Sneak Peek: Bothwell Motorsports Pro Mod Camaro
Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing. All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.
Firstly, I need to thank my co-worker Krystyna Kubran for letting me borrow her phone to take pictures (the camera on my phone sucks); I wasn’t exactly expecting a 5-second drag car in the parking lot at work so I didn’t have my camera. Oh yeah, she can out-ride the vast majority of you on a motorcycle on a race track; her street bike and former race bike is an R1 while her new race bike is a ZX-10R. Check her out on BuzzFeed. Back to the twin-turbo, few thousand horsepower drag car.
This is the engine cover. The two holes in the top are for the intakes of the turbos.
Underneath the piping is a 526ci big block V8 which is fed methanol stored in the fuel cell at the front. The turbos are angled at a steep 37 degrees. This is typically not recommended as it can lead to uneven oiling of the bearings and also oil leakage out of the center housing past the wheels (like water spilling out of a tilted sauce pan). The twin Garrett GTX5518R turbos use ball bearings of course and the ball bearing requires less oil flow compared to journal bearing setups. Also, a journal bearing setup relies on a thrust bearing to handle the thrust loads and oil getting fed to the thrust bearing is critical to survival due to the required hydrodynamic film the oil creates. The thrust bearing is located on the compressor wheel side which is uphill for the oil to go with the way these turbos are oriented. No oil to the thrust bearing, no hydrodynamic film, bye bye journal bearing turbo. Ball bearings don’t depend on oil to support the thrust loads, so the turbos can survive the tilt. You can read more about bearings in our Turbo Tech: Turbo Bearings
article. As for the oil leakage issue, more on that later. You’ll also notice no intercoolers are used; cooling the charge air coming out of the turbos is not required when running methanol for fuel. Remember back in the day, the CART IndyCars also ran methanol and did not use intercoolers on their turbo engines. Hey, those used Garrett turbos too. Anyway…
That is one pretty exhaust manifold! EGTs are monitored on each runner. Look closely, and it appears that stepped primaries are used. The engine revs up to 10,500rpm, so I’m guessing the stepped primaries are to tune for the high rpm range of operation.
The placement of the wastegate is ideal for the best boost control. Also notice the weight of the turbo is supported by a brace attached to the oil drain flange of the turbo; bracing the turbo keeps weight off the exhaust manifold to help prevent cracking of the manifold.