Manual CTIS Conversion for M-1078

After severals request to start a post on this topic, I'm going to give it a try. I purchased my M-1078 in December with the control box missing from the cab. After reading several posts on the CTIS, and learning there is a lot of people having trouble with them, I decided to go the manual route. For less than $100 I bought a regulator, valves, and fittings to eliminate the electrical part of the system. To install, just run the supply line to the inlet of the regulator, and the air line going to the tires to the bottom of the tee fitting.

I will try to be brief on how it works.

To inflat the tires;
1. Close both valves
2. Adjust regulator to desired psi
3. Open the supply air valve
4. Once tire pressure is reached close supply air valve
5. Open dump valve quickly, this will allow the tire valves to seat and hold the air at the tires, and the air will exaust from the axles.

To air down the tires;
1. Close both valves
2. Adjust regulator to a psi higher that current tire pressure
3. Open supply air valve just long enough for air to start filling the tires, then close it.
4. Open the dump valve just enough to allow some air to exaust, when this happens, the quick-release valves on the frame will start to dump the air from the tires, close it and allow the tires to deflate to the desired psi. Note: not all of the tires will deflate at the same rate, on my truck there is a range of about 5 psi difference in them, you will lower them below the desired psi.
5. To equilize the pressure of the tires, repeat the steps above on inflating the tires to there new lower psi.

tjhuffy

Much Thanks.... Great idea

One additional option of going this route is the possible additional advantage to add an air pressure powered Personal Air conditioning suite. By adding in A "T" and valve prior to supply of incoming air to CTIS? system you could power it. Might need a regulator and or additional small tank on it as well?.... Could "Y"off this to supply cooling air to two people with similar vest. Wonder if someone makes leggings too? Seat cushion ?

Interesting idea that might warrant its own thread at some point so not to hijack this one.


http://www.smithtoolsupply.com/Safety/Protective-Clothing/XS-6400.html
http://www.westernsafety.com/products/allegro2006/allegropg8.html
http://www.vortec.com/dual-action-pac-with-vest/overview


modify one of the above to plumb into one of the air cushions like:
https://www.activeforever.com/cooling-car-summer-seat-cushion-12v
http://www.ebay.com/itm/SOJOYS-Comf...-Car-Seat-FAN-Cushion-12V-BEIGE-/252332858869

The system sends around 12psi to hold wheel valves open to air down tires. If you can set your manifold to do this you may get more even pressure in the tires.

at #4...

4. Open the dump valve just enough to allow some air to exhaust, when this happens, the quick-release valves on the frame will start to dump the air from the tires, close it and allow the tires to deflate to the desired psi.

When it reaches desired PSI what do you do to stop it from deflating further?

Open the dump valve completely.

Sorry for questions. Thougt I had this "understood" but now am confusing myself. Again a Step 4 question and the "desired PSI". Does the gauge show tire PSI reducing during this step or is it a gut guess that "desired pressure" or maybe better said "desired amount of deflation" has been reached?

Nothing wrong with it being gut guess. Experience will make that a non-issue.

The gauge will only read tire pressure during inflation, the only true way to know the tire pressure during deflation is check each tire individually. That is why you deflate the tires lower than you want so you can set them equally during the inflation steps.

Two ways to answer the same question of.... what does the Inflate gauge actually show and when does this gauge actually show this?

TJhuffy said:

.... The guage shows the regulated pressure (whatever you have it set at) when the air supply valve is closed. When the valve is opened, the pressure on the guage is whatever the pressure is in the system down stream from the valve. When the tires are at the same psi as the regulator setting, the gauge will read the same as a tire pressure gauge at the tires.

Click to expand...

(different wording to explain same thing)

TJHuffy said:

. The gauge on the regulator shows the psi that the regulator is set at when the air supply valve is closed, it doesn't show tank pressure. When you open the air supply valve, the gauge will drop representing the pressure in the tires (somewhat). True tire pressure will be read on the gauge when the system has had enough time to equalize.

Click to expand...

these quotes taken from a PM discussion had with TJ. Putting them here to help others wrap their head around this idea.

Suprman said:

The system sends around 12psi to hold wheel valves open to air down tires. If you can set your manifold to do this you may get more even pressure in the tires.

Click to expand...

So if am understanding this right... to reach the 12psi* of Suprman's suggestion one could plumb in a second regulator/gauge before the dump valve. Call this the Dump Regulator and the other in the pic the Supply Regulator. This seems it could then be used during deflation to set a bleed off of air down to 12psi from the Supply line's pressure against the Wheel valves . Think; this will allow for Suprmans point of better equalizing tires during deflation AND lower pressure against the rubber in the valves thus putting less stress on them. If so this makes original step 5 an option to check if one doesn't trust their gut and want to use Inflate Regulator's gauge to better have an estimate of what tire pressure is really at.

So if this Dump Regulator was added (assuming I understand this correct) the new steps of deflation from 4 on would be:

4. Set Dump Regulator to 12psi. Open the dump valve causing the Quick-Release valves to start to dump the air from the tires.5. When your gut feels tires are deflated enough to traverse the Terrain ahead; crank the Dump Regulator open all the way. This will close the Quick Release valve and stop deflating tires.6. To verify if tire pressure after Deflation is where you want it and/or to make sure all 4 tires are pretty equal in pressure; use the Inflate procedure to bring tires UP TO desired pressure.
* in another thread somewhere I saw 16lbs of pressure was needed to hold the valves open while Superman suggest here it is 12psi. So experiment to see what is best on your system??? Your Milage May Vary as they say. Also maybe someone will chime in with the spec. pressure.

