30% of 287 is 86.1 so depending on which way the calculation is done it may work out but the bhp is measured at the wheels and then calculated back to the fly wheel so all calculations have to be done from the wheel power which is 200 bhp + 30 % for power loss = 260 if the dyno was bolted to the fly wheel and gave a reading of 287 then you deduct 30% for power loss 287-86.1=200
rolling road results wheel fly bhp?
- Thread starter thedoc
- Start date
To express power loss as a percentage, you must divide the loss (87) by the original figure (287) and multiply by 100.
Dividing the loss by the power that you now have means nothing :dunno:
That said, I agree with the doc - 30% of 200 is 60. I just don't know why he needed to tell us that
John
Dividing the loss by the power that you now have means nothing :dunno:
That said, I agree with the doc - 30% of 200 is 60. I just don't know why he needed to tell us that
John
G
GT performance
Guest
[quote author=thedoc link=topic=643.msg5018#msg5018 date=1161846084]
30% of 287 is 86.1 so depending on which way the calculation is done it may work out but the bhp is measured at the wheels and then calculated back to the fly wheel so all calculations have to be done from the wheel power which is 200 bhp + 30 % for power loss = 260 if the dyno was bolted to the fly wheel and gave a reading of 287 then you deduct 30% for power loss 287-86.1=200
[/quote]
:computer: :computer: :computer:
you lose approx 30% of the power you have at the flywheel!! you cant take 30% of the power at the wheels and add it on to get the flywheel figure. you said you got a reading of 200 ATW and 287 ATF...which is spot on. you calculating 30% of the ATW and adding it on is not the right way.
george
30% of 287 is 86.1 so depending on which way the calculation is done it may work out but the bhp is measured at the wheels and then calculated back to the fly wheel so all calculations have to be done from the wheel power which is 200 bhp + 30 % for power loss = 260 if the dyno was bolted to the fly wheel and gave a reading of 287 then you deduct 30% for power loss 287-86.1=200
[/quote]
:computer: :computer: :computer:
you lose approx 30% of the power you have at the flywheel!! you cant take 30% of the power at the wheels and add it on to get the flywheel figure. you said you got a reading of 200 ATW and 287 ATF...which is spot on. you calculating 30% of the ATW and adding it on is not the right way.
george
No. the only way to get a true flywheel reading is to remove the engine and bolt on the dyno,if this was done and you got a reading of 287 then you could say a 30% loss of this is your power at the wheels 200bhp.Because the engine was not removed and was tested at the wheels the only true reading is 200bhp so all calculations have to be done from this figure.So instead of subtracting 30% of 287 from 287 you must add 30% of 200 to 200. 287 is a hypathetical figure.
G
GT performance
Guest
NO NO NO NO
you lose 30% of your power through the drivetrain. so if your on a rolling road and you get a figure of 200bhp at the wheels then that figure is 70% of what should be at the flywheel. so if you divide 200 by 70 you will get what 1% of the at the flywheel power is, so multiply it by 100 to get 100%(or a rough calculation of what power is at the flywheel)
200/70=2.86
2.86x100= 286bhp at the flywheel.
TRUST ME!!!!
George
you lose 30% of your power through the drivetrain. so if your on a rolling road and you get a figure of 200bhp at the wheels then that figure is 70% of what should be at the flywheel. so if you divide 200 by 70 you will get what 1% of the at the flywheel power is, so multiply it by 100 to get 100%(or a rough calculation of what power is at the flywheel)
200/70=2.86
2.86x100= 286bhp at the flywheel.
TRUST ME!!!!
George
G
GT performance
Guest
by the way your right. the only way to get a true reading of at the fly power is to get it directly at the fly. but 30% is an estimation of the power loss thru the drivetrain on an impreza. so if you have the ATW figure from a rolling road you can calculate what the power is at the flywheel by taking the ATW figure as being 70% of the ATF. within a few bhp.
George
George
G
GT performance
Guest
hi yeah 287 does seem a little high. but rolling roads are always out, you could go back tomorro and it could read 170 ATW. you never know with rolling roads. the best indication is to get an apexi rsm and get it set-up for your car and then if you think your car is slower or faster then it was you can see it there on the rsm.
George
George
S
Scoobydiver
Guest
[quote author=GT performance link=topic=643.msg4961#msg4961 date=1161795841]
the figure you got for the ATW bhp is just over 30% below the figure for your at the flywheel.
your at the flywheel figure was 287bhp -30% = 200.9bhp at the wheels(ATW)
whats so hard about that??
:nana: :nana:
to get more technical your ATW/ATF= .69686 (200/287=.69686) x100/1=69.686%(to get the %)
so at the wheels you have 69.686% of the power you had at the flywheel
so the exact % of power loss thru the drivetrain on your car is 100% - 69.686% = 30.314% TA-DAA!!
George
[/quote]
.....apologies welcome - whenever youre ready of course!!
the figure you got for the ATW bhp is just over 30% below the figure for your at the flywheel.
your at the flywheel figure was 287bhp -30% = 200.9bhp at the wheels(ATW)
whats so hard about that??
:nana: :nana: to get more technical your ATW/ATF= .69686 (200/287=.69686) x100/1=69.686%(to get the %)
so at the wheels you have 69.686% of the power you had at the flywheel
so the exact % of power loss thru the drivetrain on your car is 100% - 69.686% = 30.314% TA-DAA!!
George
[/quote]
.....apologies welcome - whenever youre ready of course!!
S
Scoobydiver
Guest
@ norris, yeah that'd be me!
N
Norris!
Guest
cool, i always have a scooby bag on my back, so feel free to kick me in the nuts next time you see me 
S
Scoobydiver
Guest
hahahaha ill look out for ya buddy!