How big is it??

Bodacious

Bodacious

Comp Diesel Sponsor
Joined
Jul 8, 2013
Messages
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I've done a bit of google'ing and pretty much come to the conclusion that no one can truly calculate how large the boosted engine thinks it is do to all the efficiencies and what not.

For a general reference, The Banks article basically stated that for any pressure greater than atmospheric, the engine grows proportionally.

Again, just as a general reference using 15psi as atmospheric, when our little 5.9 (360 cu in) cummins is making 60psi of boost does it really think it is 1080 cubes???
 
Bodacious said:
I've done a bit of google'ing and pretty much come to the conclusion that no one can truly calculate how large the boosted engine thinks it is do to all the efficiencies and what not.

For a general reference, The Banks article basically stated that for any pressure greater than atmospheric, the engine grows proportionally.

Again, just as a general reference using 15psi as atmospheric, when our little 5.9 (360 cu in) cummins is making 60psi of boost does it really think it is 1080 cubes???
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The engine thinks absolutely nothing. They are stupid machines with no heart or soul, let alone a brain.
 
Bodacious said:
I've done a bit of google'ing and pretty much come to the conclusion that no one can truly calculate how large the boosted engine thinks it is do to all the efficiencies and what not.

For a general reference, The Banks article basically stated that for any pressure greater than atmospheric, the engine grows proportionally.

Again, just as a general reference using 15psi as atmospheric, when our little 5.9 (360 cu in) cummins is making 60psi of boost does it really think it is 1080 cubes???
Click to expand...

When is the last time you heard of a 1080 cube 6 cyl running to 5000rpm? It may have ingested over a 1000 cubes of air but it is sill in a 360 cube motor, IE small cube will make more HP less torque than big cube and rev higher. And 60 psi is 4 extra atmospheres so 1440 CI of air if the head can flow it , you boost pressure is always on top of atmosphere which changes by altitude/ barometric pressure. hope that helps.
 
turboram said:
When is the last time you heard of a 1080 cube 6 cyl running to 5000rpm? It may have ingested over a 1000 cubes of air but it is sill in a 360 cube motor, IE small cube will make more HP less torque than big cube and rev higher. And 60 psi is 4 extra atmospheres so 1440 CI of air if the head can flow it , you boost pressure is always on top of atmosphere which changes by altitude/ barometric pressure. hope that helps.
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It would actually be 1800 CID, since that is 60 psi of boost above ATM, which would be five atmospheres.
 
I want to insert a " Thats what she said" in here somewhere
 
What is the ultimate question? I see both sides of the question. Obviously you aren't changing the CI of the engine. However you're forcing it to "drink" that much extra atmosphere. Let's say your engine is 100% efficien(good lawd I wish) should you select an injector to fuel that amount of air that the engine is sucking /forced in?
 
And 60 psi is 4 extra atmospheres
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Yes, I was mistaken. The boost gauge reads in psig so it has already accounted for atmospheric.

What is the ultimate question?
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Well, I had some hard think'n folks at a couple of the mud events telling me that even though I was only 360 cubes, with the turbo, it acts like a 1000cube normally aspirated engine. Since I was outrunning some of the 600+ inch gassers, I got to thinking those hard think'n folks may have a point.

What has more btu per unit, Gas or Diesel??
 
I would think there would be no way to calculate how much larger an engine "acts" based on boost pressure since boost is in large part a measure of restriction. The same size engine that flowed better and could swallow more air would reduce boost and make more power. At least in my mind.
 
Bodacious said:
Well, I had some hard think'n folks at a couple of the mud events telling me that even though I was only 360 cubes, with the turbo, it acts like a 1000cube normally aspirated engine. Since I was outrunning some of the 600+ inch gassers, I got to thinking those hard think'n folks may have a point.
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A few things come into play. For one, volumetric efficiency. I'm not sure, and someone correct me if I'm wrong, but I doubt our engines are ever near 100%ve. I'm thinking your 360ci is really more like 300-330ci, at best.

Another thing is heat, which can misleadingly increase boost pressure. But, if your intercooler were good enough to get the air charge back down to ambient, then you could assume that every 15 pounds or so of boost should add another 300-330ci of atmosphere.

Diesel has significantly more energy per unit than gasoline, but it's harder to extract all of that energy. I find diesels are a little bit more of an art form in this regard.
 
Did you know that when a Top Fuel Dragster launches, it opens a hole in the universe for a split second. I don't have the math skills to prove it. I've been there though, and it happens.
 
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