When to expect a dropped liner cm870
04-03-2018, (Subject: When to expect a dropped liner cm870 ) 
Post: #13
RE: When to expect a dropped liner cm870
Don't know what going on here?
My whole post won't show up?

Here's the simple science of it...

We have a nice big pile of wood we're going to burn.
We've doused it in gasoline!
We have a 10' trail of gasoline away from the big pile so we don't get burned.
We light a match and drop it at the very start of our gas trail 10' away from the pile...

Ignition is NOT combustion.
Ignition is point at which the fuel source first starts to burn, there is NO thrust being applied to the piston at this point. This is the match igniting the start of the 10' trail...

The 10' gas trail is the speed of our flame front, and this duration is wasted energy we cannot harness in any way, but it's a necessary evil...

Now the flame reaches our gas soaked pile of wood, and WOOSH! We now have combustion! Thrust is now being transferred to the piston and we are harnessing power from our energy source.

Now the wood ignites and we have duration to our combustion, this is the power we want to harness the most.

In our trucks we are burning diesel. Without adding a supplemental or alternative fuel source, it is impossible to increase the speed of the flame front. This duration of the crank rotation is complete waste, so how do reduce the waste? We cannot increase the speed of the flame front, so we reduce the distance the flame needs to travel and we have reduced the wasted duration, or increased the response! So how do we reduce the distance the flame front travels? The simple solution is to reduce the size of the combustion chamber...or in laymans terms, increased the compression ratio. Just like making the 10' trail 5'.
Now by increasing the compression ratio we have achieved a quicker response and reduced the wasted portion of crank duration, however YOU CANNOT REMOVE THE WASTE, ONLY DISPLACE IT! So now instead of say 10° of duration from ignition to combustion, we now have 5°...but the higher compression means INCREASED RESISTANCE during the compression stroke!
Pistons move vertically.
Crankshafts rotate.
The two different forces transfer energy to each other via connecting rods...
Con rods rock at the wrist pin end and swing at the crank end...
This different energy ultimately transfers to the connected parts.
That means the con rod forces the piston that wants to travel vertically to rock slightly and creates sidewall thrust against the liners. The more we increase the compression ratio, the greater the resistance, therefore the greater the sidewall thrust...remember you cannot eliminate the waste, only displace it. This is where it gets displaced to!

Now we're going to add common rail injection to this vicious cycle...
In an 871 and older engines the fuel is injected pre-combustion with duration only into very early combustion BEFORE peak cylinder pressures have been reached.
In common rail engines the fuel system creates such extreme fuel pressures that fuel is injected THROUGHOUT the combustion cycle! Thereby INCREASING cylinder pressures!!! Directly to our now higher sidewall thrusted piston!!! Compounding the problem...

This is why raising liner heights to 0.015" is effective. The increased height clamps the liners down harder because the head gasket hasn't reached full crush compression before full clamping force is achieved. This increases the ability of the liner and block to resist the increased sidewall thrust by transferring the thrust energy into a larger percentage of the block.

All of this happens in a matter of time.
Time in an engine is measured BOTH;
-in actual time (milliseconds)
-and duration of the crankshaft
You cannot reduce duration of crankshaft, so this part happens regardless...
[i]However, YOU!!! can reduce the actual time! By downshifting and increasing your engine RPM's, you reduce the burn length, thereby reducing the sidewall thrust time requiring less resistance time and increasing the lifecycle of the engine.
Lugging an engine, does the exact opposite...


User's Signature: Why? Why do I always ask "why?" Because I can't learn or help teach others with "'cause I said so..."
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 Thanks given by: Rawze , dhirocz , stevesparts


Messages In This Thread
RE: When to expect a dropped liner cm870 - Hammerhead - 04-03-2018



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