Endless Air Project
|During my time as a navi for "Money Pit Racing" I came to appreciate the
usefulness of an endless air system. It used to get a massive workout during competitions where it would be needed to seat
beads, run rattle guns, right angled drivers, air blowers and the Airlockers of course. When out camping, I have been in
many situations where the need for a more powerful compressor would have been a god send as my older Blue Tongue and current
ARB unit I have just took way too long when it came to inflating tyres or any job that involved compressed air. So when my
mate Paul made an endless air system for the comp truck, I was intrigued and compelled to do the same.
One of the problems that I found with sourcing, modifying and installing an Endless Air into a Patrol is that there is very little in the way way of information available. Apart from word of mouth, enthusiasts in the States, forums and information scattered around various websites, one can search for a long time before they can find what they need and get the motivation or confidence to attempt it themselves. It was for these reasons I decided to document mine.
With my installation, Paul had made up a few brackets to suit the Nissan TD42T motor as he had it all jigged out in his workshop when he made one for his GQ (yes with a GU motor). So armed with one of these, all that was left for me to do was to get the compressor and other associated gear and fit it all to the Patrol. Now there are really only two types of compressors worthy of such an arrangement, the York, which is more common in the US and the Sanden units which were sold here in huge volumes on such vehicles as early model Holdens, Sigmas etc. The York is a very good unit due to its high pumping capacity and internal oil sump but it is can be difficult to fit to a TD42T due to its large size and awkward shape. The Sanden compressor on the other hand was practically made for the job and you can use either the SD7 or SD5 series compressors for an endless air setup. I ended up with a SD508 which is a 5 piston compressor capable of pumping at 9 CFM and up to 300 PSI. They are a very common compressor and very easy to modify and mount as well. Depending on your bargaining power, they can be picked up from wreckers for between $20 - $150.
Before using the SD508 as an air compressor, there are a couple of modifications that need to be done to allow it to perform reliably. To start with, we need some sort of lubrication present to prevent the compressor from seizing from heat and friction build-up. Now these units get pretty hot and when used in an air-conditioning system, it is lubricated by oil which circulates with the R12 gas. As we are now compressing air and not gas we need a substitute. Luckily there are a number of options available from automatic or inline oilers to the easier option of fitting a grease nipple and pumping grease into the compressor. To do the latter, all you need to do is remove the oiler plug in the top of the compressor and screw in a grease nipple with 1/8" thread. Then it is just a matter of pumping in around a 1/2 - 3/4 of a cup of good quality grease every 6 months or 5000km (depending on usage) to keep the compressor happy.
Now one problem with performing the grease nipple mod is that we want this grease to remain in behind the pistons and not being pumped out with the compressed air and ending up in tyres etc. If you look at the picture below (centre) of the pistons, you will notice that one piston has a lot of clean blue grease present. This is the piston which is right next to the oiler port (top of piston in picture). You can also see some burnt grease on the opposite piston which can result if there is not enough grease present in the compressor. To minimise oil or grease in the compressed air, you can either fit a coalescing filter about 1 meter from the outlet or discharge port (which can be expensive) or you can perform a small mod to the compressor to keep this grease inside where it is needed. To mod the compressor, you have to undo the 5 bolts on the rear of the compressor and remove the Cylinder Head to gain access to the Valve Plate Assembly (be careful not to damage the Head Gasket). Locate and then tap the small hole that lines up behind the suction port using a 5mm tap. Block this hole with a 5mm grub screw and Locktite and this will minimise any grease or oil from being discharged. Having a receiver (tank) fitted will will also minimise oil or grease as it should settle in the tank and not end up where you want the air.
To enhance the compressors pumping capabilities you can also drill out the Suction and Discharge holes so they are a larger diameter which will remove some restriction to the air. One needs to be careful doing this however as you can damage the face of the suction / discharge ports if the drill is not perfectly straight which could result in a poor seal when connectors are fitted. If for some reason you get a really old compressor with a paper based Block Gasket and Head Gasket or you damage the seals in any way then you can get replacement rubber coated tin seals from Heatcraft (part number 8385-9611) or Jayair (part number CP 1040). A service manual for the Sanden SD series compressors can be found on the Sanden site as well as compressor specs. In my case, there must have been some moisture ingested during its life as an air compressor and a small amount of surface rust was present under the old gasket. In this case a razor blade was used to remove the old gasket remains and then some very fine wet and dry sandpaper used to smooth the surface of all components.
