06-03-2012, 09:51 PM
n0v0s Wrote:Very good! With regards to surging, it's just a case of progressively increasing 'throttle' with revs then? I appear to do that already to some extent to stop the motor bogging down so i guess i have some 'mechanical sympathy' ey?!
Just to clarify, do you have any particular links to hand showing the actuator modification? I still need to properly familiarise myself with vnt operation, but i understand the vanes are normally vacuum controlled. Is the switching to boost control detrimental to fine vane contol then? Hence the surging at low revs? In effect, causing the accelerator position to fine tune the vane position?
How durable are the gt2056v's? What sort of boost pressure/ estimated power can they sustain and support reliably?
Thanks
Yes, your lack of throttle to stop bogging is good anyway, but it's even more accentuated with a VNT, it's mostly on the motorway you'll find it, with my turbo it's about 2400rpm when you start building the throttle, it starts spinning up and you start to hear the typical noise... You do have to lift off or change down...
Originally obviously the turbos are controlled with an ECU... Because they have boost maps, they can restrict the boost down low, so up until 3000rpm, it'll reduce the boost levels by controlling the vanes... Obviously on boost control, you can't do it, they will do whatever you set them to do, it's simply boost > vane control, the way you want to control it is basically a computer to run a lookup table with boost vs throttle position and then a straight boost limiter table with boost vs rpm, so the computer simply pulls a value that it should be at a given throttle position and then simply compares it to the boost limiter table, which it'll decide if the requested boost from TPS is higher than the boost limiter value, if so it just holds it there until the RPMs change...
With pure Boost Control the biggest disadvantage is the increase in pumping losses because on the motorway, it's not quite past the vane threshold, but just between, about 10-14psi continually... Restricting the engine, normally ECUs would open the vanes back whilst cruising, reduce the boost so it reduces the pumping losses... If you can restrict it down low with the throttle, perfect - but it's a lash up most of the time with bits of cable, springs etc... One day when I have time I'll do the ECU controller I always intended to do, I've got all the parts, got most of the software written, just need to sit down and sort it and put it on the car.
GT2056Vs are too small on the hotside IMO for our engines, I struggle with EGTs and EMPs with a 2052V, gets seriously hot if I push it much harder than it is now, you'd be better off with a 2256V or if you can find one, a 2252V, would help surge massively, increase lag sure, but it wouldn't be significantly worse than a T2 IMO, at least, on gearchange, it's literally instant...
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