Transmission Losses
Turbo Mini Forums

Just wondering what some of you guys are losing through the transmission that are running good horsepower. the rollers i use just give wheel horse power. Not pub talk power! So what would 150 at the wheels likely be at the fly with the usual SC box etc.
Ta

165/170 at a guess?

just looked at my last graph which shows 24 nana's lost from 197..

i guess robert will be the one in the know though.

these are from the tm shootout day ,,,










hope that helps :)

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

would be interesting to see what final drive was used against the losses. I know Matt uses a 2.9:1 which might account for the huge loss. Jims too. Does this show that the theory that straight cut boxes give less losses due to less suggested side loadings,is infact bollox? or is this as a result that with more torque, you expect to have larger mechanical losses at the upper end?

I tend to use an assumption that a Transverse a series gearbox has losses aproximated to 24hp, some may be less some may be more, but if you don't know, its a good figure to start with.

My rear drive car, at the last RR session, was shown to have about the same losses as Sprocket gives for the transverse transmission.Direct drive ( on fourth gear in the 5 speed box),3.7 axle ratio, 6600rpm max.
I,m told 22% is a ball park figure for most transmissions.

I thought the perccentage theory on losses was a bit of an old wives tale ?
If an engine has a flywheel figure of 100hp & loses 22% in the tansmission, it's lost 22hp right ? If that same engine then makes 200hp it's surely not going to lose 22% again as that would be 44hp lost ....
I know the losses may increase a little with more torque going through the transmission, but surely not to that degree ?

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i thought gearbox losses was calculated on rundown, after dipping the clutch at the top of the revs on a pull, making the power output of the engine irrelevant?

Yes i moved to the darkside

Instagram @jdm_brett

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Those graphs are very interesting cheers robert, i was thinking it would probably be around the 20-25 mark for losses

no probs rr , when i tested my car with a helical box , i got 24 bhp losses ,so about 7bhp more than straight cut ,but remember ,that was on a different rolling road ..but also one that used the coast down method as well.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

the run down figure also gets confused with different wheel tyre combinations and tyre pressures so its difficult to compare

well genrally i have fund that around 25 hp ish seems to be the norm on a 2.9 diff, any higher then look at tyre pressure and brakes and camber angles

always looking for them bigger bunches of bannanas

The logic of the percentage idea is now clearly skewed, so I will avoid the RR operator who gave me that info originally - I continue to live and learn,albeit slowly and imperfectly.

When the Don first went on the rollers at Dave Walkers it made 220 engine hp ,this ended up at 178 atw at the time,

carl

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Back in 2002 with the JKD 5 speeder it was 26.5bhp loss. With the KAD dogbox loss was 20.5bhp only.

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

power at wheels from the rr shootout .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I like this site:
http://www.pumaracing.co.uk/trans.htm

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

http://home.earthlink.net/~spchurch/church...sting/id12.html