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**MissaT** · 3-11-04, 3:13

I would totaly agree with this theory of exhaust gases.

In regards to the Turbo Vs NA issue, my understanding of why you can get away with a larger exhaust on a turbo than on an NA is because the turbo unit itself provides that degree of restriction to help make the scavenging effect work to its full potential (and it also has the effect of quieting the exhaust note).

The headers on NA cars are tuned (ie the length of the tubes) so that each 'pulse' of exhaust gas from the cyclinder reaches the collector exactly the same time apart from each other to help provide the smoothest and most effective scavenging. In addition, I havent really been able to explain it but a rule of thumb with NA headers is the 4-2-1 type provide a tradeoff between torque and high end power where as the 4-1 units are just made for pure high end power at the expense of lower end torque. I suppose the next logical thought would be towards optimising a turbo manifold in the same way as a set of headers to providethe most efficient, smoothest stream of gas. Apparently for engines below 400hp? (ie anything that we are likely to encounter) it makes bugger all difference.

3-11-04, 3:13	#6 (permalink)
MissaT Join Date: Nov 2003 Location: Melbourne, Australia iTrader: (0)	I would totaly agree with this theory of exhaust gases. In regards to the Turbo Vs NA issue, my understanding of why you can get away with a larger exhaust on a turbo than on an NA is because the turbo unit itself provides that degree of restriction to help make the scavenging effect work to its full potential (and it also has the effect of quieting the exhaust note). The headers on NA cars are tuned (ie the length of the tubes) so that each 'pulse' of exhaust gas from the cyclinder reaches the collector exactly the same time apart from each other to help provide the smoothest and most effective scavenging. In addition, I havent really been able to explain it but a rule of thumb with NA headers is the 4-2-1 type provide a tradeoff between torque and high end power where as the 4-1 units are just made for pure high end power at the expense of lower end torque. I suppose the next logical thought would be towards optimising a turbo manifold in the same way as a set of headers to providethe most efficient, smoothest stream of gas. Apparently for engines below 400hp? (ie anything that we are likely to encounter) it makes bugger all difference.
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