There are a ton of factors that contribute to converter clutch drag and as stall speed goes higher, converter clutch drag becomes more of a problem.
On PDD's UCC truck, we fought burning converters for quite a while and learned a ton in the process. If you could see some of the original test ports that were added to Junker Drag Truck tranny so we could measure pressures and then stand on the converter for 10 or 20 seconds at a time, it was a site to see!!! We couldn't test and do R&D quickly on the solid block UCC engine so most of the R&D was done on the Junker.
It is true that the torque converter lockup switch valve in the 47rh, 47re, and 48re valve body is dual purpose in that it shuttles to command lockup and secondly it acts as a pressure regulation valve to protect the stock converter from ballooning in reverse when converter pressure far exceeds 150 psi stock.
When the switch valve shuttles over, it changes the direction of converter charge from feeding the center of the input shaft which pushes off/releases the lockup clutch assembly to feeding the outside of the input shaft/inside of stator tube which pushes the lockup clutch assembly on and the trapped fluid under the lockup clutches and inside the input shaft is vented through the valve body into the trans sump.
When converter charge pressure at the lockup switch valve exceeds about 140 psi, the stock lockup switch valve spring collapses and valve shuttles and temporarily engages lockup to dump off the excess pressure, which quickly falls below 140 and valve shuttles back. This "hammering" affect causes the lockup clutches to drag and burn while staging at the starting line building boost. (OEM stock valve body fluid system was not designed to control a multi disk lockup converter at nearly double the feed pressure and brake boosted to nearly the stock redline)
Simple fix, add a heavier spring that does not regulate till 180 psi or higher... problem, converter balloons and on a big power race truck, crank thrust bearing failure happens quite rapidly if you stage too long, and if stall exceeds 2800 rpm or so, the lockup clutches will still drag and burn. If you stage quickly, and don't exceed 2700 rpm or so when launching, and run reasonable line pressure say 160 psi or less when staging and 200 psi or so peak the heavier spring is a valid fix. The converter still balloons at 200 psi, but usually the engine thrust will survive a while, especially if the flexplate has room to let the converter grow a little before pushing on the crankshaft.
Goerend's fix was to create a secondary converter regulation valve on their
VB to regulate both release pressure while spooling and overall lockup apply pressure to control ballooning, to my knowledge, his fix works well on the sub 2800 launch RPM trucks, I have no idea how well it works on the 3k+ launch RPM trucks like PDD's UCC Truck the GodFather.
I believe Goerend also has a proprietary defection ring built into their converter that helps redirect fluid in a way to reduce lockup clutch drag. So if you're on the verge of dragging, the Goerend deflection ring inside their race converter does help a little with lockup clutch drag.
We've had success with both DPC and Goerend converters and to quote Phil at DPC, the converter is dumb SOB that does what it's told from the
VB. Having seen inside a few other flavors/brands of converter, a correctly modded
VB can work successfully with most converters, the difference is how long the lockup clutches last.
However, regardless of converter brand or builds, we've found that if you have a big rpm truck that needs 2800 RPM or higher to stage at the drag strip, even if we disable the lockup switch valve so it can't regulate(like shim it shut so it can't activate lockup for a test, we still get converter clutch drag. When staging, the input shaft speed is zero and converter speed and lockup clutches and steels that are engaged to the converter cover are spinning at engine RPM.... so they make friction and heat quickly even with the fluid there pushing/floating them off.
We've also discovered that oil coming out the converter and through the lockup switch valve and then out to the lube/cooler circuit is more restricted than the release oil coming into the converter. In short, apply pressure (normally 15psi or less when converter is unlocked) eventually rises to match release pressure (usually within a 10 to 20psi of line pressure) despite lockup switch valve position. So eventually you end up with 150 to 180 psi release pressure and almost matching apply pressure on the backside of the clutches counteracting the release oil and causing more converter clutch drag.
After that discovery, the PDD dump valve was then created back in late spring 2018. The dump valve provides a second fluid path to evacuate apply side oil pressure when it is not wanted. The dump valve significantly lowered apply side oil pressure to near zero psi and allowed us to jamb 180 to 200 psi into the release side through the input shaft to float that lockup clutch assembly as much as possible and feed it with copious amounts of lube oil to cool those 3200 to 3500 RPM spinning clutch assemblies. Lower oil pressure on the converter turbine side also raises the stall speed of the converter a little and is a common tactic used on high-end gas drag cars for staging and launch control. In the case of diesel drag racing, the dump valve raises the stall speed quite a bit if converter clutch drag was a problem because non-dragging converters magically stall higher.....
Don't get too excited, you won't gain 1000 RPM of stall speed with a dump valve like a high end gasser turbo 400 that both restricts/borderline starves the converter with the dump valve causing cavitation and huge stall speed changes, we still need to feed the lockup release circuit on the 47re/48re to keep the lockup clutches floating and released so we can't "starve" the converter, unless we go to a non-lockup converter.... which is a current trend with some of the builders in the diesel drag race 48re industry....
In short, your converter builder is not the problem, but if you built a high RPM sled pull engine, a spring may not fix your problem either.
