24 Cylinders + 12 Blowers = WOW

[vypurr59]

After watching this vid. Something is funny. At 5:13 in the vid it shows the manifold construction. The manifold was made from wood, covered in aluminum. With the blowers mounted, it looks as if there would be a air leak, through the slots provided for the belt drives. I have very little knowledge about the diesel engine, but just looks like the blowers are there just for "wow" effect. Stacy David shared a similar vid on Facebook today. I did a little more research to find this one. You REAL mechanics may have more insight, but just looks like a big fake out to me.

[1972coronet]

24v71 Detroit Diesel . The "71-Series" (as well as the "53-Series" , as seq.) was a 2-stroke ; the "V" = V-block (e.g. , V-24). The 24 cylinder tipped-in at 1,704 cubic inches ; it was an Ocean Liner powerplant .

Blowers were necessary oxidisers atop 2-cycle diesel engines , as the 2-cycle arrangement didn't permit the engine to naturally-aspirate . These engines would rev-up like crazy ! They'd oftentimes run-backward if revved-up too high !

The lubrication system was what's known as a "Total-Loss" type (which is different from the Constant Loss lubrication system) .

[slusher]

That's a big engine....

[PappyD340]

WOW, it bet that engine takes a lot of Rotella!!

[DonW]

It looks like the wood is used to get the layout and shape before the box is fabricated in a aluminium? And presumably each blower has separate manifolding hidden by the box or it would surely leak round the belts. It seems like an odd way to build an induction system!

Enlighten us Ace!

[disabled modeler]

There is just way too much expense with all those blowers for it to be fake...plus there is a very unique sound that type of blower system will make when running. I have had to custom fab blower intakes and drives before...you have to make what ever makes it work right the blower intakes are not anything one could order out for...most likely there the only ones like them.

[Ace-Garageguy]

It looks like the wood is used to get the layout and shape before the box is fabricated in a aluminium? And presumably each blower has separate manifolding hidden by the box or it would surely leak round the belts. It seems like an odd way to build an induction system!

Enlighten us Ace!

Here's a shot of the blower airbox. The way it's shown here, the huge holes for the blower drive belts would at first appear to render any supercharging effect negligible...BUT, on closer examination, the drives are actually in chambers BETWEEN the blowers that appear to be sealed apart from the blower outputs (or will be, when this side of the airbox is in place).

Also, UNDER the lower plate of the airbox, there appear to be MORE blower housings (note the ribbed-looking things, with ribbing similar to the blowers on top) possibly drawing air from the box.

With the large amount of horsepower it takes to drive one big Roots blower, it's difficult for me to understand how power would be improved.

There is just way too much expense with all those blowers for it to be fake...plus there is a very unique sound that type of blower system will make when running. I have had to custom fab blower intakes and drives before...you have to make what ever makes it work right the blower intakes are not anything one could order out for...most likely there the only ones like them.

He's right in that the blower boxes would have to be custom fabricated. As vypurr59 (Jeff) and DonW alluded to, it was common practice (before CAD, and still is in non-CAD shops) to mock-up parts in non-metallic materials prior to expending a lot of time machining and fitting. That could explain the wood.

On the other hand, the blowers themselves could well be hollow shells with no impellers. Housings that have swallowed debris and are too damaged internally to be saved can be had cheap and polished. Again, this was common on show cars, and I've even seen hollow blowers with a carb mounted INSIDE on 4-stroke gas engines, so the things would actually run on and off their trailers.

As far as the blower's functionality and history go, the GMC 3-71, 4-71, 6-71, etc. blowers we're all familiar with were originally used to allow 2-stroke diesels to breathe, were mounted on the SIDE of the block as shown below on a 4-71 (where they blew air at slightly-above-atmospheric pressure through passages and ports inside the block) and were developed by hot-rodders into superchargers for 4-stroke GAS engines. The blowers were cheap and plentiful on the military salvage market after WW2, as these engines found a variety of wartime applications.

In the photo below of the engine in the OP, the red rectangles on the side of the box appear, on closer examination, to be over-pressure popoff valves. I can not state one way or the other if or how the multi-blower setup is supposed to work without more information, but I CAN say the top-mounted injectors are almost certainly non-functional, as these diesels use cam-driven, timed direct injection, and older diesel engines are NOT normally throttled, making the butterflies superfluous. They run at WOT (wide open throttle) and speed and power output are controlled by the amount and timing of fuel injected. Diesels also already have insanely high compression ratios, so massively supercharging one would be an interesting proposition indeed.

One other thing here that IS suspect is that the amount of 'wrap' of the Gilmer belt around the blower drive-pulley closest to the viewer is woefully inadequate. Big ol' Roots blowers take a lot of power to drive, and if that one was pumping away, the belt would be jumping cogs...guaranteed.

Photos from open internet sources, under "fair use" provision in copyright

Edited March 4, 2014 by Ace-Garageguy

[vypurr59]

Yes I do know a blower makes a distinct sound. But if you connect a belt to a blower on a bench it would make that sound also. I was looking more at the intake ports, at the bottom of the box, It looks as if the notches would be the culprit for air leakage to the compartment where the belts go through. I have never had to make a manifold, because all the parts for my big block 454 could be purchased. I had a Mooneyham 471 on a 454 in a 70 Chevelle for several years.

[vypurr59]

Thanks Ace, for the clarification. I thought this was sorta a fake out.

