My Skyline From The Uk
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I am impressed with all this level of adjustment. I didn't expect all this possibility -
Correct. In the case of the 500kw dyno plot I showed you the car actually runs two boost control solenoids for boost control and a 5psi wastegate spring. It allows me to control how much boost pressure is applied to both sides of the wastegate valve at any point and fairly accurately control boost target as a result. I've tuned it so that it's able to target anywhere from 5psi to 25psi depending on what's needed. The target tables I've set up in that car are Gear vs RPM, so every gear has potential for a different boost (and torque) curve. First and second gear have quite low boost targets, third gear actually has different target boost all the way through the rpm range as it's a stock RB25 gearbox - the boost targets have been chosen to maintain a peak of 600nm (what the owner has set as the maximum torque he's happy with putting through the stock 3rd gear) but it carries that to the rev limiter. The boost curve to achieve that is something of a ramp up, then hold, then ramp up again and the power curve looks more like a flat line haha. -
so you can decrease or increase the boost depending on the diet as you wish? by acting on the wastegate?
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That's torque and power, it's all from a single run. The boost curve is "held back" from it's peak target in the 3500rpm to 5000rpm range from memory, so it ramps hard to something like 18psi then climbs more progressively to 23psi nearer 5000rpm. It makes the torque (and power) ramp more "natural" and less hard on parts and traction, it doesn't feel artificially held back.
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Here's the torque curves from the car I ramped boost up later in the rpm to allow a slightly wider useful power curve - the power curve is a bit weird shaped also thanks to the TVIS (or whatever they call it with the 4EFTE in this Starlet) which changes the volume of the intake manifold throughout the rpm range, but you can see that the green power curve actually holds later on with the extra boost... but looks almost more like the kind of thing you'd expect from a cam or exhaust change
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