I’ve been interested in learning if putting a thermal coating on the exhaust manifolds makes any significant difference in the temperature radiated from the exhaust manifolds.

As luck would have it I have a set of ceramic coated exhaust manifolds, but at the time that I had acquired them I was on a tight schedule replacing turbo’s on the S4 and so I had not been able to establish some good baseline data.

Additionally I’ve found that people modifying theirs cars are a very optimistic group.  If I was to use an Infrared thermometer to take external temperature readings of the exhaust manifold at various points in time, and find no difference between the thermally coated manifolds and stock uncoated manifolds, the optimists would pronounce that the surface temperature of the exhaust manifold is not important, it is what happens to the temperature of the gasses inside the exhaust manifold that matters.  If I was to measure the exhaust gas temperature of the thermally coated manifolds against the stock manifolds and find no difference, then what would really matter would be underhood temperatures, that would of course be lower since the thermal barrier slows the passage of heat from the interior to exterior of the exhaust manifold, even though the surface temperature might be the same between the coated and uncoated manifolds.

Desiring to be thorough with the next opportunity to do this evaluation I assembled a few additional sensors so that I could check readings better.  On hand I now have an Infrared thermometer, an air temperature probe, a high temperature K-type thermocouple, and RS6 exhaust gas temperature sensors installed on my S4 to record the full range of exhaust gas temperatures.

I also have a stock set of exhaust manifolds currently installed on my S4 and a set of ceramic coated exhaust manifolds available for installation at my earliest convenience.

As a warm up for the more thorough testing I started my car with the air temperature probe placed 2.25″ from the exhaust manifold and took readings every minute with the Infrared thermometer to produce the chart below.

 I made some more readings the next day.

 

I’ve got the Boost Manager working partially, it’s reading the MAP but not RPM.  That’s enough to allow me to test it out on the road, which is what I did this afternoon.  I set up an injection table that was tailored toward the boost only trigger and that would approach spraying at roughly 75% of the pump duty cycle once the stock boost level had been exceeded.

I’ve not yet established at exactly what compressor outlet pressure the K03’s are operating in conjunction with the AMD IC’s, but I figured they are probably around 17-19 psi at the initial peak boost.  I therefore set the pump duty cycle to peak around that psi.

I then went out to log the car with the Boost Manager functioning and also with it disabled.  First I did a pull without the system and then a couple with it on.  The entire drive is graphed below.

During the period where the Boost Manager is active the intake air temperature drops in conjunction with the boost events, when the system is off the IAT’s either remain steady or rise.  In order to better define the outcome I’ll need to look more closely at each event.  For the time being I’m not going to be doing that because during the second pull I encountered something unexpected.

When I made the second pull, the first with the Boost Manager spraying, I found that around 4000 rpm the car bogged down.

I repeated this twice to confirm the outcome and then secured the Boost Manager by swapping to a 0% duty cycle map that would keep the pump inactive no matter the boost level.  With the Boost Manager back off I did another short pull without encountering the bog event.

It seems likely that using dual 1.0 mm Aquamist nozzles along with the Boost Manager at ~75% duty cycle is too much water for the motor to operate with.  During this drive I was using 100% water.

Following the bog I had a flashing CEL which went away after a few seconds but when checking the ECU after the drive with VCDS I saw that it had logged a Random/Multiple Cylinder Misfire DTC.

Next up I’ll need to start trying to dial back the amount of fluid being injected to prevent the undesirable results but still keep intake air temps in check.