Hi Guys,

I have heard that if you take your AFGS from a datamaster log and multiply it by 1.1, you will get your RWHP. Is this true? How accurate is the number? Is there any way to extract approx. rear wheel torque from datamaster logs? My car is a 1995 Z28 T-top 6-Speed (stock besides exhaust, CAI, gutted CAT). I am guessing that drivetrain loss is about 15% Is this an accurate guess?

Thanks.

 

Datamaster can do a guesstimate of HP/Tq and 1/4-mile times... but it's not incredibly accurate.

 

I answered this same question for you on another board. Something like "multiply AFGS by 1.1 to get rwHP" is a VERY general rule-of-thumb. It will give you a VERY crude number. It assumes a lot, including the air/fuel ratio, and overall thermal efficiency of the engine, plus assuming a drivetrain loss. How could AFGS possible be a direct connection to rwHP? How does measuring the airflow into the engine (which is a more direct measure of flywheel HP, not rwHP) possibly account for the wide variations in drivetrain loss, which could range anywhere from 12% for a really tight manual tranny setup to 25% for a loose, non-locking converter in a heavy automatic?

If you wanted to try the "rule-of-thumb" set up a spreadsheet of data taken from your data log, showing RPM vs. AFGS for the full RPM range that you are interested in. Then add a third column to the spreadsheet for your HP, multiplying AFGS x 1.1. Then add a fourth column for torgue, using the formula TQ = (HP x 5252) / RPM. Just recongize that these numbers are going to be +/- 10-15%.

As far as drivetrain loss, I measured it by comparing engine dyno and chassis dyno measurements, taken when the car was an M6, and the drivetrain loss ranged from 12.6% at 486 flywheel HP to 12.1% at 762 flywheelHP. I'd say to use 13% for a stock M6 drivetrain, and "stockish" HP levels.

 

Dynos are quite a bit more accurate! [insert smart a$$ remark here]

 

If you have a ported MAF, you cannot use the 1.1 multiplier.

I have a stock MAF and a ported MAF.

Datamaster reads the ported MAF at just about 100 AFGS less than the stock MAF. The fins that you remove when you port the MAF direct the air to the heated elements that measure the AFGS, much of the air in the ported MAF does not get counted.