NefMoto

First: is the K03-1870 the correct map for my 2.7t?

If so:
The stock boost curve seems to ramp up a few islands ahead of ideal efficiency, then as it tapers goes across the map passing through the middle island.  I plotted my tune which follows very similar to stock, just going higher then tapering to pass through the top of the middle island.  Is this ideal, or would it be better to shift the curve later so the ramp up is closer to the middle island? 

Also as you approach redline it seems the more you taper down the more inefficient you are getting.  According to my logs it seems if I brought my p/r up again as I approach redline I could stay within 2 islands of the middle.

I am totally unfamiliar with K03 tuning, but what you said seems reasonable..

Do you have plots handy we can look at? BTW ECUxPlot supports P/R vs flow graphing.. if you have a stock MAF, it can use MAF readings directly to calculate flow.

I've been using ECUxPlot to do it already(awesome btw, saves a ton of time), here is the map from s4wiki and my most recent pull, unfortunately this one wasn't to redline(ran out of room).  Also if it makes any difference I'm at pretty high elevation 5000ish ft, my baropressure this run was 840.

(http://s4wiki.com/images/7/75/K03-1870_EXA.png)

If you haven't already done so, something to keep in mind when calculating total air flow, is to divide by two. Since the car is a twin turbo you need to divide by two to get the flow for one turbo. I didn't do this when I was first trying to figure out the pressure ratios and I spend a few days being confused.

ECUxPlot has a place where you specify # of turbos :)

I've been lazy and just relied on ECUxPlot to do all my calculations(I double checked and it is set for 2 turbos)...

So what's the opinion on forcing the turbo to spool later so it is more efficient vs letting it spool as soon as it can?

Please would somebody explain the basics of the automotive turbocharger compressor map, including which parameter is on each of the x, y & z axes and what the implications are for deploying turbochargers in different applications, or post a link to where I can read a good discussion of the fundamentals.

Thanks in advance.

TTQS

http://s4wiki.com/wiki/Compressor_map

http://www.turbobygarrett.com/turbobygarrett/turbo_tech_expert

Thanks guys.

Apologies. I haven't looked at the S4 wiki in a over a year... Probably a 1.8T symptom. Sorry nyet. ::)

I was aware of the Garrett Turbo Tech website, but must have missed the compressor map section.  :o

I presume we're all aware that the Excel spreadsheet that generated the K04-2078 EYE compressor map is available here:

http://www.s4biturbo.com/k04/RS4K04.xls

Original document attached to this post if that link ever goes down

TTQS

just to help visualize...
(http://creativeion.com/rey/vw/help/s4_comp.gif)

Thanks, I've been plotting it by hand on a printed out map(this is much nicer)....so see how especially near the top I'm getting fairly close to the surge line, so what I've been trying to decide, is it better to force the turbo to spool slower and get it closer to the center island(probably won't be as fun to drive though)?

No. You always want the highest P/R you can get at a given flow as long as it is right of the surge line.

Thanks!

err sort of. as least until you hit the flow of peak efficiency, i.e. only during spool

after you've hit peak efficiency flow, you have to watch the overspin line, and you risk torque/power losses due to high IATs.