Boost target table - how does yours look...?
#1
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Hi guys,
after I got my MS3(X) running nicely I took a ride yesterday and got the VE dialed in quite a bit.
As I cruised at the Autobahn I had one spot that I had a little problem...
Scenario is - light throttle cruise TP ~30%, speed is a t 180 kph (~ 111mph) and boost is around peak (170kPa). The boost control is working perfectly well when I give the throttle a nice stab, but at that low throttle the MAP is starting to oscillate...
See:
![](https://www.miataturbo.net/attachments/megasquirt-18/45917d1339401032-boost-target-table-how-does-yours-look-boost_at_low_tps.jpg)
This is how my boost target table looks at the moment:
As you can see - at 30% TPS the boost is exactly between to different targets (I guess the MS interpolates them..?).
The oscillations can well be because of my rough VEtable - but could also be hunting between the two different boost targets. (?)
So I thought a bit about how a correct boost target map would look like...?!
How does yours look?
Thanks
after I got my MS3(X) running nicely I took a ride yesterday and got the VE dialed in quite a bit.
As I cruised at the Autobahn I had one spot that I had a little problem...
Scenario is - light throttle cruise TP ~30%, speed is a t 180 kph (~ 111mph) and boost is around peak (170kPa). The boost control is working perfectly well when I give the throttle a nice stab, but at that low throttle the MAP is starting to oscillate...
See:
![](https://www.miataturbo.net/attachments/megasquirt-18/45917d1339401032-boost-target-table-how-does-yours-look-boost_at_low_tps.jpg)
This is how my boost target table looks at the moment:
![](https://www.miataturbo.net/attachments/megasquirt-18/45918d1339401032-boost-target-table-how-does-yours-look-boost_target_sr.jpg)
As you can see - at 30% TPS the boost is exactly between to different targets (I guess the MS interpolates them..?).
The oscillations can well be because of my rough VEtable - but could also be hunting between the two different boost targets. (?)
So I thought a bit about how a correct boost target map would look like...?!
How does yours look?
Thanks
Last edited by Zaphod; 06-11-2012 at 03:51 AM.
#5
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PID is at 22/22/70 now -
Control interval is at 10ms.
with higher TPS the boost control is near perfect.
Gets to target fast, holds target till redline, doesn't overshoot too much...
Control interval is at 10ms.
with higher TPS the boost control is near perfect.
Gets to target fast, holds target till redline, doesn't overshoot too much...
#7
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I am going to try for sure - I am always a bit scared of this high D values, because I thought they would bring oscillations...
Ken seid in this thread (where some other member asked about bc tuning) at Msextra just some days ago:
Maybe 100 is sparingly...
it all depends on point of view...
Edit:
I have noticed, that the PID values on all the Miata MS2/3 tunes I have seen tend to be very close...
Ken seid in this thread (where some other member asked about bc tuning) at Msextra just some days ago:
just keep adding P to counteract the initial overshoot as you add I. Once you get it working with minimal overshoot with just P and I, and you have it holding the target across the rev range, you can add some D (sparingly) to get rid of overshoot.
![rofl](https://www.miataturbo.net/images/smilies/rofl1.gif)
Edit:
I have noticed, that the PID values on all the Miata MS2/3 tunes I have seen tend to be very close...
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