BHP & WHP CONFUSED...
14 July 2016, 11:24 AM
#31
...it similar to believing in religion, pure mentalist deranged behaviour!
18 July 2016, 07:56 PM
#37
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Mine 05 sti puts down around 270whp through it's boots, loses around 50hp through the drivetrain, when put together gives me a printout for 322bhp give or take as a median and that's at surrey rollers. Either way i prefer to know the whp as that's the end power your putting down and playing with, to me engine horse (bhp) is just an estimate used for bragging rights.
19 July 2016, 09:05 AM
#38
Only thing with using a percentage to calculate transmission loss is that as the power increases so does the loss, but why would there be an increase of a loss as the power rises, using 20% loss at 1000bhp you would lose 200bhp, compared to 60bhp at 300bhp, why would you lose an extra 140bhp all of a sudden? not saying it's wrong or right just curious!
19 July 2016, 09:13 AM
#39
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Only thing with using a percentage to calculate transmission loss is that as the power increases so does the loss, but why would there be an increase of a loss as the power rises, using 20% loss at 1000bhp you would lose 200bhp, compared to 60bhp at 300bhp, why would you lose an extra 140bhp all of a sudden? not saying it's wrong or right just curious!
i dont know but thats my assumption
19 July 2016, 09:17 AM
#40
Only thing with using a percentage to calculate transmission loss is that as the power increases so does the loss, but why would there be an increase of a loss as the power rises, using 20% loss at 1000bhp you would lose 200bhp, compared to 60bhp at 300bhp, why would you lose an extra 140bhp all of a sudden? not saying it's wrong or right just curious!
http://www.superstreetonline.com/how...in-power-loss/
19 July 2016, 10:11 AM
#41
You're talking about losses from various areas including; Air friction, oil friction, bearing friction, oil seal pull/friction, rotating masses, forces of inertia, drag, windage, pumping, heat and more, all of which are different for every engine, transmission and driveline design.
19 July 2016, 08:33 PM
#45
In theory, shouldn't a wheel dyno be able to accurately calculate the transmission losses?
If the car is at a certain speed and you put it into neutral, then with a theoretical zero-loss transmission it is only the friction of the dyno itself that will slow the machine down. But the rate of deceleration will be greater dependent on the transmission losses, so could be calculated.
I would have thought?
If the car is at a certain speed and you put it into neutral, then with a theoretical zero-loss transmission it is only the friction of the dyno itself that will slow the machine down. But the rate of deceleration will be greater dependent on the transmission losses, so could be calculated.
I would have thought?
19 July 2016, 10:17 PM
#47
Never said it was, but maybe not as clearly written as I thought
You can measure the deceleration of the dyno itself with no vehicle on it (test conditions, if you like) and get a base point of the machine's losses.
Then when a car is on it, knocked into neutral, you could (in principle) measure the deceleration...do some maths...and get a (more) accurate measurement of the specific vehicles losses?
You can measure the deceleration of the dyno itself with no vehicle on it (test conditions, if you like) and get a base point of the machine's losses.
Then when a car is on it, knocked into neutral, you could (in principle) measure the deceleration...do some maths...and get a (more) accurate measurement of the specific vehicles losses?
20 July 2016, 08:34 AM
#51
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Never said it was, but maybe not as clearly written as I thought
You can measure the deceleration of the dyno itself with no vehicle on it (test conditions, if you like) and get a base point of the machine's losses.
Then when a car is on it, knocked into neutral, you could (in principle) measure the deceleration...do some maths...and get a (more) accurate measurement of the specific vehicles losses?
You can measure the deceleration of the dyno itself with no vehicle on it (test conditions, if you like) and get a base point of the machine's losses.
Then when a car is on it, knocked into neutral, you could (in principle) measure the deceleration...do some maths...and get a (more) accurate measurement of the specific vehicles losses?
20 July 2016, 09:04 AM
#52
Agreed - think they call it "coastdown losses". But perhaps it's no better than a fixed % in practice.
I remember asking Charlie at Surrey Rolling Road about this a few years ago and, whatever the technical answer is, his advice was to use the same dyno all the time, one that's consistent, and look for changes/improvements each time rather than absolute figures.
But we *all* want the bragging-rights flywheel figures, don't we
I remember asking Charlie at Surrey Rolling Road about this a few years ago and, whatever the technical answer is, his advice was to use the same dyno all the time, one that's consistent, and look for changes/improvements each time rather than absolute figures.
But we *all* want the bragging-rights flywheel figures, don't we
22 July 2016, 10:55 AM
#57
Well that brief visit didn't last long! LOL
Looks like the whole DV thread was deleted too. Shame. I made some good points in there, shame to delete the whole thing. Was no where near as bad as other threads that seem to remain. Very odd.
Looks like the whole DV thread was deleted too. Shame. I made some good points in there, shame to delete the whole thing. Was no where near as bad as other threads that seem to remain. Very odd.
Last edited by BrownPantsRacing; 22 July 2016 at 10:58 AM.
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