EGT probe not registering temperature

[Spudman]

Hi everyone

I've recently installed these gauges

They are step motor gauges, when I connect power to them it goes through it test stage, the dial spins and then it goes back to 0, 0 = 200 degrees Celsius, so I rev the motor and get the turbo to spool and it sits on the 200 Mark and doesn't move, I believe it should be running normal around 300 degrees.

This is where I installed the probe

Now when I put the probe in I pushed it all the way in and then tightened up the locking nut.

So what I'm asking is, is there special way to place these probes, like in a little bit, half etc. or what else should I be looking at.

On my other gauge the boost one, it's not connected to the vacuum line so when it tests itself the alarm goes off because it stays on 30psi boost.

So it's set up correctly, just not reading temperature.

I hope I've explained it properly and hopefully someone can help

Thanks

Spudman

 

[Locked79]

Probe needs to sit in the middle of the exhaust stream. Have you driven the vehicle with the probe installed? If your stationary reving the engine with no load it won't read over 200. Other than that, maybe faulty wiring or probe?

 

[Spudman]

Probe needs to sit in the middle of the exhaust stream. Have you driven the vehicle with the probe installed? If your stationary reving the engine with no load it won't read over 200. Other than that, maybe faulty wiring or probe?

Nah I didn't take it for a drive, ran out of time, thanks for the response, I'll move the probe tomorrow so it's sitting centrally and go for a drive and report back.

Spudman

 

[RufusTheDufus]

The probe looks like it's a good 12 inches below the turbo. The exhaust gasses have a lot of time to cool by the time they get to the probe.

 

[IanB]

Ideally you want the probe in the middle of the exhaust stream, BEFORE the turbo, for best results. As mentioned, where you have the probe gives the gasses a lot of chance to cool, so your readings won't be "true" readings, but better than nothing all the same. Keep this in mind when tuning, if you see 400 degrees for example on your gauge, the gasses leaving the engine will be much hotter, and there's no good way to know exactly how much hotter without moving the probe.

 

[Spudman]

Thanks guys for all the comments.

As I was putting a 3 inch exhaust on last weekend, my mechanic friend said that would be a good place to put straight off the Turbo, but before I go and move it I just want to share some figures with you.

I just went for a drive and at 60mph (110kmh) the gauge was reading at 300 degrees Celsius and I was getting 10psi on the boost gauge, so does that sound about right or do you think it should be 400 degrees at that speed.

Once again thanks for your prompt responses.

Spudman

 

[cruiser_guy]

300c at 110kph sounds cold to me unless you're going downhill but then I have my pyrometer pre-turbo.

 

[RufusTheDufus]

Does the exhaust transition from the stock downpipe to a 3" pipe a few inches before the EGT probe? It's hard to tell from the photo if it's 3" pipe off the turbo. A 3" pipe will allow the exhaust to cool quicker than a smaller pipe. As the volume increases the temperature decreases.

If you need to install the probe post-turbo the best location is to tap a hole in the cast iron elbow so the probe is directly in the middle of the flow out of the turbo.

 

[Spudman]

300c at 110kph sounds cold to me unless you're going downhill but then I have my pyrometer pre-turbo.

Thanks, what should it be reading

Does the exhaust transition from the stock downpipe to a 3" pipe a few inches before the EGT probe? It's hard to tell from the photo if it's 3" pipe off the turbo. A 3" pipe will allow the exhaust to cool quicker than a smaller pipe. As the volume increases the temperature decreases.

If you need to install the probe post-turbo the best location is to tap a hole in the cast iron elbow so the probe is directly in the middle of the flow out of the turbo.

Off the turbo I managed to find a pipe that fitted snug over the standard exhaust and the other end had been expanded and fitted snug inside the 3 inch pipe, the overall length of the short pipe is around 3 inches, so the probe is about 6 inches from the turbo.

Looks like I might need to order another probe, I take it they are all the same.

Thanks for the advice

 

[cruiser_guy]

I really can't say what it should be reading post turbo.

It is entirely dependent on load, road conditions, your engine, fueling (have you turned it up as many folks do), boost pressure, gearing, tire size and a whole host of other things.

On my 3B if I get the truck working hard in steady state conditions such as a long continuous steep hill which I can do without needing to change gears all the time, I will run at 1200F at 10psi boost. If I am in steady state cruising at say 90 - 100kph, no hills or headwind I'll expect to be at 700-800F but only maybe 5psi boost. If I bump that up to 110kph I'll probably get closer to 900F and perhaps 7-8psi boost. There are others out there with the same setup as I have who may have turned their fuel up slightly and their readings will be completely different. There is no way for me to know what you're truck "should" be reading, there are way too many variables.

