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PostPosted: Thu Jun 04, 2015 1:15 am 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
I was just trolling the net looking for combustion chamber pressures, was just curious.
http://www-mat.ee.tu-berlin.de/research ... c_sen3.htm
Don't know how accurate that info is but if it's real then there is 750 psi pressure in the combustion chamber after the sparkplug fires.


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PostPosted: Thu Jun 04, 2015 12:17 pm 
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Joined: Tue May 20, 2014 4:12 pm
Posts: 98
We regularly test peak firing pressures in our
Large Diesel engines,
Our largest run 120bar approx 1700psi.
Diesels are much higher then gas engines.


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PostPosted: Thu Jun 04, 2015 10:02 pm 
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Joined: Mon Oct 08, 2007 12:39 am
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Location: Oklahoma City, OK
Cool, interesting topic


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PostPosted: Mon Oct 09, 2017 10:12 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
Apparently the site is offline now but I want to post what was on it.

Pressure Measurement in Combustion Engines
Contact Person : Dr.-Ing.Ha-Duong Ngo
Introduction:
There is a great demand in the automotive industry for high temperature (up to 500°C) pressure sensors that can be operated in combustion engines. By accurately monitoring and controlling the pressure and temperature in the combustion chamber (Fig. 1), the Engine efficiency can be raised and the fuel consumption and pollutant emission reduced. Therefore a micromechanical high temperature pressure sensor using a membrane based piezoresistive ß-SiC-on-SOI (SiCOI) sensor chip and a specially designed housing has been developed and fabricated.

Fig. 6: Dynamic cylinder pressure measured with the SiCOI sensor in the combustion chamber of a gasoline Engine at 1500 rpm. For comparison the output signal of a quartz pressure transducer from Kistler AG is shown.
Conclusions:
With a micromechanical piezoresistive SiCOI pressure sensor static and dynamic measurements have been performed. The SiCOI sensor was tested under static pressures of up to 200 bar in the temperature range between room temperature and 300°C. The dynamic pressure measurements in the combustion chamber of a gasoline Engine were performed at 1500 rpm under different loads. The work demonstrates, that the fabricated and characterized SiCOI sensor is best suited for accurately monitoring the cylinder pressure of combustion engines, i.e. the recognition of misfire, above dead center and maximum pressure.


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combustion chamber 1.jpg
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combustion chamber 2.jpg
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PostPosted: Mon Oct 09, 2017 10:14 pm 
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Joined: Tue Jan 17, 2012 3:19 am
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Location: Hope, B.C Canada
In short ---- there is about 750 psi in your combustion chamber when it lights up.


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PostPosted: Mon Oct 09, 2017 10:58 pm 
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Joined: Tue Jan 17, 2012 3:19 am
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Location: Hope, B.C Canada
That has caused me to have another brain fart ---- I think a guy could get away with no head gasket.
You could bump your compression and lower the excessive amount of squish on the FL350.
I currently have a single layer stock metal gasket on one of my spare engines. If I ever decide to run it and if I remember, I will remove it and see what happens. I see no reason to use a gasket. A little bit of the red silicone and your good I bet.


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PostPosted: Thu Oct 12, 2017 12:27 am 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
Some more info from other sites that basically say the same thing as the above info.

http://rehermorrison.com/tech-talk-90-p ... re-spikes/
Note what he says about a sudden spike and a sudden fall of pressure in a normally aspirated Engine as that's what the other info above says too.

http://performancetrends.com/Definition ... re-Lrg.gif
This is another chart I got from a different site called performancetrends and it to confirms all of the above data.


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PostPosted: Thu Oct 12, 2017 11:21 am 
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Joined: Wed Jan 14, 2009 2:10 am
Posts: 4678
Location: Carson City NV
canadian oddy wrote:
That has caused me to have another brain fart ---- I think a guy could get away with no head gasket.
You could bump your compression and lower the excessive amount of squish on the FL350.
I currently have a single layer stock metal gasket on one of my spare engines. If I ever decide to run it and if I remember, I will remove it and see what happens. I see no reason to use a gasket. A little bit of the red silicone and your good I bet.


Removing the gasket completely doesn't really do much..... been there, tried that. The lowest I have ever gotten the squish down to on a stock FL350 is .090". That massive squish band is designed into the FL350 for a reason. Its there so you don't have to run exotic fuels.

Rand


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PostPosted: Thu Oct 12, 2017 2:04 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
Randman wrote:
Removing the gasket completely doesn't really do much..... been there, tried that. The lowest I have ever gotten the squish down to on a stock FL350 is .090". That massive squish band is designed into the FL350 for a reason. Its there so you don't have to run exotic fuels.

Rand


LMAO
1) Since you have already done this can I ask if it blew out the sealer you probably used between head and cylinder ??
2) How much did it boost the compression ??


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PostPosted: Thu Oct 12, 2017 6:20 pm 
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Joined: Wed Jan 14, 2009 2:10 am
Posts: 4678
Location: Carson City NV
Mind you the change was from running only one .012" head gasket (thinnest of the 3 piece set) to running no gasket at all and using Permatex gold as the sealer between the head and cylinder. This only bumped the compression up 3 psi and the seal lasted until it was time for new rings.

Rand


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