Erratic ITB load signal

[Wilmo]

Hello,

Since about three weeks I have my ITB's finally installed on my 1982 BMW E21. Since March 2017 I drive around with a Microsquirt and did the install in small steps. First ignition only, last year I installed the K-jet hardware and now the ITB's are a fact.

So, first some data:
Microsquirt
Tunerstudio MS v3.0.28 (MS2/Extra 3.4.2)
BMW E21 M10B18 292 Schrick
GSXR1000 42mm ITB's with the TPS and MAP sensor used


This weekend we were with a small gang in the Eifel in Germany and the setup behaved pretty decently. I know that I have to visit a tuner but I think I have about 80% of the performance unleashed and I want to verify everything works without problems before we start troubleshooting the install on a dyno.


The thing is that during acceleration restrains from about 4000rpm. But not every time. After two days a moment was there that it would not go away and it was there every time we went up in the rpm. So it was time to connect the computer and isolate whether it is hardware or software.


In Tunerstudio I found this:


This is a segment from the logging:


My ITB settings at that time where like this:



As countermeasures I smoothed the MAP signal to 15% and decreased the sample window. I decreased MAP influence on ITB load to 20% and 0% but it would not go away. When I put it on 50% the error did not go away but was minimised.


It can be seen that the load calculation resonates on the ripple of the MAP signal. MAP ripples between 89.5 and 90.5.


So yeah, what to do? My first question is whether ITB load TPS switch point is 90 or 90.0kPa. I established the curve with 89.5-90.5kPa data.


The MSQ from how it is now (with the 50% MAP at TPS switchpoint is attached. The logging is too large for the upload, but it is stored here: https://www.dropbox.com/s/muswf7eu25ene ... 8.msl?dl=0

[Dennis_Zx7r]

See http://www.msextra.com/forums/viewtopic ... 25&t=69762. If Baro% is below 90% (standard value), ITB load is capped to the ITB load at switchpoint (standard 50%). One workaround is to lower the ITB load TPS switch point to well below 90% baro (and retune everything!), as there has been no change in the code that I'm aware of adressing this.

Also, I think you misunderstand how ITB load is calculated. It's 100% baro% below the switchpoint, and 100% alphaN above. On a sidenote, this is one of the points why I think the "ITB load at TPS switchpoint table" only confuses people. The table only determines what ITBLoad is displayed when baro% is at 90%.

[Wilmo]

Oh dear. I was expecting an easier solution.

Ehm. I had the idea that I switched off %baro because of problems I had earlier in the mountains. In the log, Barometer is continuously 100. The other thing is, how does the ITB Load Switchpoint know that I used 89.5-90.5kPa data? When in the other topic is stated that 85 or 80kPa can be used as well, does that mean that the chosen value is arbitrary? Why does the interweb say it is 90kPa per definition? (yes I know that there is a lot on the interweb that is not true.)


I read it now as if I have problems because of ITB behaviour in combination with bad weather coming and slightly higher altitude (Saturday night I measured 95kPa without engine running). But if I lower the switchpoint and I meet really bad weather at the Stelvio I still have problems. So what can the ultimate solution be?

Since I already use the MAP for 1.5 years I really have no reason to doubt the calibration. Maybe I can find half a kPa somewhere but there are many of them in the things I can't control.

[Wilmo]

I believe I start to understand. The switchpoint is not MAP, it is %baro. At MS2/uS it is fixed at 90%, at MS3 it is adjustable. Since I blocked baro measurement because of earlier bad results, no correction at all is done. MAP/Baro --> 90/100=90%baro --> error.

When I apply an extra MAP sensor just to measure barometric pressure I would end up like 90/95=0.947 which is on the save side.


Thanks for the help!