Exhaust Gas Temperature Gauge

After lots of web research (again!) mostly on the MR2 FAQ Board, I decided that the best place to locate the temp probe was in the branch of the exhaust manifold that serves the cylinder that runs leanest - the consensus is that this is #4 cylinder on the GZE. Happily there is a flat area on this leg which in the USA is used for exhaust gas re-circulation, the flat means that a "weld-on" boss does not have to be used. While I was having some other work done by Kevin in Droitwich (for those that don't know - he's the guy who did the transplant for me) he drilled and tapped the manifold – I supplied the 1/8 NPT tap and he supplied the drill and the expertise!! He decided to drill the manifold in-situ - he's done this before with no problems with swarf getting back into the cylinder – lots of grease on the drill tip. 

To get the drill at right angles to the flat he had to first remove the radiator and some of the intercooler pipe work. After several re-sharpenings of the drill bit he broke through and proceeded to tap the hole – lots of grease on the tap too! Then he used a small diameter magnet on a stick to clean out the inside of the hole. 

The probe tip has to be in the middle of the pipe work to get the best gas flow so it was measured and marked to get it in the proper place. The radiator and pipe work was replaced then I temporarily hooked the probe up to the gauge by running the wire from the gauge out of the car door and into the engine bay – and yes it worked The gauge can be set for high and low temperature versions of the probe and I reckoned that it was set wrongly as the temp was only showing 150^oC when it should be about the 500^oC mark. That was easily sorted. I left it until the following day to route the sensor cable properly into the engine bay and tidy up the rest of the wiring.

Here are some figures from my first two days driving

Idle after starting a cold engine 425^oC - 450^oC
Idle after a run (hot engine) 525^oC - 550^oC
Part throttle cruising at 70mph 700^oC - 750^oC
Peak reading after giving it some wellie with peak boost at 13psi 812^oC.

From what I've read these temps are about right but the research continues.

  EGT Probe in manifold runner from cylinder #4