Question about compression

[surt]

I've been reading through a lot of threads on turbos, superchargers, big bores and other ways of making significant performance jumps.

I've been wondering about compression, and more for interest than for a plan, what's stopping manufacturers from building insanely high compression engines with extremely hard steels like AUS8 or ZDP189 or in fact something specialised?

Could compression ever be raised so much that it could rival above modifications? Or is there a point at which compression is too high for the combustion to be effective, jamming the piston in their cylinders?

Has it been done before??

 

[Fastfrog007]

Cost prohibitive?

 

[Wild07]

One word....Diesels. Many n/a diesels run in the high 20:1cr. Even a lot of turbo diesels run in the high teens. Much more than 30:1 and I think you're just fighting yourself, though I'm far from an engineer or designer.
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[turbobusa2000]

I've been reading through a lot of threads on turbos, superchargers, big bores and other ways of making significant performance jumps.

I've been wondering about compression, and more for interest than for a plan, what's stopping manufacturers from building insanely high compression engines with extremely hard steels like AUS8 or ZDP189 or in fact something specialised?

Could compression ever be raised so much that it could rival above modifications? Or is there a point at which compression is too high for the combustion to be effective, jamming the piston in their cylinders?

Has it been done before??

Well they do use steel for cranks and rods but pistons are alumminum. One reason steal isn't used for pistons is it is heavy. It also doesn't transfer heat as efficiently as alumminum.

If you think about it the stuff they use in the engines we run around in now are "specialized". Nikasil plated bores, high stroke/bore ratios and increasingly high compression ratios are getting more and more like race engine design.

 

[surt]

Still thinking about different ways of creating masses of power. If you coupled that expensive fuel (is it M9?) with greater than 20:1 compression wouldn't the power be enormous? Just seems like a better alternative to the money invested elsewhere on a typical engine.

And what about nuclear power, is it really that extreme a thought to power a motorcycle from a nuclear source? If it had sufficient shielding I can't really see a downside - I can't remember if it's the inverse of this but I believe the French manage to use something like 80% of the power within their radioactive substances to reduce waste and increase the economical aspect of nuclear power.

You wouldn't need much uranium to power an engine carrying a meagre 270Kg...and imagine the cost of running it :-)

 

[megawatt]

People get upset when gasoline goes up .04 cents a gallon. Gen 1 bikes have 11:1 compression and can use 87 octane. Gen 2 bikes have more compression and ask for the 91 octane, that by itself is .20 a gallon more. You want to up the compression more then you have to use hi octane race fuel that runs at a cost of more than $12 a gallon and is not avaliable at the corner gas station. Then you will need two battery start system to deal with the higher compression. Then add a second cooling fan because of the added heat from higher compression, etc etc.

So no manufactures are not going to build a very high compression motor for the general public that run on gasoline.

 

[valkyriemc]

Still thinking about different ways of creating masses of power. If you coupled that expensive fuel (is it M9?) with greater than 20:1 compression wouldn't the power be enormous? Just seems like a better alternative to the money invested elsewhere on a typical engine.

And what about nuclear power, is it really that extreme a thought to power a motorcycle from a nuclear source? If it had sufficient shielding I can't really see a downside - I can't remember if it's the inverse of this but I believe the French manage to use something like 80% of the power within their radioactive substances to reduce waste and increase the economical aspect of nuclear power.

You wouldn't need much uranium to power an engine carrying a meagre 270Kg...and imagine the cost of running it :-)

Huh? ???

 

[AJAY]

People get upset when gasoline goes up .04 cents a gallon. Gen 1 bikes have 11:1 compression and can use 87 octane. Gen 2 bikes have more compression and ask for the 91 octane, that by itself is .20 a gallon more. You want to up the compression more then you have to use hi octane race fuel that runs at a cost of more than $12 a gallon and is not avaliable at the corner gas station. Then you will need two battery start system to deal with the higher compression. Then add a second cooling fan because of the added heat from higher compression, etc etc.

So no manufactures are not going to build a very high compression motor for the general public that run on gasoline.

