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Old 01-14-2005, 02:07 AM   #1
jefersun
Scooby Specialist
 
Member#: 37716
Join Date: Jun 2003
Chapter/Region: TXIC
Location: Houston, TX (sugarland, TX)
Vehicle:
2002 ej257 Black WRX

Default Boost gain question..

I was doing some tuning on my car and decided to finally touch the boost gain. My friend said just go to around 45 or so, so i went to 46 (from 50). I got 1 more psi max boost (18 psi), and @ 4k rpm i got +4.9 psi than with the the boost gain set at 50. I was impressed, but the overboosting didn't impress me (even though i was expecting it). So i lowered my boost where it was around 18 psi and made it so it was back around 17 psi again, holding mid 16s to redline. Yet, the thing is, i don't get that "extra" spool down low, like around 3k - 5k.

My questions is this: Is it possible to use the boost gain to get betterspool without overboosting? That is, conter-acting the overboosting by reducing the boost values in the boost map itself.. I tried this, and i just went back to what i had originally. Just wanted some experience feedback with the boost gain. Thanks.
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Old 01-14-2005, 09:37 AM   #2
hippy
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Join Date: May 2003
Location: florida
Vehicle:
2002 Impreza Wrx
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Default

This is the way it was explained to me when I was having boost control issues(course I didn't beleive it at the time, since I was having boost creep issues and things didn't seem to work the way people explained them).... A gain of 50 makes the turbo spool at a given rate, and the boost might never overshoot the target boost. A gain of 55 will spool a little slower, and the boost might never actually hit the target. A gain of lower then 50 will help the turbo spool a little quicker, but the target will be overshot.

You can't counteract the overboost of a low gain by lowering the boost(since lowering the gain creates overshoot). ie- if the target boost b4 was 18 and the boost was shooting to 20 then went back downto downto 18, lowering the target boost to 16 would just make the boost shoot to 18 and go back down to 16(just an example, might not be totally accurate). Point being, try to get the gain where you can live with the amount of overshoot. 4.9 is obviously too much overshoot. Maybe you should try a gain of 48(or even 49) instead of 46?

peace
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Old 01-14-2005, 12:57 PM   #3
jefersun
Scooby Specialist
 
Member#: 37716
Join Date: Jun 2003
Chapter/Region: TXIC
Location: Houston, TX (sugarland, TX)
Vehicle:
2002 ej257 Black WRX

Default

+4.9 is good, because that is from 10 psi to 14.9 psi, not my peak boost. Here are the before and after logs...

Before:

