fwhp and rwhp in relation to other cars

[rx7veilside]

have notice people refering to their rx7s power as flywheel power and then rwhp.now i understand the difference ie transmission loss etc.but when other cars have their power figure published they only refer to the one figure ie my old p1 was 280bhp standard and 350bhp when modded wld these be wheel hp or flywheel.a standard rx7 is 280bhp is this fwhp or rwhp.

[MikeLMR]

manufacturers always (I think) state flywheel horsepower

[20B_boy]

Generally I would say flywheel. At G-force Kevin\'s \'99 which has a factory quoted 265hp made some thing like 215ish at the wheels, Ben\'s \'99 made simliar (bit less). Its this \'control\' 18% drive train loss that u see people on here equate flywheel power from G-Force or CPL wheel power numbers from...

[Dan Norton]

Yes manufacturers state flywheel figures.....its better for sales for a start, especially when selling performance cars.

My old crx 16v si(dohc non vtec model) made 118 at the wheels, which was around 151 at the fly.

Pretty pleased with that as it was 26 bhp over standard.


Dan!!

[bill shurvinton]

Don\'t hold any sway on a fixed % for transmission loss. Its less accurate than a butt dyno. Plus losses change with RPM, so you might only have 10% at 5500PRM, but 25% at 7500RPM (and I have graphs to  back this up). Most of these losses are at the tyre interface.

For a rolling road you really have to do a coastdown for the numbers to be of any use at all. No coastdown? You might as well stick a finger in the air to get an idea of your real power curve.

An example: Last year Dave Walker wanted to dyno a racing ferrari (saloon not F1). This put out more power than his SUN RAM could take. So he sat 4 people on the tailgate. The additional weight increased the losses to the point where he could take a power run on a dyno that could only go to 240HP. The coastdown then measured these losses, added them back and gave a figure for flywheel HP.

So next time someone quotes a % transmission loss

a) ask them to prove it
b) ask them what putting 10PSI more in the rear tyres would do to the measured HP

If the dyno operator is quoting this % then I suggest you find another dyno to use.

[20B_boy]

Originally posted by bill shurvinton
If the dyno operator is quoting this % then I suggest you find another dyno to use.

At the first FDUK rolling road day at G-Force the above happened - Skippy suggested the 18% loss as a means to roughly translate wheel power to the engine; I didnt say it was right or wrong - personally I\'ve always presumed that losses would increase as power went up as the components that transmit the power from engine to tarmac are made to operate further outside of their \'designed\' operating parameters - I dunno whether thats the case, I\'m not pretending to know either! Nor am I kidding any one that a fixed loss is accurate.

To date I\'ve been to the same dyno each time, with the same car, with the same rubber, running the same pressures; if the numbers at the wheels are bigger than last time its good Then the car goes to the drag strip and runs quicker which I guess confirms the increase is there. End of.

[Archbish]

I\'m still a bit lost at the REAR wheel horsepower title.  What is everyones FRONT wheel horsepower...??

[fro]

rwhp is Road wheel horse power afaik

[maximtaylor]

omg, are FD\'s front wheel drive?

That may explain my slow 1/4 mile times then - put the soft tyres on the wrong end - back to the drawing board :mad:

Originally posted by Archbish
I\'m still a bit lost at the REAR wheel horsepower title.  What is everyones FRONT wheel horsepower...??

See you at Trax OJ??

Max

[Archbish]

Yup, (at the mo) - although my other half will be meeting the President of France, so won\'t be about I\'m afraid (which means I may have a spare ticket available...).  

It should be a laugh tho!! *grin*

Back to the HP thing - surely it should be:

FHP - as flywheel is one word
THP - as Tyre Horse Power cos it\'s rear wheel drive, so shouldn\'t really need to differentiate
HHP - Hub Horse Power
BHP - Bling Horse Power due to the increases in power due to chrome bits, spoilers, stickers and neons

Just a thought...

[Carl]

Originally posted by Archbish
Yup, (at the mo) - although my other half will be meeting the President of France, so won\'t be about I\'m afraid (which means I may have a spare ticket available...).  

It should be a laugh tho!! *grin*

Back to the HP thing - surely it should be:

FHP - as flywheel is one word
THP - as Tyre Horse Power cos it\'s rear wheel drive, so shouldn\'t really need to differentiate
HHP - Hub Horse Power
BHP - Bling Horse Power due to the increases in power due to chrome bits, spoilers, stickers and neons

Just a thought...

You forgot one other important one!Perhaps the one with most meaning for most people..............

PHP.

Pubtalk horse power!

Kind regards
Carl

[BlitzBoy]

what about HUB Dynos are those different again?

[Donato]

Originally posted by Carl
You forgot one other important one!Perhaps the one with most meaning for most people..............

PHP.

Pubtalk horse power!

Kind regards
Carl

Number of pints consumed x quantity of audience = PHP!

 

[20B_boy]

Oh for the good ol days gone by, when we all thought we had 350 at the treads with a catback, an intercooler and an ECU...

Damn that fateful FDUK rolling road day; we were such a happier crowd before hand