Due to some interest in the topic from the good people here, I'll post this description of my adventures with a Stebel air horn.
I apologize for not having everything step-by-step documented, this guide was made after the fact so some steps are not very detailed, however some of you might find it useful.
Due to the ESA and tight clearances of the 08' it is somewhat difficult to mount the horn where the stock horn goes. It is also hard to make a rugged installation of a compressor horn in this space for older GSAs. Broken brackets have been reported, and off road trails are littered with lost compressors.
Requirements:
1. No mechanical interference
2. Shock-proof mount
3. Keep the existing horn in place
4. Not overload the existing horn wiring.
5. Horn should not be obstructed by the tank or anything else reducing its acoustic advantage.
6. Would like to have splash protected expansion room for other projects, for relays, controllers, HID ballasts or other farkles.
7. Would prefer to have ample power for these farkles available.
8. Ugly and functional beats pretty and useless.
Euro bikes and a few tampered-with US bikes do not have the charcoal canisters. This is a beautiful thing. A A 90mm PVC pipe will snap right into the canister space.
I was not prepared to pay for a few meters of straight pipe, so I went right down to the DIY store and looked for a cheaper alternative. A professional would refer to this alternative as a 90 degree pan-connector. Me, being unencumbered by this professionalism, will refer to it as a shitter pipe.
1. Obtain a straight piece of pipe about 90mm in diameter. Or do what I did, and cut off roughly at the bend, to obtain a suitable straight segment. This will be our compartment for the compressor, relay and other farklish things. Besides, having such a grand piece of plumbing on your machine, will truly make your GS feel like a throne.
2. Obtain a Nautilus Compact compressor horn. I bought mine at Halfords for about 22£. You will need to carefully separate the trumpet from the horn. This is relatively easy to do. The trumpet is very light, and is easy to mount anywhere.
3. We need power. Plenty of power. I used two 8AWG wires, to have sufficient power for the compressor, future lights and other farkles.
4. The negative is connected directly to the battery post. After crimping a ring connector to the cable, I additionally soldered the end of the wire to ensure a durable connection. Same for the positive.
5. The positive terminal feeds directly into a fuse holder. A small cut out in the terminal cover allows for straight routing.
I prefer to keep my main farkle fuse as close to the battery as possible. In the event that the positive wire would get scuffed and weld itself to ground we can avoid disaster of cataclysmic proportions. (This is even more interesting on an 1100/1150, where you risk welding directly onto the fuel tank.) I was originally looking for a maxi sized fuse holder for a 50A, but did not find a suitable size holder. The mid size holds a 40 A fuse, and is easy to fit.
6. Velcro holds the fuse holder in place.
7. We will attempt to route the 8 AWG cables so that they do not hamper normal maintenance tasks.
8. Routing around the air filter, under tank.
9. The compressor is mounted inside the shitter pipe using two large cable ties. Ensure that the air intake of the compressor is clear. It should be rotated slightly from what is shown in the picture. The relay is attached with a screw, and is activated by the original horn circuit.
The cables enter the pipe on the top. A piece of plastic tube is connected to the compressor, and exits the pipe at the bottom.
10. The horn was left in place, with the relay for the Nautilus connected in parallel. I did not want to cut the original BMW harness, but I had no issues tampering with the original horn. In the end, I drilled two small holes into the horn terminals/posts, and attached ring connectors with screws to the posts. (You will need to remove some rubber goo covering the posts before you drill) All wiring is straight out of the book, so I am not including any circuit diagram.
The following picture shows the original horn and routing of the plastic hose.
11. In order to attach the hose to the trumpet, I needed to ream out the hole a bit with a drill and an appropriate tool.
The hose is shoved into the hole, and secured with a zip tie. The air pressure makes the hose expand, so this is more secure than it looks.
12. The time has come to mount the shitter pipe to the tank. As we can see, it is a perfect match for the GS.
13. This clamp is made from thick piano wire.
14. The pipe fits very snugly in the tank, and requires barely any further fastening. Being on the safe side, a notch cut into the pipe will mate with the piano wire clamp and make it bullet proof. You can also see the large zip ties holding the compressor in place in the pipe.
15. The astute observers amongst you might have noticed that the fork tubes of the GS have a similar diameter as the Stebel compressor. It was made that way for a reason. Snap!
The trumpet is very light, and I have no reason to expect that it will ever budge. It is pointing in the direction I want it to, and it is facing down and is not likely to get affected by rain and dirt. (Time will tell.) As the compressor is mounted in fairly clean air, any dirt is likely to remain on the outside of the membrane.
16. Finally I stuffed some plastic foam in the top of the pipe. It will not prevent water from entering the pipe (in extreme circumstances) but it will make it run down the sides of the pipe will hopefully prevent the typical mist/spray that gets into relays and connectors.
17. HOOONK!! Yep, it's loud.
The standard horn comes online about 1/10th of a second before the Stebel compressor gets cranking, hence it is possible to give somebody a friendly greeting without having people jump into their nuclear fallout shelters.