Bingo! You can't go to "insanely high compression" on any kind of gasoline that you buy easily. "Octane"* is really just a rating based on the ability of the fuel from auto-combusting under high pressure. As others wrote, diesel has much higher "octane" than gasoline and diesel engines run really high compression and have much beefier components to take the pressure (pistons, pins, cranks, bearings). You could also run nitromethane. I think you're pretty much limited to about 13.5 to 1 compression ratio on any type of pump gas.

* octane is actually a chemical (aromatic hydrocarbon) and I believe it is the reference standard for the "octane rating" system, but I'm too lazy to look it up. Try wiki. Nevermind, here are the details if you want to know: Octane rating - Wikipedia, the free encyclopedia

 

[surt]

Thanks everyone, I totally forgot about heat. That's really basic physics, I can't believe I overlooked it :11doh:

 

[fastblackblur]

"there is no such thing as a free lunch" no matter how you increase power it will bring its own set of problems.

I would imagine the major limiting factor on how much compression is ran in modern engines is more dependent on what fuels are widely available vs what materials are available.


nuclear motorcycle? To my knowledge, correct me if I’m wrong nuclear power plants are basically the same as conventional power plants except you replace the coal, oil, w/e with a nuclear reactor. It still is heating up water to send it through a turbine...

I don't think we'll see any portable fission generators in our lifetime...

 

[surt]

"there is no such thing as a free lunch" no matter how you increase power it will bring its own set of problems.

I would imagine the major limiting factor on how much compression is ran in modern engines is more dependent on what fuels are widely available vs what materials are available.


nuclear motorcycle? To my knowledge, correct me if I’m wrong nuclear power plants are basically the same as conventional power plants except you replace the coal, oil, w/e with a nuclear reactor. It still is heating up water to send it through a turbine...

I don't think we'll see any portable fission generators in our lifetime...

Well I did some browsing about nuclear vehicles, and it turns out the subject was considered by ford in the 50s. The largest difficulty was the bulk and weight of shielding, especially when a crash in concerned.

Evidently I'm no expert, but I don't believe nuclear powered cars are TOO far away from us, a motorbike may take longer. So long as sheilding technology is developed it seems quite plausible, and very beneficial.

I actually think I remember seeing something about a nuclear powered motorbike, it looked like a futuristic cruiser and they'd found a way to reduce weight...

 

[Kaptain Kanji]

Not only is the shielding and weight a problem for motorcycles, but a BIG thing that not many
people consider is getting rid of the nuclear waste. It's expensive to get rid of and nobody
wants it.!! The bikes of the future will be electric or hydrogen powered, possibly with a
fuel cell of some sort involved.

 

[AJAY]

Nuclear! Wow, it's amazing how a thread can change directions. Yeah, a nuclear-powered motorcycle is a really bad idea. Of course, if you want to get your 'nads cooked, go at it. Just go get your Q-clearance first.

We do have nuclear powered vehicles. Ships and submarines. Some deep-space probes use nuclear where there's not enough sunlight for solar cells.

Someone is actually trying to resurrect the truly-bad idea of a nuclear-powered aircraft. This is an idea that deserved to die in the 1950's.

 

[BusaWhipped]

Gale Banks started working on building perfomance gas engines (still does), but always found the limiting fator was the gas. That's why he switched to diesel where the fuel is no longer a problem in the equation.

 

[BusaWhipped]

Not only is the shielding and weight a problem for motorcycles, but a BIG thing that not many
people consider is getting rid of the nuclear waste. It's expensive to get rid of and nobody
wants it.!! The bikes of the future will be electric or hydrogen powered, possibly with a
fuel cell of some sort involved.

We'll have Mr Fusion by then

 

[blusmbl]

Compression is really only one means to an end, the end being cylinder pressure during combustion. That cylinder pressure can come from a high compression ratio, or the cylinder filling beyond it's volume.

Gas engines aren't designed for cylinder pressures that diesel engines experience, and even the diesel engines have to be calibrated in such a manner that the fuel/injection timing and boost pressure doesn't exceed design requirements during combustion.