Re: [debate][140hp JH?]

[Jason <jason@scirocco.org>]

At 06:21 PM 10/27/98 , Kevin wrote:
>>I'd say not...maybe at the crank since that is your baseline @ 92.  
>>A bone stock JH has anywhere from 85-90 CRANK HP!  You will 
>>lose about 22% through the drivetrain so that makes a stock JH 
>>have "maybe" 70-77 ROAD HP!  so add from there but add ROAD 
>>HP from the mods you did.
>
>No, thats impossible, In the 70's they changed horsepower rating from GROSS
>(crank hp, with no accessorys) to NET HP, which i thought was hp at the
>wheels. when VW claims 90hp, it has to be NET horsepower according to law. 

Nope... all published horsepower and torque figures are engine outputs...
the difference between SAE Gross and SAE Net is that for the net
measurement, the engine has to be installed in the car, and the power is
measured at the output of the transmission, with all auxiliaries hooked up
but not switched on.  This means that the belts are on there as they
normally would be, etc.
	In the old days, gross hp measurements were taken with the engine on the
stand, and EVERYTHING disconnected except the camshaft.  That means no
alternator, no water pump, no a/c compressor, no power steering pumps or
brake boosters, etc... and AFAIK, they didn't even have to have the stock
exhaust hooked up to the engine...  *that*'s why the gross measurements
were so outrageous..
	But the SAE Net measurements do not take into account the losses in the
driveline after the transmission, nor do they measure the losses by having
to rotate unsprung mass.  That's why, for example, my 16v put out 112hp at
the wheels... and then we did a coast-down measurement, which, with the car
in neutral, measures how fast the wheels decelerated from 110mph to like
30mph.  That measured the frictional losses in the driveline, brakes,
rotational mass, CV joints, and transmission... and then the computer spits
out an estimated value for hp at the engine... which, in my case came to 123.

	The reason the losses are so great is because at my hp peak, the front
wheels (and therefore entire driveline) was turning at just over 100mph.
That's a lot of rotation... and, as you can see, it took more than 10hp
just to turn the wheels, brakes, axles, and tranny that fast.

>thats why all the old musclecars has like 300 horsepower. Big deal, thats
>at the crank.

	Okay... and if a big ol' 400 cu in Chevy did 300 Gross, and you put it
back in the car, attached all the accessories, and measured the output at
the back of the tranny, it'd probably put out something like 250hp.  But
then, run it on a chassis dyno and measure how much power gets to the back
wheels... after turning the heavy prop shaft, the differential, both
half-shafts, the u-joint, 2 50-lb wheels and tires, and you'll probably
have an output of.. something like 180hp.

	There was a Cutlass at Dyno day.. this was funny... with the HO Quad 4..
advertised at 180hp.  The guy gets the thing on the dyno?  Power to the
wheels was in the 60s!!  Corrected at the engine was in the 170s... but
there was over 100hp lost in friction... and the dyno operator told me it's
not all that uncommon in American cars to have tremendous losses at higher
wheel speeds (although this was a bit excessive).


>Yeah, it's not had to drive in a straight line man! He didn't miss any
>shifts, so..

	You'd be surprised! :)  Do you know how many people I've raced that
thought they were going all out, but I come to find out later that they
shifted like 3000rpm under redline?  I tromped a Mustang 3.8 5-speed in my
Corolla... and the guy was *so* bummed.. and then I found out he shifted
under 4000 every time. And he insisted he went "all out"... :)

>If you wanna talk weight, I have a 100lb speaker box in the trunk, plus all
>my tools and shit!

	Ouch... so you're prolly approaching Mk2 weight, depending on how many
tools ya have... I guesstimated you were putting 112hp at the crank, Mark
Peele said 115-120... So, with that, and considering you're prolly
approaching the weight of a Mk2 with all yer shit in the car... Hmm...
let's average me and Mark, and we get 115hp... and then consider that 123hp
in the 16v did 7.7... My estimate stands firm that you're in the low-to-mid
8s for a 0-60 run, with or without all yer shit in the back...

>But I'm guessing that I'm pulling 7.5 and high 15's maybe. My friend got a
>gtech for his b=day, so we'll find out!! :)

	Now that's the man! Go for it... and doesn't the GTech have a function
where you can enter the weight and  it will give you the peak HP?  This I
gotta see! ;)

	ttyl!
		Jason


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