Dunlop auxiliary air suspension

[Boxster1971]

After much research, I just installed a Dunlop Auxiliary Air Suspension system on my Sprinter based Airstream Interstate. Initially I wanted either the Ride-Rite or VB Airsuspension full air suspensions. But then I discovered that it would require removal or relocation of the Onan generator as these two full air suspension systems require about 15 inches behind the rear axle.

I looked at the Firestone, Airlift and Boss air bag auxiliary systems. But they are all installed on just the rear axle bump stop and thus could cause serious damage to the unibody frame above the rear axle. Then I discovered the Dunlop air bag auxiliary systems sold in Europe, but not sold in North America.
http://www.dunlopsystems.com/products_airsuspension.html

The big advantage to the Dunlop system is the heavy gauge frame reinforcement attached to the rear axle bump stop to distributed the load and prevent frame damage. The only disadvantage is this system uses the less common 5 mm air tubing.

On a referral from Marcle Leisure I was able to obtain the Dunlop Auxiliary Air Suspension Kit from Watling Engineering Ltd in UK. I worked with Ben Babcock at Watling and had the system FedEx air shipped from England for £460 or $662 in June. Ben was very responsive to questions and delivery. First photo is the Dunlop kit of my work bench.
http://www.watling-towbars.co.uk/contact.html

Once I dropped the generator it was a straightforward installation. I used my wood lift blocks to get the van up high enough to do installation in my driveway. The Harbor Freight ATV/Motorcycle Lift was perfect for dropping the generator. Next photos of generator dropped, RH airbag fit check and Airbags installed.

Installation involved one complication since my Airstream Interstate Sprinter has an Onan LP generator mounted just behind the rear axle. The brackets that Airstream installed to mount the generator interfered with the Dunlop airbags and frame reinforcement channels. The fix involved cutting off about 6 inches of the brackets and reattaching one end to the stabilizer bar frame bracket. Last photo of generator reinstalled.

Next I'll post information on the compressor airline installation.

[Boxster1971]

The Dunlop kit comes with two color 5 mm airlines and a nice set of manual fill valves. I installed them inside the macerator hose compartment for easy and secure access. First two photos of the manual fill vales going in and finally installed.

I ran with the airbags for a few weeks before adding a compressor for automatic inflation. Initially tried 85 psi, but that seemed a little stiff so I lowered the pressure to 60 psi and that seemed about right. That pressure still takes the load off the third leaf spring on my Interstate and provides a slightly smoother ride. Certainly, not as good as a VB Airsuspension, but it satisfies my goals to lift the rear a bit, smooth the ride and allow me to raise the rear for those steep drives I encounter during my travels.

After being certain these airbags were going to work the next step was to add a compressor for full control of the airbag pressure. I chose the AirLift Wireless Air Gen 3 compressor system. It allows you to adjust each airbag independently if desired and includes a wireless remote to adjust the air pressure right from the driver’s seat.
https://www.airliftcompany.com/products/compressor-systems/wirelessair/

I installed the compressor under the lower drawer in the galley and placed the airline manifold on the outer wall behind the microwave. I wired the compressor to the coach batteries. The control wires to manifold are tied to the Sprinter “engine on” circuit so the system is only powered when the engine is running. Next two photos of compressor and manifold installed.

Last step was mating the 5 mm airlines in the Dunlop kit and the ¼ inch airlines provided with the compressor system. After some head scratching I found a good solution by using a Branch Tee fitting with 5 mm tubing ends and a 1/8” male pipe thread. Then I added a female ¼ inch airline fitting to make a Tee fitting with two 5 mm and one ¼ inch airline ports. I sources the parts from MSC Industrial Supply as they were the only one I could find that had what I needed in stock. Here are the details of the parts I used.

5MM X 1/8 BRNCH T SWIFT-FIT PUSH-IN FITTING; MSC Item # 50210N-5-1/8
1/4TB X 1/8 STR FEMALE PUSH-FIT PUSH-IN FITTING; MSC Item # 82900812

I mounted the Branch Tee fittings to a small bracket attached to the macerator frame. Last photo of the Branch Tee fitting installed under van near the hose reel compartment.

I'm now enjoying finally having an auxiliary air suspension that suites my needs. Next I plan to upgrade the rear shocks with a pair of adjustable Fox 2.0 Performance Series shocks. They arrive tomorrow!

