Jason Haines, Lingenfelter Performance Engineering
"Building Gen III/IV for Reliable Maximum Boost-1000rwhp+"
Since 1994, UPenn grad Jason Haines has been Project Director at LPE, building some of the sickest street-going Vettes on the planet and priding himself on producing the most drivable high horsepower cars possible. Jason stressed the importance of project planning--establishing the intended use, desired power level, rpm range, fuel type, customer expectations and budget.
As a great deal of LPE's projects are twin turbo applications, Jason described their experience and recommendations on this method of forced induction. Engines are tested naturally aspirated on the engine dyno before adding turbos to check VE, and if things go wrong the outcome is less harmful [than when the turbo kit is forcing air through the intake]. Cylinder head flow is not as critical on turbo applications, as Jason has found LS1, C5R, and LS7 heads all make nearly the same power. Money and time are better spent on turbo sizing with these builds then cam, heads, etc. Backpressure is measured to determine whether a change needs to be made to the turbo. Often the mixture is run richer than optimal to keep exhaust temperatures down, and heavier valves are used (Inconel vs sodium-filled). LPE prefers mild cams (with little overlap) with turbo builds, a girdle and billet caps on the LS7 to help NVH and keep the bottom end together. The LS7 block and 6.0L iron block or LSX, if weight is not a concern, are preferred.
Jason said strength and durability are most important, and weight or friction is not as much of a concern on these types of builds. For example, LPE uses higher-strength alloy pistons from JE and Mahle, Total Seal AP gapless top ring and aftermarket cranks such as the Moldex billet model on 1500+hp LS7 engines. LPE has also found that using a fabricated 16-injector LS7 intake manifold utilizing both the factory computer (on the primary 8-injectors) and an aftermarket PCM (on the secondary injectors) dramatically increases driveability on 1,000+hp streetcars. LPE uses a boost controller as well to improve driveability, as it delays full boost on a standing mile car, for example, until 150-160 mph using mph/rpm-based controller since traction is limited. Stainless and Inconel heat shields are needed to protect critical areas. Meanwhile air-to-water intercoolers protect the intake charge, and allow for better packaging. Jason warned that meth/water injection can potentially cause engine durability issues.
John Buck, Dynatech Engineering
"Exhausting Airflow-Unlocking LSX Power with Properly Optimized Headers and Exhaust"
Like a few other speakers, John Buck has a background in the aerospace industry following his graduation from the University of Missouri and Washington University, but his love of automotive design and engineering brought him to Sunnen Products and eventually AFCO Racing Products and Dynatech Headers, where he has worked for the past 3.5 years.
John's presentation focused on his work with Dynatech on developing headers for various LS1 applications. For example, he stated that exhaust length must be designed to optimize the exhaust pulse (350 ft-sec) and finite difference wave (1350 ft-sec). The purpose is to tune the exhaust to get all the gas out at same time or average the exhaust flow, optimum is somewhere in-between. He said longer primary tubes equate to lower rpm for peak power. He went on to state that the highly dynamic nature of exhaust flow presents special opportunities-such as when considering collector styles. A straight collector creates a strong pulse, whereas a merge collector has a gradual transition to keep gas flow up and increase scavenging as well as reflection over a large rpm wave.
John praised X-pipes for allowing the sharing of exhaust downstream, which evens out the pulses since the firing order is uneven. Unfortunately the effectiveness of an X-pipe decreases as it goes further downstream. Designing headers becomes a give and take process. While header design allows the ability to tune to a particular rpm range, packaging constraints affect primary diameter and length greatly, which often makes uneven lengths. John said matching the floor of the port to the bottom of the exhaust pipe effects performance much greater than porting. With forced induction exhaust size should increase over A.G. Bell's equation for "Four Stroke Performance and Tuning," which determines primary length and diameter.