Actual consequences of a pinging engine
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Captain
Joined: Sep 2005
Posts: 722
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From: Long Island, NY
Actual consequences of a pinging engine
We've all discussed the different symptoms of a pinging engine, but what exactly does this mean? I'm just guessing here but I'd assume it means a shorter engine life, but by how much? What will this pinging damage? Anything outside of the engine? Is it worth worrying about?
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: Actual consequences of a pinging engine
The first parts to wear from mild detonation (pinging)
are piston rings.
On that cylinder (usually it is only one or two out of 8)
the rings will wear out sooner
perhaps only lasting to 100,000 miles
before they start passing too much oil and blow by gases.
are piston rings.
On that cylinder (usually it is only one or two out of 8)
the rings will wear out sooner
perhaps only lasting to 100,000 miles
before they start passing too much oil and blow by gases.
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: Actual consequences of a pinging engine
another good article
http://autospeed.drive.com.au/cms/A_0601/article.html
sample quote: [ul][*]Some researchers have claimed that slight knock may increase the power output of an engine. The tests carried out showed no evidence of this. As knock intensity increased, more power was lost. [/ul] [ul][*]Power loss with knock at a particular speed was found to be related to the engine's volumetric efficiency at that speed. Knock had the greatest effect on power at the speeds where volumetric efficiency (and thus torque and BMEP) were lowest. At the higher speed, turbulence in the cylinder is highest. It is believed that this increased turbulence prevents the pressure waves associated with knock from transferring their energy to the cylinder walls. Their energy is then better retained in the cylinder for the duration of the power stroke and is used to drive the piston. [/ul] [ul][*]Power loss with knock of a given intensity was found to be relatively less at throttled conditions than at WOT. While the reason for this is unclear, it is thought that a lower inlet MAP will result in a lower peak combustion pressure. This lower pressure may result in less energy transfer from the knocking pressure waves to the cylinder wall. The result is more energy remaining in the cylinder to drive the piston.[/ul] [ul][*]The presence of knock was found to have a detrimental effect on efficiency. The brake specific fuel consumption of the engine increased with knock intensity at all operating points tested. The percentage increase in BSFC was found to be the same as the percentage decrease in power. The reasons for the efficiency loss are the same as for the power loss. Knock results in an increased rate of heat transfer from the combustion chamber to its walls. This heat is then unavailable to do useful work in driving the piston.[/ul]
http://autospeed.drive.com.au/cms/A_0601/article.html
sample quote: [ul][*]Some researchers have claimed that slight knock may increase the power output of an engine. The tests carried out showed no evidence of this. As knock intensity increased, more power was lost. [/ul] [ul][*]Power loss with knock at a particular speed was found to be related to the engine's volumetric efficiency at that speed. Knock had the greatest effect on power at the speeds where volumetric efficiency (and thus torque and BMEP) were lowest. At the higher speed, turbulence in the cylinder is highest. It is believed that this increased turbulence prevents the pressure waves associated with knock from transferring their energy to the cylinder walls. Their energy is then better retained in the cylinder for the duration of the power stroke and is used to drive the piston. [/ul] [ul][*]Power loss with knock of a given intensity was found to be relatively less at throttled conditions than at WOT. While the reason for this is unclear, it is thought that a lower inlet MAP will result in a lower peak combustion pressure. This lower pressure may result in less energy transfer from the knocking pressure waves to the cylinder wall. The result is more energy remaining in the cylinder to drive the piston.[/ul] [ul][*]The presence of knock was found to have a detrimental effect on efficiency. The brake specific fuel consumption of the engine increased with knock intensity at all operating points tested. The percentage increase in BSFC was found to be the same as the percentage decrease in power. The reasons for the efficiency loss are the same as for the power loss. Knock results in an increased rate of heat transfer from the combustion chamber to its walls. This heat is then unavailable to do useful work in driving the piston.[/ul]
