Installing EGT probe
10-29-2007, 01:00 PM
#16
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I just used a magnet after drilling. Tried to avoid sticking it far enough towards the turbo to cause damage. I didn't have any problems.
Try to make sure you can find the big chunk that breaks off when you break through, and drill slow as you break through to make sure they are smaller chunks. Bill (infidel) reports having seen two turbos wrecked because of the large chunk jamming the exhaust blades.
Reports suggest many shops just drill without any magnet/etc.
Try to make sure you can find the big chunk that breaks off when you break through, and drill slow as you break through to make sure they are smaller chunks. Bill (infidel) reports having seen two turbos wrecked because of the large chunk jamming the exhaust blades.
Reports suggest many shops just drill without any magnet/etc.
10-29-2007, 01:32 PM
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Go Post Turbo and Dont Worry about it
I think just go Post-Turbo and dont worry about anything. Just rely on who knows best, Cummins. I figure they know better than anyone. I stick with their recommendations regarding ETG limits and been fine. I never see much more than 900 post turbo pulling a 35' fifth wheel in Utah Mountains. I did once get 1100* for a few minutes, but no problem. I also knew a guy from a very popular shop in utah that lost number 6 from heat on a flat drive. He had his probe in the manifold, so maybe that reduced exhaust flow just enough to ruin his day???. I have buddies that pull with manifold Probes and they will get 200-300 more on the same trips at the same locations via walkie talkies. So I figure they have to deduct what they get in order to calculate the Cummins specs. I.E., if they get 1300, they should subtract 250 or thereabout to get the cummins spec. I just like to point out the fallacy that if you put the probe post turbo you have to add some number, you dont. Just go with Cummins and you will be happy and fine. Not too mention, no risk in drilling the manifold, no risk of shavings, no risk of blockage to the exhaust hole in the maniforld (which from what I can see can be about 10% loss of the hole, and no risk to a probe comming apart and going into the turbo or worse. Correct me if I am wrong, which I am sure many will do, but blocking 10% or thereabout of the exhaust hole creates unnecessary heat in the motor on the back cylinders, possibly causing damage to the motor, exhaust manifold cracking, and turbo damage from probes????. What do you all think? It seems like putting a mufler in the exhaust manifold, poor analogy, but you get the point.
V/R
Steve
V/R
Steve
10-29-2007, 02:15 PM
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I think just go Post-Turbo and dont worry about anything. Just rely on who knows best, Cummins. I figure they know better than anyone. I stick with their recommendations regarding ETG limits and been fine. I never see much more than 900 post turbo pulling a 35' fifth wheel in Utah Mountains. I did once get 1100* for a few minutes, but no problem. I also knew a guy from a very popular shop in utah that lost number 6 from heat on a flat drive. He had his probe in the manifold, so maybe that reduced exhaust flow just enough to ruin his day???. I have buddies that pull with manifold Probes and they will get 200-300 more on the same trips at the same locations via walkie talkies. So I figure they have to deduct what they get in order to calculate the Cummins specs. I.E., if they get 1300, they should subtract 250 or thereabout to get the cummins spec. I just like to point out the fallacy that if you put the probe post turbo you have to add some number, you dont. Just go with Cummins and you will be happy and fine. Not too mention, no risk in drilling the manifold, no risk of shavings, no risk of blockage to the exhaust hole in the maniforld (which from what I can see can be about 10% loss of the hole, and no risk to a probe comming apart and going into the turbo or worse. Correct me if I am wrong, which I am sure many will do, but blocking 10% or thereabout of the exhaust hole creates unnecessary heat in the motor on the back cylinders, possibly causing damage to the motor, exhaust manifold cracking, and turbo damage from probes????. What do you all think? It seems like putting a mufler in the exhaust manifold, poor analogy, but you get the point.
V/R
Steve
V/R
Steve
I understood the Cummins spec was both pre and post turbo, at least looking at dodgeram.org. The pre-turbo specs are the same (1250o), while the post turbo specs vary whether you are at torque peak or hp peak (or anywhere inbetween).
Note that the post-turbo figures on EGT are only reliable at the stock boost levels.
