Continental's CMD-350; a 350HP multifuel engine

[JasonS]

Continental developed a 350HP engine based on the 478 cubic inch "multifuel" engine.

Some interesting features other than the power output:

1. Variable compression ratio: a high of 17:1 and a low of 10:1
2. The BSFC was 0.380 lb/ hp*hr which is actually better than the LDS engine
3. Still using the American Bosch PSB injection pump
4. Aftercooler built into the intake
5. Aluminum heads, oil filter housing, and rocker covers

 

[G744]

I'm so glad "they" know the bottom end can handle those ponies...

I don't, having seen hundreds of LDS & LDT engines at Yermo with the center web blown out.

The old MSG there called them light bulb motors, 'cause you never know when they would blow out...

 

[rustystud]

Continental developed a 350HP engine based on the 478 cubic inch "multifuel" engine.

Some interesting features other than the power output:

1. Variable compression ratio: a high of 17:1 and a low of 10:1
2. The BSFC was 0.380 lb/ hp*hr which is actually better than the LDS engine
3. Still using the American Bosch PSB injection pump
4. Aftercooler built into the intake
5. Aluminum heads, oil filter housing, and rocker covers

Thanks Jason. That is some cool information !

 

[HDN]

Were there any trucks that used this motor, or was it just a one-off?

 

[Darylfraser]

This is cool stuff. I love these old brochures with the detailed drawings. A lost art it would seem.

 

[rustystud]

Hey Jason. Is there anymore information on this engine ? I tried to find some on Google but came up blank. It would be great if we could find out more of the engine specifications like valve timing and lift, and injector size. That sort of stuff. Basically, what did they do to create that much power in the same engine we have.

 

[patracy]

I wonder how the hydraulic variable compression worked.

 

[swbradley1]

I'm so glad "they" know the bottom end can handle those ponies...

I don't, having seen hundreds of LDS & LDT engines at Yermo with the center web blown out.

The old MSG there called them light bulb motors, 'cause you never know when they would blow out...

After seeing your response it makes me wonder if the web blew our from the crank breaking in two or the web broke and took out the crank. I had never wondered that until now. I had just assumed the crank broke.

Either way, it was something to see and hear when I started the truck up.

 

[G744]

It was something I never forgot, just seeing the carnage.

I suspect individual drivers never forgot their experience, either.

Probably 'cause another MSG (or higher rank) had serious words with them...

 

[Gypsyman]

I wonder how the hydraulic variable compression worked.

This was my first thought after reading the brochure. I would love to see a diagram of the design.

 

[gringeltaube]

I would love to see a diagram of the design.

This is just one of multiple solutions for VCR....

Not sure though, which way they went at Continental. The brochure talks about hydraulically operated pistons "whose position relative to the crank pin ...." so I guess what they used are these variable-length con rods, with their eccentric piston pins. The pin itself does not vary its distance to the piston; only to the crank pin.

 

[Gypsyman]

Thanks G. What an intriguing design.

 

[rustystud]

This is just one of multiple solutions for VCR....

Not sure though, which way they went at Continental. The brochure talks about hydraulically operated pistons "whose position relative to the crank pin ...." so I guess what they used are these variable-length con rods, with their eccentric piston pins. The pin itself does not vary its distance to the piston; only to the crank pin.
View attachment 884334 View attachment 884336 View attachment 884337

The question that remains is how did they activate the pistons ? Was there two oil holes drilled into the crank per piston ? One hole providing oil for the bearings and then the other providing the oil needed to move the piston in the piston ? I wonder.

 

[HDN]

The question that remains is how did they activate the pistons ? Was there two oil holes drilled into the crank per piston ? One hole providing oil for the bearings and then the other providing the oil needed to move the piston in the piston ? I wonder.

That's all I can figure, like a hydrauluc spool on an excavator, except it's spinning a lot faster

 

[Gypsyman]

The question that remains is how did they activate the pistons ? Was there two oil holes drilled into the crank per piston ? One hole providing oil for the bearings and then the other providing the oil needed to move the piston in the piston ? I wonder.

My brain went straight to this question too Rusty.

 

[gringeltaube]

It actually works by varying the oil pressure in the crank.

Here's some reading to it and two (hydraulic) schematics, taken directly from Toyota's patent:
(still need to find the list of components, in order to better understand all those numbers...)

"Toyota idea takes a conventional connecting rod and mounts the top of it to a pair of hydraulically controlled pistons. By adjusting the oil pressure, a switching pin and check valve would be able to alter which of these pistons compresses. By doing so, the length of the connecting rod changes between two lengths – a high-compression and low-compression setting.
Generally when the switching pin (*) receives a certain amount of oil pressure, the connecting rod would be in its longer length, and the engine would operate at the high compression ratio. Alternatively when the oil pressure falls below a predetermined level, the connecting rod would be in its shorter length and be in the lower compression ratio. However, the patent is clear that the company could configure the change in oil pressure have the opposite effect, too."
--------------

(*) That would be #81, clearly

 

[patracy]

Interesting. I thought perhaps it worked like the old International/McCormic tractors that started on gas and swapped over to diesel. They simply used an extra valve that allowed the gas side of things to work by increasing the combustion chamber volume (and hid the spark plug away from the cylinder). Then switched closed to allow the cylinder to achieve the higher compression needed of the diesel operation.

The varied oil pressure from the crank would allow it to operate more dynamically though. But I bet this setup lends to interesting failures.

 

[gringeltaube]

Interesting. I thought perhaps it worked like the old International/McCormic tractors that started on gas and swapped over to diesel. They simply used an extra valve that allowed the gas side of things to work by increasing the combustion chamber volume (and hid the spark plug away from the cylinder). Then switched closed to allow the cylinder to achieve the higher compression needed of the diesel operation.

The varied oil pressure from the crank would allow it to operate more dynamically though. But I bet this setup lends to interesting failures.

We still don't know what exactly Continental did to achieve VCR. Clearly, this engine never went into mass-production. Guessing high cost was a big factor, as well as many more parts to fail...

 

[rustystud]

Interesting. I thought perhaps it worked like the old International/McCormic tractors that started on gas and swapped over to diesel. They simply used an extra valve that allowed the gas side of things to work by increasing the combustion chamber volume (and hid the spark plug away from the cylinder). Then switched closed to allow the cylinder to achieve the higher compression needed of the diesel operation.

The varied oil pressure from the crank would allow it to operate more dynamically though. But I bet this setup lends to interesting failures.

I was thinking the same thing about failures too. Like what happens when a bearing starts to get loose due to wear and oil pressure drops on that rod only. Lets say oil pressure drops on that rod and that piston change it's compression and the others don't. Now we have a severe compression imbalance.

 

[silverstate55]

Interesting. I thought perhaps it worked like the old International/McCormic tractors that started on gas and swapped over to diesel. They simply used an extra valve that allowed the gas side of things to work by increasing the combustion chamber volume (and hid the spark plug away from the cylinder). Then switched closed to allow the cylinder to achieve the higher compression needed of the diesel operation.

My neighbor has a McCormick-Deering Farmall tractor that is set up that way. It’s pretty cool.