Boost Controller 'duty cycle'. What does that mean?
03-17-2009, 10:51 PM
#1
Boost Controller 'duty cycle'. What does that mean? I know on a given fuel injector what were talking about regarding duty cycle but on these AEM Tru-Boost controllers you set the 'duty cycle' but in relation to what? I know the default sensor (internal) goes up to 30 psi. Is it that? So if I want 15 psi, would I set the duty cycle to 50%? Another thing you can stipulate is that the top pressure to what ever. In my case I want to cap it at 14 psi. So is the is the duty cycle a percentage of this 14psi? It just seems like it would be so much more simple for you to set it to 12psi and that's what it would limit it to. Anyway,... anyone have any knowledge on this?
03-18-2009, 12:51 AM
#2
Duty cycle usually means what percentage of the time an electronic or mechanical device (or valve) is turned on (or open). Just like your fuel injector example. But in the injector example, the system is getting feedback from the O2 sensor(s), plus a few other sensors, as to how much to alter the duty cycle of the injectors to achieve the target AFR.
In your case, the boost controller has a pressure sensor to read the actual boost (or maybe a feed from your MAP sensor), so you'll have to try it out (start low) and see how the system responds to the duty cycle you feed it, under different conditions, and adjust accordingly until you are happy that the unit is controlling your boost the way you want. Your boost controller uses pulsewidth modulation (PWM) to effectively cycle or flutter the unit's boost solenoid until it senses the right levels it thinks should go to your wastegate. Lower duty cycles might require a higher frequency of valve cycling.
For your top pressure, if you cap it at 14, the unit may need a duty cycle adjustment by you to get it in perfect control.
I'd just start conservative and datalog if possible, see if you are overboosting at all and make adjustments. Oh and make sure to RTFM, especially the small notes around Figure 7 & 8 in the install manual.
Jim
In your case, the boost controller has a pressure sensor to read the actual boost (or maybe a feed from your MAP sensor), so you'll have to try it out (start low) and see how the system responds to the duty cycle you feed it, under different conditions, and adjust accordingly until you are happy that the unit is controlling your boost the way you want. Your boost controller uses pulsewidth modulation (PWM) to effectively cycle or flutter the unit's boost solenoid until it senses the right levels it thinks should go to your wastegate. Lower duty cycles might require a higher frequency of valve cycling.
For your top pressure, if you cap it at 14, the unit may need a duty cycle adjustment by you to get it in perfect control.
I'd just start conservative and datalog if possible, see if you are overboosting at all and make adjustments. Oh and make sure to RTFM, especially the small notes around Figure 7 & 8 in the install manual.
Jim
03-18-2009, 05:26 AM
#3
Thanks for the reply. I'd read the manual over and over before I even installed it and several times since but what I was searching for was a finite. Something like "Press buttons A and B simultaneously for (at least) 2 seconds to put the device in "Prg"(Program Mode). Release both buttons. Now briefly press the left button (only) to go to boost setting "A". Press it briefly again to put the device in boost setting "B". Press it again to put the device "Off" (runs on the waste gate spring). Repeat to go back to A, B, Off. Using this method, put the device in boost mode "A". Now press the right button to increment the Boost controller to the PSI you want to attain. Repeat for button "B". You're done!"
I think I'm going to put up a revised instruction manual on my web server because this phamplet is just not concise. I went to a lot of import sites last night looking for my answers while waiting for you good people to help me. It's very common that people like myself didn't find.
a. How to turn it "On" to control the boost. (Press and hold the left button for 2 seconds, then cycle thru what you want with the same button. Boost mode A, Boost mode B, Off, repeat)
b. What 'Crack' pressure means (The manual says how to set it but not what it does, how it affects the solenoid, benefits, dangers, etc)
c. What duty cycle is a percent 'of'.(In other words duty cycle is 100% of What?)
others..
I think I'm going to put up a revised instruction manual on my web server because this phamplet is just not concise. I went to a lot of import sites last night looking for my answers while waiting for you good people to help me. It's very common that people like myself didn't find.
a. How to turn it "On" to control the boost. (Press and hold the left button for 2 seconds, then cycle thru what you want with the same button. Boost mode A, Boost mode B, Off, repeat)
b. What 'Crack' pressure means (The manual says how to set it but not what it does, how it affects the solenoid, benefits, dangers, etc)
c. What duty cycle is a percent 'of'.(In other words duty cycle is 100% of What?)
others..
Duty cycle usually means what percentage of the time an electronic or mechanical device (or valve) is turned on (or open). Just like your fuel injector example. But in the injector example, the system is getting feedback from the O2 sensor(s), plus a few other sensors, as to how much to alter the duty cycle of the injectors to achieve the target AFR.
In your case, the boost controller has a pressure sensor to read the actual boost (or maybe a feed from your MAP sensor), so you'll have to try it out (start low) and see how the system responds to the duty cycle you feed it, under different conditions, and adjust accordingly until you are happy that the unit is controlling your boost the way you want. Your boost controller uses pulsewidth modulation (PWM) to effectively cycle or flutter the unit's boost solenoid until it senses the right levels it thinks should go to your wastegate. Lower duty cycles might require a higher frequency of valve cycling.
For your top pressure, if you cap it at 14, the unit may need a duty cycle adjustment by you to get it in perfect control.
I'd just start conservative and datalog if possible, see if you are overboosting at all and make adjustments. Oh and make sure to RTFM, especially the small notes around Figure 7 & 8 in the install manual.
Jim
In your case, the boost controller has a pressure sensor to read the actual boost (or maybe a feed from your MAP sensor), so you'll have to try it out (start low) and see how the system responds to the duty cycle you feed it, under different conditions, and adjust accordingly until you are happy that the unit is controlling your boost the way you want. Your boost controller uses pulsewidth modulation (PWM) to effectively cycle or flutter the unit's boost solenoid until it senses the right levels it thinks should go to your wastegate. Lower duty cycles might require a higher frequency of valve cycling.
For your top pressure, if you cap it at 14, the unit may need a duty cycle adjustment by you to get it in perfect control.
I'd just start conservative and datalog if possible, see if you are overboosting at all and make adjustments. Oh and make sure to RTFM, especially the small notes around Figure 7 & 8 in the install manual.
Jim
03-18-2009, 08:34 AM
#4
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I know what you mean, I have the same boost controller, also when setting duty cycle you can sit there and keep raising duty cycle with no affect and then you adjust it 3% more and it's super sensitive.
