Somethin to chew on
02-16-2007, 05:52 PM
#1
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Somethin to chew on
Here is somethin i have been wondering, and i dont remember reading about it in maximum boost... What is the limit as far as psi goes of the ammount of boost you can shove in an inturnal combustion engine before is is inefficent? and stops making power? Assuming of course you could get enuff fuel in with the air to keep a good AF ratio.
Anyone know?
Anyone know?
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02-16-2007, 06:47 PM
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I dont know if there would be a limit, assuming temperatures and fueling is not an issue. The point would come where timing would have to be retarded too far to make more power, the turbo cannot spin efficently enough, or engine parts would break from the stress, but I dont think theoritically there would be a limit
oh ya, when F1 allowed turbocharging, some cars were running close to 70psi if that means anything to ya
oh ya, when F1 allowed turbocharging, some cars were running close to 70psi if that means anything to ya
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02-16-2007, 07:58 PM
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It stops making power when it blows.
You´re limited by:
-Fuel
-Cooling
-Detonation
-Turbo efficiency / flow capacity
Yoy solve those three issues, let´s say standalone with 4000cc injectors, infinite cooling capacity, 300 octane fuel and a gigantic turbo, it would stop making power when the rod bends, the ringlands fail, the piston blows or the block cracks.
You´re limited by:
-Fuel
-Cooling
-Detonation
-Turbo efficiency / flow capacity
Yoy solve those three issues, let´s say standalone with 4000cc injectors, infinite cooling capacity, 300 octane fuel and a gigantic turbo, it would stop making power when the rod bends, the ringlands fail, the piston blows or the block cracks.
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02-16-2007, 08:18 PM
#8
And psi is just a measurement of the engine's resistance to flow. So... increase the flow and the boost needed for a given power will lower, I'm simplifying it but I think that helps get the point across.
Take any motor and boost it, after that work the heads over and get some cams capable of making power at double the stock power peak and a bottom end capable of surviving there. Now find another turbo that can efficiently make the same boost pressure on the new set up and the horsepower will be greatly increased.
Look at the performance diesel guys, they are running well into the 100s as far as boost goes.
Metallurgy is the limiting factory really.
Take any motor and boost it, after that work the heads over and get some cams capable of making power at double the stock power peak and a bottom end capable of surviving there. Now find another turbo that can efficiently make the same boost pressure on the new set up and the horsepower will be greatly increased.
Look at the performance diesel guys, they are running well into the 100s as far as boost goes.
Metallurgy is the limiting factory really.
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02-16-2007, 08:38 PM
#9
Hmmmm... this does sound like one for Corky. But I'll say something stupid just for a laugh.
Suppose you had infinitely strong engine internals and unlimited cooling... there's gotta be some theoretical upper limit.
Does it have anything to do with the fact that you can't compress a liquid? You could dump 49.5cc of fuel into a 50cc combustion chamber and then boost as needed to get a nice A/F... but it wouldn't fire. Somewhere prior to that you simply couldn't atomize it. Some sort of fuel saturation. Am I even close?
Suppose you had infinitely strong engine internals and unlimited cooling... there's gotta be some theoretical upper limit.
Does it have anything to do with the fact that you can't compress a liquid? You could dump 49.5cc of fuel into a 50cc combustion chamber and then boost as needed to get a nice A/F... but it wouldn't fire. Somewhere prior to that you simply couldn't atomize it. Some sort of fuel saturation. Am I even close?
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02-16-2007, 09:50 PM
#11
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I don't know if there is a boost limit, but there has to be an ultimate compression limit. At some point the A/F mixture will be compressed to the point where it becomes a liquid, at that point it would either stall or break the engine, no matter how strong it is made.
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02-17-2007, 03:24 AM
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is that 147psi for the miata motor? or is it the compression charge of a single piston regardless of engine? and what kind of fuel are you using to solve for your equations? different fuels offer different stoichiometric values for a given quantity of mix... so which did you use? nitro, gas, alky, blue gas, blend?
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02-17-2007, 11:33 AM
#18
well you are right to a point the higherthe compression the less movemet allowed in the substance hence going to liquid and then solid. or just skipping liquid all together. Gas is where the matter uses most of its energy in kenetic motion of the molecules. And occurs at lower pressure reading more easily or higher temps. So if you either create a serius - vaccuum or cold enviroment then the molecules will calm down.
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