why are long tubes better than shorties ?
10-08-2010, 10:56 AM
#2
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Long tubes provide more cyl scavenging. The velocity of the previous exhaust cycle pulls a vacuum on the back side of the exhaust valve and helps pull the gases out of the cyl when the valve opens rather than having to push it out. Short tubes do very little of this over stock manifolds. Short tubes yeild approx 5 hp on a stock engine while long tubes will yeild 15-20 with no other mods.
10-08-2010, 11:04 AM
#3
You have to understand how headers work to know why shorties are just for show. Headers are a tuned length system that extracts the exhaust from a cylinder, making power by lowering the pressure in the cylinder so that more of the fuel/air mix gets in easier.
When the exhaust pulse in a tube enters the collector, it expands and makes a negative wave, or suction, behind it. This suction is present in all four tubes. The length of the tube is determined by the time it takes for the wave to be at the adjacent cylinder, so it is there when its exhaust valve is at the right place for the wave to reduce cylinder pressure.
This tuned length is similar to pipe organs, where the long tubes are low tones in the organ, or low rpm in the engine. Short pipes produce high tones, or work their magic at high rpm.
Tuned length headers at the length that we put them on our engines are at a length that is still more for higher rpm, longer would be better for street vehicles, especially trucks, but there is not room.
So headers provide a big boost in power, mainly at higher rpm, what is the length of shorties tuned for? No engine that you could drive on the street. Even formula one engine's headers are longer than shorties.
It is not an airflow thing, stock manifolds will flow plenty of air.
Shorties are just for looks, or for applications that there is not room for stock manifolds, like a T bucket hot rod.
Why do they sell them if they don't work? The question should be is "why do people buy them if they don't work?".
When the exhaust pulse in a tube enters the collector, it expands and makes a negative wave, or suction, behind it. This suction is present in all four tubes. The length of the tube is determined by the time it takes for the wave to be at the adjacent cylinder, so it is there when its exhaust valve is at the right place for the wave to reduce cylinder pressure.
This tuned length is similar to pipe organs, where the long tubes are low tones in the organ, or low rpm in the engine. Short pipes produce high tones, or work their magic at high rpm.
Tuned length headers at the length that we put them on our engines are at a length that is still more for higher rpm, longer would be better for street vehicles, especially trucks, but there is not room.
So headers provide a big boost in power, mainly at higher rpm, what is the length of shorties tuned for? No engine that you could drive on the street. Even formula one engine's headers are longer than shorties.
It is not an airflow thing, stock manifolds will flow plenty of air.
Shorties are just for looks, or for applications that there is not room for stock manifolds, like a T bucket hot rod.
Why do they sell them if they don't work? The question should be is "why do people buy them if they don't work?".
10-08-2010, 12:56 PM
#6
The guy’s have made a good argument for long tubes thus far and I agree in trucks such as ours where there is plenty of room, long tubes should be the right decision. As mentioned, some vehicles with cramped engine bays can still benefit greatly though with even a set of well designed shorties over some stock manifolds or poorly designed short tube headers. Not all “shorties” need be built out of tube steel either, Sanderson Headers has been in business for more than 35 years building quality products for vehicles that range from hot rods to obscure vehicles that mainstream companies don’t all cater to. Yes, most of their products are tube steel, but for certain applications they also have cast iron headers available that incorporates individual runners to separate exhaust pulses, with cast anti-reversion baffling to prevent spent gasses from being drawn back into the cylinder during valve timing overlap, when both intake and exhaust valves are open. The cast versions are advertised as having a leak free flange design that doesn’t require gaskets and due to their design can not be used with gaskets, as they will cause a leak. They are also popular where noise is of concern, as not everyone wants the pulsing sounds that come with a set of tube steel headers.
As I said at the start, for me where performance comes 2nd to none, a good engineered set of long tubes is where it’s at, but not the only choice for some.
As I said at the start, for me where performance comes 2nd to none, a good engineered set of long tubes is where it’s at, but not the only choice for some.
Last edited by 1Bear; 10-08-2010 at 01:03 PM.
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10-08-2010, 10:16 PM
#9
I've read of some guys running them a while back with good results...a member or two on silveradoss.com seems to come to mind. I would have to guess that they're considerably more effective than shorties, but obviously not as good as an LT. I also recall some folks being very satisfied with their tri-y headers, especially down low and through the midrange...
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