Underwood rotary air compressor

[Walker]

My throttle control arrived today. I purchased an InPower DBT-LD-02 electronic throttle speed control. I went through their website and it really wanted me to buy the $400 speed controller. The one I purchased was $95. The application list on the one I bought was fairly ambiguous about what it worked on, but did say light duty (you dont get to medium duty until you have a 4500/450) trucks and SUVs.

When it got here it had a sheet in it that said 2014+, so I just tried it. It plugs right into the OBDII connector, and there are two extra obdII connectors on its harness if you need to plug it other stuff. It then has 4 blunt cut wires coming off the harness. One is to switch to 12v+ to activate RPM #1 (user adjustable for both rpms), another to switch on RPM 2, a wire used to adjust the rpms up or down by applying 12v + or -, and one last wire that provides 3amp 12+ to switch on something once all conditions are met (park brake on, no foot on the throttle or brake, etc). In my case I will use it to trigger (probably need a relay) my compressor clutch.

I plugged it in and stabbed the wires into a power port to grab 12v+ and everything seems to work just fine, so that is one less thing to worry about. I was surprised how easy it was and how well it worked.

I am trying to figure out how to wire the pressure switch in as rpm 2 so it will bump to the higher RPM when the pressure is low, without it wanting to fire everything up if I just happen to put it in park and hit the park brake. If rpm 1 switch is wired to a keyed 12v source, and rpm 2 switch gets its 12 source downstream of rpm 1 switch it seems like it would do the trick. That way the pressure switch would not be in play once the main switch was turned off.

[Whitetrash]

I went sort of apeshit last weekend over your system because I thought it was the same generic control I dealt with. I apologize you are so totally on the right track. Rpm Up Rpm down perfect you do not need any more control than that . v

[Walker]

Originally Posted by Whitetrash

I went sort of apeshit last weekend over your system because I thought it was the same generic control I dealt with. I apologize you are so totally on the right track. Rpm Up Rpm down perfect you do not need any more control than that . v

Oh no, I get it. There are so many controls and interlocks in the VMAC setup I can imagine how problematic it might be with both user error and system malfunctions. I am just happy this portion of it looks fairly easy.

[Walker]

Here is the bracket that currently holds the alternator in the bolt saddle at the top, and the power steering pump in the inverted U at the bottom. The three bolt holes in the middle and one at the bottom are what holds the bracket to the block.
The three in the middle are where the dual alternator kits bolt to with plate extending to the right (when looking at the face of the bracket). There is a half inch clearance between the belt and the front of the bracket. I am planning on milling a little off the face in that area to give me a little space to work with. Then draw up a plate to cover the three holes, extend to the right the width of the compressor 6-7”. Then I will cut out a plate to mount the compressor to, line it up perpendicular to the plate, and weld. There are a couple bolt holes on the side of the bracket I can attach a second plate to, and there are a few likely places on the head I can get a brace down to. I will also need to bolt an idler pulley, or possibly two, onto the plate so that I have sufficient wrap around my alternator, and a good approach to my power steering pump.

I found a nice bracket online for $35 shipped, so I bought it. I should be able to make everything on the bench. I have a spare alternator (bad bearings) and a spankin new power steering pump in the shop (pump was making a funny noise so I ordered a replacement, but a fluid flush seems to have cured it). I believe I can use stock GM idler pulley, of which I have a spare, but may need to buy a metric tap unless I luck out and it is one of the 3 I own.

[Walker]

I have been debating what to do about the long neck of the power steering reservoir and an answer presented itself today. I will remove the reservoir and install a shorter reservoir that I found in hot rod magazines.

[Whitetrash]

Originally Posted by Walker

I have been debating what to do about the long neck of the power steering reservoir and an answer presented itself today. I will remove the reservoir and install a shorter reservoir that I found in hot rod magazines.

So, what is the idea of the long neck? Easy fill What Make/year truck are you installing this on. Just wondering as I watch you research and put this together. I think it is coming together nicely Kudos

[Walker]

My current truck is a 2013 Chebby Silverado 2500 4wd extra cab standard bed with a 6.0 gas engine.
I have gone through a couple diesels and am back to the gas motor and for the most part am happy with it. I ha over 200k on it now and likely will drive it for another 160-200k. Although I have been looking at brand new 2019 trucks in the last wee while.

As fara as the lead Ng neck, I guess it was just an easy reach kind of thing, as the neck doesn't really hold any fluid.

[Whitetrash]

Sorta Kinda what I suspected as far as the power steering reservoir was concerned. Diesels in my mind are only justified if you do a fair amount of heavy towing or huge miles per year as in 30K+. I don't think the extra costs initial buy + extra upkeep bucks make a whole lot of sense. Back in the day when diesel was way cheaper than gasoline it made a lot more sense now not so much.

[Walker]

Yeah, I do get in 30k a year, but my heavy towing days are pretty well over. Biggest trailer I pull is my 10K flatbed with about 8k on it. I did like the piwer in the diesels, but hated working on them and hayed the cost of the parts. I haven’t done diddly squat to this 6.0 in a hundred thousand miles except PMs and a plug change, they looked like they would have made it another hundred too.