I apologize for not having everything step-by-step documented, this guide was made after the fact so some steps are not very detailed, however some of you might find it useful.
Due to the ESA and tight clearances of the 08' it is somewhat difficult to mount the horn where the stock horn goes. It is also hard to make a rugged installation of a compressor horn in this space for older GSAs. Broken brackets have been reported, and off road trails are littered with lost compressors.
Requirements:
1. No mechanical interference
2. Shock-proof mount
3. Keep the existing horn in place
4. Not overload the existing horn wiring.
5. Horn should not be obstructed by the tank or anything else reducing its acoustic advantage.
6. Would like to have splash protected expansion room for other projects, for relays, controllers, HID ballasts or other farkles.
7. Would prefer to have ample power for these farkles available.
8. Ugly and functional beats pretty and useless.
Euro bikes and a few tampered-with US bikes do not have the charcoal canisters. This is a beautiful thing. A A 90mm PVC pipe will snap right into the canister space.
I was not prepared to pay for a few meters of straight pipe, so I went right down to the DIY store and looked for a cheaper alternative. A professional would refer to this alternative as a 90 degree pan-connector. Me, being unencumbered by this professionalism, will refer to it as a shitter pipe.
1. Obtain a straight piece of pipe about 90mm in diameter. Or do what I did, and cut off roughly at the bend, to obtain a suitable straight segment. This will be our compartment for the compressor, relay and other farklish things. Besides, having such a grand piece of plumbing on your machine, will truly make your GS feel like a throne.
2. Obtain a Nautilus Compact compressor horn. I bought mine at Halfords for about 22£. You will need to carefully separate the trumpet from the horn. This is relatively easy to do. The trumpet is very light, and is easy to mount anywhere.
3. We need power. Plenty of power. I used two 8AWG wires, to have sufficient power for the compressor, future lights and other farkles.
4. The negative is connected directly to the battery post. After crimping a ring connector to the cable, I additionally soldered the end of the wire to ensure a durable connection. Same for the positive.
5. The positive terminal feeds directly into a fuse holder. A small cut out in the terminal cover allows for straight routing.
I prefer to keep my main farkle fuse as close to the battery as possible. In the event that the positive wire would get scuffed and weld itself to ground we can avoid disaster of cataclysmic proportions. (This is even more interesting on an 1100/1150, where you risk welding directly onto the fuel tank.) I was originally looking for a maxi sized fuse holder for a 50A, but did not find a suitable size holder. The mid size holds a 40 A fuse, and is easy to fit.
6. Velcro holds the fuse holder in place.
7. We will attempt to route the 8 AWG cables so that they do not hamper normal maintenance tasks.
8. Routing around the air filter, under tank.
9. The compressor is mounted inside the shitter pipe using two large cable ties. Ensure that the air intake of the compressor is clear. It should be rotated slightly from what is shown in the picture. The relay is attached with a screw, and is activated by the original horn circuit.
The cables enter the pipe on the top. A piece of plastic tube is connected to the compressor, and exits the pipe at the bottom.
10. The horn was left in place, with the relay for the Nautilus connected in parallel. I did not want to cut the original BMW harness, but I had no issues tampering with the original horn. In the end, I drilled two small holes into the horn terminals/posts, and attached ring connectors with screws to the posts. (You will need to remove some rubber goo covering the posts before you drill) All wiring is straight out of the book, so I am not including any circuit diagram.
The following picture shows the original horn and routing of the plastic hose.
11. In order to attach the hose to the trumpet, I needed to ream out the hole a bit with a drill and an appropriate tool.
The hose is shoved into the hole, and secured with a zip tie. The air pressure makes the hose expand, so this is more secure than it looks.
12. The time has come to mount the shitter pipe to the tank. As we can see, it is a perfect match for the GS.
13. This clamp is made from thick piano wire.
14. The pipe fits very snugly in the tank, and requires barely any further fastening. Being on the safe side, a notch cut into the pipe will mate with the piano wire clamp and make it bullet proof. You can also see the large zip ties holding the compressor in place in the pipe.
15. The astute observers amongst you might have noticed that the fork tubes of the GS have a similar diameter as the Stebel compressor. It was made that way for a reason. Snap!
The trumpet is very light, and I have no reason to expect that it will ever budge. It is pointing in the direction I want it to, and it is facing down and is not likely to get affected by rain and dirt. (Time will tell.) As the compressor is mounted in fairly clean air, any dirt is likely to remain on the outside of the membrane.
16. Finally I stuffed some plastic foam in the top of the pipe. It will not prevent water from entering the pipe (in extreme circumstances) but it will make it run down the sides of the pipe will hopefully prevent the typical mist/spray that gets into relays and connectors.
17. HOOONK!! Yep, it's loud.
The standard horn comes online about 1/10th of a second before the Stebel compressor gets cranking, hence it is possible to give somebody a friendly greeting without having people jump into their nuclear fallout shelters.
