Drivetrain losses Discussion thread..

[CLuTZ]

ok what about opinions from people running simular set ups?
Is the fuel issue toitally ridiculous? Or acheivable?

Absolutely achievable. Here's the dyno chart of my last Galant with a chipped ECU:

the only reason why it didnt make more power after 5250rpm, was because the chip was far too rich. If you had a similar chip, and then could lean it out abit up high- you would see a far more linear curve: more power, for longer.




dre

 

[CLuTZ]

I'm curious as to how everyone is measuring power at the crank

 

[to4garret]

basically an educated guess, normally based on airflow.

 

[iluszn]

how much is drive train loss ? difference between front/rear/awd??? i read some places and they say in a manual its some 17 - 20% and more in an auto. but nothing mentions the different configurations fwd/rwd/awd.....

 

[iluszn]

Dre. Any ideas on drivetrain loss in the VR4/GSR?? I cant find anything.. ill keep looking though. just interested thats all

 

[D3bb4]

"4WD

Drivetrain losses are about 35% - 40% odd."

"FWD

Drivetrain losses are about 17% - 22% at an educated guess."

Edit: was taken from FWD vs RWD vs 4WD By Bill Sherwood

 

[NZVR4]

"4WD

Drivetrain losses are about 35% - 40% odd."

"FWD

Drivetrain losses are about 17% - 22% at an educated guess."

Edit: was taken from FWD vs RWD vs 4WD By Bill Sherwood

is power lost through 4wd constant? for example lets say the power loss is 40% and you have a standard 205kw evo so we know that 40% will be lost through driveline giving us a power reading at the wheels what i want to know is if you have a 1000hp evo is the driveline loss 40% of that 1000hp or or do the drivelines have a fixed power loss no matter what power you run through them,i Have always believed that say hypotheticly a standard evo will loose 30kw through the driveline so a 1000hp evo would still only loose that 30kw yet a lot of people say that it looses 40% of the power regardless of what it is

i cant see how that works as surely the driveline is a given measurement off loss,how would the amount of power running through it affect how much power it robs other than heat?

 

[iluszn]

NZVR4 - I have read and read and read all sorts of forums and your question is the same question over and over and over again. And no one can answer it

Only thing they say is. Get a stock car, dyno, modify it dyno, modify dyno and so on

I guess the only way to TRULY see what it is and have it calculated is

Engine dyno
Put in car
Hub/wheel dyno

calculate loss

Do this again with modifications to bring up power considerably and do it again. I dont think anyone has done this or noted it down. but 40% power loss is HHUUUGGGGEEEE...

imagine that.. 206kw stock @ flywheel makes it 123.6kw @ wheels.
So in theory.
400kw @ fly wheel makes it 240kw @ wheels. thats a 160kw loss to drive train inefficiency.

maybe the % changes or lowers as you make more power? ie, standard power = 40% loss, double standard and get 30% loss? just speculating. not a subject matter expert.

 

[SIVART]

I think its about 25% for a 4wd car, it would depend on the ratio of the diffs to I guess

my evo is 195kw at the flywheel, - 25% = 146wkw, which would be about right for a standard evo???? I might be wrong though

 

[3zercrowd]

I think its about 25% for a 4wd car, it would depend on the ratio of the diffs to I guess

my evo is 195kw at the flywheel, - 25% = 146wkw, which would be about right for a standard evo???? I might be wrong though

Spot on!

Graeme's (80ove) Evo8 which has 195kw stock (OZ del) had a few mods (exhaust etc.) but recorded 138.2kWatw. Now up to 200+
195-29%=138kw.

*Edit* may of been Ricks Evo1 Rs tha had 146kw:?

 

[D3bb4]

I think that mechanical resistance would be the same, but it's probably a multiple of that. Also add the friction on top, and would probably calculate the losses.

so it's partly fixed, partly not - it'd be the sum of a fixed and non-fixed losses.

make sense? :lol:

 

[iluszn]

LOL makes sense and not at the same time :?

I think it will depend on
Clutch
Diffs
Gear types
Lubricants
etc
etc
etc

alot of factors. But, There just is no definite answer.

