EGT's and location of probe

Kiwif150

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Just a question for you guy's who have pyro's . If the "magic" never exceed number is 1200 deg f , how much difference does the probe location make?
The reason i ask is that i'm piling up parts that i can find here locally before i make it stateside to snag an idi and i'm wondering if i can use my current setup i have on my 5.0 f150 (used for a hydrogen boost experiment) or if i'd be better going to an aircraft style of cht gauge where the sensor is bolted directly to the head as opposed to being fitted into the exhaust.

This is my current gauge setup.
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Dieselcrawler

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bolted to the head is only telling you head tempature. you need to know what the temp of the gases coming out of the heads are. cyls 6 ans 8 fire right after each other making that location the hottest. this is why we say to drill and tap the driverside manifold as close to cyl 8 as possible.
 

gandalf

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That's right. The damage resulting from excessive heat would be in the cylinder, not in the head. The pistons are, I believe, at least partially aluminum. Aluminum has a melting temperature of about 1350*F, if memory serves me correctly. You truly do not want to melt a piston. By the time you heat the head to that temp, the piston is dead. Therefore, you want to measure EGTs as close to the cylinder bore as possible. Tapping the exhaust manifold is as close as you can get. As you move farther along the exhaust path you must adjust your allowable max temp downward.
 

laserjock

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On the engine stand. [emoji6]

If you are NA, most will say drill with the engine running and it will blow the shavings out. On a turbo, don't think that would be the best idea.

Probably best/safest to do it with the manifold off.
 

Mike_42

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On the engine stand. [emoji6]

If you are NA, most will say drill with the engine running and it will blow the shavings out. On a turbo, don't think that would be the best idea.

Probably best/safest to do it with the manifold off.
10-4, thanks.
 

Dieselcrawler

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i have never removed a manifold to drill/tap. turbo or not, hell 6.9 to 6.4 and a duramax. do it with it running. you will be amazed how much exhaust gets pushed back out the hole once you pop through it. blows everything right back into your face. wear googles.
 

SirRea63l

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I did mine in the engine bay, same location that laserjock showed. (Thanks for that pic)

I just put a small and powerful little magnet on the drill bit when it got close to breaking through. Before it got close I used a vacuum to keep the shavings cleaned out. I used the same magnet and vacuum when I tapped it.

I bought a cordless angle drill to match the cordless tools I already have and it was very easy after that. I did not have a drill small enough to fit and the angle drill has been used a lot since I got it, I was able to justify it with the War Department because it has been used a lot. :D
 

Kiwif150

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Thanks for clarifying that - when i did the hho experiment i wasn't so much concerned with placement of the probe as i was with the differential between hho and standard operation. I have it in the left side downpipe just below the manifold flange on the 5.0 and the hottest i've ever seen it has been a bit over 1350 deg when towing a loaded car trailer up a long grade at about 4000 rpm in 2nd.
 

gandalf

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This is a correction to my earlier post in this thread. The melting point for aluminum is 1220*F. I stated ~1350*F, but I was wrong.

Are the pistons pure aluminum? I really don't know, though I doubt it. Maybe some one else here can answer that. But, be that as it may, I would strongly suggest not running a sustained temperature above 1200*F. Short periods above that can usually be tolerated, but not a sustained period.
 

DaveBen

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1200 degrees is the rule of thumb on max exhaust temperatures. The pistons will not melt if you go over that temperature by several degrees as they are oil cooled and pull in fresh air and fuel to cool them off a bit. How much over 1200 will cause piston damage? I have never heard anyone state a number. ymmv
 

Hydro-idi

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That's right. The damage resulting from excessive heat would be in the cylinder, not in the head. The pistons are, I believe, at least partially aluminum. Aluminum has a melting temperature of about 1350*F, if memory serves me correctly. You truly do not want to melt a piston. By the time you heat the head to that temp, the piston is dead. Therefore, you want to measure EGTs as close to the cylinder bore as possible. Tapping the exhaust manifold is as close as you can get. As you move farther along the exhaust path you must adjust your allowable max temp downward.

Not true. You will crack those cast iron cylinder heads if you have excessive egt's. I accidentally ran about 1500 on my new engine for about 30-45 seconds. The new .030 aluminum pistons were fine for some reason, and showed no signs of damage, but I cracked my heads in about 30 different places on each one. Turned them into boat anchors.
 

Seventh

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I have a relevant question. I'm getting ready to install my banks downpipe setup on my factory turbo pretty soon. It has a port near the vband at the turbo.

If one were to use this port for the egt sensor, what would the difference in temp reading be vs the port in the manifold?

I'm not against doing the port in the manifold, however I'm tempted by how much easier it would be to just use the dp port.
 
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