TJ, Superman; anyone else... does this conceptually sound about right or is my understanding whacked


BTW- slightly related bit of information- I think adding a tid bit of air via the Inflate circuit to put a little pressure on the axle/hub seals is part of what a "Deep Water Forging" system does. This is done to counter the water pressure wanting to push water past the hub and axle seals. Least think that is how they go about it on Unimog's with their Deep Forging kit. Or maybe air is pumped in elsewhere to pressurize the axle?? Not sure. If it is via the CTIS you would do this before entering potential deep water in a stream/pond/Swamp etc. Could be easily done with TJ's set up. Just a little air pressure though; shouldn't add enough air to get to close to 12psi from what Suprman says above. If you did you might cause a valve to open.

I like the water fording idea, I would revert back to the inflation mode and hold the axles at the same pressure as the tires while in the water.

I took apart a wheel valve and figured out how it works. Even if the tire is inflated to highway pressure, a lower pressure applied through the line will actually deflate the tire, just like suprman says. The wheel valve gives the incoming air more leverage than the air in the tire, so low pressure air like 12 to 30psi will hold the wheel valve open and release pressure from the tire. Tjhuffy's setup is brilliant. It should deflate the tires just by setting the regulator to a lower pressure and sending it to the tires. When you shut off the air pressure the wheel valve has a spring that will close it and stop the deflation.

Konichiwa512 said:

I took apart a wheel valve and figured out how it works. Even if the tire is inflated to highway pressure, a lower pressure applied through the line will actually deflate the tire, just like suprman says. The wheel valve gives the incoming air more leverage than the air in the tire, so low pressure air like 12 to 30psi will hold the wheel valve open and release pressure from the tire. Tjhuffy's setup is brilliant. It should deflate the tires just by setting the regulator to a lower pressure and sending it to the tires. When you shut off the air pressure the wheel valve will close and stop deflating.

Click to expand...

GOOD TO KNOW about the leverage advantage within the system. Brilliant. Much thanks. Course you can't "shut off the pressure" like you mentioned. Would think it has to bleed it off via a something like TJ's dump valve in order to make it go away?

Hope TJ will test this.

If it works it might negate the need for the Dump Regulator that I proposed in order to bleed down the air supply line so its is holding 12ish PSI in the line. From what you say should be able to start with 12ish PSI from the get go.

Thanks for the kind words Konichiwa512. I didn't try experimenting different methods when the first one I tried gave me the results I was looking for. It would appear if the tires are at 55 psi and I wanted to air them down to 20 psi I could close the dump valve, set the regulator to 20 psi and open the air supply valve, allow the tires to deflate to 20 psi, close the air supply valve, open the dump valve and be set at 20 psi. I never gave it any thought about the dump pressure until suprman mentioned it. I'll try it out and get back with the results, and pics when I get it mounted permanently.

Coach is right about my poor choice of words. TJ should be able to set the regulator at the desired lower pressure for the tires and send it out. Once the the tires air down to the same pressure as the incoming air they will stop deflating, but the wheel valves won't close until the ingoing pressure is dumped. According to the owner's manual the CTIS pressures are: HWY- 55psi, X-C- 33psi, SAND- 20psi, EMER- 14psi. The book also warns that driving in the EMER setting will damage the tires.

The only two specifications. we are missing here to really do this right is what PSI (or range of PSI) is the wheel valve designed to be opened AND held open at. It may well be it is the same psi for both open and hold open but we just don't know yet. Anyone come across those figures before?

Assuming the same system would work on 939's?

If it has three air lines coming out of the control valve it should. Mine has an air supply in, a air out to the axles, ans a dump line to atmosphere.

I have completed the installation of my manual CTIS system. After several discussions with all of you I tried out different theories discussed and here are my results.
With regulator / tires set at 55 psi, air supply valve (ASV) open, dump valve (DV) closed; the tires didn’t start to deflate until the regulator was reduced to 41 psi.
I reduced the regulator to 20 psi and the tires deflated to the 20 psi, quick release valves (QRV) closed and tire psi was equal. I closed the ASV and opened the DV to release the air from the axles.
I did the same test from 55 psi to 30 psi and got the same results. I am very satisfied with the system, no electrical gremlins to deal with.
As to the water fording, my conclusion is the regulator should be set to the same psi as the tires, ASV open and DV closed to insure steady psi on the axle seals until you are out of the water. Lower psi than the tires could open the QRVs.

The hubs themselves nor the axle are pressurized by the ctis. There is just a pass thru between two seals. I believe the lmtv is pretty water tight. You would have to do 2-3 psi pressure into the axle vents and anywhere else you think water will infiltrate. The front hubs are independently sealed from the axle itself.

Suprman, I realize the seals dont have air on them when the air is dumped, but if the CTIS is in active inflate mode wouldn't it help keep the water out of the air lines?