Category Archives: Testing

That’s not good

While driving the other night I heard a bang sound followed by a drop in power.  Subsequent the car sounded a bit different.  Initial investigation showed that one of the two wideband O2 sensor bung plugs in the downpipe had come out.

That plug coming out seemed like an odd cause for dropping power so I continued to investigate.  An intake pressure check was good, I tested the wastegate lines and they were good.  When the car was idling there was no smoke or visible water vapor coming from the tail pipe.

I was still suspicious of a possible turbo problem so I hooked up separate pressure sensors to each compressor housing signal line and then went out to record the pressure in the turbo compressor housing.


The results are shown above.  The great disparity between the driver side and the passenger side (driver side is blue and passenger side gray), and neither matching the MAP sensor, has me concerned that the passenger side turbo may have failed.

Logging Exhaust Gas Pressure

Hooked up the pressure sensor to the exhaust manifold once again to measure the pre-turbine pressure.  I have not confirmed that the pressure sensor is properly calibrated, but the results shown below are probably in the ballpark.

The EGT is flat line because that is a probe located external to the exhaust manifold with the purpose of measuring the temperature near the surface of the exhaust manifold.  With a small air gap between the sensor and manifold surface, and 40 deg outside air to cool things, the region near the exhaust manifold was not very hot during this pull.

Exhaust gas pressure chartHere is the setup I am using to log the exhaust gas pressure.


Hitachi MAF Round 2

The disparity between the flow bench readings and the MAF Sensor conversion table, MLHFM, was larger than I was expecting to see even accounting for the rough calculation from kg/hr to CFM.

I checked the 5v output from the ATX power supply and observed that it was providing 5.138v, a good amount more than I would have liked given the sensitivity of the MAF sensor.  I decided that I would try using a dedicated 5v power converter to provide the MAF sensor with its 5v supply.  I had previously checked this other power supply, and due to the ability to tweak the output voltage I had been able to get 5.005v from the device.

maf_power_setupWith the new power supply in place I ran the Hitachi sensor on the flow bench again.

hitachi_maf_flowbenchThis time the results I obtained were:


Based on these results it’s starting to look like I’ll need to tweak the power supply to get the bench readings in-line with the stock predicted values, and then I can move on to checking an 85mm housing.