Had a couple of (relatively) free days on dyno, so did some testing with the buddy's RS6.
Bottom line is - for anything bigger, than stock turbos, stock intake is very restrictive.
Attaching a picture of 2 dyno charts & 2 overlaid airflow logs. It's the same car, essentially the same tune, but 2 different runs. One was with a stock airbox & filters. The other one with an open airbox (filter elements & airbox cover removed).
Don't mind slightly different onset, I picked slightly different runs (as I didn't plan on posting this initially).
Anyway, you can clearly see, that airflow peaks out at certain voltage & that's pretty much it, turbos can't get more air. (In the log plot, red is "voltage", which is more accurate, than the purple "airflow").
Without filters/cover - you get an extra ~22 g/s, which can translate to 30-35hp difference at 6000+ RPM!
Even then, you get a certain "air flatline", and that seems to be a restriction from the intake piping (MAF to turbos). It's already mildly ported in this car, but having something completely custom there might be much more beneficial.
Bear in mind, this is much less relevant for stock turbos. This car has loba 650s (and they struggle to make even 600 due to intake/exhaust restrictions).
EDIT:
I'm in metricland, so "tq" is newton-meters.
EDIT2:
KN filters make 0 difference, compared to paper stockers. Or, well, maybe not 0, but within 1hp. Not helping with the airbox issue, pretty much.
Last edited by nubcake; January 22nd, 2020 at 01:40.
That's some great info! I really want to try swapping the stock intake with something like the Apikol kit, back-to-back at the drag strip and see what happens in the real world. If anyone wants to loan me one of their kits, I'll do the testing!
With stock RS6 airbox I had 613hp and 864Nm
And with an open airbox I got 634hp and 883Nm
With modified RS6 turbos.
Now I run 2 rounded Simota Carbon fiber airbox and now it is only 2hp difference with or without these.
RS6/S8 engine, 6spd tdi 01E, EFR7163 turbos, custom built exhaust manifolds, S8 camshafts, MaxxEcu Pro, wagners ic's, bigger fuel rails, AN8 fuel line, 2xwalbro 450lph fuel pump
and EV14 1500cc fuel injectors in my S8/RS8
Yes the curve was higher all the way.
Here is the dyno papier from 2016:
pull 1 with airbox= 609hp
pull 2 No airbox = 634hp
pull 3 with airbox = 613hp
But now with Simota I use MaxxEcu so I don't use MAF's anymore,
but I think it should have worked with the MAF in stock place.
RS6/S8 engine, 6spd tdi 01E, EFR7163 turbos, custom built exhaust manifolds, S8 camshafts, MaxxEcu Pro, wagners ic's, bigger fuel rails, AN8 fuel line, 2xwalbro 450lph fuel pump
and EV14 1500cc fuel injectors in my S8/RS8
The biggest Simota I could find, it has 89mm neck size in and out (I think the RS6 airbox inlett is about 100mm)
Simota SM-BX-007
RS6/S8 engine, 6spd tdi 01E, EFR7163 turbos, custom built exhaust manifolds, S8 camshafts, MaxxEcu Pro, wagners ic's, bigger fuel rails, AN8 fuel line, 2xwalbro 450lph fuel pump
and EV14 1500cc fuel injectors in my S8/RS8
It'll never flow enough to hit the limit with any kind of K04, really. Too many restrictions everywhere.
If you want to run 700+ chp (equivalent of maxing out MAFs), you need to redo the whole intake tract anyway.
My own car did throw the "MAF exceeded" DTC occasionally with TD04/K04 hybrids a few years back, but that was probably just a fluke.
Last edited by nubcake; March 29th, 2021 at 00:57. Reason: Better wording
I am going to be creating larger inlets (and, informed by your and RS8's data from this thread regarding the stock airbox, I'll also be running a larger intake rather than even playing around with the stock airbox). I may even make the larger inlets for people to run on OEM RS6 coldsides. Just deciding whether or not to throw HPX MAF's on there from the get-go, but it looks like I'll leave the stock MAF's and swap them out if/when I get there. So thanks for the input on the MAF's as well, as there aren't too many people playing with the calibration on these cars.
I have some very vague shots of the championship RS6 from 2004??. Does anyone know much about it and the airbox that was developed for it. Would seem to me that subject to useability, that would be a good starting point for an intake system compared with some that are on the market for mega bucks.