Whats the compression of a running engine?

[PorkChop808]

Hi everyone,

So i am wondering what types of compression's a engine is making while its operating under normal condition. i dont mean a compression test i want to know what its making while its operating.

 

[dgallup]

My lab experience is all diesel but we were running 2000 PSI peak cylinder pressure 30 years ago. From what I understand today's diesels run 3000+.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[Lou Scannon]

There's a wide variety of engines out there so the spectrum is wide but I'd guess spark-ignited turbocharged engines peak under 2000psi, turbodiesels under 3000psi. N/A spark ignited engines probably under 1500 psi.
All the above when operating as designed, not outside the intended envelope. And I'm talking about mainstream commercial production engines, not modified engines for racing or other shenanigans.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[Marquis]

A 5.7 litre petrol pushrod engine shows measured peak cylinder pressure figures of about 62 bar.
This engine is rated at 345 Bhp.
Where this engine runs on the highway is highly dependent on the vehicle it is mounted in, it's weight, it's Cd, it's frontal area etc.
If we assume that it's running at 4 bar BMEP ( peak BMEP of this engine is about 11-12 bar BMEP)my data shows it will be running between 22 and 26 bar peak cylinder pressure.

Another example- a medium duty diesel truck engine- between 7 and 8 litre capacity.
At 1500 rpm 50% load this engine shows a PCP of 65 bar and at 1800 rpm PCP of 88 bar.
This engine makes peak power of about 220 Bhp (at 2100 rpm) and peak torque of about 550 lb ft.
The engines PCP is a modest (by todays standards) 150 bar.

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