Category Archives: Tuning

Refining Long Term Fuel Trims

The long term fuel trim for the tune I have been using with the Turbo Concepts Stage 1 turbochargers has been off a bit for the Partial Throttle condition.  Values have been high, but not high enough to throw a fault code,  finally after driving with the trims elevated for a while I decided to do something to bring them down.

Chart of Initial Long Term Fuel Trim Values
Initial Long Term Fuel Trim Values

EuroCustoms Tune vs Free

EuroCustoms is not a name I am familiar with, but it turns out that they offer tunes for the B5 S4, both stock K03’s and the BorgWarner K04’s.  I thought I’d take a look at how their $600 Stage 2 tune compared with the free Nefmoto stage 2 tune and also the NVR Stage 2++ which can also be obtained freely.

Here’s what EuroCustoms has to say about their tune:

EuroCustoms Audi B5 S4 K03 Stage 2 Tune
EuroCustoms Audi B5 S4 K03 Stage 2 Tune
  • Speed Limiter Removed: This same feature is available with the free tunes.
  • Best performance increase on the market: Without making a side-by-side comparison with all other tune options on the market this is a baseless claim and it is highly doubtful that EuroCustoms undertook the effort to test every other Stage 2 K03 tune available for purchase.
  • Improved fuel economy: No attempt to quantify the gains, unlikely to be true.
  • Improved throttle response: It is unclear what this is supposed to translate into for the operator.
  • Tuned for best optimized performance within the engines safe zone parameters: Sounds nice but is meaningless.
  • Increased performance throughout the power band and across the board: This has been the case for every decent K03 tune that I have seen.  When you increase boost pressure from stock levels increased performance follows.
  • Factory lag removed: This makes it sound as though turbo lag is like the speed limiter and with a simple change in values lag is gone.  Nothing has been quantified.
  • Thoroughly tested on the track and street: Thoroughly tested and not one bit of evidence to support the testing process?  C’mon.

In summary, many claims and nothing to back even one of them up.

Looking at some real data from the Nefmoto and NVR tunes:

K03 Tune Wheel Horsepower Compared
K03 Tune Wheel Horsepower Compared
K03 Tune Wheel Torque Compared
K03 Tune Wheel Torque Compared

With the free tunes we see respectively an increase of 45 whp, and 60 whp for the Nef and NVR tunes.  This is versus the unproven 81 hp increase claimed by EuroCustoms, which may be crank and not at the wheels.

In terms of torque increase Nef adds about 105 lb-ft while NVR pushes up to 125 lb-ft more torque at the wheels.  EuroCustoms claims an extra 107 lb-ft.  Again it is unknown is EuroCustoms is claiming the increase to be at the wheels or crank.  In either case the results are no better than the free options.

Notably, aside from the numeric values in the claims, the exact series of claims are made for the Stage 1 K03 tune, and in fact, the K04 tune that is also offered is described word for word by the very same superlatives.  Remarkable consistency or Copy & Paste of ad copy from one web page to the next.

Bottom Line:  For $600 you get no proof of any performance improvement over two K03 tunes that can be obtained freely.

Tuning Snafu

After loading a revised tune onto the car’s ECU I took a short drive and had a couple of alert lights come on the gauge cluster.  I plugged in the XTool to see what the problem was and the device could not connect with the ECU.

I decided I should return home, but now the car would not start.  I had to pull a MacGyver to get the bolts out of the ECU box, and then I disconnected the ECU, re-connected it, and then was able to start the engine to return home.  Upon arrival I hooked up VCDS and received the following alerts:

18010 – Power Supply Terminal 30
P1602 – 35-00 – Voltage too Low
16985 – Internal Control Module
P0601 – 35-00 – Memory Check Sum Error

The second one I had never seen before, but I immediately thought that maybe I hadn’t created a checksum on the latest bin that I had loaded on the ECU.  Looking in the folder with the development tunes I saw the latest file name lacked a CS at the end of the name, my indicator that the (C)heck (S)um had been set.  Doh!

It took unplugging the ECU for a while before I could get Nefmoto to connect to it, but finally it did and I was able to write a corrected file.

Lesson learned about staying vigilant when installing files on the ECU.