Fitting the compressor would have to be one of the hardest parts to this project. There is very little room to manoeuvre the compressor and trying to get at the bolts to secure it to the bracket would be better suited to a contortionist. However with a little patience and the right tools, I had the Sanden in after about 3 hours. I have seen a few different types of bracket for the TD42T motors but pretty much all of them have the compressor mounted on the lower right of the motor. The bracket that I had attached between the engine mount and motor using the 4 engine mount bolts and 2 bolts on the block just to the rear. It is a very snug fit and to allow the compressor to be connected up with a compressor belt meant having to bend and twist the vacuum pipe that goes under the motor so that it cleared the top of the bracket and didn't contact the compressor pulley. I also had to bend the power steering pipes slightly as when the compressor was engaged, the clutch plate in front of the pulley will spin which meant that it could contact the pipes. A couple of zip ties also add peace of mind as well. I had to mount the compressor so that the suction and discharge ports were facing downwards as there is not enough room to connect a fitting to the suction port due to the vacuum pump on the motor which is in the way. I only needed the compressor to be about 1" lower to mount it upright however other brackets may allow you to have the ports pointing upwards which is a better position in my opinion.
If you are installing a Sanden compressor on the later intercooled TD6 patrols, you will have clearance issues with the front cross member that joins the chassis rails between the front of the motor and rear of the radiator. This cross member is mounted further back on the TD6 to allow for a bigger radiator and this cross member will contact the clutch and pulley of the Sanden compressor. To allow sufficient clearance, people have used an oxy torch and hammer to 'manipulate' the cross member a small amount to allow contact free movement. Playing around with the compressors position on the brackets could prevent any need to modify the cross member however one has to keep in mind that the compressor pulley needs to be level with all the other pulley's that will be on the new belt so you don't damage or throw belts all the time.
To drive the compressor meant removing the power steering belt and running a longer belt around the power steering pulley, fan pulley, crank and air compressor. I measured this route with a piece of string and went shopping to find something that was close. I eventually found a Bosch 13A1450 raw edge cogged super belt which is 1450mm long. Fitting it was a little hard, even with the power steering pump fully loosened off, but once on and tightened it provided a tight and reliable drive to all accessories. A slightly larger belt would be better but the 13A1450 was the biggest I could find on a Sunday afternoon. One problem that is faced with rerouting the belt is having sufficient belt wrap on the various pulley's. By changing the configuration of the drive belt from the crank to the fan, power steering and air compressor, you now have less belt contacting the crank or driving pulley which could result in slippage when the compressor is turned on and loaded. Having sufficient tension and good quality, deep V belts should prevent this but it pays to keep an eye on it over time.
Once I had the compressor installed and connected to the drive system, it was onto getting all the air lines connected up. Firstly I fitted a 3/8" BSP to 1/2" barb 90° fitting with locking nut to the Patrols air filter housing so that the compressor was fed clean, fresh air. The fitting had a light smear of silicone on it to provide an airtight seal and also a liberal dose of Locktite for the locking nut so it did not come loose and end up damaging the turbo. This was connected to a 1/2" barb to 7/8" SAE 90° fitting on the 'Suction' port of the compressor via 2m of rigid 1/2" hose. The hose needs to be reasonable rigid so it does not collapse in on itself when the compressor is engaged and sucking air however this is not as critical on short runs as it is on longer runs. On the 'Discharge' port I fitted a 3/4" SAE to 1/2" barb 90° fitting with 800mm of high temperature, high pressure hose that was connected to a check valve via a 1/2" barb to 3/8" BSP fitting. The discharge hose needs to be able to handle high temperatures as the compressed air coming out can be extremely hot when the endless air is operating at 2000+ RPM's. The in line check valve is there to stop air stored in the tank from leaking out through the compressor when it is not switched on and is mounted to the chassis rail via a 3mm angle bracket about 200mm back from the right engine mount. Connected to the check valve is 'T-piece' fitting with 3/8" BSP connections which feeds the rest of the system.
One connection of the T-piece goes from a 3/8" BSP to 1/2" barb via 1m of 1/2" hose to the pressure switch via a 1/2" barb to 1/4" BSP fitting. The pressure switch is a Condor MDR 2 with 4 ports, an adjustable pressure setting for both cut in and cut out and an unloader port. It is designed for 240V AC compressors but these type of switches will switch 12V DC without any problems. The pressure switch is set to switch the endless air on at 100PSI and cut it out at 130PSI. It has a 140 PSI pressure gauge on one port, a 165 PSI relief valve on another, blocking / mounting fitting on another and of course connection to the compressor. I mounted the pressure switch assembly to the fuel filter / pump assembly via a 6mm angled bracket. This allowed a secure fitment with easy view of the gauge.
