Updated August, 2008

General Questions 
(M112/M113)

What is a crankshaft pulley?

A crankshaft pulley is the main pulley attached at the front of the
 crankshaft which drives all of the accessory pulley systems such as
 your air conditioning, power steering, alternator, oil & coolant systems.
  It is essentially the heart of the drive belt system from which all 
of the other pulleys receive their power, and thus must be properly 
designed otherwise problems & unforeseen complications may occur.

What is an "underdriven" crank pulley?

An "underdriven" crank pulley is reduced in diameter compared to
the stock counterpart in order to reduce the gearing and free up 
power.  This however can cause sacrifices in reliability and comfort 
of all those accessory systems and over time can even sacrifice longevity
of the engine due to the decrease flow of oil & coolant going to the engine. 
Although power can be made this way via underdriving, it is not recomended
due to the necessary sacrifices that have to be made.  Roughly 15% of gains
from underdriven crankpulleys are from underdriving alone, the other 85% 
comes from reduction in mass.  In addition, UD crank pulleys can irritate
their drivers by causing lights to flicker at night, stereo systems not having
as much power, increased stiffness in steering, and other annoyances.

Are AMS pulleys "underdriven" or stock diameter?

AMS has a strict philosophy in creating power only through increased efficiency
and not sacrificing comfort or reliability in order to achieve more power.  Thus, 
AMS only makes stock diameter pulleys in order to maintain OEM standards for 
reliability and comfort.  In addition, it ensures 100% compatability with ALL
potential future modifications.  By maintaining the stock diameter our pulley
allows performance enthusiasts to ALSO run aftermarket accessory pulley systems
as well as aftermarket supercharger systems and etc.  100% compatibility is one 
of the many benefits of our design.  

How much power does this equate to?

60% (4 lbs.) reduction in mass equates to roughly 10-15HP gain at the crankshaft 
depending on model and performance modifications currently on the 
vehicle.  The more aftermarket modifications currently on the  vehicle 
the higher the gains, as it is simply improving engine efficiency percentage.  

Aren't aftermarket crank pulleys unsafe due to the 
removal of the OEM harmonic damper?

Excellent point, yes this is true.  However, the AMS crank pulley is unique in that
it DOES NOT eliminate the harmonic damper.  In fact, the stock crank pulleys have
has numerous recalls due to the OEM harmonic damper failing, so at AMS we improved
the harmonic damper to a much stronger longer lasting design to ensure the pulley
will last the life of the vehicle and this is backed by our limited lifetime warranty.  This
can not only be viewed upon as a performance modification but also as safe 
preventative maintenance to protect yourself from potential future engine damage 
due to the stock harmonic damper failing on you, it kills two birds with one stone. 

What is the difference in sound from harmonic dampened vs.
non-harmonic dampened?

It can be drastic.  Here is a short wave sample comparing the two.  The
non-harmonic dampened pulley rings VERY loudly, much like a tuning fork 
due to lacking any dampening.  Compare that to tapping our AMS pulley, 
you can barely even hear anything, all the harmonic & acoustics are 
absorb by our harmonic damper, thereby protecting your engine
from back harmonics.  

http://www.abedinmotorsports.com/pulley/nonHD-vs-HD.wav (click)

What is the physics behind the gains of a performance crank pulley?

There are numerous factors at play here.  First Force = Mass x Acceleration.  If 
the force stays constant and you reduce the mass of the pulley, this in turn will 
increase the acceleration (mass & acceleration are inversely proportional in this
equation assuming constant Force)).  In addition, Inertia = Mass x Radius² .  As 
the mass of the pulley is reduced the necessary force required to overcome inertia
is much less.  Radius does play an even more important factor as well, however 
for reliability & engine longevity reasons we cannot change the radius of the pulley
without underdriving it, which is discourage as illustrated earlier.  

Since the AMS pulley improves efficiency, does MPG increase?

Yes this is true,  your fuel efficiency should increase as well.  The amount
will vary from model to model depending on which pulley model is installed
as well as what modifications are on the car among other things.  

Does this crank pulley act much like a light weight flywheel?

Yes, essentially they do the same thing, they both reduce the rotational
mass of the crankshaft assembly thereby allowing the engine to spin &
rev more freely thereby "freeing" up more power to be sent
to the driving wheels and thereby improving real world acceleration.

How do crank pulleys differ from accessory pulleys gains?

Accessory pulley systems work as a function of RPM.  The faster
the engine spins the more power will be freed up.  This is why
most accessory pulley systems only make significant power in the 
top 15-20% of the power band.  Crank pulleys work differently. 
They work as a function of torque.  The maximum gains for a 
crank pulley are achieved where cylinder pressures are at
their peak (this is where max torque occurs).  As a result
They create excellent low to midrange torque as well
as high end HP.  The power is created at all rpms
throughout the entire powerband.  Crank pulleys make
power from just past idle all the way to redline just as if
the entire powerband is pushed upward on the dyno versus
just one section of the powerband. 

What forms of payment do you accept?

Currently we accept any form of paypal payment as long as it is
to a confirmed address (yes it MUST be confirmed address).  The
pulley will be sent out within 24-48 hours of our purchase unless
otherwise specified.  Thanks and have a nice day!

How can I purchase one directly from the website?

Simply go to our various order pages for your specific model
 product and follow the "Order" link to make your paypal payment.