[73shark]

Nice work!

[JayP]

Tidy work. Really like the ability to level without carrying around blocks. Can the compressor also be used for other work, such as tires, occasional air mattress or an air horn?

[Boxster1971]

Originally Posted by JayP

Tidy work. Really like the ability to level without carrying around blocks. Can the compressor also be used for other work, such as tires, occasional air mattress or an air horn?

The AirLift compressor I installed can not be used for other purposes. But Firestone sells several air suspension compressors that are designed for other inflation purposes. Here is one as an example.

http://www.etrailer.com/Vehicle-Susp...one/F2545.html

[amirm]

Nicely done! And thanks for documenting it all for us.

[dapolrbear]

Nice clean install.

The VB rear air suspension in my Interstate isn't all that, it gives a smoother ride(which is great) but can't really utilize the height adjustment. It's always in automatic mode where it adjusts itself while driving or you can manually control it via wired remote, but only when the parking brake is engaged. So not sure what I can do when I encounter a steep driveway. I can stop engage the parking brake fill up the air and then when you put it back in drive and let the parking brake go the air lets out and you're back at the preset height again.

[73shark]

Originally Posted by dapolrbear

Nice clean install.

The VB rear air suspension in my Interstate isn't all that, it gives a smoother ride(which is great) but can't really utilize the height adjustment. It's always in automatic mode where it adjusts itself while driving or you can manually control it via wired remote, but only when the parking brake is engaged. So not sure what I can do when I encounter a steep driveway. I can stop engage the parking brake fill up the air and then when you put it back in drive and let the parking brake go the air lets out and you're back at the preset height again.

If there's a easily accessible switch on the parking brake, you could add another switch to simulate the brake being set. If the switch is NO, then put a switch in parallel w/ it, if NC, then put a switch in series w/ it.

[Boxster1971]

Today I drove with air bag pressure lowered to 45 psi. It actually felt better. At 45 psi all the leaf springs are engaged, but with positive up arc instead of negative down arc it had before. This pressure lifts the rear end about 2 inches. Here is photo of remote control attached to my ProClip iPhone mount.



- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter

[Boxster1971]

Added the Fox Shoxs with some difficulty. These new shocks are a LOT stiffer than my old Konis after 40,000 mile. Test drive tomorrow.




- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter

[Lotus54]

My 2006 came with the Airlift Wirelss system installed.

I don't know what pressure it had when I picked it up- I'll try the 45 you liked and see how it works on mine.

Same wireless controller, looks like the same pump. Heck, maybe the same bags...


Mark

[Boxster1971]

Originally Posted by Lotus54

My 2006 came with the Airlift Wirelss system installed.

I don't know what pressure it had when I picked it up- I'll try the 45 you liked and see how it works on mine.

Same wireless controller, looks like the same pump. Heck, maybe the same bags...

Mark

Your airbags are likely from Airlift. Both Airlift and Firestone still sell airbag kits for older Sprinters. But both no longer sell the airbags for newer Sprinter 3500 models. Airlift does sell airbag kits for newer Sprinter 2500 models, but Firestone dropped all airbag kits for newer Sprinters. I don't know why they stopped offering kits for newer or heavier Sprinters, but I suspect it was due to frame damage on overloaded Sprinters. There was one especially bad case reported on the Sprinter-Forum that had Firestone pay for some damages caused by a plumber that severely overloaded his Sprinter with Firestone airbags.

My Dunlop airbag kit is not distributed in USA. I sourced my kit from a dealer in England. The Dunlop kit is unique since it includes significant frame reinforcement pieces. The Dunlop kit is widely sold in Europe and well designed for the 5 ton Sprinters.

I really like my new ability to use the Airlift remote to raise the rear end when parking over curbs and dealing with steep driveways.


- - Mike
2013 Lounge EXT on 2012 Sprinter

[FlyFishinRVr]

Originally Posted by Boxster1971

Your airbags are likely from Airlift. Both Airlift and Firestone still sell airbag kits for older Sprinters. But both no longer sell the airbags for newer Sprinter 3500 models. Airlift does sell airbag kits for newer Sprinter 2500 models, but Firestone dropped all airbag kits for newer Sprinters. I don't know why they stopped offering kits for newer or heavier Sprinters, but I suspect it was due to frame damage on overloaded Sprinters. There was one especially bad case reported on the Sprinter-Forum that had Firestone pay for some damages caused by a plumber that severely overloaded his Sprinter with Firestone airbags.