The other side of the T-piece connected to the check valve goes from a 3/8" to 1/2" barb fitting to a 9 litre air tank via 1200mm of 1/2 hose and a 1/2" barb to 3/8" BSP 90° fitting. The air tank is mounted on the drivers side and is secured to the floor pan with 10mm bolts. This position is ideal as the tank only extends past the chassis rail by about an inch so is pretty protected. Mounted to the front of the tank is a 1/4" BSP drain cock to let out moisture and oil residue and also a couple of 1/4" plugs. At the other end of the tank, I have mounted a 3/8" BSP to 3/8" barb fitting which is connected to front and rear Nitto air chucks via a 3/8" barbed T-piece and 3/8" blue compressor hose. Also connected is the ARB setup which comprises of an ARB compressor mounted under the passengers seat connected to a 3/8" BSP check valve and bulkhead fitting which goes through he floor pan. This is then connected to the front and rear air couplings via another 3/8" barbed T-piece mounted above the transmission cross member on the drivers side. Although used as a backup compressed air system, I run the ARB compressor purely for the front and rear Airlockers. I could run the Airlockers from the endless air system but I would have to install a regulator to bring the pressure back to 100PSI max otherwise damage to the Airlockers could result.
To control the compressor I have wired in an 'On/Off' master switch located on the dash to supply an ignition switched 12VDC through the pressure switch located in the engine bay to the compressors clutch. I have routed this 'control' wire in harness flex to neaten up the installation as well as protect it from abrasions and the like.
When selecting the various fittings, switches and valves, there a few things that you should consider. Firstly try and fit the biggest, highest flowing fittings and hoses you can as this will reduce any restrictions to the air when travelling through the rest of your system. This is why I went with 1/2" hose and 3/8" fittings between the compressor and tank and 3/8" hose for between the tank and air couplings. Also do not flow your compressed air through the pressure switch to the tank / outlets as it has a tiny 4mm hole that joins up the various ports. Instead, branch a connection off the main line to the pressure switch so it can monitor your compressed air setup. Another thing to consider is that some fittings like the relief valve are not only sized at a certain pressure (PSI) but also at a certain volume (CFM) rating as well. Therefore, do not get a relief valve rated at say 2 CFM if your compressor is rated at 9 CFM as it will not discharge the volume of air needed if your compressor cannot be shut off. It is advisable to use a good quality liquid thread sealer on all fittings to stop any air leaks as well. I have used Loctite 567 throughout the compressed air system and it only drops 30PSI over 24 hours which I am happy with considering the number of connections used. Instead of using hose clamps on all the fittings, I have used 'O' Clips which provide a much more airtight clamp. These are a permanent type clamp that are done up with pinch pliers but they can be snapped off if required. I always carry about a dozen spares (along with an assortment of fittings) as well as the pinch pliers as part of my tools / spares kit.
On other installations, I have seen either fixed pressure switches (such as the ARB type) or adjustable pressure switches with unloader port used. This 'unloader' port is connected to an unloader check valve so that when the compressor stops, either due to the operator or pressure switch, the head of pressure between the compressor and check valve is released to atmosphere so that the compressor is not starting up to a pressure load. This is beneficial if the compressor is used a lot but is not really needed if used occasionally as the compressor will leak this head of pressure through its pistons over a short period of time. Also it is not necessary to fit a tank if you intend to use the compressor to just pump up tyres. However it can provide valuable storage of compressed air for seating beads and running some air tools such as rattle guns, drills or drivers. To seat beads, I found a bead seating fitting used by tyre shops to be extremely useful (pictured above). The main aim of this fitting is to get as much air as quickly as possible into the tyre so that any stubborn beads pop into submission with ease. To use, you simply remove the tyre valve and then screw the bead seating fitting onto the valve stem. Then once your air system is pressurised, connect up the air hose coupling and wait for it to pop back into place.
My Parts list:
All fittings and hoses were sourced locally at Enzed, Blackwoods and Tony Powell Hose & Fittings. The tank was sourced from eBay and the compressors were from the local wreckers.
A big thank you needs to be given to the great bunch of guys on the http://www.patrol4x4.com/forum/ site, in particular OldMav, Sootygu and BDH GU for their contributions. Also my good mate Paul Staib for his patience and help with anything to do with the Patrol.
Some bracket drawings and photos of other Endless Air installs for the Nissan TD42 and TD42T motors:
Setup installed onto Peter's (OldMav) Maverick
Setup installed onto Ashley's (Sottygu) GU TD6 Cab Chassis
Below are some useful links I found when researching this project: