You have not given enough information for me to advise a definitive decrease or increase, but it is the "Maximum rate of change" setting (max. r.o.c.) that I think you need to change.
This is found in the Variable Manager under "Advanced options".
You have not said so, but I am assuming that some of the RPM trace is sensible and properly scaled. Therefore, I assume that the "Ignition Pulses Per Revolution", which lives under "Vehicle Options"in the Data menu is correctly set.
If you are not sure, log some data driving at constant speed in different gears. I assume that you know or can find out your gear ratios. The effective tyre circumference is less than that which you measure on an unladen tyre. A better measurement is to roll the car for a few complete wheel revolutions and measure the distance...
The relationship between RPM and speed should thus be known...
![Smile :)](./images/smilies/icon_smile.gif)
Thanks to our GPS, we do not need to measure circumference directly as long as we know the gearing numbers.
If gear ratios are unknown, you can still check for sensible RPM measurement by checking to see that speed and RPM stay in the proportion to each other at different road speeds in the same gear. If the max. r.o.c. is not properly set, this proportion can change.
The setting is not critical to within a hundred or so... it is unlikely that 2400 works but 2500 does not. Rather, if 2500 is not OK, 1500 or 5000 should be tried, for instance.
If I have to guess, I'll say that your max r.o.c. is set too low. If it is too high, you would probably be complaining of inexplicable peaks in the RPM data.