Headers are more than tubes going into a collector. A great deal of thought, experience and craftsmanship are invested in header design to generate dramatic power gains.
Burn's Stainless is known for supplying quality stainless steel, aluminum and titanium piping as well as a variety of collector designs that power winners on the strip, on the circle track and on the street. While the company is known for selling quality parts, one of its most valuable commodities is its knowledge of how exhaust gas and header designs can make power. Burn's Stainless' collector designs and header software are second to none.
It would take three pages to list the winners that use Burn's Stainless products and header designs. Let's break it down like this: a whopping 80 percent in Pro Stock and over 70 percent in Winston Cup rely on Burn's Stainless for a variety of reasons.
Turbo & High-Tech Performance decided to take a trip to Burn's Stainless' Costa Mesa, Calif. headquarters to let Jack Burns and Vince Roman drop some knowledge about basic header design on us and our readers. Jack is the veteran header technician and Vince is an engineer who has all the right formulas that allow the company to create software that can compute the best design for almost any application. The software is not for sale, but fill out a Burn's Stainless tech sheet and the company can produce the correct design for a header, whether it's a Tri-Y (4/2/1) or four-into-one (4/1) design.
What are some of the power differences between a Tri-Y and four into one?
JB: From our experience, when you have a split turbine housing and you pair up the firing order with the split housing, you would essentially have a Tri-Y design. This would be great for spool up in a road race application like Toyota's GTP years ago. In a drag race application, I would think a four into one would be the way to go.
VR: One of the other major advantages with spool up on the Tri-Y on a turbo without a split housing turbo is you could design proper lengths with an increased volume as compared to a 4/1.
What effects on performance can you expect to have by merging different cylinders together on a Tri-Y?
VR: The key is to match the cylinders that are firing 360 degrees apart. There are two reasons; one is to get even firing into the collector and two, is to get the pulses far apart. You use one cylinder to fire when one of the other cylinders exhaust valves is closed. In a six cylinder it is typically one, two and three together and four five and six together because you're getting even spacing at 240 degrees into each collector. We believe that pairing the correct firing orders together is the proper way. We have seen a few headers out there that pair up differently, but for what reasons, I don't know.
JB: We have done some R&D on pairing different cylinders, but what we've found is pairing up the right way is still the best way. In a lot of cases, you might be forced to join uneven cylinders. In most cases it will be because the motor is a V or flat engine. Jumping cylinders back and forth could cause fitment problems.
How important is tubing size and length?
JB:
A lot of the tubing size and length is based off of the engine's cam profile and rpm band.
VR: We need to know how quickly a cylinder puts out its exhaust, how much time a cylinder takes to pump out exhaust, how much overlap is there between the intake and exhaust valves. There is more to it than this, but once we have the basic engine design, then we can go in and design a header for the engine.
What's the determining factor for collector design?
JB: We really want to make sure the cylinders fire into the collector to simulate a gattling gun effect. The angle you use in the collector is very important. A lot of collectors are built with a 15-degree angle. You want to have a good combination between the flow rate and amount of internal volume. If you have too much volume then you will slow the velocity.