Legend Posted October 1, 2008 Share Posted October 1, 2008 Car: '05 LGT MT, stock turbo, smaller pill Tune: Romraider I'm very pleased with my boost control and I'm to the point where any changes will be only very slight tweaks. I appreciate the stock ecu boost control and hope to utilize it when/if I upgrade turbos. But one thing I don't fully understand the purpose of is the Max Wastegate Duty table. Here is how the ecu defs define it: These are the maximum values for wastegate duty. The ECU adjusts wastegate duty in an attempt to achieve target boost within the limits defined by the turbo dynamics and wastegate tables. Wastegate compensation tables also are applied to these values. Sounds simple. I understand the definition. I don't understand the purpose though. The purpose has to be to keep overboost in check, right? I don't understand why (for 95% throttle at least), the Max value can't be pegged at the global maximum (Wastegate Duty Limit (Maximum)). From my experience, overboost can be controlled very readily if an appropriate Target Boost is selected first and then dialed in with Initial Wastegate Duty and then finessed with Turbo Dynamics. It's possible for boost to do exactly what you want without regard to rpm-dependent Max WGDC. The problem with setting Max WGDC values lesser than the global maximum, at least in my experience, is that in 1st and 2nd gears boost was being needlessly capped by Max WGDC's lower than the global maximum. Basically, in my situation having Max WGDC values of less than the global maximum under 3500rpm or over 5000rpm served to keep boost in 1st and 2nd from reaching their full potential. I'm not a fan of doing things that make me slower. When I initially started tuning I kept Max and Initial WGDC a fixed (or smoothly converging/diverging from/to eachother) distance apart. When I saw that 1st and 2nd gear were being compromised I abandoned the relationship and set Max at/near the global maximum for 95% throttle. I haven't seen a downside. Here is some data from a recent (but not current) tune. The first graph is WGDC from each gear, plotted along with Initial and Max WGDC. The second graph shows the boost (note I plotted my altitude-correct target boost). http://beeez.com/lgt/wgdc.jpg http://beeez.com/lgt/boost295.jpg So... am I in the majority or minority with this strategy? I know this makes me sound naive, but it really makes me wonder why the Max WGDC table is necessary. My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 1, 2008 Share Posted October 1, 2008 If you look at the 16 bit ecu boost control and compare it to the 32 bit ecu boost control, you will appreciate the fact that we have WAY more tables. You don't need all of them. Here's three important ones that 16 bit ecu doesn't have. TD Proportional TD integral cumulative max WGDC initial I remember when I looked at the stock Tuned by STi Liberty rom and saw that they had completely deactivated the max WGDC table. That's when I realized that the max WGDC table isn't needed and is just a crutch. BTW, nice control in 5th gear. I usually just let it have a massive dip at 2400 rpm. Link to comment Share on other sites More sharing options...
LittleBlueGT Posted October 1, 2008 Share Posted October 1, 2008 MAX WGDC can be useful. When proportional is high the proportional will stop the integral from accumulating unless there is room between the initial WGDC and max WGDC values. Make sense? Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 1, 2008 Share Posted October 1, 2008 shhhh!!!! Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 1, 2008 Share Posted October 1, 2008 Yeah, I've been using that method for a while. http://www.romraider.com/forum/topic1814-15.html There are alternative methods. Link to comment Share on other sites More sharing options...
LittleBlueGT Posted October 1, 2008 Share Posted October 1, 2008 Yeah, I've been using that method for a while. http://www.romraider.com/forum/topic1814-15.html There are alternative methods. I think I learned it from you. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
SeeeeeYa Posted October 1, 2008 Share Posted October 1, 2008 Like Legend, I also abandoned that relationship between initial and max WGDC, despite the instructions from Cobb as well as input from "professional" tuners. After MANY months of following what I was told without the kind of boost control I wanted I quit listening. My Max WGDC table is set at 90% except for the idle area. I have great boost control now with no downsides. Link to comment Share on other sites More sharing options...
Legacy_GT_Pilot Posted October 1, 2008 Share Posted October 1, 2008 Just to clarify, your max WGDC's are set at 90% for all throttle angles except for idle? I will be modifying my tune over the weekend as my meth system is getting re-installed on Friday, and I will try this and see if I can drive some improvements to my boost control. Care to share you Street Tuner map with me? I'd be curious to see what settings you're using in your other boost control tables. Like Legend, I also abandoned that relationship between initial and max WGDC, despite the instructions from Cobb as well as input from "professional" tuners. After MANY months of following what I was told without the kind of boost control I wanted I quit listening. My Max WGDC table is set at 90% except for the idle area. I have great boost control now with no downsides. Link to comment Share on other sites More sharing options...
SeeeeeYa Posted October 1, 2008 Share Posted October 1, 2008 Just to clarify, your max WGDC's are set at 90% for all throttle angles except for idle? I will be modifying my tune over the weekend as my meth system is getting re-installed on Friday, and I will try this and see if I can drive some improvements to my boost control. Care to share you Street Tuner map with me? I'd be curious to see what settings you're using in your other boost control tables. PM sent. Link to comment Share on other sites More sharing options...
Legend Posted October 1, 2008 Author Share Posted October 1, 2008 Alright well I'm glad to hear that what I've done with my boost control has been done by some of you guys... and it looks like there's more than one way to dial it in. It's nice to have more than enough tables to get the job done. I wasn't sure if I'd gone out on a limb here or not. But speaking of going out on a limb... BTW, nice control in 5th gear. I usually just let it have a massive dip at 2400 rpm. Thanks. That's a result of re-scaling the target boost table to provide the best resolution where it's needed the most - spool! I've got target boost set up every 250rpm between 2000-3500rpm (2000, 2250, 2500, 2750, 3000, 3250, 3500) to keep boost real close to my target. It also serves to keep the boost curves in 4th and 5th pretty darn close to the boost curve in 3rd. I didn't like having to reduce timing for knock events in 4th/5th due to significantly higher or oscillating boost. My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
Infamous1 Posted October 1, 2008 Share Posted October 1, 2008 I think I learned it from you. me too.... Link to comment Share on other sites More sharing options...
Infamous1 Posted October 7, 2008 Share Posted October 7, 2008 Bump for excellent boost control... Link to comment Share on other sites More sharing options...
Legend Posted October 7, 2008 Author Share Posted October 7, 2008 Thanks. Anyone else re-scale the target boost table similar to how I did? http://beeez.com/lgt/target.jpg My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 7, 2008 Share Posted October 7, 2008 I adjust the table so that I can put a corner wherever I need it. The LGT has enough resolution that it isn't a problem. For stage 2 LGT cars, I like to have at least a point at 2000, 2400, 2700, 3000, and 3200 rpm. The 800 rpm point is useless. You can eliminate that entire row. Link to comment Share on other sites More sharing options...
NSFW Posted October 8, 2008 Share Posted October 8, 2008 Is there any risk of overheating the solenoid from long periods at high duty cycle? Link to comment Share on other sites More sharing options...
Legend Posted October 8, 2008 Author Share Posted October 8, 2008 Good point about the 800rpm row, mickey. Next time I'm in my rom I'll eliminate that row and plug in a row at 3250rpm. NSFW, not sure about that overheating risk, but if it were truly long periods it might be an issue. In my graphs, above, I do peg WGDC at 96% but the duration of time is very small. I just checked the logs and it's pegged in 1st gear for 0.7s and in 2nd gear for 1.4s. I don't think it's long enough for concern. My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 8, 2008 Share Posted October 8, 2008 I think 90% is okay since that is what the JDM cars use over a very large portion of the map. As Legend pointed out, it's only temporary anyway. Anything above 90%, I'm not sure but WRX guys run higher. Link to comment Share on other sites More sharing options...
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