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Old 12-25-2007, 06:11 AM   #21
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Originally Posted by AbeFM View Post
As far as temps, I'm not sure! I've heard so many different numbers I'm always afraid to say. I think 1800 is on the high side, I wouldn't go to 2k unless you verify it's ok!
It all depends on where your probe is. My application is naturally aspirated and I easily see temps of up to 850*C (1600*F). Friends with Greddy turbos see up to 1400-1450*F. I have the probe about 1.5" away from the head; they have the probe about 2" away from the turbo, which acts a huge heatsink (remember that the purpose of the turbo is to absorb the energy of the exhaust gas - kinetic energy and heat which is in fact tiny kinetic energy in the nanoworld), so the temps AFTER the turbo are guaranteed to be lower than before the turbo. Depending on the size of the turbo as well as several other parameters, I expect to see 100-150*C of lower EGT after the turbo (ie: 950*C before, 800*C after).

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Old 12-25-2007, 08:17 AM   #22
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Originally Posted by Reverant View Post
It all depends on where your probe is. My application is naturally aspirated and I easily see temps of up to 850*C (1600*F). Friends with Greddy turbos see up to 1400-1450*F. I have the probe about 1.5" away from the head; they have the probe about 2" away from the turbo, which acts a huge heatsink (remember that the purpose of the turbo is to absorb the energy of the exhaust gas - kinetic energy and heat which is in fact tiny kinetic energy in the nanoworld), so the temps AFTER the turbo are guaranteed to be lower than before the turbo. Depending on the size of the turbo as well as several other parameters, I expect to see 100-150*C of lower EGT after the turbo (ie: 950*C before, 800*C after).

Jim

First of all; a big to elesjuan for starting this thread and to all previous posters for contributing. I repeat what I've said before; you young guys never cease to amaze me! This kind of thread is what separates you from other forums.

Now, on to my question to reverant; Jim, my question is: why AFTER the turbo? If I read your post correctly, temperatures before the turbo would be higher. And back to a question already asked: what would be the ideal (?) temperature anyone should shoot for?

I come from an era when there were no EMSs in the cars and tuners would always tune based on EGTs but I never found a tuner that could give me a solid answer. The closest was to tell me to watch out not to go over 1600 degrees

Thanks,

Rafa

BTW, MERRY CHRISTMAS TO ALL!
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Old 12-25-2007, 10:12 AM   #23
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Best to have the probe before the turbo. You want to measure "Exhaust Gas Temperature" before it is modified by the turbo and its' heatsink properties.
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Old 12-25-2007, 10:21 AM   #24
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Best to have the probe before the turbo. You want to measure "Exhaust Gas Temperature" before it is modified by the turbo and its' heatsink properties.
Ok, got it; never had a turbo car before. Still, what is the best EGT range anyone should shoot for?
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Old 12-25-2007, 11:19 AM   #25
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I found this interesting:

http://www.sdsefi.com/techegt.htm
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Old 12-25-2007, 11:36 AM   #26
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Originally Posted by olderguy View Post
I found this interesting:

http://www.sdsefi.com/techegt.htm

^ link =
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Old 12-25-2007, 11:39 AM   #27
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olderguy thanks for posting that was a good read
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Old 12-25-2007, 05:04 PM   #28
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Quote:
Originally Posted by Reverant View Post
I have found that most modern gauges lack Cold Junction Compensation. The cold junction is where the two metals join on your circuit (yes, they do join internally on the circuit). The voltage measured at the ends of the thermocouple wire is not only dependant of the temperature of the probe (hot junction) but also of the temperature at the circuit end of the wires (ie where you connect the wires to the circuit) - the cold junction.
Nice bit of information there! Well, it wouldn't be hard to run thermocouple line out of the MS and leave a connector dangling. Then your junction could be the pin of the IC, hard to imagine a big offset there.

I'm definately going to do this soon...
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Old 12-25-2007, 10:03 PM   #29
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*snip*
Wow man! Thats probably the single most impressive piece of information I've ever read on something technical like this.

Thank you very much for the info!

I do have a quasi-related thermodynamic question about turbochargers and myths of heat..

Given that an engine is turbocharged and in moderate tune to produce a good amount of power, lets say for example the temps right outside the exhaust ports are around 1500*. What differential would you say that is from the actual combustion CHAMBER vs. the probe measurement? The cylinder heads are aluminum which remove heat from the combustion pretty well, pistons are aluminum and oil cooled, plus the valves (which I wouldn't factor much cooling properties from the steel valves just wanted to mention them.) Adding on the turbo manifold which is cast iron in my case, plus the turbocharger which is cast iron. Turbos by design are mufflers and heat sinks, they use thermal energy along with gas / air flow to spin the turbine.

Taking that information into consideration, are there really benefits from adding thermal or ceramic coatings to Pistons, Manifolds, and turbine housings? Do these benefits contribute more to keeping say, my brake master cylinder from melting or the efficiency of the engines combustion process? I've heard old myths before that "header wrap" especially on high heat applications ie. turbochargers will actually cause the materials wrapped in to physically fatigue?


Quote:
Just make sure that you solder/connect the wires as near to the AD595 chip as possible and NEVER use any different wires/connectors to extend the thermocouple wire. Only use special type K wires and connectors.
So if I bought one of the K-type units I found from the other thread I need to find more K-type wire and the connectors all the way to the PCB where the AD595 chip is soldered on? That board will be inside the megasquirt case, I mounted a small expansion PCB to the inside of the cover for small circuits like this.
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Old 12-26-2007, 04:39 AM   #30
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Quote:
Originally Posted by elesjuan View Post
Given that an engine is turbocharged and in moderate tune to produce a good amount of power, lets say for example the temps right outside the exhaust ports are around 1500*. What differential would you say that is from the actual combustion CHAMBER vs. the probe measurement?
You can't readily associate the exhaust gas temperature with the chamber temperature. Let's assume for a moment that the exhaust gas is homegenous, ie all the gas has the same temperature. Which point in the combustion chamber are you interested in measuring? Piston top? Crown? Skirt? Ring land? Cylinder walls? (where and which cylinder?) Valves? There are a myriad locations and rest assured that each one will have different temperatures depending on the flow of coolant as well (is there a coolant jacket near the measurement point?)

Quote:
Originally Posted by elesjuan View Post
So if I bought one of the K-type units I found from the other thread I need to find more K-type wire and the connectors all the way to the PCB where the AD595 chip is soldered on? That board will be inside the megasquirt case, I mounted a small expansion PCB to the inside of the cover for small circuits like this.
If you need to be able to disconnect the sensor from the MS PCB, you need K-type connectors:

http://export.farnell.com/jsp/Connec...sp?sku=8598282
http://export.farnell.com/jsp/Connec...sp?sku=3810628

Jim
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Old 12-26-2007, 06:06 PM   #31
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Reverant is right, in that you're getting sort of course information here.... But, there's some interesting caveats, you might at first think it's obvious the cylinder is hotter than the gas, but it's the gas doing the heating, if it's not in the chamber long enough, the chamber won't necessarily get to the temperature of the gas (theoretically it can't) not to mention there's boundary layer issues: On broad, flat surfaces gas doesn't really "scrape" the surfaces - the whole thing about how your car can stay dirty driving at 100 mph, the boundary layer keeps the moving air from "touching" the surface of your car.
Anyway, I've heard the metal in the chamber is often colder than the gas coming out - and I assume since the egt probe is "sharp" it does a better job of measuring the temps of the flowing air.

The links didn't work to the parts, but the idea is nice! Beats soldering to the board!

