Johnny Johnny
04-13-2009, 04:30 PM
Just theorizing here - no real-world experience.
I'm currently swapping a 5.3l L33 HO motor into my Porsche 944, which will be used for daily driving, HPDE and road circuits (no strip or drag launches). The engine bay is pretty tight, so fitting a turbo or turbos up front is a bit of a challenge. I was wondering about performance benefits/drawbacks for a rear-mounted turbo for road racing use. I can see the following potential benefits of a rear-mounted turbo:
- less possibility of heat soak, resulting in lower engine bay temperatures
- lower engine oil/coolant temperature
- better weight balance
Typically, rear-mounted turbos must contend with maintaining adequate exhaust gas temperatures during the long run back from the exhaust ports. I would think that this would have a negative impact for drag racing, as the motors run in an all-or-nothing manner, i.e. little time for the exhaust track to heat up. For a road race, the temperature in the exhaust pipe would be elevated at a more consistent level, so less energy would be lost.
Of course, there are other issues to contend with, such as oil lines, increased weight from the longer pipes, etc.
Doing a search I can't find a single instance of a rear-mounted turbo on a road race car, so I'm probably just being stupid, but I thought I'd put it out there.
Any thoughts/comments/criticisms?
I'm currently swapping a 5.3l L33 HO motor into my Porsche 944, which will be used for daily driving, HPDE and road circuits (no strip or drag launches). The engine bay is pretty tight, so fitting a turbo or turbos up front is a bit of a challenge. I was wondering about performance benefits/drawbacks for a rear-mounted turbo for road racing use. I can see the following potential benefits of a rear-mounted turbo:
- less possibility of heat soak, resulting in lower engine bay temperatures
- lower engine oil/coolant temperature
- better weight balance
Typically, rear-mounted turbos must contend with maintaining adequate exhaust gas temperatures during the long run back from the exhaust ports. I would think that this would have a negative impact for drag racing, as the motors run in an all-or-nothing manner, i.e. little time for the exhaust track to heat up. For a road race, the temperature in the exhaust pipe would be elevated at a more consistent level, so less energy would be lost.
Of course, there are other issues to contend with, such as oil lines, increased weight from the longer pipes, etc.
Doing a search I can't find a single instance of a rear-mounted turbo on a road race car, so I'm probably just being stupid, but I thought I'd put it out there.
Any thoughts/comments/criticisms?