So Ive finally digitized my 16g6 map and overlaid Pressure Ratio, RPM vs Volumetric Flow. The volumetric flow is pre-compressed, so it is at atmospheric pressure and logged temp within the MAF. The Volumetric Flow was calculated via JB's evoscan formula for Mass Flow then translated to Vol Flow. I'm guessing the compressor maps are in SCFM or ACFM at 77F like garett uses? Anyway, Im running E85 so thats why the boost is up there. Im also running the stock airbox for reference. I havent looked at this before but it looks like the turbo is out of "wind" by looking at the slope of the Vol Flow vs RPM (secondary axis of 2nd graph). I plotted this two ways on both images below. I guess what I am asking is; is the turbo at capacity or am I fighting a restriction someplace else that I am missing? I know the boost tapers pretty good after 5500, so I am thinking it is out of flow. I am guessing you will want to know my mods so:
GSC S1's, FMIC, 3" TBE, 65mm TB, ported exh mani, hotside, o2 hsg, test pipe, UICP, LICP, 100%WGDC throughout RPM band w/#65 restrictor, no knock anywhere.
Any help is appreciated.

 

forgot to say but the dip in the graphs is a blip in mass flow rate and there was no hesitation during the pull.

 

That restriction is the stock airbox.

Here is some data:



btw, very cool charts.

 

You are using the compressor map incorrectly. You don't plot your boost curve or your RPM curve on the map. You plot the points of pressure ratio and airflow, in this case CFM.

And to answer your basic question, yes, the stock turbo is out of airflow and riding the 'choke' flow. That's why the stock turbo tapers so much. Mods are going to affect it to a point, but you will never find a stock turbo that holds more than 23-24 psi at redline. You can see in the map that it's approaching or at it's limit at that point.


Eric

 

Eric,

The magenta curve is press ratio vs airflow, I just labeled it as boost curve. On the secondary y-axis is engine rpm vs airflow so I could get an idea of the range of engine rpm that falls in the best efficiency islands of the turbo.

 

OK then, I just read the label as boost, so I figured you were simply plotting boost vs your RPM curve. If it is pressure ratio vs volumetric airflow, then all is well.

Edit: BTW, I posted a compressor map calculator spreadsheet in here a long time ago that has the 16g6 map as well as several others and you just plug in your numbers and it plots everything for you.


Eric

 

Eric,

I'll do a search for it. I'm really looking for the FP Green and the new FP Red maps. Do these exist?

Bryan,
Thanks for your cool comparison. Definate delta between changes. The only reason I'm not running an open element is that its pretty hot here in the summers (NC). Underhood temps get pretty high in traffic/low vehicle speeds. Im thinking about making my own airbox at some point. Do you have thoughts on switching to a larger GM MAF for a lower pressure drop at high flow rates (maybe stock is just fine). I know from logging AirTemp (within MAF) and Barometric pressure during a run, I see as flow increases both Baro and Temp drops pretty good (Im not sold on its increased underhood airflow to reduce underhood temps yet) so it looks like there may be a restriction there?

 

An open filter will help with the baro drop as well. There are a few threads in here where I, and Bryan (I think...maybe nj1266) posted tests of the Ebay open element filter. I think in mine I showed air density, temp, and baro, among other things.

Also, if you want to keep the stock box but reduce the drop in baro, you can search for the mod that jcsbanks did, which is cutting out the side of the airbox cover furthest away from the engine.


EDIT: Here, I found the two threads I was thinking about. Here is my review of the filter: https://www.evolutionm.net/forums/sh...=277802&page=5

Here is nj1266's review: https://www.evolutionm.net/forums/sh...d.php?t=280511

Eric

 

I did a search b/c I was interested:
https://www.evolutionm.net/forums/sh...map+calculator