Is there a limit for a S/C

Discussion regarding Turbocharged and supercharged MX-5s

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Kain
Fast Driver
Posts: 154
Joined: Mon Dec 22, 2008 11:44 pm
Vehicle: NA6
Location: Brisbane, QLD

Re: Is there a limit for a S/C

Postby Kain » Thu Nov 25, 2010 8:33 pm

Benny wrote:As the compressed air/fuel mixture is ignited (increasing temperature), the pressure of the gases from this heating is used to power the turbocharger (after it pushes the piston down and is exhausted out the exhaust valve), hence a turbo is powered by the pressure of the heated gasses.
Is that correct or not?

Benny wrote:What you also forget Danny, is that a lot of the rotational force of a turbocharger is not caused just by exhaust pressure, but by exhaust heat, and it is this heat that actually causes most of the rotation of the turbocharger impellor.


The inconsistencies, they make me lol. It's ok to be wrong, although I agree that it's hard to admit it after you've been an arrogant jerk about it. You are correct about the workings of the combustion chamber though. If this is something that you're willing/wanting to discuss more, I'd gladly explain it via PM, but I'd rather not crap up this thread with any more 'I know more physics than you' pissing matches.



Back to the original topic at hand, imagine a naturally aspirated car, where the exhaust suddenly drops from the usual 2 inches to 0.5 inches in diameter, then back up to 2 inches. Would that bottleneck in the flow cause a loss to the power made? Yes, yes it would. Now imagine that when exhaust goes through that constriction, the engine magically makes more power. That loss is still there, but the new magic power overcomes it and so the total power produced is greater than before. What you've just imagined is a turbocharger. Thus, there is a parasitic load associated with a turbo, but it is proportional to the velocity of exhaust gases rather than to engine RPM.

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bootz
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Re: Is there a limit for a S/C

Postby bootz » Wed Dec 01, 2010 12:09 am

Kain wrote:
Benny wrote:As the compressed air/fuel mixture is ignited (increasing temperature), the pressure of the gases from this heating is used to power the turbocharger (after it pushes the piston down and is exhausted out the exhaust valve), hence a turbo is powered by the pressure of the heated gasses.
Is that correct or not?

Benny wrote:What you also forget Danny, is that a lot of the rotational force of a turbocharger is not caused just by exhaust pressure, but by exhaust heat, and it is this heat that actually causes most of the rotation of the turbocharger impellor.


The inconsistencies, they make me lol. It's ok to be wrong, although I agree that it's hard to admit it after you've been an arrogant jerk about it. You are correct about the workings of the combustion chamber though. If this is something that you're willing/wanting to discuss more, I'd gladly explain it via PM, but I'd rather not crap up this thread with any more 'I know more physics than you' pissing matches.



Back to the original topic at hand, imagine a naturally aspirated car, where the exhaust suddenly drops from the usual 2 inches to 0.5 inches in diameter, then back up to 2 inches. Would that bottleneck in the flow cause a loss to the power made? Yes, yes it would. Now imagine that when exhaust goes through that constriction, the engine magically makes more power. That loss is still there, but the new magic power overcomes it and so the total power produced is greater than before. What you've just imagined is a turbocharger. Thus, there is a parasitic load associated with a turbo, but it is proportional to the velocity of exhaust gases rather than to engine RPM.


I rather like the technical pissing matches as they are a real debate amongst more knowledgeable people than me. I must admit that the turbocharger being dríven by 'waste' heat is a seductive argument until scrutinised. I didn't understand it but it sounded nice.

The main thing is they both "work" in increasing power. But according to mugs law, 'there is no such thing as a free lunch' more power always equals more fuel consumption, however efficient the charger. It's how you use the available power that makes a good driver.
Bootz and Boof - On the road to somewhere.


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