[Ace-Garageguy]

Thanks Ace, for the clarification. I thought this was sorta a fake out.

EDIT: !!!!! IMPORTANT !!!

I really can't say for sure if and how this actually works. There could be more to the manifolding than what shows in the photos. On MORE CAREFUL examination of the top photo in post #7, it appears that the blower drives will run in sealed chambers BETWEEN the actual blower outputs, so what we were seeing as massive air leaks won't be, when the side of the airbox is in place.

Edited March 4, 2014 by Ace-Garageguy

[Ace-Garageguy]

This has been bugging me. I came back and looked closer and found I missed a couple of things, and I got a couple of things WRONG.

MORE INFO. SEE POST #10, and revisions to post #7.

Edited March 4, 2014 by Ace-Garageguy

[vypurr59]

You may be correct that the blower drive has its own compartment, but the intake it sits on is in both of those compartments. That is where I found the notches at the bottom does not cover it. If you look at the bottom of the box in your first photo, the second bank of blowers, the notch continues into the other compartments.

I have an arrow pointing to where I am talking about.

[DonW]

It certainly wouldn't give over 3000bhp with those notches uncovered, even before the belts snapped. Maybe there are some blanking plates that haven't been fitted in that photo?

Also, no way can the driver see what's ahead of the truck!

[Ace-Garageguy]

Jeff, I see exactly what you're getting at. Again, that's why I tend to hedge on how, if at all, this setup works. There may be additional boxes that bolt over these notches and close the whole mess up, just as the side plates of the main box are missing.

The Detroit diesel 6-71 engine, on which I THINK the 24V-71 is based, lists a compression ratio of 18.7:1. Gasoline engines that are supercharged usually run much lower compression ratios than their normally aspirated brethren, but I honestly do not know enough about 2-stroke diesels to understand entirely all of what is going on with this beast.

Maybe some of our more knowledgeable truckers, or marine engine guys, will chime in.

However it works, you gotta love it. Sometimes American "wretched excess" just makes you grin.

Edited March 4, 2014 by Ace-Garageguy

[pharoah]

Wow... Somebody has more money than I do.

[Ace-Garageguy]

Wow... Somebody has more money than I do.

EVERYBODY has more money than I do.

[disabled modeler]

Wow... Somebody has more money than I do.

Me too....

[bobthehobbyguy]

One question I have if this does indeed work wouldn't all that boost pressure cause a failure?

[disabled modeler]

One question I have if this does indeed work wouldn't all that boost pressure cause a failure?

I would think they would have to be under-driven big time myself...diesels are already high compression.

[Ace-Garageguy]

One question I have if this does indeed work wouldn't all that boost pressure cause a failure?

Yeah, that's the thing. With 18+:1 static compression to begin with, IDK how much boost you can possibly run before you blow the crankshaft out the bottom of the block.

On the other hand, those old 2-stroke diesels are really pretty poor air pumps, and needed a blower just to run at all.

Not really entirely within my sphere of knowledge.

[disabled modeler]

That is true Bill...the 2 strokes needed a blower to run basically. Me I have been fascinated with them all my life...drove a few cars with them its fun. A friend of mine owned a blown 84 Z-28 Camaro with a 5 speed....giddy up.

[Draggon]

Did anyone notice in that vid, around the 2:25 mark, the covers on the drivers side airbox are missing? Also, if you look closely in the still pics posted, you can see the opposite side of the airbox just past the driveshaft and flange bearings. So how does the fuel mixture reach the cylinders?

Edited March 7, 2014 by Draggon

[Marcus M. Jones]

Jeff, I see exactly what you're getting at. Again, that's why I tend to hedge on how, if at all, this setup works. There may be additional boxes that bolt over these notches and close the whole mess up, just as the side plates of the main box are missing.

The Detroit diesel 6-71 engine, on which I THINK the 24V-71 is based, lists a compression ratio of 18.7:1. Gasoline engines that are supercharged usually run much lower compression ratios than their normally aspirated brethren, but I honestly do not know enough about 2-stroke diesels to understand entirely all of what is going on with this beast.

Maybe some of our more knowledgeable truckers, or marine engine guys, will chime in.

However it works, you gotta love it. Sometimes American "wretched excess" just makes you grin.

if they ever did a remake of Maximum Overdrive this is the truck i want them to use

[vypurr59]

This could be the biggest wiener roaster ever invented also.

[Ace-Garageguy]

So how does the fuel mixture reach the cylinders?

Diesels typically get their FUEL by timed, direct injection.

The AIR enters the cylinders via ports in their sides (for 2-STROKE Diesels). The 6-71 engine (also a 2-stroke diesel, and on which I THINK this engine is based) similar to the 4-71 (center photo in post #7), has a blower mounted on the side of the block that forces air (not "mixture") through ports and passages, ultimately into the cylinders. If you look at the top photo in post #7, you'll notice what look like blowers UNDER the bottom plate of the airbox. I believe these are the REAL blowers that allow this thing to run. They appear to be in the normal location, and would explain how the engine can run with the entire side of the top-mounted airbox open.

Remember that 2-STROKE diesels HAVE TO HAVE A BLOWER TO RUN AT ALL, because they don't aspirate normally like a 4-STROKE. 2-stroke diesels have no intake valves, and rely on ports in the cylinder wall being uncovered by the sliding piston to admit air, which is blown in by the block-mounted blower.

Edited March 7, 2014 by Ace-Garageguy