In Reply to: this is the truth... posted by Terry on February 27, 2001 at 22:47:44:
It makes perfect sense. The highest sound level will be directly out the back. So, by pointing the tips upward, the measurement device would have to be really high or really close to the car to get a similar measurement to the straight tips. You are right, though, that the upturned portion would have to be of sufficient length. Hmmm...I wonder how the highway patrol measures! ;)
I heard explanations from air turbulence for trailing cars to not scraping the tips when unloading off the trailers. THESE were far-fetched.
DTM tips curl up that way because the DTM had sound limits. There would be a guy at Pit Out or Pit In and with a microphone at knee level or so. He'd measure the sound. They started curling them up like that to direct the noise upwards away from the ground. I know this sounds rather far-fetched but it's the truth. I have heard some people say they are curled up so you wouldn't damage the whole exhaust system and manifolds if rear ended....I really think it's because of the sound.
If you don't pass sound at Laguna Seca try some large custom DTM tips (i'm talking at least a 5" curl upwards, more if you can).
I've seen it happen. Two H-Stock E36s were racing at Laguna. One had SuperSPrint straight round tips the other had the SuperSprint "DTM" tips. The guy with DTM tips passed while the straight tips guy saw the black flag. This is what led me to believe that what I was told was true...
This is good too because it directs the sound up out of the race track and is probably heard by the complaining nearby residences. WOOHOO! May they awake from sleeping in!!!! :)