Continuing the look at exhaust manifold surface temperatures, the latest check is of the stock exhaust manifolds with Swaintech white lightning coating.  I like the Swaintech product because the advertised thickness of the material is greater than other similar products.  My understanding is that the thickness of a ceramic coating is essential to  performance, with a thicker coating being more likely to perform better.

Test:

To check the exterior surface temperature of the exhaust manifold I am using an IR thermometer.

The manifold is at ambient temperature for the beginning of the test, and then the engine is started and allowed to idle for ten minutes, making surface temperature readings every minute.

Repeat-ability of the measurements suffer due to the location of the exhaust manifold as well as the manner in which the manifold heats up, shown below.

Sampling the exterior surface at the same location each time is difficult, but overall the trends should be indicative of how the differently coated manifolds heat up.  To help achieve better results the readings were made twice for each coating.

Results:

Shown below are the average results for each coating type:

The next chart illustrates the individual readings for each coating type:

Conclusions:

Under these test conditions and assumptions the ceramic coatings are shown to reduce the rate at which the external temperature of the exhaust manifold increases as recorded by an IR thermometer.  The Swaintech  white lightning coating provides an additional benefit as compared to a thinner, black colored,  alternative ceramic coating.

These results do not give proof of how the different coatings perform over an extended period of time, or under normal driving conditions.

I’ve read this comment a few times “at high rpm the K03 is just a hair dryer”.  The claim is that once the turbocharger starts to reach the upper operating region it is doing nothing but producing hot air.

In general at high pressure ratios a compressor is going to generate hot air, and as the turbocharger compressor housing warms up the compressed air will become hotter as the ability of the housing to absorb heat decreases.

What is normally implied by the hair dryer comment is that the K03, being a smallish turbocharger, relative to other options for the B5 S4, becomes inadequate at higher airflow rates.  To see how much of a hair dryer the K03 turbocharger is I matched it up with a pull I did on my car when outfitted with the larger BorgWarner RS4 K04 turbochargers.

The boost profile for each turbocharger is different, which matters a great deal, but that wasn’t what I was concerned with.  My main interest was to compare the compressor outlet temperature of a K03 turbocharger with a reasonably aggressive boost profile, versus the K04’s with an aggressive boost profile.

Here are the results:

The outlet temperature of the K03 turbocharger is a good deal less than that of the K04.  To me this is indicative of how important the boost level is versus the compressor efficiency when neither turbocharger is being operated at a point far outside of an efficient region of the compressor map.  A K03 operating at 65% efficiency is not going to generate appreciably higher outlet temperatures when compared against a K04 operating at 70% efficiency.  The K04 operating at a PR around 2.6, versus 2.2 for a K03, is more likely to generate results like those shown above.

The following charts show how three different tunes drive output results with the BorgWarner K03 Turbochargers.  The tunes consist of a stock, Lo, tune, a mid boost tune, Mid, and a high boost tune, Hi.

All results were recorded with ambient temperatures at 70 degrees Fahrenheit.  It should be pointed out that how the car was driven prior to each collect was similar, but not exactly the same, which could influence some of the temperature results, though that does not appear to be the case.

These are the boost profiles of the three tunes used for the data collection.

Results below were collected with the S4 on a dyno: