[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

*To*: quattro list <quattro@coimbra.ans.net>*Subject*: Turbos at altitude: The Final Answer*From*: Dan Bocek <dan@di.com>*Date*: Fri, 22 Mar 1996 16:02:20 -0800*Sender*: owner-quattro@coimbra.ans.net

The reason you can get a turbo to produce the same pressure regardless of altitude (within reason, of course) is because a turbo is basically a turbine, so turbine theory applies. It turns out that a turbine's flow rate is roughly proportional to the *SQUARE* of its RPM. Because of this fact, there will always be an RPM under which it flows too little, and an RPM over which it flows too much. This is why you need a wastegate: you want it to kick in when the turbine RPM reaches that "Too Much" regime so that you have a constant intake pressure from then on. If you go to a higher altitude, the "Too Much" regime is simply shifted to a higher RPM, but since you have the Square law on your side, you can achieve the same boost level you had at sea level. Since a supercharger's output is simply proportional to it's RPM (not the square of the RPM as in the case of the turbo) you don't need a wastegate. Since you don't have the Square law on your side anymore, it's boost pressure will always be relative to whatever the ambient pressure is. Dan Bocek dan@di.com

- Prev by Author:
**spring rates** - Next by Author:
**Re: Audi/Bose Stereo power connection stays on when car key is in off position !!@#$^** - Prev by thread:
**FW: FOR SALE: 1990 COUPE QUATTRO !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!** - Next by thread:
**Taking a break - Yeah, right!!** - Index(es):