wcryan

iTrader: (2)

I searched for about 30-40 minutes on google and it was either their calculations made no sense at all, or they would give you a formula that only a rocket scientist would be able to do.

Anyone know a real easy way, or even an estimated conversion method from RWHP to Flywheel HP?

06vLo

do you know your wheel hp to begin with?.. It seams most people that dyno stock, depending on your dyno used...345-353whp....If you divide 345 by 400 you get, .8625... which should represent drivetrain loss...so take the new wheel hp and divide it by .8625 and you should have your new crank hp number....

serik21

most cars dyno 325-330 stock, meaning about 18% loss so take your whp x by 1.18 that will be your ruff crank hp

wcryan

iTrader: (2)

Thanks guys!

Gary Wells

On the V2's, Ryan, an A6 auto tranny loses about 18% on the average and a M6 Manual tranny loses only about 12.5% on the average. These figures are calculated from the standard crank HP claim that the new cads, both V2 autos and manuals make 556 at the crank.

Domsz06

iTrader: (2)

and don't you have a bit of data too to support that?

vmapper

iTrader: (8)

Many dyno runs here... 0.81 is the drivetrain loss 05-V (19%)

JJSimon904

iTrader: (8)

It varies car to car of course but a safe range is 15%-20% on any car.

Gary Wells

Percentages are calculated for the loss from a set standard of 556 crankshaft HP to a RWHP dynoed value, all from Dynojet dynos through the country, and all from the A6 (6 speed automatic tranny). I did figure the average loss to be about 18.5% or there about. I have lost my figures for the M6 (manual 6 speed tranny) but if memory serves me correct, it was about 13% on the average. The 13% drivetrain loss figure for a manual tranny is about the same as those that I have seen over on the Corvette Forum, so I believe the 13% average to be correct for a Cad V1 & V2 manual tranny car. HTH


Cad bone stock RWHP & RWTQ (Auto) (Dynojet) Loss %’s:

rwhp---rwtq----loss -----locale------owner-------------date-------------dyno

429-----423-----22.9%-----ind-------wait4me--------12-10-08--------Dynojet
429-----430-----22.9%-----kali------garywells--------09-26-09--------Dynojet
436-----432-----21.6%-----uae------tagzo-------------12-17-09--------Dynojet
438-----432-----21.2%-----ohio-----drbuzz-----------??-??-09---------Dynojet
440-----427-----20.9%-----kali------cts-v-twin-------02-19-10--------Dynojet
442-----442-----20.5%-----kali------katmcrat--------07-20-09--------Dynojet
444-----442-----20.1%-----fla-------veelocity---------03-18-10--------Dynojet
447-----450-----19.6%-----ill--------prof---------------04-03-10--------Dynojet
454-----453-----18.4%-----????-----mafungu---------05-03-09--------Dynojet
457-----459-----17.8%-----flo-------lowet-------------10-07-09--------Dynojet
459-----459-----17.5%-----txs------nineball--------- 12-07-09--------Dynojet
459-----462-----17.5%-----ari------mike09v---------01-27-10--------Dynojet
460-----461-----17.2%-----nc-------heintzrac--------02-18-10--------Dynojet
463-----461-----16.7%-----ne-------intrvnton302---04-16-10--------Dynojet
465-----445-----16.4%-----txs------richeic77--------01-26-10--------Dynojet
466-----463-----16.2%-----nc-------heintzrac--------03-18-10--------Dynojet
471-----475-----15.3%-----txs------davegolder------01-07-09--------Dynojet
474-----481-----14.7%-----txs------jcampbell--------02-22-10--------Dynojet
488-----470-----12.2%-----can-----newcadman-----04-25-10--------Dynojet
Auto bone stock RWHP & RWTQ (Dynojet only) 19 samples:
RWHP Average: 8621/19= 453.74 average
RWTQ Average: 8567/19= 450.89 average
Verified 10-23-2010

JNR_Design

iTrader: (3)

As a GENERAL rule of thumb, you could use ~15% for manual transmission and ~20% for automatic transmission on a RWD vehicle (AWD may be more for instance) and there are so many factors involved, you can't just use a definite % across the board on all vehicles, so that's why I stressed 'general'.

Of course, the more efficient the transmission and drivetrain, the more power will go to the wheels, but to further confuse the issue, an engine by itself may make 'x' power, but adding accessories and A/C will obviously pull some HP...Superchargers can take a fair amount of power to run too...IIRC, a top fuel engine uses what was it like either 300 or 500 hp just to spin the compressor, yikes (but they are also 5-6 thousand hp engines). I'm pretty sure the net figures (post 1972) manufacturer's use account for basic accessories and would think a S/C too. Forgot when it was, but relatively recently, they changed the testing of the engines too, but I'd have to look for the details on what it affected.

Finally, certain viscosity oils and condition, carbon buildup, dirty injectors/filters and so on will affect whp, as will manufacturing tolerances (you could tak 100 mass produced engines from GM (or any manuf.) let's say that are identical on parts and on paper and some will make 10% less power, some 10% more and you would have any average and everything in between; they have gotten better on getting them closer, but still you'll never have 100% identical production (10% is arbitrary number I throw out, btw)....and want to say gear ratios (torque multiplication where hp is calculated from) and probably even tires/psi would affect actual power , if you want to get ****. Point is, just use a ballpark figure and you'll probably be close enough. As a last note, as you start changing the dynamics of the engine (with serious modifications), I doubt the % would stay the same either, if that makes sense...

This is why you hear the term balanced and blueprinting on serious rebuilds/builds of engines...Basically it just means that every part is made to weigh within a certain tight tolerance, all parts/assemblies balanced (can be by themself + as a rotating assy), as well as sized to be the same (within a tight tolerance) and the time for proper machining to match, torquing and so would get you the most efficiency you can expect from a mechanical rotating assembly. A step further is porting and polishing (for exhaust ports, say) where they would match all ports (manifold to gasket to head) identically and/or cleaning up casting and other manufacturing 'defects' that are on all mass produced parts...I won't go on to the other 'details' that would need to be done if you want the absolute most power possible.

wcryan

iTrader: (2)

makes sense...

Skidmarcx

^^ Agreed