> The reason I say not to pay much concern to
> the thermal efficiency of the turbo is
> because you are running an intercooler. The
> variations in thermal effeciency from the 46
> to the 57 are probably very small. The
> intercooler has its own efficiency. I think
> regardless of whether you ran the 57 or the
> 46, your intake charge temperature would be
> relatively the same once it passes through
> the intercooler. I use to run the starion
> intercooler and could easily run 14-15 psi
> mid day in the houston summers. Talk about
> freakin hot. With the 46mm I was able to run
> 17 psi of boost and that was a limit because
> of pinging above that boost pressure. I
> could have backed off the timing a degree or
> two and uped the boost to 18 or 19. When I
> went to the 57 mm, I was able to
> consistently run 18-19 psi on 93 octane pump
> gas. Now for the exhaust, the downpipe I
> have runs down to where it becomes parallel
> with the ground. I use to run the 3
> down pipe into a straight 2.5 exhaust
> with no muffler. The car sounded mean. The
> restriction from going 3 to 2.5
> creates some hp robbing backpressure. I
> would recommend going straight 3 into
> a straight through 3-3.5
> muffler, borla or sebring. The sounds should
> be tame, but this will give you awesome
> boost response and more hp under full boost.
> Also, what kind of setup do you currently
> have, block, internals, head, etc.
Yes very good points indeed, the 46mm turbo is meant for 14-15 past this point the effeciency starts to drop off . The 57mm does a better advantage above this . The 57mm has a low surge line compared to the 50mm which is a bonus and it has greater flow capabilties win win in that catagory . I currently have 78 motor N47 head which is getting yanked and replaced with a 81 L28ET F54 block P90 head stock cam . I have MSD 6A ignition, and 3 Suppertrapp stainless(somehow I knew turbo was destined).The suppertapp sounds like mid 60 ferrari, a little loud but you can adjust that with the plates . I have installed a 3.7 LSD and toyota calipers . Get LSD it is worth it . The 81 motor is from a junker with 70k miles wow, so I will do valve job and check the rest over and let her go . The efi system is from the zxt as well . By the way it was -37F today hows that for intercooling, my Pathfinder didn't skip a beat .