Miata Mailing List: October 1999, Message #47

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Bill Rockoff wrote:

> >> 193.1 HP @ 8300
>
> Cool.  14.5 lbs / hp.  (Yes, I'm imagining an Autorotor making 175 hp at the
> wheels on my (t)rusty 1.6 for a nice 13.2 lbs / hp......)
>
> And hey, lookit that, 193.1 hp at the wheels is 81% of the rated 240 hp at
> the crank.  Either drive train loss REALLY IS 15% to 20%, or I'm wrong and
> driveline loss is actually a constant power amount and Honda should beg,
> borrow, or steal a more efficient 20-hp tranny from a Miata instead of their
> obviously-inferior 47-hp-sapping unit.   Straw poll - who thinks drivetrain
> loss is mostly a percentage of the transmitted power?  Okay, who thinks
> drivetrain loss is mostly a constant value and that Honda transmissions suck
> up twice the power as Mazda transmissions?
>

Bwaaahahahahahahah!

Suck up twice the power? that is cute :)

I also pose this: who think that this very green S2000 will dyno over
200 WHP after 5-10K miles?

Seriously: High compression honda engines like the B16A, and B18C
really take a while to break in to full HP potential.

As for drive line losses, its really an estimation. Hell, if you put in
fresh oil and then Dyno, you will see a few HP more to the wheels
in many cases. I don't think its a fixed number, but I also don't think its
exactly linear.

So, a 200 WHP car rated at say 240 loses about 18%. If you
boost that car to say 400 WHP, does that scale exactly to 480 crank
HP? So instead of losing 40 HP in the drive line, you now lose
80? Why would you if the drive line losses objects have not changed:
you are just pumping a hell of a lot more air through the e ngine with
a turbo :)

I mention this example as its a very common case with import tuners
and drag racers: they can use the linear percentage to their
advantage and boast they make XXX HP with their turbo, when
the smart bear will not really care about crank HP, rather WHP.


>
> >> 131 massive ft-lbs @ 6600
>
> Make fun of 131 ft-lbs of torque if you will, but at any given road speed
> you can get more acceleration from that than you can with an engine that
> peaks at 260 ft-lbs at 3300 rpm......  if your gearing is right.  It's
> torque at the rear wheels that moves your car.
>
>

Yup. The S2000 has a good tranny, and makes decent torque for a NA 2.0
4. My roommate drove a green one yesterday, and even though he
kept it under 5000 (only had 60 miles on it!) he said it was very tractable,
and the rear end could be made to wiggle around a corner. That
is not the Honda 4 I am used to!!!


>
> >> These guys are NSX tuners that are going to make aftermarket add ons for
> S2000.   This is their base line.
>
> Thanks for the forward.  Any tuner that starts with a baseline dyno run is
> probably going about this in all the right ways.
>

With one exception: This car is GREEN. If they drive it for a few thousand
miles, slap on an exhaust, and dyno 205 WHP they can then say
their Exhaust makes 12 WHP, which really IMHO is not all that accurate.

Their base line is a good start, but just not yet. They need some more
baselines. One at 3K, then 5K, then 10K.

- b