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slug_burner

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  1. Not sure but the discos when going from 200 to 300 dti had a ten spline to 24 spline change I believe. so the 200 dti 90 gear might also be 10 spline diffs and wheel drive flanges.
  2. Turbocharger, Good to see this thread active again. All spirited driving results in a thirst, both for the driver and engine. It appears you have cracked it. Well done. We now want comparative 1/4 mile times
  3. turbocharger, I think your answer is in the data you have on post 110 quoted here. When you wound the thing up you pushed the response of the turbo down into lower rpm for higher boost, which is what you are after. So you appear to be heading in the right direction by winding in the adjuster. However if you keep pushing that way you will eventually choke the engine's exhaust by restricting the outlet too much. You would achieve the same by just blocking off the exhaust. So the answer is in reducing the orifices that the gas flows through to increase gas speed. You can only do this until you start to get non laminar flow then the turbulence will stuff things up (Corky Bell's book on turbo tuning talks about air speeds of 0.4 mach resulting in turbulent flow when sizing intercooler hoses I maybe on the wrong tram here but it is a thought) . That maybe what is happening when you get to the flattening out of your curves at approx 2500 RPM. I don't believe you are going to get the turbine to stall or surge, I think you're over analysing that portion. The flow problems are likely to be occurring at the control surface before you get to the turbine. You will need to open up the vanes as rpm rises to stop chocking the engine by building up excessive back pressure. You need to experiment by changing one variable at a time not multiple variables. Couple of things for you to consider. If the engine this turbo came off makes approx the horsepower your after then it is sized correctly and there is no need to change turbines or compressors. (Unless it is part of a twin turbo set up) Leave the control mechanism out of early experiments unless you think that the system will damage itself without the control mech present. By removing the control mech you should be able to establish a map of boost vs rpm for various (fixed) settings of the lever that control the vanes. The the lever that controls the vanes has some stops that you can screw in (not likely to be here if engine turbo came from is similar size to yours) The diaphragm capsule made by "Lara" needs more space for the original spring (or the spring needs to be cut down), one of your curves shows this. The slope of the boost vs displacement of the diaphragm is the spring rate equivalent (all the people wanting you to consider the diaphragm area are just looking for you to apply a constant so you end up with a calibrated graph in a unit of force instead of air pressure). Someone already suggested that you needed some extensions for your diaphragm capsule I believe. If your spring rate is constant (assumption to start process) then judging from your air pressure vs displacemnent curve you need a 23.5mm extension on the diaphragm housing/capsule to allow the spring to be streched a bit more and apply zero displacement at zero boost/air pressure. If you examine your ideal response (I think it was orange line) the slope is similar to the one you already have in your original spring you just need to change the c, in the y=mx +c equation also results the changing the preload. If the spring rate is variable then it is likely to be different, but you should be able to iterate to a solution. (cut spring down or increase space for spring to iterate) As the rpm raise you will need to open the vanes to stop the engine choking (the big turbo, little turbo analogy might be breaking down). With a constant geometry turbo the max gas flow before building up too much back pressure is determined by the turbine size, in your variable geometry turbo the max flow and back pressure is determined by the control vanes. Levers can be used to change the displacement range. Select a pivot point and the length either side of the pivot of your lever will allow you to get a ratio of displacement. The flattening out of the curve around where you have circled is an area that you want to avoid once you get your control system working. I suspect that this might be when you are choking off the engine maybe? or when gas speed is getting so fast that laminar flow no longer holds more likely therefore need to open vanes further. Don't forget that the fuel pump on the 300 tdi also has some control system working (you already ran into this when you did not connect the boost compensator) This will work, tidy up your set up and build things as you intend them to be when you finish ( that bit of all thread looks carp and the offset will be stuffing up your measurements providing you with artifacts of your set up) Don't be so impatient to get out on the road and experiment until you know what is going on in theory at least. For all that are applying control theory, don't forget that the engine is part of the system (choking exhaust stops engine from producing more bhp/rpm). That is why it would be beneficial to produce the map of vane position and rpm vs boost without the negative feedback system in place i.e., open loop response. Once the engine and turbo is characterised then you can overlay the feedback system to get the response you want. The dynamic (step) response can be sorted once you have control of the system. If pneumatic control alone will not do it, then consider pulse width modulating a constant pressure or vacuum source. Have a look on the megasquirt web pages and you will find boots monitors that produce linear voltage response to pressure. A PWM circuit should not be that difficult. But if your going to go that far then get some more sophisticated control going by using something like the megasquirt controller or other controller circuit that you can program. Mate you worked for cosworth, you should be eating this stuff up. I hope cosworth don't have experimental set ups with welded all thread. Good luck, a good balance of theory of experimentation should get you a long way faster than experiment alone.
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