Mike I totally agree... if it's a High performance version of a car there is
much to learn on a Chassis dyno.... as for a street car... well I don't know
... if your looking to know about Performance and what a particular upgrade
to a Part is.... there is no question it's a much better deal....
I wouldn't take the racecar (spelled backwards is still racecar) anywhere
without the chassis dyno... it just tells me if I am ready to go or not....
K
----- Original Message -----
From "Mike and Kerry Gigante" <mikeg at vicnet.net.au>
To: "Jeffrey H. Boatright" <jboatri@emory.edu>
Cc: "spridgets" <spridgets@autox.team.net>
Sent: Wednesday, November 22, 2000 4:35 AM
Subject: Re: torque III
> Another low cost option is to use a rolling road dyno and optimize what
you
> have.
>
> A few of us have run our road-race cars/engines on special stage tarmac
> rallies
> for classic cars. They close the best windy country roads and let us go
crazy
> over stages that vary b/n 3 miles and 20 miles.
>
> Twice now I have used my full race motor. The first time it was an
absolutely
> miserable pig to drive on the rally. No torque below 6000, no clutch at
the
> end
> of day 2 (3 day event). Gained time in some places, but lost time out of
the
> slow
> uphill corners where the 4.2 diff and 2nd gear were just too tall (this
was a
> straight
> cut close ratio box).
>
> Next time, with the same motor (1293cc, 310 duration cam, almost 0.5"
valve
> lift,
> 13:1 compression), the motor was completely different. It still had a
power
> band, but
> it was tractable and would actually pull from < 2000, even in top. It was
a
> much
> better all around package, with heaps more mid-range torque and the dyno
said
> only about 5% less peak HP.
>
> The difference? Well we adjusted cam timing, ignition timing, choke size
(this
> was webers) and jetting. We could have adjusted the advance curve for even
> better optimisation, but
> it was a case of diminishing returns.
>
> Given that the spridget has only 3 usable driving gears (unless you are a
gun
> double
> clutcher who is willing to risk downchanges to 1st gear changes on the
move),
> there
> is a genuine need for a reasonably broad power band. In fact, the car is
> faster everywhere
> except the real HP race tracks.
>
> I'd suggest that while my experience was with a full-race motor,
optimising
> cam timing,
> ignition timing and jetting is a worthwhile excercise if you want the very
> best out of your
> motor. Given it is a one-off expense, I consider it very worthwhile and a
good
> way to
> improive the mid-range performance.
>
> Mike
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