Engine - Rotating Mass and Parasitic Losses
Every item that the engine must turn in a circle as it operates, represents power that is diverted away from moving
the vehicle, and consumed by rotating those items. Several of these things have been specifically designed by the
vehicle manufacturer to be heavy and consume lots of potential power, because these items act to reduce noise,
vibration, and harshness. The crankshaft accessory pulley (crank pulley)(6 lb.) and the flywheel (15 lb.), are two
prime examples of this. The weight of these two items has been artificially inflated by the vehicle manufacturer,
in order to dampen the engine’s movements and vibrations, and to store centripetal force, to make the vehicle easier
to operate. Essentially, the vehicle manufacturer has traded 10-15 horsepower so that owners will not complain
about rattles from engine vibration and difficulty letting out the clutch without killing the engine. The compromise
to accept vibration and more difficult clutch engagement will yield very noticeable performance improvements.
Once Aasco, or any retailer selling Fidanza flywheels, accept an order for an Isuzu application (Isuzu Impulse,
Isuzu Stylus, Asuna Sunfire, Lotus Elan, etc.), and charge
the customer’s credit card, they check if they can actually get the product from Fidanza, and upon learning
that the product has been discontinued, they send the customer a short note stating that the product is no
longer available, and they refund the customer’s money.
As mentioned above, the crank pulley functions as a large vibration damper and centripetal force storage device.
An aluminum pulley will reduce the weight from 6 pounds to about 1 pound. Further gain is accomplished by reducing
the diameter of the pulley, so that the alternator, air conditioner, and power steering pump turn slower, and consume
commissioned Unorthodox Racing to make crank pulleys for the Isuzu and Geo Storm 1.6 liter 4XE1
and 1.8 liter 4XF1 engines. Unorthodox promised Isuzuperformance exclusive sales rights to those products, but
then made those items available to everyone, without compensating Isuzuperformance for the R&D and tooling costs
that Isuzuperformance had paid. Once the initial production run was sold out, Unorthodox solicited Isuzuperformance
to pay for another production run. Isuzuperformance declined. Unorthodox Racing then discontinued the products,
refusing to pay their own production costs so that they could fill standing orders they had accepted.
Aluminum Pulley Sets
After Unorthodox Racing ran out of underdrive pulleys, and discontinued them instead of paying to produce the
item themselves, Isuzuperformance took the matter to the extreme, by making complete aluminum pulley sets,
comprised of an underdrive crank pulley, an alternator pulley, and a power steering pump pulley. The set drops
an additional ¾ pound from the power steering pulley, and several ounces from the alternator pulley, for a 5 ¾
pound weight reduction.
Power Steering and Parasitic Power Loss
Electric Power Steering Pump Conversion
The power steering pump is a significant drag on the engine. It maintains a 500+ PSI pressure in the system
with the wheels pointed straight, and increases the pressure to 1200 PSI as the wheel is turned to its left
and right limits.
It is tempting to convert the car to manual steering by installing a manual steering rack or by looping the fluid
pipe and using brute force to overcome the resistance of the steering, the tires, and the unpowered rack mechanism.
This is ill advised. The manual rack has a much slower ratio (20:1 vs 16.1:1) and requires too much effort to
steer quickly (
See Driver Controls Section). Using a power rack without the power hooked up (looping the lines)
is even worse, because the driver is fighting the wheels, the rack, and the disabled power mechanism
Control Section). For any form of racing that requires turning the wheel to the side, power steering is the
If the parasitic loss of power to the power steering pump is enough of a concern, the alternative is to use an
electric pump. These were used as OEM on some vehicles, such as the Toyota MR2, and are popular for electric
and hybrid vehicle conversions. Electric power steering pumps are also becoming more common in newer vehicles
as manufacturers squeeze more fuel economy from their automobiles.
The primary concern is that the electric pump will use a lot of electricity, and the current draw increases
exponentially when the wheel is turned to its left and right limits. The vehicle must run a large alternator,
a large battery (not a light weight racing battery), and the power cables to the electric power steering pump must
be similar in size to the primary cables between the battery and alternator (large gauge). This is a significant
amount of weight and the high draw on the alternator will kick the magnetic field up, resulting in more parasitic
drag on the engine. These are serious concerns to be weighed before converting the power steering over to an
Serpentine Belt Conversion – A Bad Idea
The 1.6 liter 4XE1 SOHC and DOHC engines have two accessory belts. One belt for the alternator, and second belt
for the power steering pump and/or air conditioning compressor. The two belts are tensioned by tilting the
alternator and tilting the power steering pump. This system works well and reliably with no real drawbacks.