The heat damages parts before the turbo, if too high. It makes sense that you want to measure the quantity closest to where the impact would be felt (i.e. before the turbo). There are certainly more risks associated with the installation, but those can be mitigated and addressed. I would imagine that, if Cummins recommends putting the probe post turbo, it is based on wanting to avoid catastrophic failures of the turbo by improper installation (post turbo worst reasonable case is an exhaust least), and on stock engines... very few people pimp out tractor trailer engines, as they are in it for the long haul.
In any event, I would highly suggest pre-turbo, but installed competently. The probe should just enter the stream of exhaust, and care should be taken to not fill the exhaust manifold and turbo with shavings.
10-29-2007, 02:38 PM
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I actually think it is about 10% blockage
I actually think you are wrong that it is only a couple percent of blockage. If you take the size of that hole in the exhaust manifold and measure the surface area, then substract the portion of the probe that enters that path, it is easily 10%. That probe is about 1/4" wide and goes in about 1.5" or therabout. That is a significant portion of the hole, considering the hole is only what, 1.75" x about 2" or so. Also, I have to disagree that those specs from Cummins, which are post-turbo, are for stock motors. Those specs are only addressing the acceptable heat range that parts can withstand. It doesn't matter if the motor is stock or not. It only matters that you stay within those heat specifications as determined by the maker. This is not to say that pre-turbo does not do this. But it is a risk of sorts, regardless. There is a Cummins shop here in utah, called Pete's diesel, i spoke with that guy years ago, he said he has seen probes come apart partially from long term heat damage themselves. That is an added risk of going preturbo. However, going post turbo, regardless if you have a stock motor, or like mine, non-stock, you know exactly what your heat is doing and what the parts are designed to handle. I know if I stay 1K or under, all components, no matter how hard i push that motor, will withstand that level of heat. The interesting thing is that you have a lot of people now saying go preturbo, trick out your truck and run up to 1600* for a few seconds. You see the irony in that dont you? Now, because you are preturbo, you think and people do, run even hotter than what cummins says you should do anyway. And to think you can just because you have a preturbo guage is nonsense, to me. I can tell you that I know many, many people here that run post-turbo guages with great responses, and NO RISK! Versus some risk, no matter how you surgar coat it, if you run preturbo. It doesnt mean you can't run preturbo and minimize your risk, as you have pointed out. But it does mean there is risk. If I were to run a preturbo guage, I would think with the reduced opening (10% i am guessing, but I can calculate that to be exact) and RISK of reduced airflow, you have to run slightly, even 50* cooler, than post-turbo, just to mitigate those risks and damages. I am an advocate of post-turbo because that is exactly what Cummins says use. In response to the "depends on your torque range" this holds true even with pre-turbo. The difference is that Cummins spec'd it out whereas everyone else says just go with this number at all levels. A probe doesnt know if it is post or pre-turbo, it only knows the heat, doesnt care where it comes from.
V/R
Steve
V/R
Steve
10-29-2007, 03:06 PM
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I talked to the shop that installed mine before I dropped off the truck and I told them of my concerns with this; they said they used a reverse tapping drill making the larger shavings go outward and then went over the area with a magnet and vacuum...this was just how they did the installations for their customers...
10-29-2007, 03:27 PM
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Sorry to open such a huge debate, but it's been very educational. I'm going to put it post turbo, and keep it under 1000, everything should be ok. Thanks everyone for the help. Rollin
10-29-2007, 03:39 PM
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Steve--
I can see your points, and they are valid. We have to be careful in staying on topic. On one hand we have people saying what safe EGTs are based on anecdotal evidence and then we have people talking about what Cummins says-- these are different things.
As for risk, it's not zero, but it's perfectly acceptable. I accepted more risk riding my bicycle to work today. The number of pre-turbo probe failures is statistically insignificant. Not zero, just not common enough to be considered.
I initially installed my probe in the cast elbow after the turbo (POST turbo). I could never get the EGT over 900 unless towing and pulling a steady hill. Typical values were 450 on the hwy and about 800 WOT.
Based on other member's success with a pre-turbo placement (and the dearth of reported problems) I moved it to pre-turbo and plugged the post-turbo location.
The results were interesting. First, the pyro now responded much faster. The needle now moved quickly instead of crawling up and down. Second, I observed a variable temperature increase of as little as 150° to as much as 500°. So we can see that there's no "rule of thumb" for temp difference between post and pre turbo locations worth considering.
