SiWhite Posted August 29, 2007 Share Posted August 29, 2007 Evening all..... I'm almost finished installing my variable nozzle turbo onto my 200Tdi. For those who don't know much about them, they vary the angle that exhaust gasses strike the impeller, meaning at low exhaust flow (low revs) is forced through small apertures to spin the impeller quickly. Then, at higher gas flow (revs) the vanes open, reducing back pressure and spinning the impeller faster. One area of concern in my installation is actuating the variable nozzle. It's currently set to alter with boost pressure, which was easy with the old turbo's diaphram. This seemed nice at first - at low boost the vanes will be close together, spinning the impeller quickly and generating good low end torque. The problem this causes is at fast cruising speeds with lowish boost, the engine will be very 'boosty' and fast to react to throttle input. I could overcome this with a 'cruise lever', forcing the vanes to stay partially open at speed, but it's a pain. I'd like to have the vanes actuated dependant on engine speed. This would give all the low end torque benifets I wanted when fitting the turbo, bit without the spiky nature of the boost dependant system. The question is - how do I convert the changing engine speed to about an inch of movement? I had some initial thoughts about using a scrap tacho I have in conjunction with a radio controlled car type servo, but would struggle with interfacing them. I'd also thought about having a speedo cable driving a steam-engine type govenor (two spinning balls affair) driving a cable, but I'd not really want the moving parts nature of this. I'd also thought about using engine oil pressure driving a small ram, but this would alter with engine temperature on start-up. My question is - what would you do? Am I over worried about the boost-dependant system (bearing in mind it's not running yet) or should I work on an engine speed system? And if the boost's no good, how should I do the engine spped system for best reliability? Quote Link to comment Share on other sites More sharing options...
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