Superchargers - Roots vs Centrifugal
Discussion
Put this in a different section, but think it's probably better here.
I've been looking at the R8 V8 as I've found two different supercharger systems, and I'm wondering about the differences between them.
TTS Performance - Twin Rotrex centrifugal superchargers. 700bhp (advertised)
VF Engineering - Roots type supercharger. 595bhp (advertised)
Other than the obvious differences in the way the superchargers work, are there any differences in the outputs? I vaguely remember seeing stuff about Roots being more efficient down low while centrifugal are more efficient up at the top, and I can't be sure I haven't imagined it, but I'm wondering how true this is. Also, the TTS is twin centrifugal so I'm wondering if that makes a difference.
I've been looking at the R8 V8 as I've found two different supercharger systems, and I'm wondering about the differences between them.
TTS Performance - Twin Rotrex centrifugal superchargers. 700bhp (advertised)
VF Engineering - Roots type supercharger. 595bhp (advertised)
Other than the obvious differences in the way the superchargers work, are there any differences in the outputs? I vaguely remember seeing stuff about Roots being more efficient down low while centrifugal are more efficient up at the top, and I can't be sure I haven't imagined it, but I'm wondering how true this is. Also, the TTS is twin centrifugal so I'm wondering if that makes a difference.
Not sure about efficiencies but I THINK the Rotrex are less common & wonder if there are reasons for this?
Obviously twin s/chargers will produce more power than one, hence the widely different power outputs.
May well not be an issue for you but don't forget that as they use engine power to spin you will lose a potentially significant amount of MPG in the process.
Obviously twin s/chargers will produce more power than one, hence the widely different power outputs.
May well not be an issue for you but don't forget that as they use engine power to spin you will lose a potentially significant amount of MPG in the process.
To get 600, 700 BHP I suppose you'll expect to be running high boost, and with everything built. For comparison my RV8 4.6 with an Eaton supercharger producing 5 psi produced around 350, and not much more at 10psi.
The higher the boost level, the less efficient the positive displacement blowers are. If you have a blower with some internal compression then they will be optimised for a particular compression ratio and only get inefficient when you go significantly above that. So the answer will depend on the type of blower and the boost level you're aiming for.
Positive displacement blowers can be set up to produce torque at low rpm. This is great to drive but does introduce the problem of charge blow-through because there is no exhaust backpressure to balance out the intake pressure. You'll sometimes see people running 'blower' (low overlap) cams to counteract this. However, this does severely restrict breathing at high revs.
Centrefugal blowers produce very low boost at low revs and the boost climbs with revs. You may need to be in the top third of the rev range before they do anything useful. This might suit you if your base engine is already torqey and you just want to improve the breathing at the top of the rev range. They also tend to be more efficient than positive displacement blowers, so less parasitic power and charge heating at higher boost levels.
I think the availability of cheap, fast spooling turbos has taken over the market that centrifugal blowers used to occupy and this would probably be a better option all round when you're aiming for these higher power levels.
The higher the boost level, the less efficient the positive displacement blowers are. If you have a blower with some internal compression then they will be optimised for a particular compression ratio and only get inefficient when you go significantly above that. So the answer will depend on the type of blower and the boost level you're aiming for.
Positive displacement blowers can be set up to produce torque at low rpm. This is great to drive but does introduce the problem of charge blow-through because there is no exhaust backpressure to balance out the intake pressure. You'll sometimes see people running 'blower' (low overlap) cams to counteract this. However, this does severely restrict breathing at high revs.
Centrefugal blowers produce very low boost at low revs and the boost climbs with revs. You may need to be in the top third of the rev range before they do anything useful. This might suit you if your base engine is already torqey and you just want to improve the breathing at the top of the rev range. They also tend to be more efficient than positive displacement blowers, so less parasitic power and charge heating at higher boost levels.
I think the availability of cheap, fast spooling turbos has taken over the market that centrifugal blowers used to occupy and this would probably be a better option all round when you're aiming for these higher power levels.
TheOrgano said:
Put this in a different section, but think it's probably better here.
I've been looking at the R8 V8 as I've found two different supercharger systems, and I'm wondering about the differences between them.
TTS Performance - Twin Rotrex centrifugal superchargers. 700bhp (advertised)
VF Engineering - Roots type supercharger. 595bhp (advertised)
Other than the obvious differences in the way the superchargers work, are there any differences in the outputs? I vaguely remember seeing stuff about Roots being more efficient down low while centrifugal are more efficient up at the top, and I can't be sure I haven't imagined it, but I'm wondering how true this is. Also, the TTS is twin centrifugal so I'm wondering if that makes a difference.
Ignore headline numbers, and get opinions from people who've actually owned either setup.I've been looking at the R8 V8 as I've found two different supercharger systems, and I'm wondering about the differences between them.
TTS Performance - Twin Rotrex centrifugal superchargers. 700bhp (advertised)
VF Engineering - Roots type supercharger. 595bhp (advertised)
Other than the obvious differences in the way the superchargers work, are there any differences in the outputs? I vaguely remember seeing stuff about Roots being more efficient down low while centrifugal are more efficient up at the top, and I can't be sure I haven't imagined it, but I'm wondering how true this is. Also, the TTS is twin centrifugal so I'm wondering if that makes a difference.
Largely in terms of reliability, belts etc etc
But a lot will depend on your driving needs and style. Is it track ? Is it primarily road ? other ? Do you like revving the nuts off it ? Or would you prefer more relaxed torque ?
Would you want to grow in the future ? do either kit have much room left to grow ?
Roots are not more efficient, but they do produce more torque at low rpm. That has little to do with compressor efficiency.
The TTS will be twin for packaging reasons and a lot of the Rotrex are quite small and low output. As to whether this makes a belt system easier or harder, or more or less reliable, would be a good question vs a single unit.
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