High-Performance Harmonic Damper for the Porsche® 928

Custom-engineered for Modified Motors!

this part is Pikes Peak tested this part is Bonneville Tested

Think about it. We make so many changes to the 928 engine in our love of HP and performance, yet we bolt up the same old, tired, harmonic damper to the front of the crank each time. Why do we expect no harm will come from this?

The stock 928 damper was good in its day, it is a dual-plane mass damper with a single elastomeric seam in it; but even if it was in perfect condition (and none of them at this age are) they are still miss-matched after we start raising the redline, changing the crank stroke, bore, or both, and changing the flyweight of the rods and pistons.

There are 928 racers who have reported multiple failures of the stock 928 damper in their race applications. Their damper failed in a catastrophic way (it came apart!) but there are countless more engines damaged silently by the wrong damper.

The harmonic damper is responsible for two things: to absorb the vibratory harmonics and to counter-react torsional oscillations of the crank. Let's take each separately.

Vibratory Harmonics and How the Wrong Harmonic Damper Can Damage Your Engine:
The crankshaft receives multiple impacts from the rods each revolution, and at certain frequencies it will start to “hum” or resonate like a tuning fork. The right harmonic damper will absorb and nullify these vibrations. Left unchecked, these vibrations can both create and enlarge stress fractures in the crankshaft itself.

This is common enough that many engine builders believe that when they see excessive wear or failure of the #2 main bearing, the fault most likely lies in a miss-matched or broken harmonic balancer.

The wrong harmonic balancer can actually amplify the vibrations at certain rev points and make it worse than having no balancer at all!

Torsional Oscillations and How the Right Harmonic Damper Can Increase Your HP:
The other element we must consider are the torsional oscillations of the crankshaft. Because the load on the engine is attached at the far end of the crankshaft via the flywheel, the crankshaft actually winds up like a torsion spring in front of the flywheel, especially when the load is high and the throttle is on.

On the extreme opposite end of that crankshaft (where the effect of the crank twisting is the most severe) – this is where we drive our camshafts, and from them, our ignition distributors! There is enough twist in some cranks under load to retard our valve and ignition timing more than 10 degrees, with matching losses in HP and performance.

A harmonic damper of the right size and configuration for the engine will reduce and absorb this twist, adding accuracy to the timing and valve events and often adding between 10 and 30 HP to the typical V8.

If you bore the engine, change the weight of the pistons or rods, add a stroker crank, or change the redline of your motor, the old stock harmonic damper may not be able to keep up with your changes and rob you of either a lengthy service life or maximum HP.

The 928 Motorsports LLC Custom Harmonic Damper:
Our harmonic damper was designed as a collaborative effort between ATI engineers and 928 Motorsports. The finished product is a Super Damper that is configured precisely for your Porsche 928 engine and application.

Rather than a single elastomeric ring like the stock 928 balancer, our balancer has 8 separate synthetic rings that will be matched precisely to the harmonics of your engine by ATI engineers. Thus, these dampers are custom-tuned to your initial engine setup after you answer a few questions for us.

After that, the damper can be re-configured should you make even more changes to your engine.

The ATI Super Damper®, U.S. Patent #5,425,287, is the only damper designed exclusively for high RPM performance engines. The proven elastomeric design is actually two dampers in one: a 4" inner diameter and a 7" diameter damper contained in 2 shells that bolt to the crank hub. The inner and outer shells are available in steel and in aluminum to contain the steel inertia weight.

The inertia weight has 8 computer-machined grooves to retain the proper durometer o-rings (dyno tested for each application), and installed at ATI. O-ring life has been tested to over 3 million cycles in Nextel Cup competition (6500+ RPM, 500+ miles) and 10 years (188 - 11 round weekends) in drag racing. The unit is rebuildable to new specifications by installing new O-rings.

All units are SFI manufacturer certified and exceed SFI spec. 18-1.

Custom Damper Application for your Porsche® 928

928 Motorsports has done all the work for you! We already have the crankshaft snout profiles, and full dimensional specifications in a fixture at ATI. We have also designed-in elements to work with the unique Porsche 928 characteristics (like our firing order, for example).

All we need from you when we order your Custom Harmonic Damper is:

Bore: Stroke: Max RPM: HP need:

…we will take care of the rest!

++ The 928 Motorsports LLC/ATI Custom Damper is a Special Order item and is not returnable.

Lead times for us to get this part after we have ordered it have varied from 60 to 120 days. We will lend you a good used stock harmonic balancer if you need one until this part arrives so you can continue to use your car.

Item Part Number Price (USD) Shipping* Availability
High-Performance Harmonic Damper for the Porsche® 928 ++ ENG-HPHD $1,123.50 U.S. Only: $30.00
All Others:
In Stock! Typically Ships Same Day!

* Domestic US shipping shown. International shipping will be calculated based on location.

++ The 928 Motorsports LLC/ATI Custom Damper is a Special Order item and is not returnable.