Rwkw Vs 4wkw

[Antimatter]

Guys - here is a question that has rattled around my head for some time (be nice to me - newb)

what is the difference (in particular on a gtr) between rwkw and 4wkw. Is there much in it? If so is there generally a recognised formula to convert the two i.e. RWKW x 0.? = 4WKW.

Futhermore - once you have a KW at the wheels figure - is there a similar conversion to KW at the flywheel?

love to get some clarity on this subject - Thanks!

[mad082]

very rough calculation for rwkw to flywheel kw is convert your rwkw to hp, and the rwhp is close to flywheel kw.... works roughly for stock cars, but is by no means accurate.

[shrike_73]

rwkw to flywheel kw is about 20% difference.

rwkw X 20% should give you flywheel KW.

Ive read its about 17-20% difference depending on the car but i think 20% is about right.

Unsure about 4wkw ?

[Bo0oSt]

umm not to sure what u mean by the rwkw to the awkw but the way i understand is rwkw is basically how mani kw ur puttin out at the rears where as awkw is wht ur puttin at all 4 wheels... usualy a awd drive train u loose about 40percent of the power or so i was told about WRXs so im guessin if u got a GTR ur loosin a bit of power through the awd system just by havin that draivetrain where as a rear wheel drive would only loose like 20 percent due to it only being rwd and much lighter....

sorry man i dont really know wht ur askin lol

but i gave it a go

[krzysiu]

If i remember correctly the Ice performance GT-R made 617kw in rear wheel drive and 593kw in All Wheel Drive. 24kw loss by giving power to the front wheels

Edited May 26, 2006 by krzysiu

[Craved]

rwkw to flywheel kw is about 20% difference.

rwkw X 20% should give you flywheel KW.

Ive read its about 17-20% difference depending on the car but i think 20% is about right.

Unsure about 4wkw ?

im pretty sure Sydneykid stated a 60kw loss through skyline drivetrain in RWD .. so thats 80HP.

awkw to rwkw no idea lol

[mazgtr]

HPI/ZOOM magazine did this with there silver R32 GTR running twin TD06'S. There tested the car on both a 4wd and rwd dyno, in both 4wd and rwd mode.

I think the difference was about 4% less with 4wd on a GTR.

Rwd to engine is about 80%. i:e your car makes 80kw at the rear wheels, its makeing about 100kw at the engine.

On something like a WRX thats full time 4wd its about 35%. So a STI with 206kw at the engine will make about 130kw-140kw at the wheels.

The GTR isnt fulltime 4wd, so the drivetrain losses arent the same as an Evo or Wrx.

Id say 20% loss from engine to wheels in rear wheel figures.

And 25% loss from engine to wheels in four wheel figures.

So if you have a 300KW @ THE ENGINE GTR,

In theory it would make 240KW at the rear wheels.

And 225KW at all four wheels....

Cheers.

[Guest Mashrock]

so with a bit of luck i am making about 350kw at all 4's

*give or take about 25-30kw.

f**k i need to shut up and just get a dyno done

[blind_elk]

As a guide, I had my RB20DET GTS4 run on a dyno that claimed to be able to calculate fwkw from rwkw.

The results:

AwkW - 115

RwkW - 145

FwkW - 175

[R31Nismoid]

There is very little difference 4WD --> 2WD in the GTR etc.

The difference is minimal enough not to worry about

[Denver]

Before everyone gets way off the mark here..

Drive train losses remain static, they do not change, give or take a hp or two, due to better oils etc..

Don't follow the % rule, its wrong, and % losses calculated by coast down calcualtions are incorrect..

best way to explain this is like so, roughly a RWD car will loose about 25ish hp, as your only driving a couple of gears in the box, at 1 to 1 ratio, and the diff gears, so, if your car is making 200hp to begin with, you could say roughly, your making is 230 at the fly wheel, if you then mod the motor, but alter nothing in the driveline, and it now makes 400 at the wheels, its only going to make 430 at the fly wheel, not 460 for example if you where to use the % rule..

Automatic, and 4wd losses are higher, due to the nature in which they operate, but again the figures remain pretty constant, better oils, or driveline components alter this, but again the figure doesn't really move a heck of a lot, it remainds pretty constant, unless of course something is broken, and there is greater friction..

the 60kw figure quoted before im pretty sure is the loss you'll see from a gt-r in 4wd mode, as 60kw is a LOT of power loss for a manual RWD car..

also, a large portion of the driveline loss you see on rolling road dynos, is from the tyres, stuff like over/under inflation of the tyres, weight in the car, and tyre wrap around on the roller affect the figures, so if you dyno your car one day with the tyres at 36psi, then a week later they've gone down to 20psi, you will see less power, as the tyre is wraping around the roller more, more wrap, more friction, more friction the more power needed to over come it, so a lower reading will be seen, hub dynos eliminate this, which is why you will always see a slighly higher reading, and in some cases a bigger reading by comparision to a roller, as you eliminate wheel spin on the roller..

Edited May 28, 2006 by Denver

[Swiper the Fox]

We ran our car on Mainline Dynolog dyno in front of hundreds of people at last years Autosalon Final Battle in both 2 wheel and 4 wheel modes.

The difference

1 kilowatt

[paulr33]

slightly offtopic but when you dyno a GTR does it just drop straight to 50;50 split once it picks up the rears slipping heaps (or at least it thinks they are) or is more like a 30;70 split.

was that done with a torque split controller? or just lettting it go by itself?

[Turbine]

Their is just too many variables to figure with that question I think.

Manual trans - Auto trans

High stall converters - stock converters

Final drive ratios - drive train weight

Temperature - oil used

RPM

It goes on

I like to think that what ever power you have on the ground, that you use all of it.

[Guest Mashrock]

yeah what i was thinking with the gtr. dosnt the fronts only kick in if there is sideways force on the g sensor and loss of traction noticed?

[allblitz]

So i guess my mate being told that his 211awkw gtr would be equivalent to 261rwkw is a load of bull tish

[R31Nismoid]

definately. thats about 60.123 rwkw of inflation

[RB30-POWER]

slightly offtopic but when you dyno a GTR does it just drop straight to 50;50 split once it picks up the rears slipping heaps (or at least it thinks they are) or is more like a 30;70 split.

was that done with a torque split controller? or just lettting it go by itself?

not entirely answering your question but I have read that a GTR will never acheive a 50/50 split, even though it may show it on the guage, the front will always slip some compared to the rear.

[nfi]

slightly offtopic but when you dyno a GTR does it just drop straight to 50;50 split once it picks up the rears slipping heaps (or at least it thinks they are) or is more like a 30;70 split.

was that done with a torque split controller? or just lettting it go by itself?

Not being an expert but having driven one on a number of occasions, GTR's distribute torque to the front wheels just by nailing it. Infact it doesn't have to floored or breaking traction. Any decent gforces even in a straight line will cause the guage to fly up to 50%. You can even be turning a corner with no throttle and it will start to distribute talk to the front which helps keep it stable.

[T04GTR]

the guage is for KG/METRES OF TORQUE. not a percentage.

sooooo,. if you were to mesure the torque somehow at the front tailshaft with a torque wrench it could suply up to 50kg/m of torque before slipping.

its hard to explain. but its esentally a auto transmission that spends it life slipping. graduly feeding power to the front via a multi plate wet clutch

but. the power loss through 2wd/4wd. would be a good indication of how eficantly the transfercase is and how slippery the front dif oil is. also front wheel bearing drag.

so if anyone wants to do a back to back test with old diff oil and tranfercase oil.

then replace it all with new stuff and compare the differance id be interested at the results