Egt Probe Placement

[KiwiRS4T]

It seems the EGT probe should be as close as possible to the exhaust valve. It has been suggested that in the no 1 runner would be best because it will be running leanest. Can we take that as a given or can anyone who has six probes confirm that before tuning no1 will be hottest? (RB30/25 with a Sinco top mount manifold).

[DVS JEZ]

Think u have it back to front. Cyl 6 is normally leanest.

Are u doing this for tuning purposes?

U can run a single probe in rear housing of turbo

[KiwiRS4T]

I have a GT3540 with a .63 rear and stock pistons. It has been suggested that if I run too much boost (20psi atm making 280awkw so want to go to 25psi and then look at cam timing) I can melt the pistons so want to fit a gauge to keep an eye on the EGT. So you reckon on top of the rear housing between the cam cover and the pipe that leads to the W/G?

[R31Nismoid]

Be more worried about the ringlands letting go simply due to age or a slightly bad batch of fuel more than melting pistons outright.

Cannot say I've ever seen anyone post here that they melted stock pistons, motors let go long before that happens (and it's usually det/age related)

[zebra]

If your tuner says his tune would melt pistons than I would find another tuner....

[KiwiRS4T]

I have complete confidence in my tuners. Its people on this forum that have said that the .63 rear was too small and would choke/overheat. The point of the EGT gauge is to help the tuners in their job - they know its my daily driver and only part-time track car and that I am poor so they won't tune it on the ragged edge and knowingly endanger the motor!

[DVS JEZ]

Ok sweet. Yes drill and tap into the housing. Keep temps below 900 degree's C

[GTSBoy]

And yes, the spot you described is the right spot. As close to the flange as you can manage, even though that seems like it migth be buried fairly deeply on the back side there.

[KiwiRS4T]

Cheers!

[zebra]

I have complete confidence in my tuners. Its people on this forum that have said that the .63 rear was too small and would choke/overheat. The point of the EGT gauge is to help the tuners in their job - they know its my daily driver and only part-time track car and that I am poor so they won't tune it on the ragged edge and knowingly endanger the motor!

Ahh got you

[DVS JEZ]

Having a big external gate will help the small housing breath alot

[kitto]

Sorry to hijack!

I'll be chucking EGT's in my manifold once its been made. But i'll be putting them in every cylinder.

Reason - So my tuner can trim each cylinder until they are all equal. I'll also have them hooked up to a logger.

I've heard mixed opinions, do you put the EGT as close to the manifold flange as possible? Or about an inch away from the flange?

How deep do you mount the EGT in the pipe?

Should i be getting open tipped or closed tip EGT's. Open tip react quicker, but i would think using closed tip will be better for the life of the sensors.

Cheers.

[GTRNUR]

Placement of the sensor and the temperatures you look for will be determined by what you are trying to achieve. Depth? Just don't expose thread to the gas stream.

After running twin EGT sensors in the manifolds pre turbo, I will never do it again. The cast iron manifold has a higher thermal expanson rate than the inconel that the sensors are encased in. The sensors use a 1/8th BSPT thread. The combination of the differing exapnsion rates of the materials and tapered sensor thread means you have to perodically re-tighten the sensor, or risk exhaust leaks. To give you an idea of the effect of this. Sensors that were tight and leak free could be turned by fingers only after a few heat cycles up to 850 degrees. Cast iron, steel and stainless all have this issue.

If you are just trying to balance each cylinder, its just as easy to use a set of well matched injectors, and fine tune the trims on the dyno at moderate cruise load and a laser temp probe on each port as its exiting the head. A cruise load in 4/5th at 100km/h roller speed should see around 700 degrees egt with a 14.7 afr if your ignition settings are correct. If you have your injectors individually flow tested, you can run the bigger flow injectors where you see the hotter egt's, and then trim by ecu injector corrections to get it perfect.

EGT is useful for economy tuning too. You'll see hotter than 700-720ish at cruise speeds if your ignition is too retard, and it can also produce heat induced detonation. Advancing the timing further cools combustion chamber temps and EGT's, as well as it makes more torque, and then you can pull more fuel which further cools the combustion chamber in a lean burn situation (not under load).

I'm now using an egt sensor in the dump pipe in the same place as you would run the narrow band sensor. 2-3" from the turbo. Based on data I have from the pre-turbo sensors, I lose 50 degrees across the turbo. Peak EGTs meaured here are around 800-810 @ 7500 rpm with a 12:1 AFR.

