transmission loss

[turbo]

hi there what is the transmission loss on a mr2turbo have been told 15% ,18% and 21% does anyone no the real figure please

[splashnatz]

there isn't a "one size fits all" percentage figure for transmission losses, it varies from car to car.

[raptor95GTS]

i'd guess around 25-30HP max. Anything much higher would boil the oil and melt the box but some folks have had 75+tranny loses.

[CM1GT]

from what i've heard, read and been told by dyno operators its about 15% at the hubs and 18% at the wheels, although it will vary from car to car and condition, saw an article in banzai last month that claimed 25% transmission loss on a front engine front drive yaris!

[RobCrezz]

Easyest way is just always use the Wheel HP figure. Unless you have your engine out of the car on a proper engine dyno, the Flywheel figure is useless.

[roadwolf]

How can the transmission loss be measured in percentage, just because your engine turns out more power the transmission loss doesn't change. The average loss is 15 BHP on front wheel drives and 17BHP on rear wheel drives. For MR2 read front wheel drive.

[raptor95GTS]

if you increase the torque of the input to the gears there will be a slight rise in energy lost through meshing but aye it's not going to be anything huge

[jimGTS]

How can the transmission loss be measured in percentage, just because your engine turns out more power the transmission loss doesn't change. The average loss is 15 BHP on front wheel drives and 17BHP on rear wheel drives. For MR2 read front wheel drive.

maybe on cars pushing 80-100atw like your modded corsas and saxos, but not on higher hp cars....

losses are generally around the 17% area....

25-35hp on the NA, and generally 35-45hp on mildly modded turbos....

have seen this on countless dyno days ive been to.

[raptor95GTS]

Just because you've seen the same flywheel figures guesstimated the same way countless times on the same type of equipment doesn't make it in any way factual.

And so the arguement continues..................

[skinthespin]

I will add some engineering if I may!

You are all correct! Some parts of the transmission have constant energy los, some (gears meshing as someone has said) lose more energy the more power they are asked to transmit, so you get some constant losses and some percentage losses, then on top of that you have manufacturing differences between cars, different oils etc.

thats without factoring in the minefield that is the inaccuracy in the rolling road, the differences caused by different tyres and atmospheric conditions, we have a very expensive dyno here but the same bike can read differently depending on the day.

there is no single figure for losses but if you pick a fairly similar car to you in terms of power and tyres you wont be far wrong!

HTH

[jimGTS]

Just because you've seen the same flywheel figures guesstimated the same way countless times on the same type of equipment doesn't make it in any way factual.

And so the arguement continues..................

lol, maybe so....

"factual" on them dynos anyway then..

[roadwolf]

Extract from dynamometer-info.co.uk



Basically its NOT ever a percentage! Or close to one and it never can be.

Because if I were to take for e.g. 2 stock old GSXR Suzuki race rep 750 bikes, both would give me say 100rear wheel HP in 3rd 4th and maybe 2 less in 5th and 6th.
The two less are simply aerodynamic losses on the wheel and tyre due to the 170mph wheel speeds...

Now, add 50bhp of nitrous to the 2nd bike.
Dyno it and it makes almost 50 BHP extra! There are NO EXTRA losses other than one or two hp, in thrust bearings and gear faces etc.

Now, add another 2nd 50 BHP of nitrous to the 2nd bike in the form of another stage - now it makes 100 BHP more.
If it were a percentage then the second kit would show a smaller power increase! But it doesn't of course.

I have done this sort of thing so many times and always with the same result.
Once the motor has overcome the frictional losses that are simply speed related, nothing else seems to change much.

Now the manufacturer claimed 112 BHP at the motor, so 100bhp represents 12hp losses. Or about 12 "percent" if you prefer!
But the second bike with the extra power has only 5 or 6 percent losses now! if you were expressing it as a percentage!

Now take the "touring" version of the same bike engine with its smaller carbs, low compression, smaller valves, softer cams etc.
Manufacturers engine claims are now 70bhp. But on the dyno we see only 58 or so...
So its losing almost the same 12bhp.. But now its a whopping 17.4 percent transmission losses! But its the SAME transmission...

