Heres how I chose my compressor.
I don't agree with the majority about choosing a turbo that is at its maximum to acheive the power you want. Sure you end up with more "area" on a dyno plot, but running a turbo well out of its efficiency creates heat. Heat is bad mmmkay.
I made this mistake on my ae86, running a tomei m8270 (which is comparable to a gt2876r, sort of) and sure it makes 430hp on pump and looks awesome ( and will peel 4th gear as the turbo spools on the street ) but the IAT's and the car in general runs way too hot. On the street its fine. On the track it only takes a lap for it to get too hot. I'm looking at upgrading to a gt30 frame turbo.
Don't select a turbo from someone elses dyno!!
This point gets lost on forums. Also, don't just read a review that says "OMG I have this turbo and its da bomb!" Have they tried another turbo either side? Probably not. They're probably just amazed at how much better it is than their previous turbo, and ignore the fact (and will probably get annoyed when you ask) if they considered a different turbo either side. You can't trust or read into someones review that has not reviewed/experienced anything comparable. /end rant.
AE86 dyno for reference. Great for street. Great for forum steez. Not efficient. Not good for track. Two lines are 0.9 bar, 1.1 bar.
Anyway, heres the 3 compressors I shortlisted.
If you think my boost levels are too high, remember this is at the turbo, not the motor. I have assumed a system with 2psi pressure loss.
The gtx2863r I think it well suited to either a stock fuel system (260whp ish) or a 300whp car that is a street car, with light track work.
THe gtx2867r I think is well suited to this power level and boost. You can see how it passes through the islands where they are at their widest.
The gtx3071r I feel is oversized for 300whp on anywhere but track only. I would use this for track only even those the compressor efficiency is marginally lower because the gt30 turbine is much more efficient in this same range over the gt28. But i want my car (even though its a track car) to be decent in slower targa type racing as well. I also think to really see the gains of this turbo, you need to be aiming for more power, for me, that means built motor, box yada yada. I know some are getting 400hp - over9000 hp on the stock motor / box. But they're not tracking them. (Well I don't believe they are.) And if they are, thats great news for me, it means my selection has a good amount of redundancy.
I realise all turbos will do well more power, you can see this on the comp maps, but the efficicency falls away, and I'm not going there. The gtx2867r has its peak efficency basically right were I want it, basically smack bang in the middle of the revs I use at the track (5500 - 7500) If anything its marginally to low, and I'd prefer it a little higher, but theres so much variations/assumptions/estimations in this, that it would be wrong to look at it in that much depth.
Anyway, thats how I made my decision.
