[200hp/tonne]

Originally Posted by arthur93

So a couple of questions;
1. In regards to the efficiency islands, what is deemed to be efficient? This i could not find anywhere. I know you want to be at the central island, but is there any tolerance to say over 65% is deemed efficient?

2. @ 3,500RPM, all 3 are below the 64% efficiency island. To me, this says it is inefficient in creating boost at that RPM. Is that correct or does it mean it won't make boost then. Reason I ask is I have heard many owner's of the full race kit making 13PSI by 3500RPM with the 7163.

3. Can the compressor map assist in determining what the power band will look like? For the 7163 and 6758, at peak RPM, they are pretty much smack bang in the 74% island. This to me says, the turbo is now the happiest and will easily make the boost. For the 6258, it is within the 74% up to about 7,000RPM and by 7,500RPM, drops to 68%. Does this mean power will drop off, or it will be able to maintain the power, but it less efficient?

4. What should my goals be when looking at the compressor map. To make sure I am to the right of the surge line and to the left of the far right? Or to spend as much time in the efficient islands as possible?


5. From what I can gather, the 6758 and 7163 look near identical with my plots; so between the two the 7163 is a no brainer. But looking at the 6258, it seems it has very good mid range and dies off towards redline. So it looks like 7163 vs 6258?

Efficiency is not an indication of how "happy" a turbo is or how much power it will make. High efficiency = colder air at intercooler entry; Low efficiency = hotter air at intercooler entry, so efficiency is used mostly for intercooler design.