How accurate is using MassAirflow in grams/second to calculate horsepower? I just realized this is loggable data and im seeing almost 550 MassAirflow gm/s

 

That changes based on the diameter of the pipe the maf is in and the placement. But can be used to compare with other near identical setups.

 

Since our cars don't have a MAF sensor its probably based on MAP and IAT readings.
So you are getting an estimation from an estimation which probably is not going to be very accurate.

 

We’re MAP not MAF so you’re comparing either injector milliseconds or VE numbers (if VE based ECU) and those numbers are a calculations and mostly different car to car.

Overall just using a virtual dyno software is most likely the closest you’ll get to an actual dyno and it would have to be on the same stretch of road, conditions and gear.