My Dunlop airbag kit is not distributed in USA. I sourced my kit from a dealer in England. The Dunlop kit is unique since it includes significant frame reinforcement pieces. The Dunlop kit is widely sold in Europe and well designed for the 5 ton Sprinters.

I really like my new ability to use the Airlift remote to raise the rear end when parking over curbs and dealing with steep driveways.


- - Mike
2013 Lounge EXT on 2012 Sprinter

Mike are you at all concerned about crud getting on the shock shaft and causing a leak? On my motorcycles that have a similar exposed shaft there is some sort of flap or other protective covering but I don't see anything like that on the Sprinter. Over time I would think road grit would work into the seal and then you'd have a problem......

[Boxster1971]

Originally Posted by FlyFishinRVr

Mike are you at all concerned about crud getting on the shock shaft and causing a leak? On my motorcycles that have a similar exposed shaft there is some sort of flap or other protective covering but I don't see anything like that on the Sprinter. Over time I would think road grit would work into the seal and then you'd have a problem......

I'm not concerned about the shock shaft. The Fox design has multiple wiper to keep crud on shaft from entering the shock. All the Fox shocks have this same design and are widely used on off-road vehicles. They are designed for 50,000 mile life in on-road use.
http://www.ridefox.com/product.php?m...=30&ref=filter



- - Mike
2013 Lounge EXT on 2012 Sprinter

[Lotus54]

I didn't see sprinter listed on Fox's website.
What model are they?


(I already know not cheap)

Mark

[Boxster1971]

I bought my Fox Shoxs from Agile Off-Road. They specialize in vans and build Fox products for Sprinters. I found out about Agile Off-road over on the Sprinter-Forum. They offer several different Fox shocks for Sprinters from $130 to $335 each. Contact them for a specific quote on your van. They build them to order and it takes about a week.

http://agileoffroad.com/ride-improvement-package/


- - Mike
2013 Lounge EXT on 2012 Sprinter

[Lotus54]

Thanks,
How are they working for you?

[Boxster1971]

Originally Posted by Lotus54

Thanks,
How are they working for you?

Drove the van last two days, about 150 miles, with the new Fox shocks. What a difference! Now have nice solid feel without any extra rocking.

[felixkagi]

[QUOTE=Boxster1971
I installed the compressor under the lower drawer in the galley and placed the airline manifold on the outer wall behind the microwave. I wired the compressor to the coach batteries. The control wires to manifold are tied to the Sprinter “engine on” circuit so the system is only powered when the engine is running. Next two photos of compressor and manifold installed. [/FONT][/SIZE]



Did you make that wiring connection in the compartment under the drivers seat?

[Boxster1971]

Originally Posted by felixkagi

Did you make that wiring connection in the compartment under the drivers seat?

The AirLift wire bundle has everything connected to the vehicle "Ignition ON" source. It is my view that this is too much of an additional load on this circuit. First I split the wire bundle that came with the AirLift compressor to wire it like the Firestone systems. That way I could power the compressor from Coach batteries and the Air Manifold ECU from the Sprinter engine on circuit.

I did not want to remove the driver seat to get to the engine on (aka Ignition On) terminal under the seat. Since the Air Manifold ECU only requires a low power (~1A) connection I just tied it to the Ignition On wire located under the rear lounge seat on the Battery Isolator Manager (aka Battery Separator) with a small 2A in-line fuse. That meant pulling the 10AWG and 16AWG wires from galley to the electrical compartment under the rear lounge seat.

The main 10AWG wire for compressor went to a spare fuse position on the main coach 12VDC distribution panel with 15A fuse.

The only complication was the AirLift requirement to connect the negative ground wire for the Air Manifold ECU directly to the Sprinter battery. Both AirLift and Firestone say the Air Manifold ECU require this good connection to operate correctly. So, I had to run the 16AWG negative ground wire from the galley to the battery under the driver seat.

The compressor 12AWG negative wire can just be grounded to the frame near the compressor.