PHP Code:
3049  +1.7 2.8  98  20    00   W/B  +32.6   14.4 +21.0  -1.5 330.00 2.4  12.67
 3100  
+2.1 2.9  99  20    00   W/B  +32.9   13.6 +21.0  -1.5 330.00 2.4  12.61
 3138  
+2.5 2.9  98  20    00   W/B  +33.0   14.0 +21.0  -1.5 330.00 2.4  13.09
 3208  
+2.9 2.8  98  20    00   W/B  +32.7   14.6 +21.0  -1.5 330.00 2.4  13.65
 3258  
+3.1 3.0  98  20    00   W/B  +32.8   15.6 +21.0  -1.5 330.00 2.5  13.65
 3300  
+3.5 3.0 100  20    00   W/B  +32.7   16.0 +21.0  -1.5 360.00 2.5  13.47
 3370  
+3.7 3.0 100  20    00   W/B  +32.8   16.6 +21.0  -1.5 360.00 2.6  13.23
 3408  
+4.1 3.0  99  30    00   W/B  +32.7   18.6 +20.0  -1.5 330.00 2.6  13.14
 3418  
+4.7 3.1 100  30    00   W/B  +32.8   18.9 +20.0  -1.5 360.00 2.6  12.99
 3512  
+5.1 3.2 100  30    00   W/B  +32.8   19.5 +20.0  -1.3 360.00 2.7  12.68
 3576  
+5.7 3.1  99  30    00   W/B  +32.9   21.2 +20.0  -1.5 330.00 2.6  12.46
 3607  
+6.2 3.2 100  40    00   W/B  +32.0   22.9 +19.0  -0.8 360.00 2.7  12.30
 3687  
+6.8 3.2 100  40    00   W/B  +31.4   23.9 +19.0  -0.8 360.00 2.8  12.06
 3762  
+7.2 3.4 100  40    00   W/B  +30.8   25.3 +19.0  -2.4 360.00 2.7  11.84
 3935  
+7.6 3.5  98  40    00   W/B  +30.7   26.9 +19.3  -1.2 330.00 2.9  11.68
 3880  
+8.6 3.4  98  50    00   W/B  +30.5   28.5 +18.1  -1.8 330.00 2.8  11.52
 3944  
+9.6 3.5  98  60    00   W/B  +30.4   29.5 +16.8  -2.4 330.00 2.9  11.42
 4035 
+10.4 3.7 100  60    00   W/B  +29.6   32.7 +17.0  -2.7 320.00 2.9  11.43
 4166 
+11.7 3.7  98  60    00   W/B  +29.4   33.9 +17.0  -2.9 280.00 2.9  11.27
 4235 
+12.7 3.7  99  70    00   W/B  +29.2   34.8 +15.0  -2.8 280.00 3.0  11.14
 4312 
+13.1 3.9  98  70    00   W/B  +27.4   37.6 +15.4  -2.8 280.00 3.1  11.23
 4391 
+14.1 3.8  98  70    00   W/B  +26.2   39.2 +15.6  -2.8 280.00 3.1  11.20
 4480 
+14.7 3.9  98  80    00   W/B  +25.5   42.5 +16.0  -1.9 280.00 3.2  11.14
 4578 
+15.1 4.0  98  70    00   W/B  +24.6   42.0 +16.0  -3.0 280.00 3.2  11.01
 4714 
+15.9 4.0 100  80    00   W/B  +23.4   47.9 +16.0  -4.3 320.00 3.1  10.96
 4755 
+16.6 4.1  98  80    00   W/B  +23.3   49.0 +16.0  -1.5 280.00 3.3  10.89
 4866 
+16.6 4.0  98  80    00   W/B  +23.7   47.2 +16.0  -3.1 280.00 3.2  10.58
 4997 
+17.4 4.0  99  80    00   W/B  +28.3   47.2 +16.1  -4.7 280.00 3.2  10.48
 5151 
+17.0 4.1  98  80    00   W/B  +29.2   46.3 +16.5  -4.7 280.00 3.2  10.73
 5192 
+16.1 4.1  99  70    00   W/B  +30.9   46.2 +18.0  -4.6 280.00 3.2  10.93
 5257 
+16.1 4.1  98  70    00   W/B  +30.7   48.5 +18.1  -6.0 280.00 3.2  10.89
 5402 
+15.7 4.2  99  80    00   W/B  +30.9   52.3 +17.0  -4.8 280.00 3.3  10.95
 5500 
+15.3 4.2  99  70    00   W/B  +30.8   51.5 +19.0  -5.3 280.00 3.3  10.95
 5555 
+15.5 4.2  99  70    00   W/B  +31.1   51.9 +19.0  -4.5 280.00 3.4  10.83
 5640 
+15.3 4.2  99  70    00   W/B  +31.1   51.7 +19.0  -4.9 280.00 3.4  10.83
 5630 
+14.9 4.3  99  70    00   W/B  +31.9   51.4 +19.0  -5.0 330.00 3.4  10.87
 5827 
+15.3 4.3  98  70    00   W/B  +32.0   55.4 +19.0  -5.2 330.00 3.4  10.89
 5899 
+15.7 4.3  98  80    00   W/B  +32.3   57.1 +18.0  -5.8 330.00 3.4  10.89
 6016 
+15.7 4.3  98  80    00   W/B  +32.2   57.9 +18.0  -4.6 350.00 3.5  10.93
 6071 
+15.9 4.3  98  70    00   W/B  +33.4   58.0 +19.0  -5.3 350.00 3.4  10.86
 6184 
+16.1 4.4  98  80    00   W/B  +33.6   56.9 +18.7  -4.7 350.00 3.5  10.81
 6313 
+15.9 4.3  98  80    00   W/B  +36.3   59.7 +19.0  -4.0 350.00 3.5  10.81
 6265 
+15.9 4.3  97  80    00   W/B  +37.1   59.7 +19.0  -4.6 350.00 3.5  10.73
 6373 
+15.9 4.4  98  70    00   W/B  +38.0   58.9 +19.0  -5.5 350.00 3.4  10.76
 6459 
+15.3 4.4  98  70    00   W/B  +38.4   60.8 +19.1  -5.1 350.00 3.5  10.96
 6523 
+15.3 4.4  98  70    00   W/B  +38.1   59.5 +19.1  -4.9 350.00 3.5  10.96
 6613 
+15.3 4.4  98  80    00   W/B  +37.9   62.1 +19.0  -4.0 350.00 3.5  10.80
 6680 
+15.7 4.4  98  80    00   W/B  +38.2   62.0 +19.0  -3.4 350.00 3.6  10.65
 6706 
+15.7 4.4  98  80    00   W/B  +38.1   60.2 +19.2  -3.4 350.00 3.5  10.52
 6858 
+15.5 4.4 100  70    00   W/B  +38.9   60.9 +20.1  -4.4 380.00 3.5  10.55
 6901 
+15.5 4.4  98  80    00   W/B  +38.8   61.9 +19.4  -3.7 350.00 3.6  10.73
 7047 
+15.9 4.4  98  80    00   W/B  +38.7   62.9 +20.0  -3.7 350.00 3.6  10.81
 6988 
+16.1 4.4  98  80    00   W/B  +38.9   60.6 +20.0  -3.3 350.00 3.6  10.74
 7230 
+13.5 2.2   0  00    00   W/B   +5.3    6.4 +24.0  -1.0 ECU.   1.4  10.95 
After:

PHP Code:
3030  +3.3 3.0  98  20    00   W/B  +32.6   15.4 +21.0  -1.5 330.00 2.5  13.39
 3075  
+3.9 3.0  98  30    00   W/B  +32.6   16.1 +20.0  -1.5 330.00 2.5  13.36
 3132  
+4.3 3.1  98  30    00   W/B  +32.4   16.7 +20.0  -1.5 330.00 2.5  13.17
 3211  
+4.9 3.1  98  30    00   W/B  +32.2   18.3 +20.0  -1.5 330.00 2.6  12.99
 3293  
+5.3 3.1  97  30    00   W/B  +32.1   19.0 +20.0  -1.5 330.00 2.7  12.74
 3397  
+5.9 3.2  98  40    00   W/B  +31.9   20.2 +19.0  -0.7 330.00 2.7  12.42
 3390  
+6.6 3.3  96  40    00   W/B  +31.2   22.2 +19.0  -0.7 330.00 2.7  12.25
 3479  
+7.4 3.3  97  40    00   W/B  +30.4   24.0 +19.0  -0.7 330.00 2.8  12.09
 3576  
+8.2 3.4  98  50    00   W/B  +29.7   26.0 +17.0  -0.1 330.00 2.8  11.84
 3635  
+9.0 3.5  97  50    00   W/B  +28.4   29.1 +17.0  -0.2 330.00 2.9  11.53
 3716 
+10.2 3.6  97  60    00   W/B  +27.8   32.1 +16.1  -2.4 330.00 3.0  11.14
 3827 
+11.7 3.6  97  60    00   W/B  +27.8   34.0 +16.5  -2.2 330.00 3.0  10.86
 3903 
+13.1 3.8  97  70    00   W/B  +26.3   36.4 +15.0  -2.7 330.00 3.2  10.80
 4020 
+14.9 3.7  97  80    00   W/B  +25.7   41.0 +15.2  -2.5 280.00 3.0  10.80
 4151 
+16.1 3.8  97  80    00   W/B  +25.3   39.3 +15.5  -2.5 280.00 3.1  10.68
 4203 
+16.8 3.9  97  80    00   W/B  +24.1   41.8 +16.0  -2.1 280.00 3.1  10.68
 4368 
+17.2 4.0  98  80    00   W/B  +23.4   45.4 +16.0  -2.2 280.00 3.3  10.74
 4456 
+17.4 4.0  96  80    00   W/B  +21.9   45.2 +16.0  -1.0 280.00 3.3  10.81
 4516 
+17.6 4.0  96  90    00   W/B  +21.9   47.1 +15.0  -2.2 280.00 3.3  10.93
 4675 
+17.8 4.0  96  90    00   W/B  +21.6   45.6 +15.0  -1.8 280.00 3.3  10.89
 4721 
+18.0 4.1  97  80    00   W/B  +22.3   51.8 +16.0  -4.3 280.00 3.3  10.71
 4830 
+17.8 4.0  95  80    00   W/B  +21.7   49.5 +16.3  -1.5 280.00 3.3  10.59
 4916 
+17.4 4.1  96  80    00   W/B  +23.8   50.6 +16.0  -3.5 280.00 3.3  10.43
 4930 
+17.6 4.1  96  90    00   W/B  +26.6   54.0 +16.0  -2.9 280.00 3.4  10.48
 5128 
+18.0 4.2  96  90    00   W/B  +27.1   56.0 +16.0  -2.9 280.00 3.4  10.68
 5159 
+18.2 4.2  97  90    00   W/B  +28.2   55.8 +16.0  -2.5 280.00 3.4  10.55
 5274 
+18.4 4.2  97  90    00   W/B  +27.5   56.9 +16.0  -2.6 280.00 3.5  10.23
 5385 
+18.0 4.2  96  80    00   W/B  +29.2   54.5 +17.0  -4.8 280.00 3.4  10.05
 5537 
+17.2 4.3  97  80    00   W/B  +29.4   53.2 +17.0  -5.3 280.00 3.4  10.34
 5592 
+17.2 4.3  96  80    00   W/B  +30.8   54.4 +17.4  -5.6 280.00 3.4  10.89
 5678 
+17.0 4.3  97  80    00   W/B  +31.1   53.4 +17.7  -4.7 280.00 3.4  11.06
 5777 
+16.4 4.3  97  80    00   W/B  +31.2   54.6 +18.0  -5.6 330.00 3.4  11.12
 5931 
+16.8 4.3  97  80    00   W/B  +31.2   58.3 +18.0  -5.4 330.00 3.4  11.12
 5941 
+16.6 4.3  96  80    00   W/B  +31.6   58.9 +18.0  -4.5 330.00 3.5  11.08
 6049 
+16.4 4.4  97  80    00   W/B  +31.3   59.9 +18.1  -4.6 350.00 3.5  11.01
 6093 
+16.8 4.4  97  80    00   W/B  +32.0   60.0 +18.6  -4.7 350.00 3.4  10.87
 6218 
+15.9 4.4  96  70    00   W/B  +33.8   59.5 +19.0  -5.8 350.00 3.4  10.81
 6325 
+15.5 4.4  97  70    00   W/B  +36.7   60.7 +19.0  -5.7 350.00 3.5  10.89
 6410 
+15.3 4.4  97  80    00   W/B  +37.2   60.0 +19.0  -4.3 350.00 3.5  11.05
 6410 
+15.7 4.4  97  80    00   W/B  +36.6   62.4 +19.0  -4.1 350.00 3.5  11.01
 6587 
+16.6 4.4  97  80    00   W/B  +36.7   62.1 +19.0  -3.8 350.00 3.5  10.80
 6640 
+16.1 4.4  96  80    00   W/B  +37.4   63.0 +19.0  -3.9 350.00 3.5  10.67
 6747 
+15.7 4.5  96  70    00   W/B  +37.7   60.6 +19.4  -4.8 350.00 3.5  10.59
 6844 
+15.5 4.4  96  70    00   W/B  +38.0   61.9 +19.9  -4.4 350.00 3.6  10.67
 6844 
+14.9 4.4  96  80    00   W/B  +38.0   61.7 +19.1  -3.9 350.00 3.6  10.83
 6872 
+15.3 4.4  97  80    00   W/B  +38.4   63.3 +19.3  -3.6 350.00 3.5  10.87
 6930 
+15.5 4.4  96  70    00   W/B  +38.5   60.4 +20.7  -4.4 350.00 3.5  10.83 
Yea i konw the AFR is rich too, i fixed that later. I ended up going down to 10.8 ish and holding around 11.1 all the way to redline.. could have gone leaner, didn't bother. What about my timing, should i add some mroe degrees? I haven't bothered to touch my timing map in ages..
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Old 01-14-2005, 01:01 PM   #4
jefersun
Scooby Specialist
 
