gt2259 questions (quick and stupid)
 

Alright, so I'm finally getting my shit together here. I'm planning on buying the BEGI manifold/downpipe/etc and using a GT2259 since I'm getting it for damn cheap. Chinacharger prices, for the most part. I don't plan on having any more than 200hp, so this will work out just fine right? It's either this or the 2854 in the BEGI Shanghai kit, but that seems a bit oversized for my plans.

Have you not noticed all the threads with guys getting bigger injectors, larger turbo's, different setups, etc etc etc? You know why it is? it is because boost is addictive like crack. If you dont want to leave any room whatsoever for more power, sure go with such a small turbo. just my .02

Heh I can understand, my buddy with a B5 S4 has the boost bug bad, he just dynoed at 430whp after getting the car stock a year ago. This needs to be my semi-reliable form of transportation for a bit till I'm out of school so I think a conservative-ish setup that's efficient in that range will keep me satisfied for a while.

edit: I mean, I'm correct in my assumption that the 2259 will spool significantly quicker than the 2854 yes? They're both journal bearing.

Alright so I mucked around with the turbo calculator a bit

linky..
http://i39.tinypic.com/29mnorc.jpg
I'll be ordering the bits soon, good thing these are so cheap :D

looking for 190rwhp?

Are you really planning on running ~20psi? Or are my eyes crossed?

I don't see an issue with it, the turbo is smaller.

the air it will flow at 20psi will be hotter than hell

That's one of the problems I saw with it.

The other had to do with turbine housing flow restrictions at that volume/pressure. Are you planning on running a large external WG?

I had not thought about that, am I doing this completely wrong? The maps for the 2554r seem similar.

go through the center of the island

The fellows who are generally running 2554's are not running much more than 14 psi at their peak (with exceptions I'm sure) and are fighting the creation of excess heat with that unit at those pressures.

A smaller compressor will typically make more heat than the larger when trying to move the same volume of air. And you typically must create a similar amount of psi in the exhaust manifold to what you are creating at the outlet of the compressor. Basically, the exhaust has to push hard on the turbine to make the compressor push hard on the boosted air. This means more heat.

The compressor map tells you where the area of highest efficiency occurs for a given compressor wheel. That's why you were instructed to aim for the middle island in the map. The higher the efficiency, the less heat created, and the happier the engine. We all want happy engines. That may be a fine turbo, but you might consider that it will move cfm's more efficiently and with less heat at a lower pressure ratio (boost level) than what you have plotted. Responsiveness at much lower RPMs might be very good with that size turbo, but don't expect it to be a fireball at 7100 RPM also. They rarely do both exceptionally well.

The trick is finding a turbo where it's sweet spot and the engine's sweet spot match for your needs.

Edit: I think that might be a pretty good turbo for lower to mid range RPM responsiveness and driveability. I am looking forward to a re-plot of the graph with lower PR's. It might turn out well.

Doesn't the greddy 15g begin failing at 15psi+?

Couldn't imagine an even smaller turbo holding 20psi any better ;p

Most turbos can support a lot more than 15psi, even this 2259, but once you start asking for more mass flow volume than it can handle efficiently, it'll crap out fast.

You could run the above turbo at 30psi and as long as your not outputting more than 25 lb/min or so, it'll work just fine.