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Power is in the Eye of the Beholder: Testing Turbo manifold crossover merges

Posted By: Steve Baur
Written by: Chad Stephens
Photography courtesy of Brian Tooley Racing

Brian Tooley, and his company BTR (Brian Tooley Racing), are names synonymous with the LS engine platform. Upon closer inspection, with all preconceived notions cast aside, this man and his operation have significantly more to offer the racing industry and the world of performance. Those who have personally dealt with Mr. Tooley couldn’t have miss ed his passion for a detailed and skeptical approach to engineering and his constant desire to improve things, not only to satisfy his own curiosity, but more importantly to provide his customers with the best end products. 

Tooley, however, got started in the automotive industry with cylinder head and induction airflow development, and out of pure observational curiosity, noticed a specific component on a recent turbo build that caught his attention. He was left wondering if there was room for improvement within the turbo merge section, something that had previously never garnered any notable attention. These ideas often creep into technical minds, manifesting, growing, and unable to subside until definitive answers have been obtained.  With the ability and tools required to run accurate back-to-back testing, Tooley took the logical path and used his fully equipped facility for implementation and testing to confirm if there was any merit in his thoughts.
As Tooley describes it, “For a while, I had been wanting to perform some consecutive tests of a hand-fabricated turbo crossover merge flange versus a popular CNC machined design.” This idea quickly moved into reality when the supply of a popular CNC merge design was potentially facing limited supply. Because of this, Brian finally found the time and committed to it. During the assessment on the engine dyno some interesting discoveries were observed in the process.

Proving out power through Dyno testing: Seeing is believing
Dyno testing aides in comparing ‘theory’ versus the ‘reality’ and once the numbers start to roll in, the findings can be reverse engineered by analyzing the data thoroughly to draw conclusions. More often seen than not, the modifications we assume will give the greatest results (more airflow, larger cam, bigger exhaust, etc.) actually do not. Great builders/tuners are fully prepared to accept this fact as it a sign that something new can be learned in the process, as they know how to decipher the results. The old adage applies “If the results don’t match your theory, it’s time to change your theory”.
In these instances, where the eyes can be misleading, our brain needs to step in and make the necessary connections to prove what the results are revealing. Once we do, we will see things in a different light, and that’s when the doors to new possibilities open. Seasoned veterans crave these pivotal shifts of awareness because they know that is where valuable knowledge and real advantages are found. 
The test engine employed in this search for answers was a well proven, stock block 6.0 LS with a production 4.8 crank, TFS GenX 220 cylinder heads, Holley Hi Ram intake and one of BTR’s custom HR cams. Run slightly detuned, the 76 mm turbo was limited to 20 psi of boost keeping things safe and consistent. To start with, both merge flanges utilized an open design. Looking at the results of the dyno pulls afterwards it undoubtedly confirms first that the CNC machined merge shows less back pressure then the hand fabricated version. 

The red line on graph represents the CNC flange, while the black is the hand prepared merge. As seen in the dyno graph, the CNC-milled flange offered a solid gain clear across the board with no significant tradeoffs (losses), which is a solid win in anyone’s book. As observed, the curve started mostly equal until 5000 rpm, where the boost kicked in and peak gains of 32.33 horsepower with an added 24.98 worth of torque were noticed. With additional boost, surely increased gains would be garnered.

Post dyno, the theory on the hand-constructed merge results is that the exhaust gases from one side of the engine could be "cutting off” or choking, to a degree, the exhaust gas from the opposing side. Externally, it looks good, but internally you can see the exhaust gas from one side is potentially colliding with the exhaust gas from opposing side, at a 30-degree angle. During this stage of testing, remarkable differences from minor shape changes can be found if felt worth pursuing. 
Moving forward Tooley says, “The last and true back up test was to throw the engine back in the car (a well-known Tin Soldiers-built Xtreme Street Camaro) it came from and prove it out on the track.” The dragstrip is the ultimate place to confirm these potential gains, a final verdict of the process. In the end, the best iteration used resulted in a hydraulic roller cam record 154mph in the 1/8th at a past NMCA LSX Shootout.   

“We have the math and modelling to quantify predictions, but are we learning if they always match our expectations,” Tooley said. When the results go as anticipated, he feels like nothing was really taught, and that he has found “The days you were wrong are our best days.”
The takeaway is to never stop searching within your own program, even at the smallest of details. There will always be room for improvement and the limits are only as far as we are willing to pursue them. Throughout racing, this author has learned that the most successful people never stop searching for areas to improve, which one might say is the true meaning of “The power is in the eye of the beholder.” 
Brian Tooley Racing
2100 Filiatreau Ln, 
Bardstown, KY 40004, United States
(888) 959-8865

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