I can say that 300c sounds cool to me for driving at 110kph in what I'd assume to be steady state conditions and a boost somewhere around 6-7 psi.

 

[Spudman]

Thanks for the advice mate, I haven't adjusted the fuel.

300 degrees Celsius = 572 degrees Fahrenheit so yep it needs to be around 400 degrees which 750 degree Fahrenheit which seems to be the consensus

 

[Pebbles]

I have a turboed 2H and mine sits on about 350 on normal road conditions. Turbo is sitting on about 8psi at 100kms.
I think its reading right, and I would not be worried about it at all.

Like the other guys said though, I would be adding maybe another 30-50 degrees on the reading to allow for the real temps at the turbo.

 

[cruiser_guy]

Thanks for the advice mate, I haven't adjusted the fuel.

300 degrees Celsius = 572 degrees Fahrenheit so yep it needs to be around 400 degrees which 750 degree Fahrenheit which seems to be the consensus

As you have the pyrometer mounted AFTER the turbo I would be MUCH more conservative on setting the fuel higher. As I said, my readings are from a pyrometer mounted BEFORE the turbo.

For me, the pyrometer is there to ensure I don't melt my pistons so I want to get a reading as close as practical to the combustion chambers. That's why my pyrometer is mounted in the exhaust manifold.

I have not seen any data on heat loss through a turbo but the consensus is that there is a fair amount of heat loss there due the pressure drop through the turbo. That's basic physics and thermodynamics.

 

[Spudman]

I had another chat with my mechanic today and he's telling me it is reading right and that is where they mount them on trucks.

Another way to tell is using a laser heat gun measure it prior the turbo at the turbo and after the turbo and what variations we get, I'm going to try this, I know I can't test it whilst driving, but just sitting in the driveway should give the right results.

I've also decided not to adjust the fuel, as I am very happy how it it running at the moment.

Thanks everyone for the advice

 

[Spudman]

I have a turboed 2H and mine sits on about 350 on normal road conditions. Turbo is sitting on about 8psi at 100kms.
I think its reading right, and I would not be worried about it at all.

Like the other guys said though, I would be adding maybe another 30-50 degrees on the reading to allow for the real temps at the turbo.

Thanks mate, I appreciate you advice

 

[cruiser_guy]

...I know I can't test it whilst driving, but just sitting in the driveway should give the right results.

Sitting in the driveway will NOT show the temperature difference because there will be little to no pressure drop. The temperature change/drop is DIRECTLY related to the pressure drop so the worst case will be at maximum boost. No pressure drop = no temperature drop.

 

[Spudman]

Sitting in the driveway will NOT show the temperature difference because there will be little to no pressure drop. The temperature change/drop is DIRECTLY related to the pressure drop so the worst case will be at maximum boost. No pressure drop = no temperature drop.

Yeah I know you're right, I was just going to test it after I went drive and just see for peace of mind if there was any difference.

Thanks

Spudman

 

[Pebbles]

Take it to a Dyno?

 

[niffa]

Spudman I have 12ht top mount intercooler 15 pound boost and fuel screw wound out 1 turn ish. I sit on 300 at 100kph. 10 psi boost and my probe is post turbo. If I push hard up a steep hill in 4th with ac on and 4 ppl and 200 litres of fuel on board I will see just under 500 degrees. Live in adelaide if I go up south eastern freeway (very steep start for approx 5klm) I sit on 95kph and guage reads a constant 450 degrees, this is a good reading because the hill is very long and i believe I get a true heat soak on the probe because its such a long climb. I wouldn't be worried

 

[Spudman]

Take it to a Dyno?

I would luv to do that, but the closest place is 700 kilometres away
Thanks

Spudman I have 12ht top mount intercooler 15 pound boost and fuel screw wound out 1 turn ish. I sit on 300 at 100kph. 10 psi boost and my probe is post turbo. If I push hard up a steep hill in 4th with ac on and 4 ppl and 200 litres of fuel on board I will see just under 500 degrees. Live in adelaide if I go up south eastern freeway (very steep start for approx 5klm) I sit on 95kph and guage reads a constant 450 degrees, this is a good reading because the hill is very long and i believe I get a true heat soak on the probe because its such a long climb. I wouldn't be worried

Thanks Niffa

That's good advice,