atf v's atw
01 July 2007, 05:34 PM
#2
Scooby Regular
Varies from car to car. 4wd tend to have the most transmission losses, as you'd expect. I'm sure people will weigh in with all kinds of figures, but in my experience, forget flywheel power and pay attention to wheel power. The more wheel power you've got, the faster you are, the less you have the slower you are. Simple as that.
01 July 2007, 06:08 PM
#4
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Its measured at the wheels then calculated back to flywheel by measuring rundown losses on most dynos.
Dyno Dynamics rolling roads just estimate a figure and add it to the WHP when run in shootout mode. If you want bigger numbers just pump your tyres up real hard
The losses are not a fixed percentage throughout the rpm/mph range, beware of anyone telling you they are !
Its difficult enough trying to compare different rolling roads flywheel figures, just forget about comparing WHP figures as the design and operation of the rolling road can put the losses at anything from 40-140bhp !
Andy
Dyno Dynamics rolling roads just estimate a figure and add it to the WHP when run in shootout mode. If you want bigger numbers just pump your tyres up real hard
The losses are not a fixed percentage throughout the rpm/mph range, beware of anyone telling you they are !
Its difficult enough trying to compare different rolling roads flywheel figures, just forget about comparing WHP figures as the design and operation of the rolling road can put the losses at anything from 40-140bhp !
Andy
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01 July 2007, 11:26 PM
#12
Scooby Regular
LOL what he said ^^^ quick.
Something putting a genuine 453hp out at the wheels would be turning out at least 500bhp at the flywheel but there's no reliable way of telling short of removing the engine and putting it on an engine dyno, and then whatever it makes there on its own bears no relation to what it does when fitted to the car! But if you want a number, call it 500 horsepower. That's all it is though, a rough guesstimate and nothing more. As Andy says, it's not just a question of adding a fixed percentage back and calling it the trans loss. Trans loss is a lot more complicated than that when you think about everything involved - there's no way one single percentage can come close to representing it.
Something putting a genuine 453hp out at the wheels would be turning out at least 500bhp at the flywheel but there's no reliable way of telling short of removing the engine and putting it on an engine dyno, and then whatever it makes there on its own bears no relation to what it does when fitted to the car! But if you want a number, call it 500 horsepower. That's all it is though, a rough guesstimate and nothing more. As Andy says, it's not just a question of adding a fixed percentage back and calling it the trans loss. Trans loss is a lot more complicated than that when you think about everything involved - there's no way one single percentage can come close to representing it.
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