Quote:
Originally Posted by bikenfool
Care to elaborate? That link doesn't say anything about how to get BFSC data. I think measuring torque or hp accurately outside of a dyno would be tough.
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Really easy, at least with a manual transmission. Measure the acceleration with an accelerometer and calculate the force required to achieve that acceleration using the mass of the car. Work back from the tires with the gear ratios to find torque at the flywheel. With the engine speed known you can then calculate the power being used.
With a torque convertor between the engine and transmission it's a bit harder to obtain engine power but it will still be possible to find the power from the transmission back.
Quote:
Originally Posted by P-hack
tough, a little bit, for any hope of accuracy you would have to do some coastdown tests and have you and your vehicle weighed with a consistent fuel load (and tire psi) and warmup to determine CDA and CRR. Plus you want consistent atmospheric conditions.
HP to the wheels would be a function of drag at speed and change in velocity.
Fuel consumption would be monitored by an injector (or other accurate source).
Speed is the VSS signal (or rpm if using different gears).
Map is indicitive of load.
So you log fuel rate, speed, map. Accelerate at different map values using your foot and determine the hp required (and fuel consumed)between steps as you accelerate. Build the bsfc chart row by row by keeping map consistent during each run (As practical).
Standard testing, run in both directions and average, repeat. Flat test area with no wind is best.
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It's so easy, you could gather a lot of data, analogous to logging fuel trims when engine tuning. Define cells of load vs rpm and fill them in as you drive. Most errors will average out.
Yes, you would want to ignore the data collected while the engine was at lower than normal operating temperature.
Because of the effect of road speed on aero and rolling drag maybe produce separate maps for each gear ratio. Enough coast down tests should get a reasonable measurement of these losses anyway.