Cylinder pressure during detonation?

[Mike T]

I've been reading a little on detonation but haven't found any published #s of what kind of pressure a cylinder may experience during detonation. I've read that a boosted or race engine may see as much as 1500 psi under heavy load conditions without detonation.

Any Ideas or educated guesses on what pressure spikes may be during detonation?? 3000psi or more??

 

[Jerryl]

https://www.savvyanalysis.com/articles/detonation-and-pre-ignition

 

[EVIL]

I think the pressure is something like 10X or more.
It's a lot. I can't remember exactly.

D

 

[Mike T]

So it would seem that there's not a huge increase in cylinder pressure but a very abrupt rise in cylinder pressure during detonation ?

 

[Mike T]

I think the pressure is something like 10X or more.
It's a lot. I can't remember exactly.

D

Sorry... I was referencing the link before reading your post. The graph was showing slightly elevated cylinder pressure but it was instantaneous. Maybe the graph was just an example?

Another thought....maybe cylinder pressure increases at 10x the rate?

 

[SHADOWII]

I have read of our v6's as much as 3000, w/some nitro fuel cylinder pressures reaching 6000, from an interview w/John Force on the TV.

 

[750H.P.V6]

Without a pressure transducer in the combustion chamber it would be difficult to determine the actual pressure. On a similar tangent I work in diesel engine R&D testing and since diesels are compression ignition I'd thought I'd share what kind of cylinder pressure we see there. Under heavy load conditions it's not uncommon to see 175 to 200 Bar of cylinder pressure. That works out to approx. 2600 - 3000 psi.

Neal

 

[Mike T]

I've heard 6000+ on the nitro cars also.

The main reason I'm trying to understand a little more about cylinder pressures is that a friend has ran his car in the 10s many times (even a few low 10's)on stock type head gaskets. He said that he has always tuned for zero knock and that was the key to having the stock gasket work so well for so long.

In comparison my car only made it 10,ooo miles before the head gaskets gave up. In every cylinder the fire ring was pushed back but not broken.
I always kept an eye on knock and seemed to have it under control. I almost always had a log going while running it hard and most of the time there was zero knock and I can only recall 3 or 4 degrees 1 time.

I was running the car on the interstate pretty hard (running a friend) when it made a very small pop in the intake and it was all down hill from there. This was one of the few times that I didn't have a log going and I wonder if all of the head gasket damage happened during this one incident or if it was detonating a little bit all along.

 

[bison]

Cylinder pressure vs crank angle. It's easy to change the pressure in the cylinder in non detonation situations by changing the timing. I disagree about the cylinder pressure comments in the article. A naturally aspirated high compression engine can easily have higher cylinder pressure than a turbocharged engine with more than double the output and half the displacement. The much denser charge of the turbocharged engine has a much longer acting effect on the piston on the power stroke than a high CR NA engine.


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[Jerryl]

Agree with Bison. The indicated pressures in the article seem way low . . . . Prove thay you can't trust or apply everything you read on the www. Lol

 

[Mike T]

So if I'm understanding correctly...... a na race engine may have a higher cylinder pressure in the first 90 degrees of the power stroke than a turbo engine with more fuel and air in the cylinder to burn?

 

[TTipe]

So if I'm understanding correctly...... a na race engine may have a higher cylinder pressure in the first 90 degrees of the power stroke than a turbo engine with more fuel and air in the cylinder to burn?

I high compression NA engine has chamber pressure like being slapped in the face ( high amplitude spike). A turbo engines chamber pressure is like being shoved into a wall and being held there ( wider pressure wave with a smaller amplitude).