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A happy story about exhaust temperature pyrometers

GTSBoy

By GTSBoy,
in Engines & Forced Induction

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GTSBoy Grand Master

GTSBoy

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<Cool Story Hansel>

Of the 3 cheapy Pro-Sport gauges I have in my car, one is an exhaust pyrometer.  Probe is installed in a hole drilled in the exhaust housing.  I installed it years ago, and it has provided interesting information since.  But this week it paid back the purchase price and installation effort several fold.

The other day I booted the car out of a corner and at decent load&revs in 2nd gear the gauge went over the ~950°C alarm temperature I'd set and flashed red.  I went along fairly gently after that, but noticed that the exhaust temperature would climb a lot faster under any moderate load than it normally would.

So, theories started to multiply in my head.  Dead injector?  Soft fuel pump?  Thermocouple sheath finally burnt off an thermocouple junction exposed to full exhaust flow?

Had a look under the bonnet and the FPR sense hose was connected and there were no problems with the AFM hose clamps etc.  Thought I'd add the idea of a dying AFM to the list of theories.  Fuel pump seemed like the obvious one, seeing as it is a Bosch 040 that has been in the car for a loooooong time.

Slapped the car on the dyno just now.  Mixtures were perfect.  Well not perfect, but they certainly were not lean.  Under any real load it was better than 12:1.  Ran it up harder and under decent load it was pinging its tits off.  Quite nasty.  Had some fairly aggressive timing in a couple of areas of the map, but it didn't used to ping there.  So we pulled some timing out and silenced the pinging.  There does not seem to be anything else wrong with it.  Right at the top of the revs/load it is as rich as buggery - some power to be found there later, but we'll deal with that another time.

 

Result?  Can only really be a bad batch of fuel.  I filled the tank on Saturday at a different outlet to my usual 1 or 2 places.  Suffered the high exhaust temps on, maybe, Wednesday.  All the driving between filling up and that time was commuting to work and back in horror traffic so no opportunities to load up and get any warning.  Too coincidental to be a coincidence, for my liking anyway.

Anyway, the pinging was bad enough that if I had continued on blithely thrashing it (if the opportunity presented itself) with the stereo turned up I never would have heard anything and it could have cost me the engine.  I'm happy.

</CSH>

Edited by GTSBoy
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GTSBoy Grand Master

GTSBoy

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Yeah, obviously proper knock detection is the best way to deal with pinging issues.  But.... further information relevant to my case in particular.....the ECU is Nistuned, so it actually has a knock sensor and good knock logic that actually appears to work.  But it doesn't do enough.  A proper aftermarket ECU with the ability to get really brutal with chopping the timing back would be required.

We could tell that the ECU wasn't happy.  It was idling with 5 degrees of timing when we started!

The point of my post was just to point out that the pyrometer is a bloody good bit of gear to have on board.  It could have warned me of a dying fuel pump, but it turned out to warn me of something else.  Not bad in my books.

V28VX37 Veteran

V28VX37

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Posted

Nice one, thanks for sharing, great result!

I had a similar deal with my water temps at Sandown couple of weeks back, would have cooked it a lot worse if it wasn't for the nagging Defi alarm.

Also I often hear 'but you won't have time to look at gauges on the track', which is true – except for a quick glance on long straights. It's still much better than not knowing, and the alarms and max readings (checked after each session) are the real deal.

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