Compression vs combustion pressure

[nk14zp]

Has anyone calculated if the combustion chamber pressure increases the same amount as the compression?

 

[Deets066]

What is the difference?

 

[Motorhead]

 

[thomas1]

One is before it goes boom, the other is after?

 

[DSS]

Explain yourself Zippy

 

[Majorpayne]

Explain yourself Zippy

Is that a personal question?

 

[Philbert]

I think that it is an interesting question, and hanging around to hear what our saw geeks come up with.

We measure engine compression with atmospheric air, or unburned mix, while hand turning a cold (maybe warm) saw.

During combustion, temperatures and acceleration increase dramatically; if compression could be measured while the engine is running under load, how would this compare to our 'static' measurements?

Philbert

 

[2manyhounds]

Wanna see how this plays out here,

 

[AVB]

This may not be exactly what your looking but this is from the compression diagnostic sheet from Briggs.

Pressure from expanding gases can be over 500 psi with temperature at the flame front may be as much as 3000 degrees.
@ 3600 rpm the piston would accelerate instantaneously to around 25 mph.

When you take in to account that the Briggs usually have a operating static compression of around 140 psi you get general idea that ratio is between 3 to 1 to 4 to 1. I know not exact science but give a good estimate.

 

[nk14zp]

If the compresion is 200 psi and the combustion presure is 2000 psi would raising the compresion to 210psi=2100 combustion psi or 2010psi?

 

[AVB]

it would in theory raise it to 2100 but from I what have seen it would be 630 to 840 if what Briggs indicated is correct. And the 200 psi would somewhere between 600 and 800

 

[fordf150]

are you asking about the dynamic vs static compression or


static compression vs true combustion pressure