Supercharger boost at high altitude

[Toyota86.ir]

It seems superchargers boost level decrease at high altitude but turbochargers will fix the boost level even at higher altitude.

at sea level if both supercharger and turbocharger make 8.5psi then at 1200m above sea level the supercharger make 7.3psi and turbo make 8.5psi.

this means 0-60 time records of supercharged engines will increase at higher altitudes.

I think turbo is more logical than supercharger for those live in high altitude.

any idea about centrifugal superchargers?

[xsnapshot]

Originally Posted by Toyota86.ir

It seems superchargers boost level decrease at high altitude but turbochargers will fix the boost level even at higher altitude.

at sea level if both supercharger and turbocharger make 8.5psi then at 1200m above sea level the supercharger make 7.3psi and turbo make 8.5psi.

this means 0-60 time records of supercharged engines will increase at higher altitudes.

I think turbo is more logical than supercharger for those live in high altitude.

any idea about centrifugal superchargers?

Any supercharger is spinning at a fixed RPM at any given engine RPM. As you go up in altitude, the compressor is still operating at a certain Pressure ratio. You will get less boost because it cannot speed up to compensate.

A turbo has a wastegate that can be held shut to allow the compressor to spin faster and yield similar boost levels.

At high RPM a turbo will take longer to spool up, and it will need to be pushed harder to maintain similar boost pressures as at sea level.

Don't equate 0-60 too strongly with boost. A roots supercharger might make 300whp at 14 psi, whereas a turbo might make 300whp at only 10 psi. However 0-60 times may be identical.

You can't really say one is better than the other (super vs turbo) without knowing what application you are using it for. Some like the "instant" response of a supercharger.

A turbo is easier to keep at a fixed boost level sure. But you could also use a smaller supercharger pulley to do the same thing. It's just more of a pain in the ass to change it.

[Toyota86.ir]

Originally Posted by xsnapshot

Any supercharger is spinning at a fixed RPM at any given engine RPM. As you go up in altitude, the compressor is still operating at a certain Pressure ratio. You will get less boost because it cannot speed up to compensate.

A turbo has a wastegate that can be held shut to allow the compressor to spin faster and yield similar boost levels.

At high RPM a turbo will take longer to spool up, and it will need to be pushed harder to maintain similar boost pressures as at sea level.

Don't equate 0-60 too strongly with boost. A roots supercharger might make 300whp at 14 psi, whereas a turbo might make 300whp at only 10 psi. However 0-60 times may be identical.

You can't really say one is better than the other (super vs turbo) without knowing what application you are using it for. Some like the "instant" response of a supercharger.

A turbo is easier to keep at a fixed boost level sure. But you could also use a smaller supercharger pulley to do the same thing. It's just more of a pain in the ass to change it.

We live in tehran , tehran altitude is 1400m above sea level .we need to get more power at less boost.
I planned to go for 380bhp HKS supercharger v3 E85 but hks will be limited to 320bhp in my city but avo turbo (E85) at 10psi will make 380bhp in my city.