Understanding Compressor Maps And Expected Bhp

[rtune]

I have a dumb question to do with compressor maps..

http://www.ztechz.net/id6.html

they appear to be the basis for those charts we all see that list type of turbo and

minimum to maximum HP operating range for the turbo..

So my question is, what is that max? a best-case max? or a max assuming a

stock engine? If you are at the documented max, is there anything else worth

doing apart from buying bigger turbos?

eg, this little table is quoted sometimes:

GTSS 46.6mm 60.1mm 0.60 0.64 280ps

2510 47.7 60.1 0.60 0.64 300

2530 47.7 60.1 0.60 0.64 320

2540 51.7 76.2 0.60 0.64 350

GTRS 51.2 76.2 0.50 0.64 400

so those numbers at the end: 280ps, 300ps, 320ps, 350ps, 400ps .. (per turbo)

are they the absolute max, the sweet spot, exceedable with engine work?

[Dale FZ1]

A compressor map shows the flow capacity and efficiency of a given compressor across a range of pressure ratios. Doing all the calculations will get you into the ballpark of what the compressor can do to support a targeted level of engine performance/output.

But you can't ignore two things:

1. The compressor ultimately feeds, and is driven by, a turbine. So turbine flow capacity and efficiency is as much a determinant factor on what the turbocharger is capable of. A bigger turbine A/R can liberate more max hp, but it may be detrimental to overall engine performance if it slows down turbocharger response too much down lower in the (engine) rpm range.

2. Engine airflow efficiency is also a governing factor of output. It is entirely possible to achieve more hp from a given engine:turbocharger combination by virtue of improved breathing into, through, and out of the engine via manifolding, porting, valve size increase, and cam spec.

There are various ways of getting that bit more. Some approaches are going to prove expensive and add just a small % overall improvement, while others are much more productive. As the power output gets larger, so too do the hurdles (financial and engineering) you face to make good % gains and maintain reliability. Don't view the numbers you've quoted as absolute, but as a pretty good guide and you'll do ok. By way of example, two members here are running GT3076 combinations on a RB25 and and RB30/25. Both have hit a ceiling of ~ 310-320rwkW, which puts them around 500 crank hp. That is right what Garrett rate that turbo's capacity at.

Hope that helps clarify things a bit.

[rtune]

Ok thanks, to be more specific, I am pretty sure my car (in compliance) has two GT2860R-7s on it,

or at least the nissan oem version of this turbo. The specs I can find match the GT2860R-7.

Nismo pdf quote 260ps each, but garrett and pages like this

http://www.theboostlab.com/products/GT2860R.html

quote "up to 310" for the "-7" (and 360 for the "-5").

So it should be possible to hit 400kw (536hp) at all four on a 2.6, or is that dreaming?

best way?

* boost to 1.4bar

* water meth injection?

* port/polish?

* hiflow the turbos