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  #11  
Old 04-16-2012, 07:03 AM
norbs norbs is offline
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Originally Posted by TurboNova View Post
Moving the pressure sensor will net you the same problem.... you still have to tweak the PID values until you get them right for your combo.

It does work, but is a little bit of a time consuming deal if you have not done it before. The closed loop takes some runs with data for awhile until you get the PID control correct for your application.

Moving to the top of the gate is meant to use a absolute pressure sensor like a 0-100psiA that is used for oil/fuel pressure.
Why could i just not rescale the sensor, like a typical set up any sensor on an analog input? The pressure on the top of the gate is never going to be higher than boost pressure in my application.
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  #12  
Old 04-16-2012, 10:58 AM
TurboNova TurboNova is offline
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Originally Posted by norbs View Post
Why could i just not rescale the sensor, like a typical set up any sensor on an analog input? The pressure on the top of the gate is never going to be higher than boost pressure in my application.
You could rescale it but remember that it reads vac first and you don't want to be looking at that. But you will end up with the same PID issue.
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  #13  
Old 04-16-2012, 08:40 PM
norbs norbs is offline
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How about if i go with the 50 psia sensor, or is it also no good? It has a response time of less than 1 ms per rate of change it says in the specs.
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  #14  
Old 04-17-2012, 01:26 AM
TurboNova TurboNova is offline
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that would be fine but you may be limited to 25psi of boost or so. Going on top of the wastegate is about a 2:1 ratio of pressure to boost.
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Old 04-17-2012, 09:22 PM
norbs norbs is offline
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What if I throw in a 4 port solenoid with this combo? I really would like to experiment with the 4 port setup...
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  #16  
Old 04-18-2012, 03:41 PM
TurboNova TurboNova is offline
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I don't think the 4 port will change anything with the max boost from the sensor.
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  #17  
Old 04-18-2012, 05:28 PM
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Originally Posted by TurboNova View Post
I don't think the 4 port will change anything with the max boost from the sensor.
I understand. I have given up on closed loop map mode it just does not react fast enough since the gate gate is at 100% duty cycle until the boost target is reached, this is just a bad design. No amount of PID tuning is helping the situation. We will be trying the analog * method next. The gate is too small for the car adding to the problem, However open loop we get no spikes.
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  #18  
Old 04-18-2012, 08:52 PM
Turbobitt Turbobitt is online now
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Originally Posted by norbs View Post
I understand. I have given up on closed loop map mode it just does not react fast enough since the gate gate is at 100% duty cycle until the boost target is reached, this is just a bad design. No amount of PID tuning is helping the situation. We will be trying the analog * method next. The gate is too small for the car adding to the problem, However open loop we get no spikes.
Norbs,

I would make it a point to experiment further with closed loop analog 8. There are to many variables involved when trying to reliably control boost in closed loop mode.

1 - Back pressure(both intercooler and turbine)
2 - Wastegate size(Both area pressure is working against and flow capabilities)
3 - Wastegate springs
4 - Wastegate diaphram area
5 - Pressure source
6 - Solenoid response
7 - sensor response

When I look at my data logs using closed loop analog 8, it is trying to control boost indirectly by controling pressure on top of the gate. In my logs, the pressure on the top of the gate will start to be regulated before it reaches full boost. I believe this is the solenoid response you are looking for.. Without honing in the PID, I only had about 1.5 psi spikes. My turbine was large compared to the compressor, therefor backpressure was low. My wastegate was also large but had a 20lb spring. With this set-up, I was able to achieve 35 lbs boost using only manifold pressure as supply pressure. Using CO2 would give instant pressure for faster response.

Allan G.
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  #19  
Old 04-18-2012, 09:01 PM
norbs norbs is offline
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Thanks Allan, for the explanation. I have put the PID settings all over the map and nothing is working to reduce the inital spike in map closed mode. We will definitely try the analog mode next.
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  #20  
Old 04-18-2012, 09:07 PM
Turbobitt Turbobitt is online now
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Originally Posted by norbs View Post
Thanks Allan, for the explanation. I have put the PID settings all over the map and nothing is working to reduce the inital spike in map closed mode. We will definitely try the analog mode next.
Norbs,

Check your e-mail. When I look at my logs, the target pressure pressure appears to be 22 psi and climbs as high as 28 psi but the resultant boost pressure doesn't vary anywhere near that amount.

This is the big benifit to closed loop analog 8.

Allan G.
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