THE FEATURES OF DFV TECHNOLOGY

So what is DFV? It is Dual Flow Valve technology – and it sets us apart from our competitors. Only Öhlins has DFV technology on its road and track products.

With DFV, the dual flow valve gives the same characteristics on rebound as it does on compression, thanks the damper fluid having a consistent path of flow in both directions. This means that the wheel and tyre can quickly and effectively resume their important position back on the ground, providing grip and traction. The new Öhlins R&T range uses DFV technology on every single fitment, making it the perfect upgrade for the enthusiast that needs comfort and agility in the one unit.

Figure 1: (Compression flow) At low shaft speeds, oil flows mostly through the shaft jet bleed (lower dotted arrow). At higher shaft speeds, oil flows mostly through the compression ports in the piston (upper dotted arrow). At very high shaft speeds, or during sudden shaft accelerations, oil can also escape through the compression ports in the DFV, increasing comfort.

Figure 2: (Rebound flow) At low shaft speeds, oil flows mostly through the shaft jet bleed (lower dotted arrow). At higher shaft speeds, oil flows mostly through the rebound ports in the piston (upper dotted arrow). At very high shaft speeds, or during sudden shaft accelerations, oil can also escape through the rebound ports in the DFV, maintaining tyre contact with the road.

Because DFV opens more quickly and easily on minor road imperfections, ride comfort is surprisingly supple and more akin to an OEM strut than a coilover set-up. Over undulating surfaces, the compliancy of the R&T units allows the car to crest bumps and pot-holes, whilst still keep stable and in control. Traction is always maintained at its optimum level. When comparing suspension, why settle for second best?

Figure 3: (Vehicle – no DFV) Without DFV the oil can not flow through the piston quickly enough on the rebound stroke after hitting a bump, so the tyre is not able to stay in contact with the road.

Figure 4: (Vehicle – DFV technique) The DFV valve opens, letting the oil flow quicker through the piston on the rebound stroke after hitting a bump, enabling the tyre to stay in contact with the road.

When adjusting ride height on coilover units, it’s worth comparing how it’s done. On many inferior designs, height is adjusted by raising or lowering the lower spring platform. This has the effect of compressing or extending the spring, which can limit the suspension travel that may cause topping out. The Öhlins method is to leave the spring seat in its perfect position, whilst the lower flange spins easily on the threaded body, to allow you to adjust with absolute precision whilst maintaining the perfect characteristics that we took so long to design in! Once you’ve set it all up, the adjuster simply locks off to maintain your exact settings.

Dampers will get hot. That’s one thing that you can be sure of. As the piston moves within the damper, it generates friction – and therefore, heat. Although we can’t stop heat, we can deal with it, and this is yet another way that Öhlins differs from the competition. As the heat increases, the viscosity of the damper fluid can change, altering the car’s handling characteristics. Our unique needle bleed valve expands with temperature, closing the gap that the fluid travels through, maintaining a consistent damping rate. The best thing of all? You won’t even notice! All you’ll feel is that the car responds consistently, lap after lap, turn after turn. Allowing you to concentrate on braking points and apexes whilst the Öhlins technology takes care of the damping.

Figure 5: Thermal Expansion

These kits all work well ‘out of the box’, but there’s still plenty of adjustment for you to set things your way. You like stiff and reactive? Or soft and forgiving? It’s all there. Too much low speed rebound damping can have an adverse effect on grip, so the easily accessible adjuster at the base of the Öhlins units allows small, but positive increments of fine tuning, so you can take into account every single parameter. Sounds complicated? Nothing could be further for the truth. Just a few clicks either way from our factory settings will soon have your car responding precisely to your inputs and driving style.

Most of the Road & Track McPherson struts also feature camber adjustable upper and lower mounts to give you the possibility to fine tune your wheels for the right occasion – whether you want to go for a ride in your neighborhood or take your car for a spin at the track on a weekend.

The BMW M front shocks utilize monotube DFV struts with separate spring preload and height adjustment.  For the rear, inverted, aluminum DFV shocks come with height adjustable spring perches. Separating spring preload from height adjustment allows precise height adjustment without affecting suspension travel. Considering the F82 M4 is already tuned as a high performance street car with track capability, Öhlins took the approach most drivers will utilize track-oriented tires and tailored the suspension to match. The tuning approach minimizes understeer without the necessity of aggressive alignment settings or wide front tire fitments, while still maintaining safety and comfort on the street.

Applications:

• 99-04 Porsche 996 Carrera 4 / 4S
• 99-04 Porsche 996 Carrera Turbo / Turbo S

Please note: pictures are representative and may not be model-specific