OK, after about a year of screwing around getting all the parts together I have finally built a charging system for my Ground Control Advanced Design Coil-overs. Pics of the unit are attached.

This is in answer to the issue of the nitrogen gas slowly leaking out of these shocks until the pressure gets so low the shock's function is impaired. They stop dampening the coils well and make the front end jounce around - scary in a high horsepower car. Jay, the owner of Ground Control, acknowledges that early adopters of his shock system (like me) can have shocks that leak slowly over time due to the fact that the Locktite they used does not harden well without enough oxygen, and since the shocks use nitrogen (inert, doesn't overheat as easy as normal air, etc), the Locktite stays moist and doesn't seal well. After about a year of investigation working with Locktite's engineers Ground Control now uses a special hardener that has eliminated the problem. I still have the older shocks so I"m stuck until I take them out and have Jay rebuild them, and I'm too lazy and drive the car everyday, so......

Jay provided me with the basic schematics and design to build my own charging system. I wanted this so I wouldn't have to keep trying to coordinate having him charge them for me at his shop - it was a hassle for both of us. This system is a variation of several systems that they use in the assembly process. Fortunately their main plant is only about 20 minutes from my house, and Jay was great in making himself available to help me.

If you want to build your own system (say you have these shocks but you live somewhere far from Northern California), here are the basics. One piece (the dill chuck), is the most important and difficult piece to get:

Parts:

1 - Dill Chuck, model 8921 (very important). You pick the fitting end size to match what sized hose and fittings you get. I went with 1/4" npt, but -3an or -4an works well, too.
1 - Cylinder of Nitrogen Gas (I chose the size 40 bottle, but you can use size 20 to keep it very compact). This cylinder will probably last me for years......
1 - 4' to 6' Stainless Steel Braided hose (lined with inert nylon or other inert flexible polymer material). Size based on your desires and fittings you order. I went 4'.
1 - pressure regulator.
Various amounts of fittings (I went with brass) to attach the hose to the regulator and the chuck to the other end of the hose.
1 - tube of TFE Teflon pipe compound (important to stop leaks).
1 - spray bottle with light mix of water and dish soap (leak finder).
Various box wrenches to put this all together

Note on the Dill Chuck - you need model 8921 for these shocks, which mates to the Schraeder valve on the shock body. This chuck is not to be found in stock anywhere in the world due to its exceptionally low use in the market - you will have to order it. I got mine through Borg Equipment and Supply (offices in Rancho Codova, CA and Los Angeles CA). It went on backorder and took 6 MONTHS to arrive. The other components I purchased through Barnes Welding Supply in Sacramento, CA. Both of these vendors came recommended by Jay. The chuck will cost around $60, and the other parts cost me $241 since I actually bought the bottle vs. renting it.

Assembly:

Straightforward assembly - pressure regulator to cylinder, male to male fitting into regulator, hose end to fitting on one end, and chuck on the other end with extentions and additional fittings if you need or want them. Use the TFE paste on the fittings - it will help prevent leakage and you won't have to tighten the fittings against each other so hard to stop any leaks.

Testing:
It took me several attempts to eliminate all leaks since I didn't use the pipe compound the first time. Once you have it all hooked up, tighten the chuck against the Schreader valve but make sure you don't have the chuck set to actuate the valve (back the adjument **** on the chuck all the way off). Open up your cylinder valve to presurize the regulator (back the regulator off so you don't yet flow air to the hose). Use the spray bottle and squirt around the fitting where the regulator goes into your cylinder to confirm no bubbles (bubbles = air leak). If you are leaking, crank it down with your wrench - make sure you used pipe compound to make your life easier. Your pressure regulator should now hold steady on the cylinder side. Now you can crack open your pressure regulator to flow just a tiny amount through the hose. Listen for leaks and apply wrench accordingly. When you can turn off the cylinder valve and the entire system stays pressurized when connected, you will have killed all of your leaks.

Note - the chuck presses a small copper seat against the Schraeder valve. You may need to give it a couple of cranks to tighten and press the valve into this copper seat to get a good seal. Once it makes an impression, you can just use your hand to tighten and remove the chuck, but the first couple of uses will require a wrench (sort of a break in period).

Use:
It is best to start with no pressure in the system and first activate the chuck valve to let the shock gas pressurize the system, then use your regulator to bring the charge up to 150 psi. Go slow so you don't overshoot and overpressurize the system - Jay says you can run 180 psi if you're going to be on the track, but 150 is fine for the street. Once the pressure is equalized, back the chuck valve off (this seals the shock valve), then back off your pressure regulator, then disconnect the chuck from the shock valve body. Put the Schrader valve stem cover back on and you have a topped up shock.

The difference between freshly topped at 150 psi and 100 psi is night and day. The car is once again the slot car I love :-)

So, here is something new under the sun for our beloved FDs.

Beast

 

Beast.......I thank you! You just made my life so much easier. I have been wanting to check the psi on these shocks the last year or two. I thought it would have been as easy as going up to the local race shop. But they probably wouldn't have this special chuck. I will be ordering these parts and the write-up was spectacular. Can't wait to play with the compression and rebound settings again. The car has been down too long.

 

I'm glad to help - after using the Big List and Forum as a resource for so long, I have to give back to the community when I can. I figure this is going to be a pretty thinly used write-up since the AD shocks were expensive and I don't know that they sold very many, but I love 'em and the only downer was they slowly went south and needed to be topped every 4 to 6 months. This solves all problems.


I know that Max Cooper has them and he may benefit from this, but beyond that I don't know of any others with this setup. Most went Koni yellows or Tein.....Jay got to the market a bit late for the RX7 but he sells the hell out of them for BMWs and Nissans....

Jay was trying to build a pressure test device but it is an engineering problem - there is so little volume in the shocks that the mere act of trying to measure the pressure results in a loss of too much nitrogen. Sort of like a quantum physics problem - the act of observing changes the state such that what you think you see really isn't there - it moved 'cause you bounced a photon against it. He eventually gave up. I think you'd need to use some expensive electronics to do something like that - not cost feasible.

Beast

 

If the volume is really so small he'd probably have to use an electronic transducer of some sort so you could read pressure without any of the gas escaping from the shock and into the measuring equipment.

I haven't seen the business end of the AD shocks up close but I assume they use a plain schraeder valve; nothing special? I believe R12 a/c fittings are the same size and professional R12 a/c gauges allow you to seal to the stem and then actuate the valve inside manually with a ****. Is the Dill valve different?

 

Great write up Beast. Thanks for showing everybody exactly what it takes to make this system. That will surely save people some money and *** pain in the future.

Zach

 

Damon, I'm not certain since I havn't looked at the business end of an R12 charging system in a long time. What psi are those rated to? If they can handle the pressure, then maybe those are are viable alternative. Jay's a pretty sharp dude and I would have guessed they'd have figured out another way if it was available, but I can ask him if he ever thought or tried to adapt a/c fittings.


Thanks for the nice words, Zach. Again, sorry I don't get around to the local gatherings-just too busy.

Beast

 

Great job Eric... it looks exactly like our PENSKE shock system nitrogen rig!


-Bern