How Does the Ohlins DFV Valve Work?

Another cool part about the DFV shocks is that the damping is temperature-sensitive.  As a shock gets hotter, the fluid loses viscosity and thins out.  On most shocks, this causes the shock to loose damping and fade.  When cold, the fluid thickens.  This can cause the shock to ride hard on cold days.  The DFV shocks have a special feature to counter this.  The shaft that goes to the needle valve is made out of a special alloy that expands and contracts in proportion to the fluid temperature. When the fluid is cold, the shaft gets shorter and allows for more fluid flow through the valve, keeping the ride from getting harsh.  When the shock gets hot and the fluid gets thin, the shaft expands moving the needle valve lower reducing the flow and keeping the shock from fading.

The Ohlins DFV series of shocks, struts, and coilovers are surprisingly affordable and they are available for a wide range of cars.  There are also universal kits available so you can adapt DFV suspension to your car with a minimum of complex fabrication.   We look forward to testing this line in the near future!

Sources

Ohlins USA

Ohlins

 

13 comments

  1. Õhlins is really trick stuff. I remember from repairing and doing maintenance on them a few years back.
    The TPX/TTX Rally struts are really something else.
    Twin-piston, 2-way compression, low-speed rebound adjustment and additionally You could adjust how hard it bottoms out.
    Õhlins calls it Progressive Damping System. It comprises a small short cylinder at the top of the strut and a small piston at the end of the shaft.
    Basically, You could call it a triple-piston strut.

  2. Huh, OK… so if I’m picturing this correctly (I’m making guesstimates at the DFV piston port design from the shims) what you end up with is a pretty steep force vs velocity plot at low speed where it’s just the needle valve flowing, then the DFV valves blow off like a digressive piston to soften “mid” velocity, then eventually the port to/from the DFV chokes and it’s working through the linear main stack? Kind of the opposite of the Penske digressive blowoff option where it’s needle/main stack/added valve; probably a much lower speed blow off. Maybe like Penske’s VDP in F/V graph shape (obviously not in mechanism)

    What’s using the valving to control kerb strike motion get you? At least on racing oriented dampers, I’m seeing a lot more trickery to try to avoid high speed force, though obviously that’s going to be application specific. This is not me trying to launch into an Ohlins vs Whoever Else argument – that’s a cool tuning tool, I’m just wondering why you’d want it on track.

    1. That’s exactly how it works. A lot of buzz nowadays is getting a regressive or at least a leveling off compression curve to handle those curb hits. That’s the 5th adjustment of the newer 5-way shocks. Not sure if this is really what our sedan based cars need but I can see it as valuable with lighter cars. I need to work on a car with this and get some experience.

      1. I’m working on an SCCA GT-3 car for the next race car, so suddenly shocks get easier when they’re 1/2″ rod ends on either end. Doing a lot of thinking about shocks lately, as I don’t see why revalved circle track Bilsteins wouldn’t be a horrible place to start – not optimal but cheap.

        Actually, have access to some weird stuff at work now – playing with a bunch of servohydraulics. Seriously thinking of doing a quarter car model on some vertical sliders, putting it on top of one of the actuators, weighting it accurately, and running sine sweeps or other things to look at transmissibility. Not as ideal as a real 4-post rig, but the price is right.

  3. I’ve been looking tho get a set of these since there came out here in Japan where I live, sadly the lack of users and reviews made me hesitant. Tho there’s a popular “myth” here in Japan where it is Ohlins that makes HKS coilovers (Hypermax IVs at least). It was either Ohlins or RS-R for Street/ track single adjustable set that I was choosing from.

    Thanks a lot for this in-depth write up Mike, you’ve educated me yet again.

  4. Ohlins R&T are made in Japan. The more expensive TTX line is made in Sweden. Not sure about the HKS coilovers, but the R&Ts on my WRX came with rebranded Cusco top hats.

  5. I was luck enough to find a used set of Ohlins for my CL9 Acura TSX/Honda Accord. They were built with some crazy low ride height and crazy high spring rates (24kg/mm fronts). I have since spoken to Ohlins USA and got inserts and more reasonable spring rates and I must say the ride is very very impressive (coming from ground control/koni set up. Great write up and I appreciate the MotoIQ team going the technical route.

    1. Koni FSD does something completely different. It uses a second set of bypass valves that basically makes the dampers not work unless you stroke them a certain distance. It’s a very clever implementation of stroke-sensitive damping but it’s a nightmare to tune.

      Great for ride comfort on the street if you use stock springs, but a fairly useless feature for racecars and tuned street cars.

      1. Do you have a link to how the parts are? I am pretty sure they are not position sensitive butI have never seen a picture of them.

  6. I have a 2002 Nissan Sentra Spec V. A V6VQ manual installed..ABS NOT functioning..do I need. Maxima ECU module or wire harnees to replace Spec V?? Also have 300 Z front calipers..stops well with G Loc 12’s..HELP PLS?

  7. I had an Electraglide with the heavy duty harley shocks on it that were still rubbish and I ordered Ohlins fork inserts and there rear shocks and springs and it still handled the same but the ride was transformed very supple but extremely progressive, all I’m really saying is that these guys know what there doing. Thanks Michael.

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