Experience with environmental correction
So guys, I'm wondering what your experience is.
Yesterday we had a really high air pressure locally (1045mbar) and I've noticed all the cars I tuned where all reading very low.
As a reference, I tune about 30 of these cars (Clio 4 RS 200) a year so I know how they should perform.
The cars on standard software consequently end up around 255-260nm on my dyno, yet the first one yesterday on 100% standard software only did around 240nm.
After tuning all parameters looked well in my datalogs, yet power output would still be very low compared to others I've tuned.
So as a reference I turned off the correction and loaded raw log, guess what, bang on 258nm and power as expected aswell.
Now I'm wondering, what is your experience? I reckon with N/A cars the environmental correction will be true, but with turbo cars (which regulate boost themselves) not so much. Seriously considering turning off environmental correction because of this from now on.
Which standard are yuo using?
I found SAE give strange overcorrection if temperatures are over or under the nominal value.It is only good when the environmental parameters are close to default values. If you play with manual data,its not hard to get 10% correction which seems too high for me.
Which correction do you use?
DIN 70020 since it is available. I found a webpage with many different correction factors,but i am unable to find it now. You can play with manual data enter to see what correction factor will be the result for SAE VS DIN.
@tutuur, you bring up a good point. Ambient air pressure makes a big difference to the compensation factors, but if the car's ECU compensates such that the turbo pressure is independent of the ambient air pressure then we don't really want to compensate for it.
This is of course different for naturally aspirated cars, and also for super charged cars when there is no regulator.
There is no difference in the correction factors between NA, Supercharged and turbo gasoline engines in the standards. I think this because it is assumed the turbo pressure is controlled with differential pressure (turbo pressure - ambient pressure) rather than absolute pressure.
The strange thing is that both the ISO and the SAE correction formulas have different corrections for turbo diesel engines vs NA diesel engines. See attached.
I don’t know the equation behind it but judging from the 2 variables they are very different indeed!
I’ll play with the correctiins next time I have some spare time and see what it does 🙂
For the record, this does remind me the Maha on which I tuned before let you select what kind of engine it was. Probably because of the correction factor