ausmini :: View topic - Drivetrain loss

Can anyone tell me what the approx percentage of drive train loss is normal in a mini?

it says on the dyno sheet "not corrected"

what exactly does that mean?

It means the torque is measured at the wheels. That's why it is so high.
divide it by the [diff ratio x the gear ratio used] and you will be somewhere near it, but low due to drivetrain losses.
These losses are not all in the gearbox, a major one is the tyres. Sticky fat ones give lower dyno readings than hard old skinny ones do.

sounds like a lot of trouble for not much gain considering i am not after the absolute maximum power from this engine :lol:

just wanted an explanation, and thanks for your feedback guys i now understand what "corrected" power is.

not really any point in working out the percentage of drivetrain loss if the figures are not corrected anyhow is there :lol:

horsepower at the wheels was 53 and i suppose that was an ok result considering its my first ever mini engine build :lol:

the aim was to make sure the engine mixtures were ok and there was no danger of it having some catastophic internal disaster due to a lean mixture or something similar. mixtures were great right through the rev range so i am happy with that for now.

30hp loss is about right. Mine on engine dyno (much more accurate) had 120bhp, on the rolling road dyno it had about 84hp (but was running very rich, i suspect it's now closer to 90hp)

Dynos vary heaps, they are only good for tuning, and comparisons on the day. Even then they vary a lot.

Lillee wrote:

30hp loss is about right. Mine on engine dyno (much more accurate) had 120bhp, on the rolling road dyno it had about 84hp (but was running very rich, i suspect it's now closer to 90hp)

Nah you had ~74HP then mate, I have the records...
Mine made 86.6 on the same day, I have the trophy.

Author:	jester99 [ Tue Oct 05, 2010 5:04 pm ]
Post subject:	Drivetrain loss
Hi guys and gals, Can anyone tell me what the approx percentage of drive train loss is normal in a mini? also, i notice now after i had my car dynoed today that the torque output is much higher than other mini engined dyno sheets i have seen. is 194 ft/lb of torque right? or is that a misprint? if my engine is making 53HP at the wheels, around what would that be at the flywheel? cheers jason

Author:	Harley [ Tue Oct 05, 2010 5:17 pm ]
Post subject:	Re: Drivetrain loss
jester99 wrote: Can anyone tell me what the approx percentage of drive train loss is normal in a mini? 10% of your oil every 2000 kilometres is a normal loss.

Author:	GT mowog [ Tue Oct 05, 2010 5:19 pm ]
Post subject:
About 20% losses through the drive train, but there can be other variables like tyres, tyre pressure and even how it has been strapped down. The 194 ft/lbs torque would have to be incorrect. I'd expect to see between 60 and 90 ft/lbs from an engine like yours. The 53 HP quoted has that been corrected?

Author:	jester99 [ Tue Oct 05, 2010 6:10 pm ]
Post subject:
it says on the dyno sheet "not corrected" what exactly does that mean?

Author:	drmini in aust [ Tue Oct 05, 2010 6:15 pm ]
Post subject:
It means the torque is measured at the wheels. That's why it is so high. divide it by the [diff ratio x the gear ratio used] and you will be somewhere near it, but low due to drivetrain losses. These losses are not all in the gearbox, a major one is the tyres. Sticky fat ones give lower dyno readings than hard old skinny ones do.

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Drivetrain loss https://www.ausmini.com/forums/viewtopic.php?f=2&t=66127	Page 1 of 2

Author:	jester99 [ Tue Oct 05, 2010 6:19 pm ]
Post subject:
ok, well thats got me buggered i have no idea what diff ratio i have or what ratio the 3rd gear i have is

Author:	GT mowog [ Tue Oct 05, 2010 6:35 pm ]
Post subject:
jester99 wrote: it says on the dyno sheet "not corrected" what exactly does that mean? drmini in aust wrote: It means the torque is measured at the wheels. That's why it is so high. divide it by the [diff ratio x the gear ratio used] and you will be somewhere near it, but low due to drivetrain losses. These losses are not all in the gearbox, a major one is the tyres. Sticky fat ones give lower dyno readings than hard old skinny ones do. .....And there is also Air Pressure, Altitude, Humidity and Temperature corrections that should be applied, although on the Temp, you really need the Air Temp of that going in to your Carb, rather than just the Air Temp of the day. You can look these up for yourself and note them on the back of your sheet.

