I've heard a lot of guys say that they would never drill and tap another exhaust manifold for an EGT sensor because of the possibility of creating exhaust leaks. I've also heard a lot of people say that the best place for an O2 sensor is in the downpipe rather than the O2 housing.

So could you place the EGT probe in the vacated O2 housing bung? I understand the logic in positioning the EGT probe as close to the exhaust source as possible, but given that in general we are observing changes in temperature rather than the temperatures themselves, is the location of the sensor that critical?

Okay, figure since you chimed in on my thread I would share some of my days obsessed reading with you. According to autometers Installation instructions on a turbo charged car the best place to put it is before the turbo for the most accurate reading. You may place it post turbo however your readings will be a couple hundred degrees lower than preturbo.

I spent a lot of time when i built my car, looking at the exact same problem. Many people put the EGT probe before the turbo, because of the response time, and accuracy. But then at the same time, people put them after the turbo, because an EGT probe will destroy the turbo. However, many other articles are out there saying, that you don't want to rely on the EGT gauge for tuning, or performance, rather as an indication that something is going wrong. If it leans out suddenly. I personally have mine taped in a couple of inches down into the down pipe. And i can see every little change, from gear changes, to slight blips of throttle, and revving the engine in the driveway.

I honestly don't think it makes that much of a difference, because your going to get the information whether its above the turbo, or below it. You really would want to use it in combination with a few other things.

Just my .02 /ubbthreads/images/graemlins/smile.gif

Thanks guys. Chris, I was actually just reading about the turbo damage thing, I seem to remember something about the TRE probes having smaller tips that wouldn't do that. In any event you both seem to have confirmed what I thought initially anyway. Every thing that I have read about tuning with an EGT suggests that you should look for changes in temperature and be aware of the critical exhaust gas temperature (i.e. the failure point). That being the case I can't see why using the O2 housing wouldn't work as long as the readings are consistent and you experiment carefully with the AFR whilst checking the EGT to see what temps you get as the AFR starts getting dangerously lean.

I see the EGT in the very same light as I see dynos. The figures themselves are meaningless but you can use the fluctuations in the readings to tune pretty effectively.

Provided that you are either logging the WBO2 readings or are staring at the gauge during a pull. I mounted my wideband in the GVR4 in the downpipe just ahead of the firewall at the prescribed 12* angle. I usually gave myself a 200* buffer from maxing out the gauge (1600*) and never cooked anything. But I never used the wideband after I got my tune dialed in. However I've got the WB in my diesel truck mounted in the collector area of the manifold, pre-turbo. Interesting to note that the 4G63 motor would idle in the 600-700* range while the diesel does it at 200*.

I've got this NIB Defi EGT kit, but I've had several people tell me I should just sell it, because it's unnecessary with on-board wideband.

And here you guys are, discussing EGT probes. Why are you running EGTs? How useful is an EGT gauge on a race car - seriously?

I think for tuning a wideband is the way to go and I would agree that an EGT for tuning is redundant if you have an AFR gauge installed. But unless you get into the habit of watching the AFR once you have established a tune I think it gets somewhat redundant. I'm looking more for gauges that can be linked to a warning system whereby if readings go above or below a certain level, I get notification via an obvious warning light or an audible alarm.

Maybe the EGT is superfluous with the wideband installed because as you go leaner the temps rise. You are probably right in that only a 4-runner EGT system is likely to offer any advantage over the wideband since it allows you to see if a single cylinder is running lean (blocked or malfunctioning injector, misfires etc).

Like you, I already have DEFi EGT gauge and probe. I think I will install it anyway. I just see it as insurance. I doubt I'll use it for tuning, just set it to activate a warning light if it sees temps over X degrees.