Re: Edmunds head
Posted by Guscha On 2011/3/22 18:53:22
Quote:
Yes and ...
An engine is a system that consists of many parts. To intelligently increase the system performance requires to change more than just one part. The higher pressure impinges on pistons, valves, bearings, head gasket, combustion, ...
If we nevertheless change only one part then this part has to combine two functions: the target improvement and countermeasures to alleviate bad effects.
The Edmunds probably has smaller, more shallow combustion bowls to increase the compression ratio and with that the performance. Increased compression increases the knock susceptibility. Therefore it needs countermeasures.
The improved thermal conductivity (aluminum) and the more simple combustion chamber shape (no hotspot edges) are those measures.
Please compare the Edmunds head above with a --> 288AT combustion chamber.
The center mounted spark plug has a Janus-faced character. It increases the combustion speed to obtain a higher performance yield but reduces the length of the flame front.
What's the meaning of the lengths of the flame front?
Please take a look at the picture:
A - side mounted spark plug with long combustion front
B - center mounted spark plug with short combustion front
A > B and with that it decreases the knock resistance because a long way gives more time for knocking. Therefore the center mounted spark plug doesn't need a countermeasure.
And how about C?
C - a second flame front ("the knock")
To mistake misfire for engine knocking isn't uncommonly. Misfire is a self ignition without ignition spark but engine knocking occurs when:
" ...combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front ..." [wikipedia]
Ross, the Edmunds makes the combustion more efficient (fuel efficiency).
As you know when we drive more slowly (with less rpm) then the combustion chamber is filled with more residues. That increases the probability of a hot spot occurrence. The Edmunds decreases the knock susceptibility by more efficient combustion. And when we drive faster (with higher rpm) the Edmunds allows higher pressure without knocking.
The improved combustion behavior enables:
1) to use low-octane fuel or
2) to drive longer or
3) to drive faster and
4) to drive cleaner
5) ... to be continued
6) ... to be continued
7) ... to be continued
Attach file:
(16.71 KB)
...On the Edmunds I have seen, the combustion chamber shape is very simple and the plug is between the valves--quite possibly a better location for very high speed...
Yes and ...
An engine is a system that consists of many parts. To intelligently increase the system performance requires to change more than just one part. The higher pressure impinges on pistons, valves, bearings, head gasket, combustion, ...
If we nevertheless change only one part then this part has to combine two functions: the target improvement and countermeasures to alleviate bad effects.
The Edmunds probably has smaller, more shallow combustion bowls to increase the compression ratio and with that the performance. Increased compression increases the knock susceptibility. Therefore it needs countermeasures.
The improved thermal conductivity (aluminum) and the more simple combustion chamber shape (no hotspot edges) are those measures.
Please compare the Edmunds head above with a --> 288AT combustion chamber.
The center mounted spark plug has a Janus-faced character. It increases the combustion speed to obtain a higher performance yield but reduces the length of the flame front.
What's the meaning of the lengths of the flame front?
Please take a look at the picture:
A - side mounted spark plug with long combustion front
B - center mounted spark plug with short combustion front
A > B and with that it decreases the knock resistance because a long way gives more time for knocking. Therefore the center mounted spark plug doesn't need a countermeasure.
And how about C?
C - a second flame front ("the knock")
To mistake misfire for engine knocking isn't uncommonly. Misfire is a self ignition without ignition spark but engine knocking occurs when:
" ...combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front ..." [wikipedia]
Ross, the Edmunds makes the combustion more efficient (fuel efficiency).
As you know when we drive more slowly (with less rpm) then the combustion chamber is filled with more residues. That increases the probability of a hot spot occurrence. The Edmunds decreases the knock susceptibility by more efficient combustion. And when we drive faster (with higher rpm) the Edmunds allows higher pressure without knocking.
The improved combustion behavior enables:
1) to use low-octane fuel or
2) to drive longer or
3) to drive faster and
4) to drive cleaner
5) ... to be continued
6) ... to be continued
7) ... to be continued
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