The 1.8 liter 4XF1 engine uses a single serpentine belt to run all three items: the alternator, power steering
pump, and air conditioning compressor. The belt is tensioned by a spring loaded, automatic tensioner pulley.
The automatic tensioner pulley does not hold tension very well, often causing the serpentine belt to squeal,
especially between shifts and upon downshifting, and the problem is exacerbated by wet weather, puddles, and
water splashed onto the bottom of the engine and belt when driving on a wet road. (Also, it does not appear
that new tensioner mechanisms are available any longer).
Serpentine belt conversions have been marketed for other brands of automobiles and other engines. The claim was
that converting the engine to run on one belt would reduce friction, though that single belt runs all of the same
mechanisms at the same speed, providing no reduction in load, and that belt makes more switchbacks around more
idle pulleys, for no real reduction in friction. But the fact that someone was selling it for other vehicles,
spurred interest among Geo Storm and Isuzu car owners, who quickly formulated a way to switch the 1.6 liter 4XE1
engines over to the 1.8 liter 4XF1 accessories and serpentine belt (complete with oil pump, oil pan, front
mounted alternator, and rear facing oil dipstick, because the front mounted oil dipstick will not work with the
serpentine belt system).
Of course, the serpentine belt from the 4XF1 still suffers from the same tension, slippage, and squealing problem,
when installed on the 4XE1 engine, and provides no performance improvement.
A much better alternative would be to convert the 1.8 liter 4XF1 engine over to the multi belt system of the
4XE1, providing more reliable and trouble free accessory operation, and the added convenience of using the more
readily available oil pump assembly with the conversion of the oil pan and front mounted oil dipstick.
Air Conditioning Disable
For those who want to reduce accessory drag as much as possible, but do not wish to remove the air conditioning
system from the vehicle, or loose the expensive Freon in the air conditioning system, it may be desirable to
switch to the non-air conditioning accessory belt, and simply not drive the air conditioning compressor. The
shorter belt runs the power steering pump, but leaves the AC compressor out of the loop. The AC will not be
functional while the shorter belt is in use, but the AC is rarely used on the track, where that little extra
bit of power comes in handy.
The flywheel is the heaviest rotating item attached to the engine. An aluminum flywheel with a steel friction
plate will drop 6 pounds from the rotating mass, and provide a durable surface for the clutch to ride against.
The power improvement is very noticeable. However, feathering out the clutch becomes more difficult and
requires more concentration. The engine speed while letting out the clutch will need to be increased slightly,
and the window between killing the engine and spinning the tires will become smaller.
commissioned Mueller Fabricators to make flywheels for Geo Storms and Isuzu engines, and paid
all of the research, development, and tooling costs in exchange for exclusive sales rights. Mueller did not
honor that promise, and made the products available for wholesale purchase to everyone, without any compensation
to Isuzuperformance for paying to have the products produced to begin with. Mueller made a very good product,
but the company closed around 2006.
After Mueller Fabricators closed,
then commissioned Fidanza Engineering to do the same, and paid all of the research,
development, and tooling costs a second time. Fidanza promised Isuzuperformance exclusive sales rights to the
Isuzu and Geo Storm applications. Fidanza did not honor that promise, and made the products available for
wholesale purchase to everyone, without any compensation to Isuzuperformance for paying to have the products
produced to begin with. After a year or two, Fidanza had run out of their shelf stock that was paid for with
Isuzuperformance’s R&D and tooling fees, and Fidanza asked Isuzuperformance to pay for another production
run, or sell stock back to Fidanza to fill orders they had accepted for products they could not supply.
Isuzuperformance declined the request. Fidanza then discontinued the products for Geo Storm and Isuzu engines,
instead of paying their own production costs to make the product themselves.
Aasco is not a product manufacturer. Aasco purchases flywheels from Fidanza, and sells them under their own
name. Like many online retailers (THMotorsports, Andy's Autosport, etc.), Aasco has fed all of the part numbers
from one of Fidanza’s out-of-date catalogs into their website, and they accept orders for everything that they
have a part number for. There is some pretty good evidence backing this up:
- Aasco’s product listings always use stock photos of Fidanza products.
- Aasco’s part numbers are identical to Fidanza’s part numbers.
- Aasco has never successfully delivered a flywheel for an Isuzu vehicle (because Fidanza discontinued
After two choruses of paying all the costs to have two other companies make aluminum flywheels,
Isuzuperformance has developed their own line of aluminum flywheels, with better clearance around the oil
pump, lower weight, and incorporating a crank angle sensor for sequential fuel injection when used with the
Isuzuperformance Programmable Computer System.
