Has anyone installed the Londaon Stainless header? If so, what are your thoughts. It is the same company that builds the Quicksilver exhaust, which I already have, and is supposed to work well with it. I understand the header is 2 1/2" dia. whereas the QS exhaust is 2 1/4" dia. I also was told by several people that this "neck down" is sometimes good. Thoughts?

 

The LS header is actually manufactured by Milltek in the UK, while LS makes the Quicksilver exhaust and just sources the header directly from Milltek.

It is a very nice unit - the nicest out there right now. It uses a 4-1 design with both O2 ports and a 200dpi metallic race cat.

The unit typically yields 7-9 horsepower depending on the other modifications you have done.

As far as the reduction from the 2.5" to 2.25" at the cat-back side of things, there is a difference between backpressure and reduced flow characteristics. A step isn't very efficient at doing anything but disturbing the flow (it causes backpressure, but not efficiently - the energy loss from the disturbance is greater than the backpressure gained). The backpressure is somewhat important because of torque, but more so in a normally aspirated car than in our supercharged car. A better way to provide the necessary backpressure is through correct muffler size and design, with the primary splitting into the correctly sized secondaries. For instance, if the outlet of the header is 2.5", it would be better to have a match there, then at the rear of the car, step into smaller secondaries or provide mufflers that give the correct backpressure. The correct backpressure really depends on what you want from the system. Less backpressure usually relates directly to more horsepower, while you may sacrifice some torque in the process.

Hope that helps!

Randy
720-841-1002