I hear Borla is bringin out some shorty headers for the C6. What is the difference between the two? What is the advantage or difference between the two regarding price, sound, performance?

 

I don’t know the price of the shorties, but I have found that most shorties carry the same price tag as long tubes but no where near the performance gains. Other then being 50 state legal, I don't see the point on getting shorties. On the LS1's the stock manifolds flowed almost as good as shorties. I would assume this to be true on the LS2's as well.

 

Callaway claimed only 8 HP for their shorties.

 

shorties stand for "short on hp" ...

 

ST headers are simply more efficient exhaust manifolds because they offer less resistance to flow (smoother ports).

LT headers act as a power enhancer by extracting exhaust energy to help pump mor air through the enging (air pump) creating power. These are the only real exhaust system that deserve the name headers. A header should be chosen to match the exhaust opeing of the valve to the intake vavle opening event. The collector should be chosen to match the exhaust vavle closing event with the previously chosen header.

 

Say what?

 

Yes, real long tube headers extract energy from the exhaust gasses flowing out of the combustion chamber and deposit this energy into the incomming fresh mixture to put more mixture into the next power stroke.

There is a multistage process that happens:

A) exhaust valve opens with the cylinder still pressurized to 70 PSI or so.
B) this valve opening sends a positive pressure wave down the header pipes where it meets the rest of the header pipes and the collector.
C) when this positive pressure wave hits the collector, a negative pressure wave (about -13 PSI) is reflected from the gasses entering the collector's larger volume
D) this negative pressure wave travels up the header tube, while the remains of the positive pressure wave travels across the collector.
F) just before the negative pressure wave arrives back at the still open exhaust valve, the positive pressure wave bounces off the constriction at the other end of the collector.
E) the negative pressure wave arrives (about -11 PSI) as the intake valve is opening, and begins to draw fresh mixture into the cylinder even before the piston starts its downward journey on the intake stroke.
G) just before the exhaust valve closes, the postive pressure wave (about +7 PSI) arrives and pushes any fresh mixture back into the cylinder that may have been pulled into the exhaust port.

As you can see, to make this process work, the time it takes the waves to travel down and up the header and accross the collector and back must be synchronized with the cam timing at the valves. The length and diameter of the headers sets one timing interval between exhaust valve opening and intake opening, while the length and diameter of the collector should be matched to the overlap time on the cam.

In a race engine, a properly tuned header system can add as much as 20% to the power of an engine, in street applications numbers in the 5% to 7% are realizable. This 5%-7% is over and above a similar set of manifolding that is smooth enough to add virtually no resistance to the flow, but does not utilize the wave effects of the headers.

 

Soooo basically...scratch shorties off the list huh?...Thanks for the info!

 

Yes, I am familiar with "Exhaust Scavenging". You were just making a very easy thing sound complicated.