This may sound backwards, but for a purpose built race car, the smallest alternator that will keep the
battery charged, can be a very good choice.
The manufacturer designed the charging system to support all of the electrical accessories of the vehicle,
when turned on all at the same time, with the air conditioner cranked all the way up, and the charging
system seriously compromised by neglected maintenance and age. The redundancy in the system keeps the car
owner from complaining that the vehicle is broken or poorly designed, even when the vehicle is abused and
maintenance is neglected. But it also means that the vehicle is hauling around an alternator that is
oversized, especially for use on a purpose built race car, which has all of the electrical accessories and
air conditioner stripped out of the vehicle.
There are three different sizes of alternators used in the 4X series engines.
All of the Geo Storms (and 90-93 Isuzu sister cars) use the largest, 75 amp alternator. But this engine
series is shared with the Isuzu I-Mark and Chevrolet/Geo Spectrum (4XC1 and first generation 4XE1). The
I-Marks and Spectrums with air conditioning use a 60 amp alternator. And the I-Marks and Spectrums without
air conditioning use a 45 amp alternator. Each of these steps down in amperage is accompanied by a reduction
in weight, diameter, and the amount of power used by the engine to turn the alternator.
- 75 Amp; 1990-93 Geo Storm, Isuzu Impulse, Stylus, Asuna Sunfire.
- 60 Amp; 1985-1989 Chevrolet Geo Spectrum and Isuzu I-Mark With Air Conditioning.
- 45 Amp; 1985-1989 Chevrolet Geo Spectrum and Isuzu I-Mark Without Air Conditioning
One caution when reading alternator ratings. The ratings are made for maximum output at maximum rotating
speed. So alternators are rated for how much electricity they produce at engine redline. Cars are rarely
driven at engine redline, and almost never driven on the street for extended periods of time at redline.
A street driven car spends a lot of time sitting at stop lights, often with the headlights on, as well as
other electrical devices. And the electrical output at idle speed is 1/5th the alternator rating. So the
75 amp alternator puts out about 15 amps at idle. The 60 amp alternator puts out about 12 amps at idle.
And the 45 amp alternator puts out about 9 amps at idle. The electrical draw of the headlights and the
engine itself is ~12-14 amps. Meaning the system comes very close to deficit electrical production, and
running off the battery.
There is a tradeoff of charging power vs. weight and size with these alternators. This is especially
important when considering a smaller, lighter weight, 150-350 CCA racing battery (which is also a trade of
smaller size and weight for reduced electrical output and reserve). For dedicated race car that is not used
for daily transportation, which is serviced and overhauled between races and can sit for long periods between
races on a charger to maintain the battery, the smallest alternator and tiny racing battery may work well.
But this combination on a street driven vehicle will cause problems. The 45 Amp alternator and 150-350 CCA
battery combination will not maintain 12 volts with the use of the headlights and will not start the engine
in sub-freezing temperatures. The combination of the middle size 60 Amp alternator and a medium size 500+
CCA battery can be daily driven for summer use, but is still not adequate for sub-freezing temperatures.
Year round daily driver use will require either the 75 Amp alternator and a medium sized battery, or the
65 Amp alternator and the a full sized battery, and this still will not be as reliable as the 75 Amp
alternator and a giant, heavy battery.
These are all Delco/GM style three wire alternators built by Denso in Japan. The Denso alternators are
considered by those in the industry to be higher quality than the Delco equivalent, and the Denzo cores are
The Delco/GM single wire "mini" alternator is popular for hotrods. These are the smallest case size (45 Amp
size) used on the Isuzu 4X series engines, though the case design is slightly different for a different style
hinge and mounting bracket. The mounting could be modified to accommodate these alternators, but there are
some cautions. The standard amperage output for the GM alternator is 35 Amps. This is not enough power to
run the Geo Storm. There are higher output variations available up to 80 Amps, but the cost is $320+. And,
these are Delco alternators, considered less reliable and durable than the Denso alternators. Additionally,
the resistance of the electrical field (which causes the drag on the engine and consumes horsepower) for a
high output 80 Amp alternator in the small case, will likely measure out almost identical to the large frame
75 Amp standard alternator. So this becomes a self defeating effort.
Be aware that the 4XC1 and 1st generation 4XE1 DOHC engines use a different alternator pulley. Early 4XC1
appear to use a single V belts and single V pulley. Later 4XC1 and 1st generation 4XE1 DOHC (I-Mark RS) use
a slightly smaller diameter four V pulley than is used on the Geo Storm. Using one of these alternators on
a Storm may involve switching out the pulley on the alternator and/or using a slightly shorter 4 V Rib belt.
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