Transmission Power Losses

[R2D2]

Some of you will know that I'm studying tuning the M271 Engine from C180k spec to C230k spec.

The BIG question is how much are transmission losses on an auto. My car measured 141bhp at the wheels which equals what exactly at the flywheel?

Flywheel HP -Transmission Losses = HP at the wheel

193bhp -27% = 141bhp at the wheels

185bhp -24% = 141bhp at the wheels

180bhp -21.5% = 141

175bhp -19.5% = 141

170bhp -17% =141

So what are the transmission losses and can anyone offer any evidence to support their theory.

Thanks in advance.

EDIT: I've just checked the graph and it peaks at 104kw if that helps anyone!

 

[GrahamC230K]

What you need is a stock w203 C230K on a dyno to get the RWBHP!

 

[R2D2]

True that would help! Failing that ..........


BTW. I just found a conversion table and 104 kw= 142.48 bhp at the wheels.

 

[R2D2]

This would incicate 21% losses
http://www.mbclub.co.uk/forums/showthread.php?t=23527&page=2

 

[andy_k]

link

Andy

 

[R2D2]

Interesting link, its a bit complicated isn't. I've seen estimates between 25% and 18% for a Mercedes Auto. What do you reckon Andy?

 

[bolide]

Depends if the torque convertor's locked up or not. If the TC only locks up in 4th, and you run it on the rolling road in 3rd, then it's all a guesstimate

I think the only way to measure is before & after runs and to look at the gains (or losses!)

Also with the kind of tuning you're doing I suspect the torque gains at lower rpms and the shape of the torque curve are going to be more important to you than outright power gains. Otherwise you wouldn't be starting with a C180...

Nick Froome
www.w124.co.uk

 

[fuzzer]

your crazy dude but entertaining all the same in the nicest possible way lol

 

[R2D2]

your crazy dude but entertaining all the same in the nicest possible way lol

Well a boys gotta know these things!!! The quoted power figures are meaningless without knowing the transmission losses. I think it was Graham who said in another dyno thread at the end of the day only power at the wheels counts because thats what you can measure!

 

[vixpy1]

I've found 25% is a good guestimate for the Mercedes Autos.

you should really work at the before and after wheel figs though..

 

[R2D2]

I've found 25% is a good guestimate for the Mercedes Autos.

you should really work at the before and after wheel figs though..

So does that mean my car has 190bhp already because 190 -25% = 142.5bhp at the wheels, or am I being thick?

 

[vixpy1]

So does that mean my car has 190bhp already because 190 -25% = 142.5bhp at the wheels, or am I being thick?

I should clarify my point i think..

I've found 25% to be a good guesstimate...'on the Dyno Dynamics Dynos which we use'

if it was done on an American dyno the loss will be smaller because they over read at the wheels..

 

[R2D2]

It was done by Sanspeed, I'll contact them and find out what type it is. Thanks for your help. Maybe I should get you to do it as well. Do you do ECU reprogramming?

 

[R2D2]

Still awaiting the answer from Sanspeed but meanwhile I have ordered a G tech.

 

[GrahamC230K]

...... meanwhile I have ordered a G tech.

Oooh which one??
:bannana:

 

[R2D2]

What 'ave I done. Is the start of a G tech GTG. G tech Pro, does 0-60, 60-0, 1/4 mile time, 1/4 mile speed, cornering G force and best of all actual bhp. It knows the timing, speed and acceleration, you just type in the cars weight and it tells you what power you have in order provide the performance it has measured.

Wish it would come!!!

 

[R2D2]

Having had this conversation with many people and also on other forums. I reckon that manual mercs lose about 16-18% and autos 22-25%.

This means that assuming the dyno that produced the measured 143bhp at the wheels for my car is correct (and remember the stop watch concurs) then my car must be producing 180-185bhp without modding it. Not bad for a c180 that is only supposed to produce 143 at the crank.

Hopefully my g tech will arrive this week and then I can measure the bhp more accurately and get performance figures accurate to the 1/100th of a second.

 

[R2D2]

Somebody asked what type of dyno I had used. Sanspeed have just replied with "Its a Bosch 2WD inertia chassis dynamometer." For those who know about these things is that good bad or indifferent?

 

[GrahamC230K]

Bad in terms of accuracy.......

http://www.g-force-motorsport.co.uk/rolling.html

http://www.g-force-motorsport.co.uk/inertiameasurement.html

 

[R2D2]

hmmmmm. Thanks for the link.