The earlier link was odd - mostly I have heard what it said before - the tuning systems they sell are a bit simplistic, and it seemed to be dumbed down just a bit? Anyway, I'm learning stuff, keep it coming. :-)
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Old 12-26-2007, 06:26 PM   #32
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Abe: I sifted through that link Reverant posted and found the parts he was trying to post. Javascript on the page makes links hard to post on a forum.




Went to the root page http://www.farnell.com clicked on United States, Connectors, industrial, Thermocouples.

Good find!! They're not too expensive from there either.

Even found this on there!
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Old 12-26-2007, 06:38 PM   #33
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http://www.egauges.com/vdo_indS.asp?...ad&PN=R660-6PL

Place in the states, I think thats acceptable wire for a thermocouple using one of their sensors like this one: http://www.egauges.com/vdo_indS.asp?...1_5&PN=R650SPL

Add those K-type plugs for the megasquirt case and you're golden!
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Old 12-26-2007, 07:03 PM   #34
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k-type in green? That's just weird. Green is... I forget, not k type. Purple is t, J is brown? I don't remember.

Anyway, if it's labled k, it's probably right. And yeah, adding them in the case would be great. It's on my short list of must-do's

I think I still like the probe I got better, very exposed tip, must be pretty fast. Then again, you can get even more exposed so.... It's always a trade off.
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Old 12-26-2007, 07:08 PM   #35
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One thing left to find... According to Reverant the wires from the Case plug to the board need to be thermocouple wire also? Where would one find say 6" of that type of wire, or will regular copper work in that position?
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Old 12-26-2007, 07:57 PM   #36
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You should keep the same metal as far along as you can - you could get a thermocouple passthrough, which will work great but be pricey. Personally, I'll probably just use a pigtail, or mount the board right near the edge so the thermo standard connector can plug in through the side. The trouble with changing wires outside the box is there's more likely to be different temps inside the box than outside.
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Old 12-26-2007, 08:22 PM   #37
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Okay I think I have a good solution.

I'll cut a small notch in the endplate of the case to run the cable through inside then mount one of the K-type sockets directly to the board. That way the sensor plugs into the harness cable, then that cable plugs into the circuit board but can be disconnected easily. Hopefully that'll work.
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Old 12-27-2007, 05:01 AM   #38
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Quote:
Originally Posted by AbeFM View Post
k-type in green? That's just weird. Green is... I forget, not k type. Purple is t, J is brown? I don't remember.

Anyway, if it's labled k, it's probably right. And yeah, adding them in the case would be great. It's on my short list of must-do's

I think I still like the probe I got better, very exposed tip, must be pretty fast. Then again, you can get even more exposed so.... It's always a trade off.
Green is K-Type in the UK (imperial) while it is yellow in the US. Chromel/Alumel (+/-) cables are respectively Green/White in the UK while Yellow/Red in the US.

Jim
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Old 12-27-2007, 05:04 AM   #39
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Originally Posted by elesjuan View Post
One thing left to find... According to Reverant the wires from the Case plug to the board need to be thermocouple wire also? Where would one find say 6" of that type of wire, or will regular copper work in that position?
The plug I posted is PCB-type, which means that you solder the connector to the board. If you want a connector that you can attach to the case, then cut some wire from the thermocouple sensor's own wire.

COPPER WILL NOT DO!!

Jim
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Old 12-27-2007, 02:38 PM   #40
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The place I posted sells the sensor, with connectors, and the cable by the foot as well.

Maybe it didn't make it into this thread.

http://www.teamrip.com/accessories.html

pics of my probe:
http://abefm.smugmug.com/gallery/4022112#234090908

Oh, the guy is terrible with email, etc - the parts came, just after I started to worry they wouldn't. Effectively, it was fine - pay and nice parts come. But don't expect to start a conversation with the guy.

If anyone's looking for open-element ones, I have a friend who found some cheap. Might be worth checking into, though they don't last long. If I were going to bother running 4 sensors (hint to no one in particular) wouldn't it be worth having them FAST?

Last edited by AbeFM; 12-27-2007 at 05:48 PM.
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