Wormhole

The temp is actually higher at the test tube area since it receives a constant flow from all runners, opposed to the pulsating on/off pattern at one runner on the manifold. I typically see 1600 F and over.

Oddjob

>"The temp is actually higher at the test tube area since it receives a constant flow from all runners, opposed to the pulsating on/off pattern at one runner on the manifold. I typically see 1600 F and over."

Interesting, off hand I wouldnt have thought the pulsing effect would allow time for the probe to cool inbetween exhaust stokes at high rpm.

Does that location work well, would you recommend it? Do you have any ball park A/F ratios and boost levels that correspond to temps at that spot (the 1600 plus)?

Thanks.

tazman

I talked to Tim and he said he would weld a bung in for an EGT for me! He said he would just have to remove the coating where he had to weld.

Wormhole

Think of it like the candle trick when you were a kid. You could move your hand over the candle back and forth, but if you left it in the center for too long you scorched your hand. Same dynamic principle but on a larger scale. The probe itself is very sensitive to temperture changes.



I chose the location mainly because I don’t intent to use the EGT to tune, but rather as a safety devise. I wanted something that would pick up a problem on any cylinder, but didn’t want 4 probes. Given that I think it’s a great location being the closest to the collector.

Boost doesn’t seem to change the EGT much, the most noticeable changes are at higher RPMS. At ~5200 and above it reaches the limit on the Autometer gauge (1600F), that’s at about 12.8 A/F now.

944Hater

WRONG! At WOT nearing redline, the pulses are too close to allow fluctuations that ANY thermocouple will register fast enough. Think about an engine turning at 7000RPM. If you put the thermocouple in a single runner, that runner will see ~58 (7000RPM/2cylinders per revolution/60 seconds per minute) exhaust pulses per SECOND. Putting the thermocouple closest to the head will yield the best measurement.

I think you were moving your hand over your own candle too fast as a kid and now your probe is too sensitive to work properly!

Wormhole

Let me guess 944hater is from the DSM board. For those wondering, I was having a little fun with a friends account in one of the ricer private boards. NABR for those familiar, so ignore the fool. He was never any good with physics and his statements prove that.

It doesn’t matter how close the pulse is, the difference has been tested by others to be 100 degs F.

944Hater

Yes Worm**** you are correct it is I your good friend of about 20 years. That “little fun” you had with my account resulted in me getting kicked out of my Private Board which is the furthest thing from a ricer board. The reason it is private is to weed out all the **** heads who ask stupid questions and give bad advice, much like the crap you do here. Why is it that every single reputable gauge manufacturer recommends putting the probe closest to the head? Why is it that every knowledgeable racer puts the probe closest to the head? Because they are smart. Because they actually take the time to remove the components from their car prior to doing an install unlike yourself.

(intent or intend, devise or device, learn how to pick the right word Mr. Physics)

The only reason why you put the probe where you did was to avoid spending a whopping 20 bucks to get a bung welded in. If it is a known fact that a particular cylinder will go lean (#4 in your case) due to poor fuel delivery etc, why would you choose a location that is so far away from the source of heat? And it does matter how close the pulse is. Tell me Wormdick, what thermocouple do you know of that will react fast enough to give your candle theory any merit whatsoever. None, I’ll save you the time. Do you think your Autometer probe will react fast enough. What a joke.

Here’s a little Physics lesson for you. Since you like candles so much I'll use an example you can relate to. Take two matches and light them. Measure the temperature of one. Now hold the matches together and take another measurement. The temperature doesn’t rise!, however the energy does. If you have two separate cylinders next to each other firing at different times, their exhaust runners can be treated as separate heat systems. When you put two different systems together, the hotter system will warm the cooler and vice versa until they reach a state of thermal equilibrium. Now tack on the heatsink effect of your runners. Now tell me Mr. Hawking , how the hell can the temperature at the collector be HOTTER than the source of a single system. It CAN'T. It is PHYSICALLY impossible, but you knew that already because you watched all those shows on the discovery channel.

I know you’re bitter because my DSM will run circles around your Porsche on the street but that’s no reason to disrespect my privacy and pull the act you did. For everyone else here, I apologize for making this a public discussion, I tried to make it as amusing as possible.

adrial

944hater,

Nice introduction to the boards, no really.

