked with VGT turbos on our engines before.....really after all the work the usual ext WG set-up just can't be beat in terms of cost and practicality.
I understand the type of variable valve you originally asked about (like a camera shutter), I agree it may be difficult to control the robustness of that design. It would have to react quickly to control EBP and still control manifold boost pressures. Still interesting though.

mekkis

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaX &raquo;</TD></TR><TR><TD CLASS="quote"> it would provide a straight through path for the dumped exhaust gasses, compared to all current wastegates that require the gasses to make a 90 degree turn to go through the gate. </TD></TR></TABLE>

No, all common external wastegate setups require the exhaust gasses to make a turn in excess of 90 degrees. Think of the positioning of wastegate flanges on top of the way current wastegate design causes the gasses to flow... full 180 degrees is most common, with flow losses due to restrictions that turn into greater manifold pressure that kill off flow out of the chamber on exhaust stroke and encourage reversion on overlap with intake stroke.

If you want higher wastegate efficiency, do two things:

1) Use the largest possible wastegate you can find.

2) Feed your wastegate, not turbine, with a good merge bend collector.

DaX

iTrader: (1)

This is one reason I went with a sidewinder - the wastegate is fed with a nice low angle merge collector. I'm using a 40mm gate also.