In-Depth Testing: Ohlins Road & Track Coilovers for 992 Carrera

In-Depth Testing: Ohlins Road & Track Coilovers for 992 Carrera

For many years Flat 6 Motorsports has recommended the Ohlins Road & Track Coilover system for a variety of Porsche applications. Ohlins delivers a world-class coilover system that balances performance from the street to the track. Ohlins' patented Dual Flow Valve (DFV) technology delivers uncompromised performance. It's unique design gives fine tuning adjustment for low speed driver's inputs while providing a bypass for high speed rebound inputs (think bumps and potholes) that gives Ohlins a compliance advantage over it's competition.  

Background on the DFV (courtesy of Ohlins USA):

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 tire 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 tire 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 tire 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.

Flat 6 Motorsports visits Ohlins USA:

We had the opportunity to take our Project 992 Carrera T to Ohlins USA's facility in Hendersonville, NC. We often visit vendors to learn more about their products and methods. However, this visit provided a special opportunity. We were able to utilize their Shake Rig to test and validate the performance of the Road & Track system

The Shake Rig is an impressive testing instrument. It provides up to 7 points of simulation for various road or track conditions. They can even simulate various race tracks! Many motorsports teams test with Ohlins to dial in plans and settings for competition. The Shake Rig uses a host of sensors and accelerometers to capture data relative to road inputs. 

For our testing, we simulated vertical forces at different speeds (2 inches per second, 4 inches per second and 6 inches per second). This baseline test simulates different road forces one would experience on a track. With the help of their test engineers, we tested a variety of settings with the adjustable dial on the coilovers. This controls the effective compression and rebounding of the shock. 

Testing different settings allows the engineers to find different levels of grip. The 992 T weighed in at 3,204 lbs with fluids and about 1/3 tank of gas (our T has the extended range tank). Of course, like all 911's, majority of the weight is in the rear of the vehicle (~62%). After adding sand bags to simulate driver's weight, the engineers ran through a series of tests. 

After a full day of testing, we were able to find the optimal level of grip with the settings and set-up of the car. The engineer recommended 8 clicks (from full stiff) in the front and 6 clicks (from full stiff) in the rear. These settings allow response and feel from the dampers with maintaining high levels of grip. 
Driving Impressions on the Street:
After leaving the Ohlins USA facility, we took advantage of the local roads in the mountains of western North Carolina. Right away, you can feel the compliance of the suspension as the car went over small imperfections in the road. The set-up also provided more grip than needed for the street. We're running wider Cup 2 tires that act like an adhesive through corners. With an incredible amount of mechanical grip, the Carrera T blasted up and down the windy roads. 
A unique photo opportunity:
Driving Impressions on Track:
The following morning we headed to Road Atlanta to test the set-up on the track. Surprisingly, the settings recommended by the engineer were so compliant on the backroads, we didn't see a need to turn them down. Road Atlanta is a great place to test suspension as it has tons of elevation change, curbs and forces making the suspension work. The car handled incredibly around the circuit. It felt balanced without understeer. It gave incredible confidence and communicated so well through the dynamics of the car. Turn in was sharp and the vehicle provided good rotation through the turn when commanded. We didn't find ourselves searching for grip lap after lap. The car handled the curbs with ease. This is a key area where you can feel the difference of the DFV technology. The car doesn't get upset or unsettled, it's almost like a cheat code relative to the stock SPASM dampers. The system offers great support and control but also incredible compliance. The car never bounced around track, it felt like the tires were consistently maintaining a contact patch to help grip the car up. We were very impressed with the performance on track. It easily can take seconds off laps with the improvement to feel and confidence. The stock SPASM is a tad over dampened in it's sport setting and too soft in it's comfort setting, which provides understeer and numbness. The Ohlins gives a large range of adjustment with the clicker settings to further dial in the system to your preference. We found the balance so good, we didn't feel the need to make adjustments. We did some slight street testing prior to the trip and weren't far off from the recommended settings. 
Overall, we find the Ohlins Road & Track system to be the best available on the market for the 992 chassis. It delivers the uncompromised performance a 911 owner expects. For the enthusiast looking to get more out of the platform, we highly recommend this kit. 
Next article Project 992 Carrera T - Breaking In