Building a 10,000 rpm NA engine.

[oab_au]

Originally Posted by SVXRide

Tony,

Think of it as more bang for your buck. You're compressing the air in the mixture more, so you get a more powerful explosion from the air-fuel mixture. The increase in the force generated by the more powerful explosion far outweighs the addition energy needed to compress the mixture. Note: You do need to be mindful of not getting to the spontaneous combustion pressure!

Cheers,
Bill

Originally Posted by Dessertrunner

Thanks Bill, got to wonder if its also a better explosion as well.

Here is the design for the adapter plate to fit the BMW throttle so they can shoot the fuel direct to the back of the valves.
Tony

https://dl.dropboxusercontent.com/u/...20Assembly.pdf

How many times must I tell you blokes, there is no explosion
The gas just burns to heat up the air.

The advantage in raising the compressing ratio is to squeeze the gas into a smaller volume, so that it will have a greater expansion rate when heated.

Harvey.

['E']

Aren't all explosions an expansion of molecules through heat?

[oab_au]

Originally Posted by 'E'

Aren't all explosions an expansion of molecules through heat?

Depending on the rate of expansion.

Harvey.

[Dessertrunner]

Hope you are all sitting down,
I was wondering if the way to increase the compression ratio is to weld the head. Build up volume to reduce the chamber size.

So what do you think.
TOny

[BackWoodsBob]

you'd have to weld the head from the inside out... no?

[Tireiron]

Adding material and welding into the actual chamber will change the flow characteristics of the chamber drastically, not to mention the risks of creating hot spots. You would need to fully redesign the combustion chamber and add material evenly and completely blend and smooth the chamber out. Keeping in mind the angle opening of each valve and the angle of the spark plug and watching out for the flow through the head.

[SVXRide]

Tony,

What Tireiron said. I've seen it done on heads before (never EG33 heads!) and you need immediate access to a flow bench and a lot of intense effort so as to not bugger up the works. Better off attacking things from the piston side of things.

Cheers,
Bill

[bazza]

Originally Posted by Dessertrunner

Evan,

This leads me to the question why does higher compression give more power???? Anyone know.
Tony

High compression just means you're burning more air per stroke. Air contains the energy and is the hardest thing to get into the cylinder (fuel is easy). More air contains more energy and that's all we're really ever chasing. Increasing engine efficiency (via cams and better exhausts etc etc) just means we're trying to get the most air into the engine and burn it as efficiently as possible.

A turbo just cheats and increases the air density of the intake charge.

[Dessertrunner]

Not sure how you get more air into the chamber Bazza as the stroke volume is still the same. How do you see more air getting in.
Tony

[bazza]

Originally Posted by Dessertrunner

Not sure how you get more air into the chamber Bazza as the stroke volume is still the same. How do you see more air getting in.
Tony

I'll get back to you on this as I've confused myself lol.

[Dessertrunner]

There are plenty of computer simulators that can indicate how much increase in power can be expect by increasing the compression my issue with these is:-
- They don't talk about the gains at higher revs, by this I mean if higher compression enables you to move the maximum torques higher up the rev range then the gains are even greater because torque turns to HP.
- I have never seen one of these calculators for a flat engine, and my instinct is that our engine behave differently. We have short stroke, big bores, hi valve area. Its a whole different ball game.

You can't compare the behaviour of a flat engine to a V8 or straight 6, to do so is a insult to our intelligence.

Tony

[SVXRide]

Tony,

Volume does remain constant, as it is a function of the head and the stroke of the piston. A turbo increases the mass of air within the fixed volume, thus increasing the density of air involved in the combustion events (i.e., the higher the boost - psi - the higher the engine output due to the increased amount of air mass packed into the fixed volume).

Cheers,
Bill

[oab_au]

Not easy to grasp.
When I load a .38 bullet case, I use a certain amount of powder, If I want to get more velocity, without using more powder, I just push the projectile back down into the case further, to reduce the space that the powder is in. This gives a higher pressure, due to the higher expansion pressure.

The cylinder is the same, you have a 550cc volume of fuel, if we squeeze this volume into a smaller combustion space, the expansion pressure is increased, so the torque is higher.
The torque does not increase as the rpm increases, the resultant torque remains the same.

Harvey.

[Dessertrunner]

Originally Posted by oab_au

Not easy to grasp.
When I load a .38 bullet case, I use a certain amount of powder, If I want to get more velocity, without using more powder, I just push the projectile back down into the case further, to reduce the space that the powder is in. This gives a higher pressure, due to the higher expansion pressure.

The cylinder is the same, you have a 550cc volume of fuel, if we squeeze this volume into a smaller combustion space, the expansion pressure is increased, so the torque is higher.
The torque does not increase as the rpm increases, the resultant torque remains the same.

Harvey.

Hi Harvey,
I accept most of what you say, except I think most people believe that there is some increase in cylinder fill as a result of the higher cylinder pressure.

Do you think there is a higher fill level from higher compression?

Tony

[oab_au]

Originally Posted by Dessertrunner

Hi Harvey,
I accept most of what you say, except I think most people believe that there is some increase in cylinder fill as a result of the higher cylinder pressure.

Do you think there is a higher fill level from higher compression?

Tony

Had to read that a couple of times.

No the cylinder 'fill' won't increase, due to the increase compression ratio.

The volume of air we get in the cylinder, changes as the breathing changes, through the rpm range.

There will be changes in the Combustion pressure, due to the higher ratio, but this is what provides the torque increase.

Don't know if what is what you mean Tony.

Harvey.