Guest plainswolf Posted September 17, 2004 Share Posted September 17, 2004 What percentage should be used when approximating net horsepower from a gross HP number? Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 17, 2004 Share Posted September 17, 2004 Do you mean flywheel HP Vs rear wheel HP? There is about a 15-18% loss on manual tranny car and a 18-20% on a auto tranny car. If thats what you mean. Quote Link to comment Share on other sites More sharing options...
Guest plainswolf Posted September 17, 2004 Share Posted September 17, 2004 No... what I mean is that desktop dyno, from what I've been told, gives you the 'gross horsepower' rating of an engine. Now this is the standard way that all engines were rated up until the 70's I believe. gross HP is what you get with no waterpump, alternator are used. It may actually be more accessories but I'm not sure. 'Net horsepower' is the the standard way that all engines for quite some time have been measured, that is with at least a waterpump and alternator hooked up, and probably more.. I was just wondering if there was at least a rough percentage used of a gross horsepower figure to caculate out net HP.. Quote Link to comment Share on other sites More sharing options...
Guest goldeh2 Posted September 17, 2004 Share Posted September 17, 2004 gross horsepower is power rated at the crank with no accessories. net horspower is power at the crank with accessories. I don't know if there's a rough percentage to get one from the other. Quote Link to comment Share on other sites More sharing options...
johnc Posted September 17, 2004 Share Posted September 17, 2004 Horsepower in the US Brake Horsepower "Brake Horsepower" was a term commonly used before the 1970s and is sometimes also referred to as "Gross Horsepower." It used an old SAE standard (J245) to perform the measuring. That standard just focused on the measurement side, not the process itself. The term indicates the brake, the device for measuring the true power of the engine. Stating power in 'bhp' gives some indication this is a true reading, rather than a calculated or predicted one. However, several OEMs started to strip their engines of essential ancilliaries for the purposes of getting a high horsepower figure to use in marketing the car. SAE Horsepower As part of the passage of the Clean Air Act in 1972 (and also in preparation for it) SAE developed a new engine horsepower testing standard as part of its efforts to meet the new EPA testing regime. That standard was SAE J1349 "Engine Power Test Code – Spark Ignition and Compression Ignition – Net Power Rating Standard" and is pretty much in current use as SAE J1995 as revised. The standard specifies a basis for net engine power rating, and a method for determining net full load engine power with a dynamometer. A dynamometer places a load on the engine and measures the amount of power that the engine can produce against the load. Wheel Horsepower Since the release of low cost in floor dynamometers a new way of measuring horsepower has gained favor, "Wheel Horsepower." Its based on measuring a vehicle driveline's ability to accelerate a mass with a horsepower number calculated from the mass acceleration measurement. At this point SAE has not released any horsepower rating standards regarding the process, measurement, or calibration of floor dynamometers so the numbers published are not verifiable. What's Coming (from a press release on the SAE web site) "The current test, which originated in the early '70s and was last reviewed in 1995, allows automakers to claim horsepower and torque figures higher than what most owners will actually experience. The SAE Power Test Code Committee – chaired by David Landcaster, General Motors Corp. engineering group manager – is revising its standard for measuring horsepower and may suggest that automakers have an independent observer verify the numbers they claim for horsepower and torque. The standard will also set a procedure for how to test torque, which is also heavily advertised by car manufacturers." I was just wondering if there was at least a rough percentage used of a gross horsepower figure to caculate out net HP.. No. Quote Link to comment Share on other sites More sharing options...
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