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Mobile air compressor

Posted: Mon Dec 19, 2016 5:29 pm
by nicky1
Hi all,
I recently got a 2 cylinder Lister diesel given to me. It's about a 400 lb engine so it's not an option for a re-power in a GT. It had crossed my mind to run a hi CFM air compressor with it. I have read about some 4 & 6 cylinder gas engines converted to an air compressor. I remember a lot of years ago a tire shop had a Wisconsin v4 that ran on 2 cyls and pumped air on 2.... not a high enough volume like would be needed for sand blasting.
Does anyone have an opinion on converting a 4 or 6 cyl engine to a compressor and power it with this Lister? I think the Lister is about 20 hp. A 4 cyl diesel would be great but a little harder to come by. Just a pipe dream as i'm always needing something blasted.
nicky1

Re: Mobile air compressor

Posted: Tue Dec 20, 2016 6:43 am
by BigMike
Years ago there was a similar kit for an air cooled VW engine. Everyone I talked to about it thought it was a good idea but I don't know anyone that ever built one.
I think it would be easier and more efficient to couple a compressor and run it off the engine.

Re: Mobile air compressor

Posted: Tue Dec 20, 2016 8:00 am
by chzuck
I was at a show a few years back and some one had a v-8 where one side was a compressor. It was either a manufactured piece or a kit that was available. A year ago at another show there was a Model T engine that was half compressor. I will see if I can find those photos.

Re: Mobile air compressor

Posted: Tue Dec 20, 2016 8:15 am
by chzuck
Here are the two photos. It was a Model A engine.
IMG_1052 (Medium).JPG
IMG_1052 (Medium).JPG (179.57 KiB) Viewed 4317 times
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IMG_5998 (Medium).JPG (370.73 KiB) Viewed 4317 times
IMG_5999 (Medium).JPG
IMG_5999 (Medium).JPG (324.01 KiB) Viewed 4317 times

Re: Mobile air compressor

Posted: Tue Dec 20, 2016 11:20 am
by nicky1
Very nice photos. I have access to a Wisconsin V4 that maybe can be converted to a compressor and be driven with the Lister engine.If I remember my High school math this would be a fairly good compressor volume wise at say 700 RPMs. I guess experimentation will tell the story. :idea:

Re: Mobile air compressor

Posted: Fri Jan 12, 2018 1:02 am
by DaveKamp
Yeah, it's been over a year, but I'll add my 0.02 at the risk of necroposting...

When converting an internal combustion engine to an air compressor, realize that the automotive engine's compression ratio determines what you'll be capable of in terms of output. If the CR is naturally low, then you can expect that the compressor's absolute max pressure limit will never exceed what the CR is designed to. For this reason, if you're gonna do a conversion, you want a high-compression head/piston combination.

1 atmosphere is 15psi. To get from atmospheric pressure to 150psi, you'll need a 10:1 compession ratio. If it's a flathead (like that Model A, you're looking at 5:1cr... unless you fill in that cylinder head, and bring the piston up close, you'll be limited to oh... 60psi (in theory...) but more like 45psi... because Combined Gas Law (adiabatic expansion/compression) works on paper, but doesn't happen in the real world.

The commercially-built air compressor engines that were 'successful' were either overhead valve head designs with the chamber volumes filled (technically referred to as 'volume excluders) and flat-top pistons on the compressor cylinders... or...

In the case of V6 and V8 conversions, one entire bank of cylinders used a specially-built cylinder head. Oh, and the lifter bores were plugged (so they didn't spill oil) and they had intercooling... because they ran some cylinders in SERIES with the others to act as high-pressure and low-pressure cylinders... like two and two, or three and one (V8)... or two and one (v6)...

And of course, the compressor side didn't run nearly as hot as the combustion side, but the engine coolant flowing through the block caused thermal expansion, which did somewhat 'challenge' the compressor's efficiency. I never saw a compressor-head conversion with cooling passages (not engine coolant anyway). On those conversions, the manufacturer ALWAYS ran different connecting rods and pistons on the compressor side, for higher CR... and frequently iron pistons rather than aluminum... for better dimensional stability under non-ignition compression heating).