Tuning

WG Refinement

Matching 8 psi preload wastegates with the TTE550 sparked some discussion over the potential need to adjust the tune to accommodate this component pairing.

I’ve been satisfied with the responsiveness from the TTE550, but in the interest of finding out if “doing it the right way” would make any difference in the results I decided to undertake an effort to Calibrate the Tune’s KFLDRL table.  A detailed report on one persons attempt to do this is documented on the Nefmoto site and I’m using that as a starting point for my effort.

After setting CWMDAPP and KFLDRAPP appropriately I began by collecting 0% and 10% data.

 

0% N75DC
0% N75DC
10% N75DC
10% N75DC

 

An early observation is that I can likely refine where I am collecting data without adversely affecting the outcome.  Attempting to log boost data from 1000 to 6500 rpm in every gear is time consuming, risky, and not possible due to the speeds reached in 6th gear at 6500 rpm.  I’m not interested in conducting this work on a dyno so I am limited by conditions on public streets.

With the intent being to capture the maximum boost pressure achieved at a particular engine speed for each duty cycle setting, it looks as though I am able to use 6th gear to record from 1000-2500 rpm, 4th gear from 2750-4000, and 3rd gear from 4500-6500.  I believe this will produce ‘good enough’ results and reduce the amount of measurements I need to make.

Go to top

Some additional measurements, 20% and 30%.  These were made at ambient temperatures about 20 degF greater than the other two, which raises the question, should the fixed wastegate duty cycle boost pressure be recorded at the same temperature?  I would think so, but then if it did matter what does that say for the KFLDRL results that are being tabulated and how they hold across different temperature ranges.

20% N75 DC
20% N75 DC
30% N75 DC
30% N75 DC

These latest results are prompting me to also drop taking measurements in 4th gear since I’m not seeing any value added from those readings.

I will be logging 3rd and 6th gears with only the <3000 rpm region of the 6th gear data being used.

Shown below are the composite 3rd gear results thus far.  Note: The 10% DC pull was very short.

0-30% Fixed WG Duty Cycle Boost Readings
0-30% Fixed WG Duty Cycle Boost Readings
The Turbo Engineers, Turbo Selection

Claim: TTE550 has RS4 K04 response

With the TTE550 turbochargers installed on my S4 I can start to measure the performance of this product and compare the results to those obtained with some of the other turbochargers that I have used.

The performance claim that leads off the description for the TTE550 is:

RS4 K04 response with near RS6 unit power yet still keeping RS4 turbine housings.

Because keeping K04-like response is one of my top features to have from a turbocharger I am quite interested to see how that claim works out.

Initial results do not bode well for the product to live up to the claim.  Shown below is a chart comparing the 2-11 time for the K04’s and TTE550’s.  This metric is used to illustrate how long it takes for each turbocharger to build from 2 psi to 11 psi, for a given starting engine speed, that is when 2 psi is produced.

TTE550 vs. BW RS4 K04 2-11 psi response time
TTE550 vs. BW RS4 K04 2-11 psi response time

This chart does a good job at showing that the K04’s, the blue dots, increase pressure measured by the MAP sensor more rapidly than the TTE550, for all of the engine speeds I have measured thus far.

A couple of points about the data on the chart.  The K04 data was collected when the temperatures were generally cooler than during the two days that I recorded TTE550 data.  The lines would likely get closer together, meaning more similar performance, under the same temperature conditions.  With that, I do not believe temperature affects would be great enough to bring the lines together.

I’ve also not completed tuning with the TTE550’s.  Past experience has shown that fine tuning is more about controlling overshoot on initial boost ramp, not how quickly the turbocharger spools up.  I believe it is very unlikely that tuning will do anything more to increase the 2-11 time of the TTE550’s

While these initial results cleary show that the TTE550’s do not have RS4 K04 response, from the perspective of looking at the turbocharger dimensions this is not at all surprising.  The TTE550 is essentially an RS6 center stuffed into a K04 housing.  Beyond that, it uses a compressor wheel that is larger than the RS6 compressor, and it uses an extended tip compressor wheel on top of that.  On the turbine side an RS6 size turbine wheel is found, but also with a clipped wheel, not a feature that increases responsiveness.

Given the physical differences between the two products it is not surprising at all that the TTE550 does not match the RS4 K04 in response.

 

Audi B5 S4 Information and Testing