The reason the temp difference can vary so much is that the turbine will convert exhaust energy to work, and the more work it's doing, the more heat it's converting to work. In other words, as the boost levels climb, the difference between pre-turbo and post-turbo temperatures increases.
Commercial rigs use post-turbo probes because they engines are mildly tuned and the concern is primarily turbo shutdown since the engines are prone to long runs of high heat. Because the TURBO is what is primarily being monitored, the probe is located after it.
But in a performance CTD application that is much more aggressively tuned, we are more concerned with the ENGINE itself, not the turbocharger. We will be pulling shorter blasts of more severe usage, unlike the previous commercial-usage example.
People on here aren't recommending 1600° EGT limits, just saying that they have been done safely. Remember, it's not TEMP that melts things, it's HEAT. You can run your finger briefly through a 500° flame and not get burned, but if you dip that hand in 200° water, you're gonna get a bad burn. The difference is the amount of HEAT your skin absorbed versus the temp of the heat source it was exposed to.
A consideration here is time. Heat transfer takes time. So it's not JUST how hot something is, it's how long we are exposed to it. For example, you can die of hypothermia in 80° water if you are floating out in the ocean. Just a measly 17°-19°, but it will kill you given enough time.
So the pivotal question is how much heat it takes before I endanger something at risk. The most vulnerable component isn't the cast iron block or head, or the steel valves or the inconel turbine wheel. It's the aluminum piston. So we should be concerned with PISTON temps. Piston temps are related to EGT, but only loosely. The actual temp of the pistons depends not only on EGT but also on timing, total HP production, and many other variables.
Give me an engine with radically advanced timing, and I can melt a piston with "safe" EGTs quite easily, as the member on the other thread has discovered. Under the conditions that melted this piston, the EGT would appear even "safer" if monitored AFTER the turbo.
Even if you had an endless supply of perfectly cool boost and could keep tons of fuel at low EGT, piston temps will still go up as total power production goes up. Even if you are completely burning all that fuel, it's still a bigger bang dumping more heat into the pistons.
Higher compression ratios help lower piston operating temps as well as EGTs, all else being equal.(if a person can't see how this is true, let me know and I'll explain)
So we can see that if a person tows heavy loads regularly with a stock or mildly tuned truck, a post-turbo probe may be more appropriate for their application.
But for a more aggressively tuned truck (like mine) where you are overfueled, a pre-turbo pyro is a much more appropriate (and SAFER) choice. After all, the odds of probe failure are much lower than the odds of piston failure when severely overfueled.
Questions, comments, counterpoints welcomed.
Justin
I can see your points, and they are valid. We have to be careful in staying on topic. On one hand we have people saying what safe EGTs are based on anecdotal evidence and then we have people talking about what Cummins says-- these are different things.
As for risk, it's not zero, but it's perfectly acceptable. I accepted more risk riding my bicycle to work today. The number of pre-turbo probe failures is statistically insignificant. Not zero, just not common enough to be considered.
I initially installed my probe in the cast elbow after the turbo (POST turbo). I could never get the EGT over 900 unless towing and pulling a steady hill. Typical values were 450 on the hwy and about 800 WOT.
Based on other member's success with a pre-turbo placement (and the dearth of reported problems) I moved it to pre-turbo and plugged the post-turbo location.
The results were interesting. First, the pyro now responded much faster. The needle now moved quickly instead of crawling up and down. Second, I observed a variable temperature increase of as little as 150° to as much as 500°. So we can see that there's no "rule of thumb" for temp difference between post and pre turbo locations worth considering.
The reason the temp difference can vary so much is that the turbine will convert exhaust energy to work, and the more work it's doing, the more heat it's converting to work. In other words, as the boost levels climb, the difference between pre-turbo and post-turbo temperatures increases.
Commercial rigs use post-turbo probes because they engines are mildly tuned and the concern is primarily turbo shutdown since the engines are prone to long runs of high heat. Because the TURBO is what is primarily being monitored, the probe is located after it.
But in a performance CTD application that is much more aggressively tuned, we are more concerned with the ENGINE itself, not the turbocharger. We will be pulling shorter blasts of more severe usage, unlike the previous commercial-usage example.
People on here aren't recommending 1600° EGT limits, just saying that they have been done safely. Remember, it's not TEMP that melts things, it's HEAT. You can run your finger briefly through a 500° flame and not get burned, but if you dip that hand in 200° water, you're gonna get a bad burn. The difference is the amount of HEAT your skin absorbed versus the temp of the heat source it was exposed to.