So if it really WAS a percentage fitting the same nitrous systems to this bike would give LESS power!
But guess what! 100 extra total would be seen again... No 17.xx percent loss....
Which of course is correct because it uses the same transmission and wheel and tyre..

If you measure the power required to "push" the transmission/wheel as far as the clutch at the same road speeds in the same gear it will say the same thing (12bhp). The losses on both bikes will be identical 12hp (at max - speed not power dependant) required to overcome the rolling resistance of the parts, tyre, chain, oil etc.

This loss isn't a constant but increases and changes with speed and gear ratio.
There is also a small element of this that increases with torque, but at least on bikes transmissions this is pretty small...

Hope your head doesn't explode!


Burgerman




Another reply!!!

To: [email protected]
Sent: Saturday, May 22, 2004 10:02 PM
Subject: Re: email from the Dyno Information pages


Thanks for the reply. I am talking car. 267bhp measured at the wheels. Roller guy reckoned 30% loss on fly wheel BHP any thoughts
Cheers Chris

One third of your power (approx) is 89bhp!

If you REALLY lost 89 BHP as "waste" power it would show up as heat!
Into the oil and castings...

To convert this to watts multiply by 760...
Result = 67540 watts apparently went as heat!!! That would run a small town...
Your transmission would have melted, the oil boiled away in a massive cloud very quickly...




Burgerman.

[jimGTS]

imo that proves nothing....

50 shot of nos, how accurate are shots of nos?? there not, could be 45, could be 55...which on a bike, would greatly influence the percentage!


last part of that post, 30% is obviously rediculous, going by 15-17%, he should only see losses of 50-55hp, not 90hp...

i for one am not saying its a percentage only, higher the hp you go, you will see more losses, but not in a linear way with percentage...ie at 500atw, i seriously dout losses are 100hp! to get 600 at the fly.
but for mr2s around the 150-350hp area, 15-20% is pretty accurate on the dynos we all use.


if you seriously believe a 2wd car will only see losses of 15hp from 150hp to 1000hp, then that is up to you. but no dyno will EVER show losses of 15hp at 1000hp.
this is pretty much what your saying.

[raptor95GTS]

lol, love it. How cares about facts, lets go with the bigger figure.

[roadwolf]

I'm not saying that the loss will be the same from 150 to 1000. What I am saying is as you yourself have said about losses not being linear, is that saying cars lose 30% through the drive train cannot be true, as the more power you produce does not create a pro rata loss through the transmission.

[jimGTS]

noone should be stating losses of 30%! thats prob even a little high on 4x4 cars!

am sure noone on this site would say 30% thats for sure, lol.

im just saying, for 95% of the cars on here, with power ranges from 150-350, 15-18% is pretty bang on.

[EarL]

Spot on Jim.

Take two cars (independant of make). Both cars make 150bhp at the wheels. The transmission loss for both cars equates to somewhere in the region of 17% as they're both RWD (generally FWD cars suffer more loss, typically around 20%).

Modify one so it makes 500 at the wheels.

Does the higher power one have the same transmission losses as the stock one? No, of course not. It will lose a shed load more.

My old Rev1 made 266 bhp at the flywheel, which equated to 220 bhp at the wheels, which comes out at somewhere around 45bhp or 17% loss.

The same car when fully rebuilt, made 452 bhp at the flywheel, which equated to just over 380 at the wheels. That equates to around 72 bhp loss. The same (or near enough 17%).

EarL.

[raptor95GTS]

Spot on Jim.

Take two cars (independant of make). Both cars make 150bhp at the wheels. The transmission loss for both cars equates to somewhere in the region of 17% as they're both RWD (generally FWD cars suffer more loss, typically around 20%).

Modify one so it makes 500 at the wheels.

Does the higher power one have the same transmission losses as the stock one? No, of course not. It will lose a shed load more.

My old Rev1 made 266 bhp at the flywheel, which equated to 220 bhp at the wheels, which comes out at somewhere around 45bhp or 17% loss.

The same car when fully rebuilt, made 452 bhp at the flywheel, which equated to just over 380 at the wheels. That equates to around 72 bhp loss. The same (or near enough 17%).

EarL.

I thought FWD has less powertrain loss than RWD, I really am a dumb ass