What is the DFV on Ohlins coilovers and what does it do?
The DFV stands for Dual Flow Valve. Ohlins DFV Road & Track coilovers have a constantly adjusting valve inside the damper. As it the case with all coilover suspension kits, the more you spend, the higher the quality of the valves you get.
In the case of the DFV, the valve has three types of adjustment.
1. Hardness/softness – Set by user
2. According to temperature of oil inside damper – Active/automatic
3. Compression speed damping – Active/automatic.
Adjustable dampers – Ohlins Road & Track DFV coilovers.
Like any high quality coilover suspension, the user can adjust the hardness of the suspension manually. The user can set the suspension according the where the car is being driven and how the car is being driven.
The Ohlins DFV adds two more dimensions to the adjustability of the suspension, both are active, both happen automatically and neither need any human input.
The first dimension adjusts to the temperature of the oil inside the damper. As the oil heats up the valve expands, limiting oil flow. In short the damper maintains consistent performance regardless of temperature and how hard the car is being driven. This to my knowledge, is unique to Ohlins in the road car suspension market.
The second dimension is compression speed of the damper. Under normal driving (road or track) the damper exerts the force required to control the car’s body.
However bumps in the road want to compress the suspension much quicker than normal braking or cornering. When a car hits a bump the suspension is forced to compress much faster and this creates much higher pressures inside the damper. With the DFV, the extra pressure is used to open a bypass valve which allows the oil to pass through the damper more easily.
Basically when there is a spike in pressure inside the damper, the DFV opens much wider allowing the damper to compress more easily. This allows the bump to be absorbed by the suspension instead of the force being passed into the body of the car.
In effect, the damper becomes much softer when a wheel hits a bump.
When the pressure inside the damper returns to normal so does the size of the valve.
This give the Ohlins Road & Track suspension total control of the car while at the same time giving a comfortable ride.
The only reason a “hard” suspension is uncomfortable is because it does not yield when it hits a bump. The Ohlins DFV does yield for the fraction of a second required for the damper to absorb the bump.
The DFV valve gives the best of both worlds. It allows you to run a hard suspension so you get can the maximum performance from your car and it also gives you a comfortable ride.
As I said before, the quality of the valves used in a coilover suspension is probably one of the biggest factors in setting the cost.
Ohlins Road & Track coilover suspension kits start at around 2,500 Euro whereas D2 for example starts at around 1000 Euro.
Both the Ohlins and the D2 (STREET Model) are a lightweight suspension kit, both have huge damping adjustment and both have a lot of height adjustment.
The difference comes in the ride comfort and that is due to the valves. The DFV system is a much more complex valve because it can adjust to heat and pressure, the valves in the D2 can not.
What does this mean on the track?
Both systems will perform well on track. The Ohlins will have the edge in stability simply because the driver will be able to attack the kerbs more without it upsetting the car as much.
On the road the Ohlins will offer better control and better ride comfort. To match the control of the Ohlins you can increase the stiffness of the D2 but the ride will suffer.
To match the comfort of the Ohlins you can make the D2 softer but you will lose the ultimate control.
To be fair to D2, their ProRacing model suspension kit does give the user the option to tune the high speed bump seperately from the low speed bump but this has to be done by the user.
D2’s ProRacing damper gives just over 11,000 adjustments settings which makes the tuning process a long one whereas on the Ohlins you do not need to worry about the high speed bump settings, the DFV does it for you.
The prices of the Ohlins Road & Track and D2 ProRacing are comparable ie in the 2-4,000 Euro range.
The D2 ProRacing suspension kit is also targeted at professional motorsport users ie people who are used or are prepared to learn about the art of suspension tuning. The Ohlins Road & Track is a much more user friendly, fit and forget solution because it does not have so much adjustment.
All in all the Ohlins Road & Track coilover suspension is perfect for the driver who wants the control of coilover but does not want to sacfrice comfort and does not want the hassle of a coilover kit which gives independent, high and low speed bump and rebound adjustment.
Think of Ohlins Road & Track as the coilover suspension a car manufacturer would fit. It gives performance and simplicity.