Member#: 37716
Join Date: Jun 2003
Chapter/Region: TXIC
Location: Houston, TX (sugarland, TX)
Vehicle:
2002 ej257 Black WRX

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Quote:
Originally Posted by hippy
... A gain of 55 will spool a little slower, and the boost might never actually hit the target. A gain of lower then 50 will help the turbo spool a little quicker, but the target will be overshot.

You can't counteract the overboost of a low gain by lowering the boost(since lowering the gain creates overshoot)...
So instead could you lower your target boost, lower than you actually would like it, and then lower the boost gain? Theoretically this would imply that you would reach your "desired" boost (say low 17psi) with quicker spool, is that correct? I'll try this too when i log in the future...
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Old 01-14-2005, 01:33 PM   #5
hippy
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Member#: 36528
Join Date: May 2003
Location: florida
Vehicle:
2002 Impreza Wrx
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You could do that if you know where you're gonna be spoolin every time. Ie- If ya punch the gas at 4000rpm and have low boost values with a low gain and the boost shoots up, then you could have higher boost values at higher rpms to keep the boost where ya want. If ya spool at the higher rpms though(where ya have higher boost values), you will go over the boost you want. If ya don't put higher boost values at higher rpms, the boost will shoot up(however far past the target boost), then drop down to your target boost. It's better to put the boost value where ya want it, and make the overshoot something you can deal with. On the same note though, if ya put higher boost values in lower rpm areas where ya don't make as much boost, that could help the turbo spool quicker. Course, this is just my understanding of it.

peace
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