All posts by Jeff

Tuning

RS4 MAF Tuning

Progress with the Nefmoto community 2.7T Stage 2 tune has spurred my curiosity to find out why the results I’m seeing with a Hitachi MAF equipped car are significantly different from two others car that are participating in the tuning project, but are equipped with Bosch S4 MAF sensors.

Bosch MAF vs Hitachi MAF equipped S4's with Nefmoto Community 2.7T STage 2 Tune
Bosch MAF vs Hitachi MAF equipped S4’s with Nefmoto Community 2.7T STage 2 Tune

 

I don’t have an S4 Bosch MAF on hand, but I do have a Bosch RS4 MAF, which I decided was close enough to try out in order to see if the car behaved, or rather logged, much different than with the S4 Hitachi MAF.

With that end in mind I replaced the stock airbox with a RS4 airbox, the Hitachi MAF for the RS4 MAF, S4 and RS4 accordion hoses were also swapped, and the stock y-pipe was pulled to allow the RS4 accordion to attach to an RS4 y-pipe.

RS4 MAF installed on Audi B5 S4
RS4 Airbox, RS4 MAF & Accordion, RS4 Y-Pipe

After the hardware was swapped and I verified that I was getting a good reading from the sensor using a first draft of the revised tune, I began to look more closely at the tables that needed to be tweaked in the ME7 code.

A few that need to be changed are:

  • MLHFM
  • MLOFS
  • KFKHFM
  • KFMLDMX

The KFKHFM table is turning out to be one of discovery, I’m needing to adjust this table quite a bit more than I had expected in order to richen up the AFR.

Upgrade Work

Silly Rabbit Motorsport SMIC

Today I got around to installing the Silly Rabbit Motorsport B5 S4 SMIC’s.  These have the RS4 sized inlet and outlet piping along with water/methanol bungs for use with the Aquamist injection nozzles.

SRM IC with RS4 piping & water/methanol bung
SRM IC with RS4 piping & water/methanol bung

The mounting tab on the top end tank is a nice feature for holding the intercooler steady.

SRM SMIC
SRM SMIC

For now I’ll be using them without the shrouds.  I have them but decided to hold off installing them until later.

Sensors, Testing

Boost Manager Profile Analysis

With the Boost Manager operating and Aquamist’s Flow Sensor recording I logged my S4 to see how the pump duty cycle map that I had created worked out.

Boost Manager Water Methanol Injection System Profile Analysis

I’m attributing the jumpiness in the water/methanol flow to sensor noise which I hope to minimize in the future.

The water/methanol pump duty cycle map is based upon engine speed and manifold pressure (MAP).  As is shown by the left line with arrows, activation of the pump takes place around 2000 rpm once MAP reaches about 6 psi of boost pressure.

At 10% duty cycle the pump is essentially still off with respect to the flow volume, this was first shown when I conducted a calibration session with the water/methanol injection system.  I have the pump at such low duty cycle to get things moving in anticipation of the system injecting a measurable quantity of fluid shortly thereafter.

When engine rpm reaches 2500 and MAP passes 11 psi the pump duty cycle increases and the flow rate increases quickly.  The flow rate tracks with the increasing rpm, though I have some refinement to do in order to match engine speed better.

A couple of other parameters that would be useful to look into are airflow, via the MAF reading, Fuel Injector Duty Cycle, and intake air temperature.

At the right side of the chart the flow rate drops, despite engine speed increasing, because the MAP is dropping and then lowers the pump duty cycle.  This is another area of the chart that will get some attention to refine the pump duty cycle and better manage the fluid flow rate.