16-05-2012, 12:49 PM
Don't some of the VAG people who have done this use an actuator off the throttle arm on the pump too, since that essentially gets you your throttle input?
Then it's "just" a matter of mixing the boost actuation signal via the 'shaft' with the throttle signal via another pusher...
Blend together the signals with cammed pushers to get some curved response vs input and you might get a reasonable VNT pusher.
Obviously that is heavily simplified but iirc the VAG people were messing with that on mk3 diesel Golfs back in the mid 00's, and had a fairly refined system.
Surely it's just taking that and adjusting the variables with the appropriate non-linear action amounts (via cams or whatever else they used)
I'm surprised though Ruan, is the feedback loop really that bad? I'd imagined with just boost actuation you would still got ok performance for the total power output vs running similar power on a wastegated turbo. Or is the 'closed' restriction that significant at cruising/steady state conditions it is actually higher than a closed smaller wastegated turbo anyway?
Making a little ECU to control two boost actuators sounds like a cool idea. One look up table, two inputs, one output
Now go do that with I guess duty cycle operating vacuum control solenoids? Get the calibration of those into the mapping by simply driving and adjusting till it reads the right value (live mapping)
Crude but as effective as it'd need to be for Td use!
Hmmmm
Dave
Then it's "just" a matter of mixing the boost actuation signal via the 'shaft' with the throttle signal via another pusher...
Blend together the signals with cammed pushers to get some curved response vs input and you might get a reasonable VNT pusher.
Obviously that is heavily simplified but iirc the VAG people were messing with that on mk3 diesel Golfs back in the mid 00's, and had a fairly refined system.
Surely it's just taking that and adjusting the variables with the appropriate non-linear action amounts (via cams or whatever else they used)
I'm surprised though Ruan, is the feedback loop really that bad? I'd imagined with just boost actuation you would still got ok performance for the total power output vs running similar power on a wastegated turbo. Or is the 'closed' restriction that significant at cruising/steady state conditions it is actually higher than a closed smaller wastegated turbo anyway?
Making a little ECU to control two boost actuators sounds like a cool idea. One look up table, two inputs, one output
Now go do that with I guess duty cycle operating vacuum control solenoids? Get the calibration of those into the mapping by simply driving and adjusting till it reads the right value (live mapping)
Crude but as effective as it'd need to be for Td use!
Hmmmm
Dave