nterry Posted April 14, 2014 Report Share Posted April 14, 2014 I have set up closed loop boost controll on a mr2 3sgte. I have a question about what the vipec needs to detect the gear its in for lowering boost in 1st and 2nd gear. nathan Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted April 14, 2014 Report Share Posted April 14, 2014 Hi, you need to have a VSS digital input. EG: DI 1 setup as the source of the vehicle speed, EG: LHR WHEEL or just ground speed. Under Digital Inputs you will see a Gear Detection Tab. It is easier to use the ECU calculated option for the gear detection. You can select User Defined if you know the ratios etc. Once you have configured the gear ratio setup, you then use the Boost Gear Target Trim Table and the Boost Gear Wastegate Trim Table to add or subtract duty cycle from the boost table to reduce the boost in lower gears. Regards Dave. Quote Link to comment Share on other sites More sharing options...
Thom Posted April 14, 2014 Report Share Posted April 14, 2014 Trimming boost with either the Boost Gear Target Trim Table or the Boost Gear Wastegate Trim Table kind of throws out of the window the logic behind the PID settings from the closed loop boost control, as pondering the values in both tables before peak boost is reached is pretty much like modifying P & D. As far as I have noticed it is not possible to trim P & D directly in function of gear, but this would make things a lot easier when controlling boost in closed loop... Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted April 14, 2014 Report Share Posted April 14, 2014 Hi Thom, using Closed Loop Boost control via PID tuning is to achieve a desired boost pressure repeatedly and reliably regardless to an extent, of the operating conditions. The end result is a predefined value you setup in the software, so after setting up your desired boost target eg: 250 Kpa and set up your PID control to achieve this pressure, quickly, precisely, smoothly as possible, the end result will always be the same 250 Kpa. So for example in first and second gear you have massive wheel spin you can reduce the value in the Gear Target Trim table to lower the boost in these gears to reduce wheel spin. Used in conjunction with the Gear Based duty cycle trim table to help smooth or stabilise the process. PID control is still used in the base process, however there is no PID control for each gear as such, therefore offset tables must be used to achieve a desired result for each gear. Regards Dave. Quote Link to comment Share on other sites More sharing options...
Thom Posted April 14, 2014 Report Share Posted April 14, 2014 Hi Dave, Here is what's mentioned in the Help file : "With a base duty cycle of 50%, a proportional gain of 5.0 and a current error of 10kPa, the base duty will be trimmed to 55% = (50 + (5.0 * -10 * 0.1%)" Since P directly ponderates the value of the base duty cycle, trimming the DC table (in function of gear or whatever) has the same result as modifying P would, but the Maths show, looking by the formula, that ponderating P (& also D) in function of gears would allow smoothening the boost curve with more finesse than ponderating the base duty cycle in function of gears, especially during the most relevant Stage 2 of the closed loop algorithm, when both P & D are active. Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted April 14, 2014 Report Share Posted April 14, 2014 Hi Thom, what you are saying is correct. I am however trying to keep the reply to the O/P simplified for now. Most people setup their boost target tables with TPS,MAP or MGP as their Y axis. I assume (which I shouldn't) that the O/P has done the same. In closed loop the Y axis should be setup as Target Boost. He states that he has already set up his Closed Loop Boost Control and simply wants to know what is required to setup gear input for the ability to reduce boost in 1st and 2nd gears. Changing his Boost Target tables etc to GEAR Y AXIS etc, may or may not be an issue for him. However I believe if it is already setup that the trim tables are the easiest option for him. Sorry, I should have explained my reply a bit better as above, to save any confusion. Regards Dave. Quote Link to comment Share on other sites More sharing options...
Thom Posted April 14, 2014 Report Share Posted April 14, 2014 Agreed Dave, and sorry - I had overlooked the initial issue, but it made me think of an issue I have, and which I think coud be relevant to this topic, if you don't mind me posting here : I do not get any wheel spin in 3rd or 4th gear, but since the turbo loads quite a bit earlier in 4th gear, I was thinking that it would be great to be able to use separate values of PID for 3rd gear to improve spool in 3rd gear. Since this is not possible, and if I follow the logic behind the existing two gear trim tables, then I can increase the trim in 3rd gear by pondering the duty cycle table to get a sharper boost build up during Stage 1 and 2. However, by doing this, will D be still high enough to avoid any boost spike in 3rd gear? Inversely, isn't P still going to be "too high" for 3rd gear? The point I'm trying to make here is that we use the same P & D values for boost curves between gears that will necessarily not have the same sharpness from one gear to another. Sorry for splitting hair, but Close loop boost control used to give me a hard time until I eventually figured out I needed a soft WG spring, and I have become a bit maniac on this topic ;-p Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted April 14, 2014 Report Share Posted April 14, 2014 Hi Thom, Yes I remember giving you some help back in the early days of your boost control issues and discussing WG spring pressures with you. Using the trim tables will take some finesse to achieve the desired outcome you are after. However with good data logging parameters should be easily overcome. You could also use a combination of advanced open loop control to do some testing in conjunction with full closed loop control. Leave closed loop control selected and set proportional , integral and derivative set to 0 to go into advanced open loop mode. However at the end of the day I personally would leave it set up in full closed loop control and adjust the gear trim tables and then adjust the PID values if required. Using the Gear Based Duty Cycle Table to make the transitions smoother. Nothing like a challenge to test the brain out anyway. Give it a go and have some fun, post back your results. Would be good to hear your findings. Regards Dave. Quote Link to comment Share on other sites More sharing options...
nterry Posted May 12, 2014 Author Report Share Posted May 12, 2014 dave thanks for input closed loop boost control is working nicely. nathan Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted May 12, 2014 Report Share Posted May 12, 2014 No worries, glad to help anytime. Regards Dave. Quote Link to comment Share on other sites More sharing options...
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