Engine scale ability

Hi I was wondering if a engine is scaleable in size? Like if I built a engine twice the size of the original blueprint and injected twice the fuel would it go twice as fast.

like...twice as many cylinders or double the displacement

youre not going to bore a 4L motor to 8L, there just isnt enough space in the block

as in RPM, the actual motor speed? no

vehicle speed? probably no

the speed at which the motor will send a piston through the block? yup


I'm actually interested in like scaling a jet engine. Which yes Ik is completely different then a engine in a car. I'm looking for a engine that provides some where around 1000lbs of force but can't find one so was thinking if I got my hands on some blueprints for a different jet engine if I can scale it to provide the 1000lbs I'm interested in.

Pi R squared might come into play
testing equip:
Big homemade rocket:
Machining rotor blades for a modern turbo-jet or turbo-fan engine in basement? see above.

Ya I was thinking of machining the blades. I have access to a lath, mill, and cnc so I was thinking of making my own.

Be keen to see this. I've actually wired up a Motec Dash to monitor a small jet engine (ex-helicopter?) in a jet boat of all things. Wasn't much to it electrically. Interested to see what you come up with.

I hate to burst your bubble but there is not fucking way ANYBODY can make a homemade jet engine, especially not with 1000 pounds of thrust. The tolerances are way to precise to make each turbine blade exactly balanced and then there is the matter of getting the right materials and being able to machine them. Last but not least is the safety aspect. More than likely your first engine is going to explode spectacularly. Do you have ballistic blankets and a bunker strong enough to contain that? Can you afford to blow one up to test it to destruction to determine what it's limits are? Do you have a Masters Degree in Mechanical Engineering and Thermodynamics?

I thought not. Look into used helicopter engines.

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Engines (like most structures) are not sizeable. Especially engines, as they have so many parts, some of which are moving. You have to redesign the structure. If you made a car engine 100x bigger, it may break under it's own weight. If you made it 100x smaller the engine might explode with high pressure. You would run into all kinds of issues. You may be able to get away with small differences in size due to tolerances, but not much more without redesign.

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Ok, thank you.

That does not work.
Structure of materials does not scale and so doesn´t the overall system.

Yes and No...but mostly no.

If you think about an engine as a controlled explosion, then yes, twice the air and twice the fuel at a given compression ratio will somewhat scale.

But an engine is 80 mechanical and 20 percent chemical.

Thermal management will not scale, centrifugal forces will not scale, and pretty much any nonlinear forces in the engine will not scale.

The other issue is that materials also do not scale that well either.

If you want to burn twice as much fuel, then the turbine will have to spin twice as fast in order to push the necessary air for the proper air fuel ratio to be achieved.

That alone will put FARRRRRRR more stress on those turbine blades than originally intended. So you would either need to use a much stronger metal for the blades, or you would have to make the blades in such a way that they are perfect at the molecular level.


Ever heard of something called a factor of safety. Basically it's how much something can take before it breaks vs what it's supposed to take.
Cars have a factor of safety of about 25-40. Bridges about 30-50. Depends heavily on the bridge tho.

Anything that has to do with flight is a factor of 1.4.
Yeah. All planes every last one of them is made such that almost anything over what is expected breaks it.
That's nuts. Think about that.
So no don't try to machine anything unless you have a few hundred thousand dollars in machinery and have state of the art x ray defeaction equipement to see how the structure of the metal is oriented.

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