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Old 07-11-2012, 08:40 AM   #14 (permalink)
TDI Vanagon
Join Date: Jul 2012
Location: Kentucky
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Originally Posted by amdown View Post
You do not have t o accelerate rpm up to 4000 to "exercise" turbo actuator. it makes full movement already up to 1900 rpm, when ecu is "asking" full boost from turbo. when you rev up engine higher, the actuator acualy decreases turbo pressure. The exhaust gas flow and heat is what actualy cleans vanes of vnt turbo. when you realy want to clear a turbo vanes drive for a mile or two with rpm at about 3000-3500, then the heat an lean burning from the engine will burn up all the ash in turbo and exhaust system.

That's a new one on me!

So, the little old lady driving style (babying it) isn't what causes the VNT15 to stopping working?...........Hmmmm

Well, I've disassembled "numerous" VNT15s for cleaning. I've yet to find one with the VANES all clogged up! The ACTUATOR operates the internal levers that in turn move the VANES in the path of the Exhaust blast coming out of the manifold. Soot gets blown back into the "internal" working parts of the VNT15 away from the exhaust gas blast. That soot, along with moisture, during slow warmup will eventually restrict the movement of those parts. I've seen VNT15s that the ACTUATOR would not move but the VANES were perfectly clean! After disassembly, cleaning and re-assemble, the ACTUATOR had full movement with no restriction at all!

There's a "ton" of info about the VNT turbos on the net and specifically at the TDIclub.

The ACTUATOR operates per the N75 valve which is re-acting to ECU demand. As demand for more power (during acceleration) the angle of the VANES is changed by demand of the ECU to direct the exhaust gas on to/across the blades of the Turbine for additional boost. I run a ScanGauge and have never seen maximum boost at 1900 RPM, quite the contrary!

I repectfully disagree with your assesment of the operation of a VNT15! Reading and hands-on are quite different.
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