Author:	jester99 [ Tue Oct 05, 2010 6:41 pm ]
Post subject:
sounds like a lot of trouble for not much gain considering i am not after the absolute maximum power from this engine just wanted an explanation, and thanks for your feedback guys i now understand what "corrected" power is. not really any point in working out the percentage of drivetrain loss if the figures are not corrected anyhow is there horsepower at the wheels was 53 and i suppose that was an ok result considering its my first ever mini engine build the aim was to make sure the engine mixtures were ok and there was no danger of it having some catastophic internal disaster due to a lean mixture or something similar. mixtures were great right through the rev range so i am happy with that for now.

Author:	GT mowog [ Tue Oct 05, 2010 6:48 pm ]
Post subject:
jester99 wrote: sounds like a lot of trouble for not much gain considering i am not after the absolute maximum power from this engine just wanted an explanation, and thanks for your feedback guys i now understand what "corrected" power is. not really any point in working out the percentage of drivetrain loss if the figures are not corrected anyhow is there horsepower at the wheels was 53 and i suppose that was an ok result considering its my first ever mini engine build the aim was to make sure the engine mixtures were ok and there was no danger of it having some catastophic internal disaster due to a lean mixture or something similar. mixtures were great right through the rev range so i am happy with that for now. Your main reasons for having the Dyno Tune are sound, but it can be useful to have reliable and repeatable Engine Output figures for a later time when you go tinkering..........

Author:	TheMiniMan [ Tue Oct 05, 2010 10:08 pm ]
Post subject:
If you like a "Rule of thumb" for drive train losses in a mini,,, then expect to see that wonderful "reported" std Cooper "S" engine HP out-put to be 74hp (cough) at the engine,,, dribble away to only about 44hp at the wheels & a nice 1100 from 50hp back down to 30hp -----------------------------ish--------------------------------- so take "almost" 20-30hp losses depending-------------------------ish------------ (with std helical gears & std-ish tyres pumped to 30lbs on an average-ish day, down a hill with a back-wind ---------------ish-------------------

Author:	Lillee [ Tue Oct 05, 2010 10:34 pm ]
Post subject:
30hp loss is about right. Mine on engine dyno (much more accurate) had 120bhp, on the rolling road dyno it had about 84hp (but was running very rich, i suspect it's now closer to 90hp) But as GT mowog suggests, you go back in winter and magically will have more hp......

Author:	TheMiniMan [ Tue Oct 05, 2010 10:55 pm ]
Post subject:
oh just pump up the old hard skinny conventionals run it up at night time cool the fuel tank down with some ice wrapped towels wheel align dead straight with good hard tie bar bushes spray mist of ice cold water across the carb inlet don`t strap the car down very tight lightweight motor oil in the wheel bearings instead of grease etc etc etc

Author:	drmini in aust [ Wed Oct 06, 2010 7:37 am ]
Post subject:
Lillee wrote: 30hp loss is about right. Mine on engine dyno (much more accurate) had 120bhp, on the rolling road dyno it had about 84hp (but was running very rich, i suspect it's now closer to 90hp) Nah you had ~74HP then mate, I have the records... Mine made 86.6 on the same day, I have the trophy. Dynos vary heaps, they are only good for tuning, and comparisons on the day. Even then they vary a lot. I saw a 140HP (on engine dyno) 1152 turbo get 125 ATW, a 140HP stroker 1400 get barely 100. Same days, same dynos. Hint- the turbos ran in 4th gear, not 3rd.

Author:	Panthersteve [ Wed Oct 06, 2010 8:10 am ]
Post subject:
drmini in aust wrote: Dynos vary heaps, they are only good for tuning, and comparisons on the day. Even then they vary a lot. Forget about the figures, just use it like you intended, to get it tuned.

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Author:	Lillee [ Wed Oct 06, 2010 9:39 am ]
Post subject:
drmini in aust wrote: Lillee wrote: 30hp loss is about right. Mine on engine dyno (much more accurate) had 120bhp, on the rolling road dyno it had about 84hp (but was running very rich, i suspect it's now closer to 90hp) Nah you had ~74HP then mate, I have the records... Mine made 86.6 on the same day, I have the trophy. 84, 74, what's the difference. 120 flywheel hp happy?