All of the turbochargers I have had my hands on lately have been put on the flowbench to have the airflow through the turbine housing recorded.
The most recent B5 S4 suitable turbocharger to show up is a pair of the Audi RS6 K04 turbo’s. Because in OEM form these will not fit on the 2.7T engine this pair has been modified to work with B5 S4 components.
Audi RS6/K04 Turbocharger mounted to Flowbench
Unlike with the TTE turbo’s that also showed up with turbo to downpipe studs firmly stuck in the turbine housing, I chose not to pay a shop to remove the studs out of the RS6 turbo’s turbine housing. Instead I’ve modified the adapter used to attach the turbocharger to the flowbench to accommodate the studs.
Following alteration of the adapter I went through the normal process of testing an article on the flowbench, beginning with a calibration test. Results of the flow test are shown below:
Audi RS6/K04 Turbocharger Flow Test
It is clear that the airflow through the RS6 turbine housing is substantially greater than of that through the RS4 K04 and FrankenTurbo F21 turbochargers. (The F21, TTE550, and TC Stg1 flowed approximately the same so I have omitted the TTE550 and TC Stg1 data from the chart to make following the lines easier.)
I have found the results on the flow bench to correlate with the exhaust back-pressure readings that I have made on my S4. That the RS6 K04 turbocharger is able to flow higher than RS4 K04’s comes as no surprise, the magnitude of the increase is the most noteworthy finding from this test.
I did some extensive driving around beforehand and then stopped to ship out a car part before I returned to take the reading shown above. What is noteworthy about the chart is the intake air temperature, beginning around 100 degF. It was warm today, but still only 66 degF, hardly like the temperature on a hot summer day. Boost onset was a bit slow.
I drove for a while allowing the temperatures to stabilize and then took a number of additional readings, shown in the chart below as red.
Turbo Concepts Stage 1 vs BW K04
It is clear that the warmer temperature is adversely affecting the initial boost rise of the Turbo Concepts turbo’s – as warm temperatures have done with all the turbochargers I have measured.
Note that one red dot way up high, just past 2000 rpm, that’s the high temperature pull. I’m very interested in seeing how these turbochargers perform in hot weather, but I’ll have to settle for the Turbo Concepts Stage 2H turbochargers for that effort as I plan to swap out the turbo’s in the coming weeks.
Today I also took delivery of the tools that I hoped would break the axle bolt free on my front passenger side. As mentioned previously, my 1/2″ drive socket extension had snapped trying to get the axle bolt out.
I used the last couple of days while awaiting the arrival of a 3/4″ drive breaker bar and six-point socket to apply Kroil to the stubborn bolt. Today the reinforcements showed up. Upon seeing these tools my optimism rose:
Breaker Bar Torque Rating
My old standard breaker bar looks like a toy next to the new behemoth.
Breaker Bars Compared
And then, ready to give it a go.
Breaker Bar (post successful loosening)
As a keen eyed observer will have noted, that’s not the position the bar would be in if trying to loosen the passenger side axle. The picture is the victory shot after the Titan made that bolt it’s bitch. Actually the bolt put up a good fight, but thankfully it broke free without any excitement.
Not long after Fedex stopped by with some B5 S4 goodies.
034Motorsport B5 S4 RS6 Downpipes
034Motorsport’s downpipes with…
Flanges for the RS6 turbine housing.
Also tucked in the box were these guys;
Audi RS6/K04 Turbochargers
A pair of Audi RS6/K04 turbochargers that have been modified to fit on the 2.7T engine.
While I’m excited by the opportunity to begin evaluating RS6 size turbochargers I’m left debating if doing so now makes sense, or if I should complete my assessment of the Turbo Concepts Stage 2H.
The first order of business will be to stick these on the Flowbench and see how they compare with the RS4 turbine housings.
Finally, with all the work that is taking place on the Avant now seems like a good time to swap out the rear differential for the MFactory Helical LSD that I picked up a couple of months ago.
With that goal in mind I’ve pulled out the rear differential.
I’m beginning to take the engine out of the Avant as the first phase of a three engine rotation, the engine from my Silver S4 will be going into the Avant, the spare engine I have from the Nogaro that I parted over the summer will be going into the Silver car, and the Avant’s engine will be sold.
B5 S4 Avant Engine Pull
Progress will only get so far before I have to pause and wait on some more tools to arrive. The passenger side axle bolt was apparently over-torqued, and my 1/2″ drive extension snapped trying to loosen the bolt. I’ve got an order in for some 3/4″ drive tools to go at it again.
