I am setting up and on board air system on my truck. I have a friend that works on school busses that has found a district that is scrapping a bus. I'm going tonight to get the receiver tanks off the bus.

He was telling me that the school busses that use the Cummins 6BT engine have an air compressor in the same place our engines have the vacuum pumps (in between the timing case and PS pump). Has anyone considered replacing their vacuum pump with a air compressor and installing an electric vacuum pump? I figure I can get away with it on a 1997 because my brake booster runs off the PS fluid pressure and not vacuum.

The other way I thought I could do it is to come up with a compressor that ran off the PTO on the transmission. Anyone seen on that runs this way?

I want to get a compressor that runs off the engine because the electric ones I have seen displace small volumes or don't have the power to pump up to 150 PSI in the receiver tank. I have read reviews on compressors that claim they can but really can't. A compressor that is driven by the engine will have enough power.

Input appreciated.

Bob

 

I saved a file that used a york engine driven ac compressor off an old Volvo car. It was belt driven and had its own oil sump for the bearings so would just pump air. They rigged up a pressure Governor and the necessary fittings to it and it worked just fine. Now I searched for the article and cant find it just yet. It was well written too. Hope this helps a bit

 

If memory serves, there isn't enough room or something interferes with mounting a compressor on the accessory.
Unles you plan to run air tools, etc. a mounted compressor is way overkill. Class 8 trucks compressors only average 8-10% run time with spinner filters, active air suspension, brakes, & horns.
The governors on air systems are usually set to cut out at 130 psi.

 

That's right, there isn't enough room under the hood in the spot where the vacuum pump normally goes.
Seems that most folks who want air end up going with an electric compressor.

 

There was another thread on here about under Hood air. Someone found a system that fits first-generation trucks, Isabelle driven and I believe you that your air compressor. Also I have seen a 12 old electric compressor system that is belt driven. Try googling, 12 V air compressors, under Hood air compressors. I found these two and a bunch more.

http://oasismfg.com/Home.html

http://www.fourwheeler.com/techartic...ide/index.html

Mike

 

If you had a 24valve you could run this:

http://www.kilbyenterprises.com/KE-3000N-K.htm

I'm not sure why it won't fit a 12valve, any ideas?

They sell the bracket kit separate, so you could piece the rest of the system together cheaper.

 

There is no room to put an extra compressor on a 12 valve engine. I like my air conditioning too much to convert it.

 

There is room for compressors on the 12V, but most of the ones I have had or used were for stationary use only. That is not to be used while the vehicle is in motion, only for running on a work site. I have a VMac 28 CFM -150psi compressor in my garage but it takes a major fab to put it in and you can't use it unless you are parked. Water cooled and runs at about 1500 Rpm max.

 

How does it attach to the engine? Why can't you use it while you are driving?

 

There is a fabricated mounting plate that attaches to the alternator side of the engine block. You have to remove the battery and do some massaging to the inner fender to get it to fit. Extra pully bolted onto the damper with a separate set of belts and tensioner. Throttle kick up controller, tank , pressure switch etc....

The unit can only run stationary due to the RPM limit of 12-1500 RPM. The unit I have was a sheave ratio of 1:1 to the crank.

I was at the VMAC site but they only sell screw compressors now, not my old recip.. They are smaller anyway to fit but cost about $12,000 installed.

 

Last Friday I went with a friend who is a school bus mechanic to check out a bus that was going to be scrapped. After 4 hours and a lot of undercarriage dirt I emerged with 5 large air tanks. They are 36" long and about 8" in diameter. I think I can get at least two mounted on my truck.

I think I can fill them using my shop compressor before I leave and use a small 12V compressor to fill them on the trail. I may plumb them in a way to isolate the individual tanks so I don't work the 12V compressor too hard.

Anyone ever set up a system like this?