Justin,
One a normal engine the crank has a 200mm pulley on the crank, a 100mm
water pump pulley and a 50mm alternator pulley.
(For every 1000 engine rpm, alternator 4000 rpm water pump 2000 rpm). These
alternator & water pump speeds are OK for mum tootling around town at 1500
rpm in top gear with the aircon going ,1000 watt stereo cranked right up,
headlights on etc as the alternator needs to be spinning at 6- 8000 rpm to
produce enough current to run all these appliances. The conventional
alternator looses generation efficiency over about 8-10000 rpm.
On a vehicle used mostly between 2000 - 7000rpm an alternator turning at
up to 28000 rpm is like having a brake on you engine. The water pump speed
is a similar problem as the stock water pump starts to cavitate after about
8000 rpm (4000 rpm crank speed ). This is why companies have brought out
electric water pumps for cars, because the water pump chews the most power
when it is needed least. On sporting engines used through a wider engine
speed range, you do not need the low engine speed power generating and
cooling capacity.
By fitting a half size (100mm) crank pulley, you slow the alternator and
water pumps down to half speed reducing the amount of power these items rob
from your engine. (With 100mm crank pulley, engine 1000 rpm, alternator
2000 rpm water pump 1000 rpm). The inertia load on the engine is halved
making it more responsive, freeing up some kilowatts that would have been
used to spin these components at high speed.
If your vehicle only has a low electrical load and is used for race or
highway cruising most of the time, fitting a larger alternator pulley
(100mm) will further reduce engine load.
Most race cars used for sprint meetings or hillclimbs do not run an
alternator and use an electric water pump and a thermo fan. This saves them
up to 5-6 Kw at 8000 rpm engine speeds from a stock fixed blade setup. I
run a 100mm alternator pulley and small crank pulley on my daily driver in
city traffic using all normal accessories (stereo and heater fan etc rear
screen demister) all the time and never have any electrical problems even
at night with all lights on.
A normal flywheel stores energy so when you take off from a standing start,
even at low engine speeds the engine will not stall due to the heavy
flywheel's inertia. With a light flywheel you have to use more engine speed
and a balanced clutch/throttle action to start moving. The technique
requires a little practice at the start to get used to but also allows
faster starts and much quicker engine response.. Also during gear shifts,
engine speed drops very rapidly. This means quicker shifts and reduced
synchro loadings but requires more skill to not "miss a gear".
The fuel pumps are electrical, internal 6 micron filter, same as the Nismo
item.
Cheers
Feral Errol
----------
From: justin darragh <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: FeralDatRat
Date: Friday, August 18, 2000 12:42
Feral,
Could you explain the L-series crank and alt. pulleys to me. What are they
for. Also the flywheel, why race only? Are the fuel pumps stock fitment?
What are your recommendations for a clutch on a turbo set-up(L16/4speed)?
Thanx
Justin
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