Wacky Turbo Comparisons

Within the last few days a couple of dyno charts have been put forth showing some impressive performance from the TTE 550 and FT 21 turbochargers.  Since both of these turbochargers are strong candidates for going onto my B5 S4 I decided to try and match up the results.

This is an exercise that must be approached with a great deal of consideration for the significant differences underlying the dyno charts.  These differences include:

  1. The dyno’s the cars were recorded on
  2. The conditions when they were produced
  3. The way measurements are reported
  4. The cars
  5. The fuel

There are enough points of difference here that a comparison should only be considered a ballpark estimate for how the turbochargers may compare under more controlled conditions.  Those more controlled conditions will hopefully be realized on another day, so for now I’ll charge onward with a crude comparison.

What I do know about the respective charts and vehicles.  The TTE 550 turbo’s were installed on a well modified B5 RS4 operating on 99 RON fuel with WMI spraying washer fluid.  The dyno chart displayed results at the engine, using an approximate 20% drivetrain loss.

The nature of the dyno readings meant that I needed to convert from NM to ft-lbs, and also apply the drivetrain  loss, more calculations than I’d like to do when trying to match performance, but necessary given the way data was presented for each vehicle.

The FT 21 turbochargers were installed on a stock motor B5 S4 operating with E85 fuel.  Dyno recording was made on a Mustang dynamometer and reported at the wheels.

And the comparison results…

tte 500 versus ft 21 dyno results
TTE 550 comparison with FT 21

Based on these *rough* curves it looks as though these two turbochargers match up well, but this comparison is far from being definitive.

TTE 550 Getting More Interesting

Previously I’ve shown a dyno chart provided by The Turbo Engineers of their TTE 550 turbocharger for the B5 S4 and RS4.  The TTE 550 is on my candidate list as a potential replacement turbocharger for my B5 S4 and the dyno chart comparison of the TTE 550’s versus the same car (B5 RS4) with K04 turbochargers was encouraging.

While the dyno chart was showing encouraging performance from the TTE 550 I was skeptical of the K04 turbo results being representative of what a K04 equipped car would produce when tuned for performance, the comparison numbers on the chart are apparently for a stock RS4.

I came across a dyno chart from the same shop, MRC Tuning, that was of a K04 equipped S4 in a seemingly tuned state.  Below is an overlay of the K04’d S4 torque and horsepower curves and the TTE 550 dyno’s.  It’s evident that the base dyno chart does not illustrate well the performance differences between the TTE 550 and K04’s in a typical state of tune on a modified B5 S4 or RS4.  The differences in performance for tuned cars are not as large as they appear on the dyno chart alone.

On the other hand, what is impressive is how well the TTE 550 can match the K04 in low end performance with nearly identical torque and horsepower numbers below 3000 rpm.  Above 3000 rpm the TTE 550’s have a solid advantage over the K04’s all the way to redline.

TTE 550 vs RS4 K04 Dyno chart overlay
TTE 550 vs RS4 K04


What’s up with the poll?

You may have noticed in the lower right corner of your screen a small box that says “Poll”.  I am in the process of deliberating over what turbocharger pair to install next on my S4.  I have put some of my thoughts in these pages, but I was interested in learning what visitors to this site would seek in an aftermarket turbocharger if faced with some of the limitations I am.


I’m moving the poll to this post so that I can expand the use of the polling feature.


The final numbers for the poll are shown below:
Chart showing Power vs Spool Poll Results
Power vs Spool Poll Results

Audi B5 S4 Information and Testing