The summer before last I threw a motor in my truck that was built for boost, low compression, reverse split cam, etc... At the time I had no FI kit and was just running it N/A with plans of doing something a little different to satify my F.I. needs. I kinda hinted at doing something unique and original but my idea never got any footing because CurtD ended up selling his Turbo kit which was one notch above exceptional in quality and that kinda took the wind out of my sails design wise. Anyways, since I'm probably not gonna ever get around to doing it, thought I'd see share and see if it would of even been possible.
I have an uncle who's the Chief engineer for one of the major airlines companies and is in charge of repair on all their commercial Jets. I approached him a couple years asking about an electric motor that could spin a turbo (Nothing novel there really). Just thought since most of the S/C and turbo systems were adding 40-50lbs of weight in the engine bay, why not add 80lbs of motor and battery back behind the rear end and have instant boost for 30-40 second periods at a time. Anywho, I wasn't really serious about it but just wanted to hear what he had to say. What he did say was actually intersting since he suggested instead of using an electic motor why not use an A.P.U.
A.P.U. stands for Auxiliary Power Unit. They are small power systems that are independant of the plane's main power and propulsion systems and are located in the very tail end section of the plane. Bigger versions have been known to be used as propulsion in helicopters. There are three things APU's are used to power on a plane, Hydraulics, Electrical Generator and Air compressor.
An APU is basically a small gas turbine, the smallest ones are no bigger than your average home welding unit sans tank or other accessories. Maybe 24"x12"x12" in size, weighs 50-100lbs and runs on whatever fuel you want to put in it, and depending on variables are good for 40-70hp. The compressed air units that are on planes are used as starting air for the bigger propulsion gas turbines as well as supply air for the cabin so as the pressurize it during flight. (That's why when your sitting on a plane and they start the main engines the air supply on a plane shuts down momentarily).
Anywho, my idea was to mount one of these back behind the axle where the spare tire usually goes. Obviously there would of been lot of modifying as far as compressor size and what not to make it work, but I thought the idea would of been cool, as well as the sound it would make! It would essentially provide unlimited amount of cfm's from idle to redline without any boost variations or parasitic losses inccured with belt driven system or the pumping losses which Turbo's suck up.
I thought this idea would be even better suited to work on Diesel's actually, but obviously I never went anywhere with it.

I have a bunch of youtube video's of the ones I was looking at but they are all on my computer at home, and most of the ones on Youtube are a bit bigger than what I was planning on using. People have used variations of them to power go-karts, motorcycle's, tractors...you name it. They all come in varying sizes. I wish I had pictures and what not to post up but if you type in Auxiliary Power Units into Google you'll get pages and pages of pics of them. Most of them are the bigger versions used in Tanks and helicopters and planes but there are some of the smaller versions.

Just wanted to get some thoughts on it and see how crazy I was for thinking this!!

 

kool

 

Hmm, well its an interesting idea, but I think the biggest thing will be adapting the drive system....if its a shaft powered unit, how are you going to transform that rotational energy into something useful? If its a big air compressor then you are esientially going to be putting a remote mount turbo/supercharger on your truck.

Unless I am completely misunderstanding I dont think you would be happy with it unless you are just going for something different and unique.

 

Its going to be a loud SOB, I work on APU's almost everyday. Na, thats ok.

 

http://cgi.ebay.com/AiResearch-Missi...#ht_942wt_1039


only piic I could find on egay

 

The motor made more sense to me..... But, you would have to use a serious gearbox to get to centrifugal or turbocharger-type speeds. High speed drive trains (vibration, resonance, coupling, mounting, balancing, bearings, lubrication) are a challenge.

The control systems and auxiliary systems an APU would require would seem to negate the benefits.

 

I like the idea except for two things:and, wouldn't it need to be running continuously? Otherwise you would have to wait for it to come up to speed when you wanted boost (?).

 

Roughly 45 sec to start, stabilize, and output air. At least ours.

 

What about scavenging the air compressor + APU from a jet? My only concern would be possible compressor surge at low load situations (assuming it will keep up with the total airflow).

 

I thought about something similar a while back -- using an aux compressor to spin up / build exhaust pressure on a monster turbo for launches. You could plumb a boost sensing valve into the pre-turbo exhaust, and dump a ton of compressed air to help build the back pressure. Then once the turbo is at boost, the valve closes, and you rely on the exhaust as normal.

With the APU, you could just use an electric valve, powered by the APU. When you kick the APU off, the valve closes, etc.

Instant boost at idle with turbo losses to hp?