Tranmission Losses
Discussion
GAZBOY!MrFlibbles said:
Hey gents - anyone know what is the % transmission loss on a Mr2 Turbo?
A guy on another forum reckons he's running 309bhp at the fly with just a decat and a air filter, on standard boost....
Standard boost is 7 psi...equates to 200 bhp on the 3sgte.
Ps, if you wanna pull his leg and separate fact from fiction, ask him what rpm his 309 occurs at, then ask how much torque it makes and also what revs that figure occurs at....then see if the two match or are fairly close.
If the two numbers are miles out then its bar-room bullshit...
>> Edited by deltafox on Friday 17th June 21:10
IIRC standard boost on the rev 1 + 2 cars is 11psi giving a health 225 bhp. on the rev 3+ it's 13psi which is a rather lovely 245bhp 
Gazboy said:
Gazboy said:
It loses 13% through the tranny according to G-Force, iirc.
Too low Gaz, if it was a 'shootout' flywheel estimation of thier dyno then it would have been about 17-18%. 'shootout' is the only way our dyno's can give flywheel estimations.
It's on their website somewhere Charlie.
Regarding tranny losses, surely a gearbox, clutch, diffs & tyres use the same amount of power? How could a Hyundai Getz only need 11bhp to run it's transmision, vs 55bhp for a 6 spd Supra? Although I concede that the Supra's tranny is a lot heavier than the Getz. Maybe better example would be comparing a Lotus Esprit S4 (260bhp) vs a V8TT (350bhp), which used the same tranny iirc. ??????
Losses are'nt fixed.. they increase with the power of the engine. The tyres alone take 10%.
vixpy1 said:
Losses are'nt fixed.. they increase with the power of the engine.
That made me wonder...say you have 'Car X' running 200bhp, with a certain amount of transmission loss.
Are you saying that if you take the same car, but whack up the boost and get 300bhp, the losses go up as well? (just before the engine melts
) Shirley the tranny still requires the same amount of power to make it move?
wedgepilot said:
Losses are'nt fixed.. they increase with the power of the engine.
That made me wonder...say you have 'Car X' running 200bhp, with a certain amount of transmission loss.
Are you saying that if you take the same car, but whack up the boost and get 300bhp, the losses go up as well? (just before the engine melts
Shirley the tranny still requires the same amount of power to make it move?
It is a contentious issue, and one which is fiercely debated inside the industry, but yes. Certain parts in the transmission will absorb a fixed hp, but other parts, and mainly the tyres.. absorb more power as you feed more power into the transmission.
Have a look at:
www.pumaracing.co.uk/power3.htm
I think the loss percentages it quotes are a little pessamistic, but it is a good technical overview of what happens.
The simple answer is that you CANNOT 'measure' or 'calculate' flywheel figs using a chassis dyno. It is ALWAYS and estimate!
The power at the wheels is what the dyno measures, nothing more!
Gazboy said:
Is this why a lot of 'RR's' have hub dyno's?
It is one of the reasons some RR's use to justify thier hub dyno's.
they still have the transmission losses, just not the tyres. Losses tend to be in the region of 7 - 10 % on hub dynos.
The other reason is that you prevent tyre slip, but quite frankly, unless your running 1000bhp skylines all day, this is not an issue.
The are lots more problems with them, but i would say that.. cos I have a different type of dyno
deltafox said:
Hey gents - anyone know what is the % transmission loss on a Mr2 Turbo?
A guy on another forum reckons he's running 309bhp at the fly with just a decat and a air filter, on standard boost....
Standard boost is 7 psi...equates to 200 bhp on the 3sgte.
Ps, if you wanna pull his leg and separate fact from fiction, ask him what rpm his 309 occurs at, then ask how much torque it makes and also what revs that figure occurs at....then see if the two match or are fairly close.
If the two numbers are miles out then its bar-room bullshit...
Like an F1 car with 300lb/ft and 880bhp then
m12_nathan said:
deltafox said:
MrFlibbles said:
Hey gents - anyone know what is the % transmission loss on a Mr2 Turbo?
A guy on another forum reckons he's running 309bhp at the fly with just a decat and a air filter, on standard boost....
Standard boost is 7 psi...equates to 200 bhp on the 3sgte.
Ps, if you wanna pull his leg and separate fact from fiction, ask him what rpm his 309 occurs at, then ask how much torque it makes and also what revs that figure occurs at....then see if the two match or are fairly close.
If the two numbers are miles out then its bar-room bullshit...
Like an F1 car with 300lb/ft and 880bhp then
if i remember correctly most F1 cars make most torque around 300 ft.lb @ 14500 rpm. so,
300x14500/5252 = 828hp, pretty close id say.
>> Edited by Silverstone on Sunday 26th June 16:18
Just for informations sake, a chap I once knew from mr2oc, called Graham Day had a stock rev 3, unichipped it, with a mongoose exhaust, and maybe a filter, and was RR'd at just over 300 bhp. That was done at Owen Developments near Aylesbry.
By the way, aren't stock 3s-gte's 225-245 bhp depending on which rev you go for? Where do you get 200 from? The US turbo's were 200 bhp, but not sure if they were 3sgte's, or a variation of some other toyota engine?
By the way, aren't stock 3s-gte's 225-245 bhp depending on which rev you go for? Where do you get 200 from? The US turbo's were 200 bhp, but not sure if they were 3sgte's, or a variation of some other toyota engine?
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