[kitto]

Interesting read there GTRNUR.

My manifold will be a steam pipe but i'm sure it will have the same issue. That is really annoying. High temp thread lock didn't help? Surely someone has sorted this issue out, many people have EGTs, more so in drag cars.

Depth, yeah, how far do i stick the probe into the pipe? You say not to insert the thread. But i was planning on using compression Glands for the EGT. So there will be no thread inside the pipe. But do i insert the EGT so the tip just hits the gas stream, or so the tip is in the centre of the gas stream?

I have brand new Xspurt injectors, but i'm not going to bother flow testing them. They are supposedly closely matched from the factory anyway.

Not only will i be using the EGT's for cylinder trimming, but i think they will be a good tool for diagnosing any faults with or letting me know early on that one cylinder has an issue.

[GTRNUR]

In a drag car, not a problem in the intake runners. Its not as though you put 25,000km/year on a drag car... street cars on the other hand.

Thread lock won't help it. Virtually all adhesives will cook off at 800 degrees given enough time. Even using a copper gasket in the end of a bung welded onto the header pipes won't last forever as copper has twice the expansion rate of most iron based metals.

A compression gland might work depending on what the gland is made of. If its exhaust rated they might use an inconel olive around the sensor.

Sensor depth will depend on the sensor. For example, the PLX devices EGT probes have a 1/2" nipple on the end of a 1/8th BSPT thread. Only the nipple goes into the stream.

The R34 GTR EGT probe for the MFD is about 35-40mm long, and goes all the way to about the center of the gas stream in the dump pipe. The R34 sensor also uses an olive style flange on the sensor, which seals up against the surface of the sensor bung in the dump pipe. Basically the same as a compression gland.

[scotty nm35]

My temps rose around 100c from dump to manifold. I have mine mounted in a stainless pipe, no issues with it coming loose. Is there a reason other fabricators aren't using schedule 10 stainless for manifolds?

I agree, an egt sensor is a useful tool and can help calm the tuner's mind on what the exhaust temps are like. What worries me about multiple sensors is their accuracy, not sure I would want to tune with them unless I tested them first, nor connected to the ecu for live adjustments either, especially long term with potential damage and carbon buildup...

[DVS JEZ]

Scotty with individual sensors its always best to swap them around to check the sensors for the exact reason ur worried about.

Kitto- have u priced up the individual sensor kits. Most of them only do 4 sensor kits. Gets expensive very quickly

[kitto]

I'll be using these, plus a kit of 2.

http://www.ebay.com.au/itm/110764934919?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 You can get these in enclosed tip or open tip and with stainless mounting options as well.

What depth would you suggest to mount these at?

The 0-5V signal will go into the racepak logger dash.

I'll be using E85.

[GTSBoy]

Standard approx 3mm diameter thermocouples like that should lock up properly in the compression fitting. Having said that, the nut on mine keeps coming loose. I must crank it up properly the next time I get an opportunity.

As to how far to inser them.....million dollar question. In an individual runner, I would not want to stick them too far into the gas flow. This is for reasons of upsetting the gas flow (the effect might be small, but best to minimise such things.). By the same token, you have to stick them in far enough so that they will actually work, andnot be dominated by conduction too/from the manifold wall. If you stick the tip of the thermocouple in so it is only fluch with the inside wall, then it will see only a little gas directly, but will be in reasonable thermal contact with the manifold wall. So when you get onto the gas and the EGT goes up, but the wall is still cold, the TC will lag well behind the real gas temp. And of course, when you button off and the wall is nice and hot, the TC will read high for long after the gas is cooled down. Given that the junction in a ~3mm sheath is about 2mm back from the tip of the sheath, I'd say you'd need the tip inserted maybe 5-6mm inside the wall at a minimum to get a decent measurement of the gas temp without too much interference from the wall. Maybe 10mm to be absolutely sure, and hopefully not cause too much flow disturbance.

The same is true if you use a single TC in the turbine housing inlet region. If it's in the dump, you can probably stick it in a good 25mm or more without upsetting the gas flow too much (the TC occupies a much smaller % of the dump cross section than it would in a manifold runner, where the velocity would be somewhat higher).

You can get an idea of the maximum intended insertion on the kit linked above by the length of TC that can be pushed through the fitting. You'd probably only get 25mm maximum through into the gas stream. Probably too far in a runner.

[urtwhistle]

I have used Exhaust gas technology gear in the past and its dam good and there also have quick delivery.