Strange MAP sensor data

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fmbo
Posts: 16
Joined: Sat Jul 11, 2015 2:59 pm

Strange MAP sensor data

Post by fmbo »

Hi everyone!

I'm trying to use RaceCapture 2 as a scrutineering system to measure MAP and RPM on the competitiors cars, but sometimes data I get from RC2 logger is quite strange.

Last weekend I was acquiring MAP data from turbocharged Subaru BRZ using MPX4250A sensor and noticed a very strange behaviour. For the majority of the race time pressure value changes quite significantly (+- 0,2 bar) with each measurement (rate is 10 Hz, i.e. 10 times a second). IMO, this is quite strange and doesn't look like a real behaviour. Screenshot below:

Image

However, after ~ half of the race (lap 10 out of 18.) picture started to look much more normal:

Image

Here are 2 laps compared with each other:

Image

As car has its own AIM logger, they've shared their data with me and (as I've expected), AIM data doesn't show any +-0,2 bar jumps:

Lap 4:
Image

Lap 10:
Image

2 laps compared:
Image

I would greatly appreciate any reasonable ideas about causes of such behaviour of RaceCapture & MPX4250A sensor.

brentp
Site Admin
Posts: 5986
Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Hi,

One possible reason is smoothing between the two systems. The RaceCapture inputs are currently configured to have zero smoothing on the input channels. The firmware supports configurable smoothing, but the smoothing level is not settable in the software UI, yet.

You can still adjust the smoothing by editing the configuration file directly and then reading and writing it back. The configuration value is 'alpha' and the value is between 0 and 1. 1 = no smoothing at all, and a small number (0.1) is significant smoothing.

Hope this helps,
Brent Picasso
CEO and Founder, Autosport Labs
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fmbo
Posts: 16
Joined: Sat Jul 11, 2015 2:59 pm

Post by fmbo »

Thanks! Will try it next weekend and update you about the results.

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