 

[lozza]

i read an interesting commentary from a powertrain design engineer who knows the inside and out of these losses and he said they are around:

14% FWD man
16% RWD man
21% RWD auto
25% AWD man

these losses come from man trans (4%), auto (10%), driveshaft (1%), diff (5%), axles and hubs (2%), brake drag (5%)

other things that effect these are altering ride height (axle geometry) and use of low friction lubricants

 

[Jayz-1]

Now most of the time power measured at the wheels compared to power measured on an engine dyno is different not due to drivetrain loss, but heat, if the engine isnt stuck in an engine bay, it can get rid of the heat easier.
So people put there car on an engine dyno and make 100kw, then put it in the car and at the wheels they make 50kw, thats not 50% drivetrain loss, its actually making less power due to the heat in the engine bay then the drivetrain loss.
From what i have been told drivetrain loss isnt that much different between FWD / 4WD / RWD, nor can you exactly put a percentage on it (although its easier to refer to it as a fixed percentage), as if you think about it, 25% drivetrainloss in a 500kw car is 125kw loss.
You would need a massive radiator to keep the tranny cool if it was mechanically that inefficiant to lose that much power...

I would say 10% FWD, 12% RWD and 15% AWD MAX (since people like to calculate it in a percentage)

The above has been told to me by a very very smart man, and although its different to what most people say, i believe this is accurate.

Thank you
Jason

 

[EVO-00X]

I remember the basic theory of a stock early EVO with 205kw at flywheel is pulling approx 145kw at all 4 wheels. Thats a 60kw loss in stock form, and its almost the exact same figures for a WRX. I dont think its % based at all, and the 60kw loss will happen no matter how much power you have. I've always gone by the assumption that an AWD EVO will lose between 60-70kw going through all four at any given power figure (once you're up and running it doesnt take as much to keep the rotating assemblies moving so percentages doesnt even come into it), and FWD cars will lose somewhere around 20-30kw.

 

[olly]

when you read up on the power (kw) of cars, most of the time it is measured at the fly.
So if you just run a stock car on the dyno, it would tell you the power at the wheels and you could just do some simple calculations

Eg.

Lancer CC GSR
141kW @ 6000 RPM at the fly
I think I've read they pull around 110-115kw atw stock? (correct me)

so 115/141 x 100 = 81.5% so its around a 20% loss through drive train. I'm sure if you did this for the other evo's it would be very similar.

 

[coop1er]

Hey there. This is a subject that I find interesting and have some experience in, so I will give you some of my thoughts. At my last work, I used to operate a 4wd dyno dynamics dyno and I tested a lot of different vehicles from Skylines to 550hp Mack trucks. It is my belief that dyno's when operated correctly and calibrated, are quite accurate as the results on our dyno were repeatable and within a few percent of other dyno dynamics dynos.

There is a case for heat as a cause of lower power figures as I recall that some vehicles would always make the most power on there first run. To counter this, some engines would make more power the warmer they got(without getting too hot that is). In any case it was only a relatively small percentage.

Most drivetrain loss comes from the combination of windage and gear losses. Windage is the resistance to the rotating components caused by the oil and gear losses(no doubt not the correct term) is the loss of power due to the fact that gears are trying to rotate apart from one another. But the fact that they cannot makes them heat up and heat is also generated in the bearings and the heat is a lost form of energy.

As for how much power is lost through a drivetrain, well it depends. For example a 100kw rwd might lose 33% but the same drivetrain with 300kw probably will lose considerably less than 33%.

Some examples:
One type of vehicle I used to dyno made 96kw at the flywheel (factory specs) but would make 56-60kw at the wheels in rwd on the dyno and the 4wd version with the same engine would make 45-50kw.
A prime mover with 500hp at the engine would make 400hp (80%) at the wheels with the bogie 4wd locked.

Hopefully some of this has been interesting or helpful.

 

[iluszn]

We have all spoken about KW and HP from fly wheel to wheels.

However, I have not brought up Torque. I guess if your making more torque that would help lessen that % of loss through the drive train? Just a theory but you never know.

 

[EVO-00X]

At the end of the day the power figure at the wheels and torque readings associated with it are easily obtainable via a dyno and all that we have to compare by. There are just too many opinions and variables to consider when trying to ascertain the power at the flywheel unless you know somebody who can measure it [properly].

 

[NZVR4]

here's something else to add into the mix,quite some time ago a gtr skyline was run in both rwd and 4wd on the same dyno and recorded the same power reading which would indicate the same amount of driveline loss,this was an r32gtr which i always thought ran rwd untill the attessa sensed slippage in the wheels and would engage the front wheels,so am i correct in thinking that a gtr would only spin the rear wheels initialy on a dyno hence the power readings being the same? i have never been at a dyno of a gtr so cant confirm for myself

I have driven an r32 gtr in the wet for myself and when i threw it sideways i could feel the front wheels engage and pull it back into line without my effort or input,im not really a skyline person so thats all i have based my theory on-is this correct or am i way off mark?