I wasn't aware that #4 cylinder goes lean due to poor FUEL delivery, hmm. Can a 944 hater such as yourself explain that to me?

I'm gonna guess that your little match demonstration doesn't apply because the exhaust is a closed system (aside for the heat lost through the pipes themself). Can anybody verify? Danno?

944Hater

Adrial,
I know it's a terrible introduction which is why I apologized at the end of my post. My screen name was created out of anger for my buddy but in no way represents my feelings towards 944's. I respect their engineering prowess and demonstrated skills on the racetrack. Wormhole's car is the exeption to the rule. Reading through previous posts I made a comment about the number 4 cylinder going lean because it seems to be a common point of failure for a couple of people. Not knowing these engines I cannot definitively answer whether this is a fuel delivery issue (single fed fuel rail) or an airflow issue due to intake manifold design but I'm sure some of you know the answer. The match theory is absolutely correct, closed system or not. Placing a thermocouple in an exhaust collector will not increase the temperature measurement. Take another example. Instead of two matches, light the whole book. Is the temperature of the flame hotter?...no. Is there more heat?...yes.

adrial

Lean #4 is due to the intake manifold according to some.

Again your book of matches theory leaves out the changes in pressure and volume when the 4 exhaust pipes come together. (My elementary knowledge of fluid flow tells me that pressure in a pipe is constant everywhere, but the exhaust of a turbo car is far from a basic system) If anything is going to cause temp to increase, I believe it will be that.

Wormhole

Rory, Welcome to the board. I hope you accept my apology. It really was harmless, and I did not intend to get you kick off your forum.

Instead of disputing fundaments, here is some real data. Since you’re a Talon guy you should appreciate this. This is a test that was done on your car a 92 Talon (I believe yours is a 91)

In summary they experienced 150 degs hotter in the collector then in the runner.

http://www.stevetek.com/R-EGTprobeLocation.html

944Hater

Adrial,
You are correct about my theory omitting the factors of pressure and volume. I was making a simplistic analogy. Surely you would agree that the forced air into your engine is also a closed system. So, would you now agree that you can experience pressure drops at different points of that system due to intercooler design/pipe sizing etc.
You are absolutely correct...except this statement would only apply to a pipe that has a constant diameter. At the collector, the diameter changes thus affecting pressure and velocity.

For Reference Purposes:

pressure drop (psi) = 5.68x10^-9 (q * u * l) /d^4

q = flow rate (gal/hr)
u = fluid viscosity (cPs)
l = length of pipe (in)
d = diameter of pipe (in)

John,
I do accept your apology but I will still make you pay by abusing you next time we meet on the highway. Without bad mouthing anybody I will say that you should not believe everything you read. For all you know this guy could be out to sell his fuel system (which has been abused and disproved time and time again). There was a time when I thought this to be a valid paper however I have been able to push the stock fuel lines well beyond the suggest limits in this paper and have not had any issues with cylinder#1 going lean. Furthermore, in the Conclusions portion of this paper Steve goes on to say that mounting the probe in a runner is highly recommended. Even if I am proved incorrect and, (due to collector design and factors which may be overlooked in this discussion), the temp in the collector is higher due to some law of Physics, it still is NOT representative of what is going on in the cylinder. That being said, I still believe that if you have an engine with a cylinder that tends to go lean, put the EGT probe as close to that exhaust port as possible to determine whether or not you are truly melting valves.

Wormhole

Rory, my statement was the collector is the hottest location. The BEST location can be disputed, and as you already know has several variables that need to be considered. Besides the temp is relative, knowing the melting point is what is important. To say one location is the best is a blanket statement that is incorrect. If you are using as a tuning device then the best alternative would be to use a thermocouple on each runner along with a CHT and your wide band. Maybe next time you won’t blow through your head gasket.

Oh and next time it will be on the track if you have it in you……. I’m off to Shawnee, so have a good new year.

eclou

Does anyone have a picture of the actual EGT probe? The fitting on the CO2 sample port of the xpipe is the exact thread size and pitch of wheel stud. Mine tube cracked and is capped by a lugnut.