New KOH shock tech talk

[Mac5005]

Just trying to get some more tech going on, and get some brains working.

Pretty cool tech to me, ymmv.

Ken @BRUISER was kind enough to invite my dad @moldman05 and I and many other out to the lakebed this year to help with pitting and to experience KOH.

Jason scherer won the 4400 class this year and said that fox made some huge changes just before the race that raised his top speed close to 20mph in the desert.
This made everyone wonder what kind of special changes those were.

Talks of Fox’s new live valve system with servo controlled valving, and active suspension control dominated the hearsay.

After thinking about it for a couple days and on the plane ride home, curiosity got the best of me.

I reached out to Jason to ask, what were the changes? I couldn’t stand it, I just had to know.

Thankfully Jason being an awesome dude responded and was open and honest about the changes that were made.

He said larger bypass tubes and a nitrogen valve instead of the spring in the tube. Says it holds the car up longer and takes the hit smoother.


From the pics I have and I was looking for the servos, it didn’t have servos on any bypass tube or c/o resi.

It took me a few hours of thinking and chewing on what he told me, and I went down the google rabbit hole looking for exploded diagrams.

After chewing on this info,

It actually doesn’t look too crazy to remove the spring from the bypass tube, add a few orings to the tube end cap, replace the adjustment bolt with a schrader valve, and use n2 pressure instead of a mechanical spring.

Then can change n2 pressure to adjust the bypass tube(s).

It’s very Interesting thinking about the psi/force differences between the two and the practical real world differences.

So no active suspension on ultra4 stuff, yet. Currently only available in ford raptors and new rzrs. It’s crazy thinking about how the live valve/active suspension systems will change ultra4 when it becomes available and implemented.

Fox has already shown servo adjusters bypasses and now servo adjusted dampening in the reservoir with the new rzr.

 

[Fabrik8]

Also Colorado ZR2, awesome Multimatic dampers.

The problem I can see with just replacing a coil spring with a Schrader valve and nitrogen is that you're building in all of the inherent functional differences/downsides of an air spring, like thermal dependency, hysteresis, non-linearity, etc., without any other changes. What I'm saying is that changing out to an air bypass spring is likely more involved from an engineering/developing standpoint than just swapping some existing parts out with some new parts. You might need to change bypass orifice sizes, bypass piston stroke, etc., to properly work with the big differences in how an air spring functions. You did mention larger bypass tubes, so that's the kind of changes I would expect would need to go along with a spring change like that.

 

[Mac5005]

Also Colorado ZR2, awesome Multimatic dampers.

The problem I can see with replacing a coil spring with a Schrader valve and nitrogen is that you're building in all of the downsides of an air spring, like thermal dependency, hysteresis, on-linearity, etc. What I'm saying is that changing out to an air bypass spring is likely more involved from an engineering/developing standpoint than just swapping some existing parts out with some new parts.

The multimatic dampeners use spool valve technology different than the current fox tech ?



I would think the quickest way to implement a late to the party change, would be as minimal of part changes as possible.

Already know it was a different set of bypasses with larger tubes. What other changes would you think fox would make, to implement those changes? Essentially each bypass tube would have an IFP to apply pressure to the plunger.

I think it’s understood that in Jason’s application subsequent pre race tuning would demand results to use for KOH. Otherwise bolt the proven bypasses back on for the race.

How long before someone else tries it? Personal or factory.

 

[Fabrik8]

The multimatic dampeners use spool valve technology different than the current fox tech ?

Yes, I thought you were just talking about things that already use active suspension.

Speaking of spool valves, you could use spool valves to control the bypass springs, or replace the bypass orifices with spool valves. Formula1 has been using Moog spool valves for lots of different active suspension duties on and off for many years, DTM has as well.

 

[Mac5005]

Yes, I thought you were just talking about things that already use active suspension.

Speaking of spool valves, you could use spool valves to control the bypass springs, or replace the bypass orifices with spool valves. Formula1 has been using Moog spool valves for lots of different active suspension duties on and off for many years, DTM has as well.

Wanna go in depth on the difference of using spool valves like the zr2 system vs what’s being used on the rzr?

I have no idea how fox actually achieved it, I’m just taking what he said, looking at the diagram and thinking about the simplest way to achieve what Jason described.

I think it’s understood that my bench racing about it, is a vastly simplified explanation of what fox probably actually did.

Just trying to get some more tech discussions going on.

How long will it be before you can buy a reservoir system with servos, sensors, and controller to adapt to all the Offroad coilovers in use?

Or is Polaris paying enough that it will be a long time before it’s commonly available.

The price point on the rzr with active suspension isn’t THAT much higher (10%) on the dynamix model.

Not sure the price point difference on the raptor or Colorado.

Can’t wait for the day you can bolt on a system and achieve what it does.

 

[Mac5005]

Also Colorado ZR2, awesome Multimatic dampers.

The problem I can see with just replacing a coil spring with a Schrader valve and nitrogen is that you're building in all of the inherent functional differences/downsides of an air spring, like thermal dependency, hysteresis, non-linearity, etc., without any other changes. What I'm saying is that changing out to an air bypass spring is likely more involved from an engineering/developing standpoint than just swapping some existing parts out with some new parts. You might need to change bypass orifice sizes, bypass piston stroke, etc., to properly work with the big differences in how an air spring functions. You did mention larger bypass tubes, so that's the kind of changes I would expect would need to go along with a spring change like that.

Larger bypass tubes are proving to be much more effective especially on the rebound side even with the conventional coil spring and adjuster.

Biggest hurdle with most rigs for what we do is relatively lightweight sprung mass vs relatively heavy unsprung mass is getting the axle to rebound fast enough.

 

[Fabrik8]

Larger bypass tubes are proving to be much more effective especially on the rebound side even with the conventional coil spring and adjuster.

Biggest hurdle with most rigs for what we do is relatively lightweight sprung mass vs relatively heavy unsprung mass is getting the axle to rebound fast enough.

Makes sense about the bigger bypass tubes. It's intuitive that the quickest path to higher rebound rates is to increase bypass flow, and you may not know that the existing bypass tubes aren't large enough until you try it (or have a good simulation model, which is arguably the better but more expensive path to optimization). There's going to be some point of diminishing returns where additional tube size doesn't add anything, or you start messing up some other important parameter, and I would think that Fox has all of that stuff modeled so it can be explored via simulation.

Just out of curiosity, are they changing the shape of the ports where the bypass tubes meet the damper tubes, so the larger bypass tubes don't change the timing of how fast the damper piston shrouds/exposes the port to the damper tube? Making a oval port instead of a larger diameter circle, etc., so you expose more bypass flow sooner versus piston displacement. I'm debating with myself how important that would actually be, and I'm probably overthinking that. I don't know enough about bypass dampers to understand all of the nuances.
Actually, nevermind. I forgot there are orifices in the main damper tube that control the timing of flow into the bypass tubes, so the shape of the bypass tube where it meets the damper tube doesn't really matter. I still have a lot to learn about these weird dampers.

 

[Mac5005]

I think tube placement and length/overlapping tubes have more effect on the timing than actual port shape and location in regard to the piston position.

This makes the flow near ride height the greatest and the progression at either end even more non linear.

I would think with larger tubes, and larger radius bends, with the tubes still close to the body, the entry ports would naturally become more oval.

I also think the smaller tubes and bypass valves would act as an orfice at high flow rates, making the valve act like a hard stop or rate plate. This would be somewhat easy to determine a larger tube and orfice is necessary.

The same is true for too small of a reservoir hose and fittings.