55K Pulley Specifics

Just how much lighter are your pulleys versus stock?

AMS 55K pulleys are 60% (6.2lbs) lighter than stock 

For the 5.5L Kompressor motors, How come you do not OD?

AMS does not feel that overdriving the supercharger on the 55K motors
is safe without a software tune.  It introduces too many problems
such as Intercooler pump failures, overly lean or rich conditions, as
well as severe decrease in gas MPG and overall reliability & longevity
of the engine.  

Why does your pulley make less power than OD 55K pulleys?

Again,  This is due to our stock diameter design.  It is not design
for all out maximum power gains like an OD pulley.  However, the
advantage of the stock design is improved engine efficiency, better
gas mileage without any of the headache or hassle of the OD systems,
plus it retains the stock belts and is much easier to maintain.  Also,
our pulley is significantly less expensive than those alternatives (from 30-70%
less expensive).  The difference between our pulley & an OD pulley as
far as fuel efficiency can be drastic.  This is perfect for those 55K
owners looking to improve the performance of their cars a decent amount
while still retaining stock reliability, driveability, better fuel mileage,
less headache, freer revving engine and saving a lot of money in the process.

How much fuel savings could I achieve?

Typically the results are roughly between 2-4mpg depending on the
pulley model and vehicle you have.  Assuming you drive 10,000 miles
per year (on the conservative side) on a car that normally get 15mpg avg 
in the city, if you were to gain 2mpg (thereby increasing your gas mileage to 
17mpg) you would save roughly 78  gallons of gasoline.  At $4 for premium gas 
(which may be conservative in the future) you would save nearly $312 
in gas alone.  Therefore, the pulley would pay itself off in less than two 
years of driving from the fuel consumption savings alone.  For the E55K 
motors the gains should be roughly 3mpg due to the more 
aggressive weight reduction, this will vary with mods. 

M104 Pulley Specifics

Just how much lighter are your pulleys versus stock?

The AMS M104K pulley is our most aggressive design.  The weight
reduction is 77% ( 7 lbs. ) lighter than stock 

How come your M104 pulley only fits 94-97 models?

The AMS M104K pulley is our most aggressive design.  The weight
reduction is achieve by removing the stock mass timing ring thereby
greatly reducing its center of mass and inertia,  this is what gives the 
M104 such amazing gains, even more than our V8 models.  For this 
reason it will not work on the older '90-'93 model year M104s due
to the elimination of the crank TDC sensor pick off of the crank
pulley itself.  The later M104.994 eliminated this front sensor and
as a result it is not necessary and is merely a hindrance to performance.  

What MPG gains can I expect?

Typically, we have noticed that for every 2lbs removed off the 
crank pulley there is an improvement in roughly 1mpg in fuel
efficiency.  The M104 pulley is 7lbs lighter than stock giving it
an estimated improvement of roughly 3.5mpg.  This however
does not factor in the greatly reduced inertia and the smaller
outer dimensions of the pulley itself.  Therefore, it could potentially
be more, however to remain on the conservative side our official 
estimate is 3mpg.  Over time the pulley will pay for itself.   

Why are the M104 dyno gains so abnormally high?

Again, this has to do with AMS very special design for our
M104 crank pulley.  It is so unique in its design compared to
our other models due to the ability to eliminate the TDC timing ring.
This is one of the biggest reasons why most M104s, although 6-cyl, are
still not that fuel efficient, much of this is a result of the poor stock
crank pulley design.  As a result, this design allows for the engine to 
transfer much more of its power to the rear wheels versus being
lost due to inertia & inefficiency.  

DYNO GUARANTEE 

Our New  Dyno Guarantee program for our C36 AMG pulley. Certain rules apply but we are now backing our claims 
so our customers can rest assure that our claims are legitimate and fair. Here are a few of the basic rules:

- Car must obviously be in proper running condition and not low on power (can affect the numbers.)

- Both before & after dynos MUST be performed on Dyno Dynamics brand dyno.

- Pulley must be installed and allowed 7 full days of driving for proper adaption time.

- Results will be comparable to the dyno chart on our website give or take a few HP.

We stand by our products and our quality and we want to insure that people know that. We 
are now officially the ONLY Mercedes Benz Tuner to have a true Dyno Guarantee, and we
are proud to offer this program to our customers to ensure their satisfaction by offering a refund*.

Performance Header Specifics

What improvements do your Performance Headers make?

Obviously the make answer is power.  They are designed to help the 
M112/M113 engines breathe better.  Our headers are made from T304 
stainless steel and they are TIG welded for maximum strength. We also
has incorporated thicker gauge tubing as well as thicker one piece flanges
which are superior to the competition's headers because they prevent 
warpage of the header and the header flange.  All our headers come
with a limited lifetime warranty.  Typical gains are roughly 10-15HP. 

Do I have to modify my stock exhaust to use your headers?

No, AMS chose to make a performance headers that utilized the stock 
mounting locations in order to ease installation as well as to allow our
customers the choice to remove the modification in the future.  Once 
you install long tube headers on your vehicle you are stuck with them
and cannot remove them due to having modified the stock exhaust
downpipes.  With our headers you do not have to worry about this, 
It is truly a headache free bolt on modification with no major
modification required to your exhaust system.  

* $100 restocking fee applies

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