End of the K03 Journey

Today I dyno’d my S4 with K03 turbochargers and a couple of different engine tunes capping a long process of collecting baseline performance data for the car on these turbochargers.

Along the way I received some significant support from Nye and Daz at the Nefmoto forum and Doug at FrankenTurbo.

The charts below show the final results on the dyno but are only a portion of the data collected on ET Tuning’s Dynojet dyno.  More results will be posted as I plot the data showing various comparisons.

Best numbers from the two stock tune pulls: 253 wtq / 237 whp

BorgWarner K03's With the stock B5 S4 tune
BorgWarner K03’s With the stock B5 S4 tune


Best numbers from the two Nef tune pulls: 362 wtq / 283 whp

BorgWarner K03's on the Nefmoto B5 S4 community tune
BorgWarner K03’s on the Nefmoto B5 S4 community tune


Stock pulls vs Nef tune pulls

Stock tune vs Nef community tune on K03's
Stock tune vs Nef community tune on K03’s

The ‘proof I was there’ shots.

Post activity on the dyno
Post activity on the dyno


I also did a set of pulls using the NVR Stage 2++ tune that used to be available on the Netmoto site.  This tune came with a warning to ensure the K03’s were in good shape as it runs a lot of boost.  This is apparent through the mid-range where the torque remains strong compared to the Nef tune that immediately begins ramping down the boost pressure following the initial spike.

Best numbers from the two NVR tune pulls: 375 wtq / 303 whp

Chart of NVR Stg2++ vs Nef Community Tune
NVR Stg2++ vs Nef Community Tune

The DynoJet software has a function for reporting the area under the curve (AUC) for the torque and horsepower.  As a way to illustrate the performance difference from the stock to Nef to NVR tunes as a percentage value, rather than horsepower or ft-lbs, which can be contentious since dyno’s can read differently, I’ve tabulated the various AUC values and show the percentage increase as the tune is made more aggressive.

DynoJet reported Area Under the Curve Comparison
DynoJet reported Area Under the Curve Comparison

Now for the charts…

Boost comparison of all three tunes:

Manifold Air Pressure
Manifold Air Pressure


Mass airflow:


Here’s an approximation of where these three tunes land on the K03 compressor map.


Fuel Injector Duty Cycle (you want to play, you got to pay):


Timing:  This is a single sample of Timing from each tune.  If all six timing curve lines were shown  it would be hard to read due to the overlap in timing values.

Chart of K03 Dyno Timing Curves
K03 Dyno Timing Curves

The chart below illustrates the temperature rise that occurs in the turbocharger with the different boost levels that each tune operates at.  Temperature out of the turbocharger is recorded approximately 18 inches downstream of the outlet coupler, which allows for some temperature drop before the reading is taken.  This means that the temperature exiting the turbocharger is greater than shown below. The tunes were recorded in the following order: Nef, Stock, NVR.

Air temperature into vs out of the turbocharger
Air temperature into vs out of the turbocharger

The next chart shows the temperature of the exhaust gasses going into the turbine as recorded by the RS6 exhaust gas temperature sensors (upper lines).  The temperature of the gasses leaving the turbocharger turbine housing are recorded downstream at the bottom of the downpipe (lower lines), prior to the catalytic converter, by a K-type thermocouple.  It’s expected that the exhaust gasses will have cooled some by the time they reach the thermocouple.  The downpipes are ceramic coated with the Swaintech white lightning coating and then wrapped in DEI exhaust thermal wrap which may help reduce the heat loss through the downpipe.

Pre & Post Turbine Exhaust Gas Temperatures
Pre & Post Turbine Exhaust Gas Temperatures

Interestingly the significantly different manifold pressures developed by each tune do not appear to have an affect on the exhaust gas temperatures.

This next chart shows the intake air temperatures as recorded by the vehicles temperature sensor inside the intake manifold.  Even though these pulls were done on K03’s and with a little help from some water-methanol injection, I am still impressed by the performance of the SRM intercoolers.

Intake Air Temperatures
Intake Air Temperatures

I decided to supplement the intercoolers with WMI as a result of prior experiences on dyno’s having absurdly high intake temperatures.  None of the tunes were adapted for WMI so I wanted just enough liquid to help keep temperatures down over several pulls.  I went with a pair of Aquamist nozzles, one sized 0.5 mm and the other 0.6 mm.  Together with the TorqByte WMI controller I had the setup configured to flow no more than 300 mL/min.  By comparison, on a pair of 1 mm nozzles the system can flow up to 1000 mL/min.

One of the hopes I have with using the dyno is to be able to come back later and produce similar results.  To see how realistic this may be I dug up a set of DynoJet logs that I made with my car in 2005 just prior to having APR’s Stage 3 kit installed.  At the time the car was equipped with stock intercoolers, AWE-Tuning’s downpipes, and a Supersprint exhaust.

Fast forward to 2015 and a mostly stock version of my S4 is going back onto a DynoJet, this time with SRM intercoolers, Autospeed downpipes, and 034 Motorsport’s 3.5″ single exhaust, along with a WMI system.

Here’s how the results from two different dyno’s separated by about 900 miles and ten years panned out.   2005 it was about 70 degrees at the dyno, in 2015 it was around 60 degrees.


To help better break out the results I exported the data and reformatted it.


Lastly, the intake air temperature differences:


The DynoJet dyno results look fairly consistent.

Another question that can be asked is how accurate the DynoJet figures are at representing the true torque and horsepower produced by the car.

As a cross check I like to look at road calculated values and compare them with what the dyno is reporting.  The curves below are for each of the tunes on the street.

Road Calculated Horsepower and Torque Curves
Road Calculated Curves

Here are the peak values tabulated along with the peak MAF reading, which I have found correlates pretty well with the wheel horsepower figures when using a stock MAF housing.

Chart of Road Calculated Maximum Values
Road Calculated Maximum Values


Here are each of the tunes broken out with a Road versus DynoJet chart:


Chart of Stock Road vs DynoJet
Stock Road vs DynoJet


Chart of Nef Road vs DynoJet
Nef Road vs DynoJet


Chart of NVR Road vs DynoJet
NVR Road vs DynoJet

I believe the DynoJet reads higher than what the true values are, but the repeat-ability of the device makes it a good tool for what I am using it for.

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