Home Brew APU

I just looked up this tripac system.

2 diesel engines, two a/c systems, two alternators, it makes idling the giant main diesel engine seem smart.

With electronic injection, I dont see why these supposed engineers cannot figure out how to limit fuel just enough to spin the engine's rotating mass and the accessories, thereby saving fuel and not having to install redundant systems.

Well, after everyone switches to APU's they will come out with that system I'm talkin about, thats business for ya.

 

Sounds like a guy I was parked next to some time back, only his unit was putting out fumes so badly that I had to move. It was also loud and obnoxious....mostly noxious!

 

You know, this isnt a stupid concept at all. Dodge and chevy have made engines in the past few years that will basicly shut down fuel to 4 out of 8 cylinders at highways speeds and then kick back in under throttle to improve fuel economy. It's not a stupid idea at all to think that with some ingenuity and planning someone could come up with a way to make these big 12 and 14 liter engines fire on only 4 or possibly even 2 cylinders while under idle just enough to keep constant electrical power going to run heaters and air conditioners and general electronics. I know that running on 2 or 4 cylinders would not be adequate enough to heat or cool properly from the normal heating and air but it could be enough to run a seperate hvac system of some sort. I would like to think there is an engineer somewhere that could write a fuel programming system smart enough to take an engine from burning a gallon an hour at idle to half of that or less. There is technology out there smart enough to make things like this happen. Whay do we need APU's when we have gigantic powerplants under the hood already,We just need to find more creative ways to use what we already have.

 

Mostly the green weinies want the big engine stopped when the truck is stopped. They really prefer a battery type APU.

 

you could get a honda genset. much quieter than the industrial ones. if you wanted to be fancy you could hook the gennie exhaust into the stack on the tractor. besides the hondas run clean

 

Well... there's some problems with that.

First, idling a 500hp or-so diesel engine is really bad for it. It drastically cuts down on the life of the engine. Low-power idling will cause the temperature of the engine to be low, and moisture to form in the cylinders. That combines with the sulpher in the fuel (even if it is ultra-low sulpher fuel) to form sulphuric acid. The acid scores the cylinders, eventually causing blow-by and fuel to get into the oil. Hello early in-frame.

The best way to idle the engine is at RPMs that keeps the engine at normal operating temperature (high idle) - which will burn a lot of fuel - but will help with the moisture problem. Its roughly ten times the amount of fuel a Tripac consumes. So you're faced with a real expensive engine repair (eventually) or a lot of extra fuel expense. And even at high-idle, the engine will need an in-frame sooner.

Strapping a generator to the catwalk is all well and good... until you turn the rig really tight, and the trailer mashes the generator. And... the vibration problem - will probably kill the generator and/or air-conditioner (Mr. Murphy really knows when to kick a good man) when you need it most (summer day in say Casa Grande AZ) when you don't have the extra scratch to buy a new one. Definitely go for an RV unit if you're going that way. I've seen them mounted to the roof of a sleeper...

 

I agree with "Independent". It seems that every parameter about fuel injection can be controlled to limit our speed/rpm/caloric intake, etc., etc. Why couldn't there be a switch/control be put in the cab, so that when we need to idle, only on every third stroke of the piston would fuel be injected? We could run at high idle (therefore keeping temps up), and the firing order could still be disributed across ALL cylinders (to reduce/eliminate the previously mentioned condensation issue). Why? Follow the money!!! It's, probably, not anything that hasn't been thought of already. The engine makers are in the business of selling engines.

 

cylinder temp would still be down,so it would perpetually be warming up, never really fully up to cyl temp. you still are racking up the engine hours on a big expensive engine. oh yes you could order up a programming like that on the series 60's. drivers hated it, it ran rough as if it was missing, did not exactly sing you sleep. even if they are not firing you still have to overcome the friction of 6 big pistons pumping up and down. it is never going to come close to the lower fuel burn of the genset

 

And you're still contributing to diminished engine life on something that is more expensive to do an inframe on than paying for a APU.