A consideration here is time. Heat transfer takes time. So it's not JUST how hot something is, it's how long we are exposed to it. For example, you can die of hypothermia in 80° water if you are floating out in the ocean. Just a measly 17°-19°, but it will kill you given enough time.
So the pivotal question is how much heat it takes before I endanger something at risk. The most vulnerable component isn't the cast iron block or head, or the steel valves or the inconel turbine wheel. It's the aluminum piston. So we should be concerned with PISTON temps. Piston temps are related to EGT, but only loosely. The actual temp of the pistons depends not only on EGT but also on timing, total HP production, and many other variables.
Give me an engine with radically advanced timing, and I can melt a piston with "safe" EGTs quite easily, as the member on the other thread has discovered. Under the conditions that melted this piston, the EGT would appear even "safer" if monitored AFTER the turbo.
Even if you had an endless supply of perfectly cool boost and could keep tons of fuel at low EGT, piston temps will still go up as total power production goes up. Even if you are completely burning all that fuel, it's still a bigger bang dumping more heat into the pistons.
Higher compression ratios help lower piston operating temps as well as EGTs, all else being equal.(if a person can't see how this is true, let me know and I'll explain)
So we can see that if a person tows heavy loads regularly with a stock or mildly tuned truck, a post-turbo probe may be more appropriate for their application.
But for a more aggressively tuned truck (like mine) where you are overfueled, a pre-turbo pyro is a much more appropriate (and SAFER) choice. After all, the odds of probe failure are much lower than the odds of piston failure when severely overfueled.
Questions, comments, counterpoints welcomed.
Justin
10-29-2007, 03:58 PM
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Hohn:
First that is a great reply. You obviously have taken the discussion to a more accurate and detailed position. And I agree and understand the engineering you are discussing. However, (there always is one), like you said, if you run an agressively tuned motor, you can burn it up even when the pre or post turbo pyro says you are okay. When you get to that extreme of engineering, your pyro is no good anyway. So now you have gone from needing it post or pre turbo to not needing one at all. Your limit is determined by your own knowledge, not by a gauge, and most people dont have that sort of knowledge. I am only saying that putting a guage post turbo and running the EGTs within the range determined to be acceptable to the engine (regardless of mods, after all, parts don't know if you are modified or not, they only know tolerance levels of their respective materials), you will not gain what i believe to be a greatly enhanced benefit to run the pyro pre turbo aside from getting to see the needle move faster and farther. We all have friends that run their trucks with lots of mods and pre and post turbo. The only difference from my perspective is if you run it pre-turbo you assume a certain level of risk in installation and in operation. That level of risk, like you point out, is very minimal in some cases, and with a lack of experience or education, greater in other cases - such as shavings in turbo by misinstallation.
If I moved my pyro to preturbo, i would see greater response and higher temps more accurate to the piston. But it would not help my operation one bit. I already run what I run and it would not limit me more so and it would also not give me more room to go. If I ran the motor hotter, i am kidding myself about reliability, and it certainly is not going to run cooler (after recalculating for pre versus post turbo numbers).
I actually had a friend of mine say something very interesting once. He said, "pyro gauges are worthless". In hind sight, he maybe right with a reasonable tuned engine. He has a plate, intake, exhaust and Injectors. And he laughs when he is asked what his pyro numbers are. He said he used to watch them all the time for a couple of years. Then he realized he had no reason unless the vehicle started acting weird. It then became a diagnostic tool rather than a safety tool. I am more and more starting to agree with that. I guess the exception would be drag racers, but then again, like you said, a badly tuned or very agressively tuned engine will blow up anyway and the guage becomes useless, kind of like my friends said.
Hey, you did a great write up. Very intelligible.
Thanks,
V/R
Steve
First that is a great reply. You obviously have taken the discussion to a more accurate and detailed position. And I agree and understand the engineering you are discussing. However, (there always is one), like you said, if you run an agressively tuned motor, you can burn it up even when the pre or post turbo pyro says you are okay. When you get to that extreme of engineering, your pyro is no good anyway. So now you have gone from needing it post or pre turbo to not needing one at all. Your limit is determined by your own knowledge, not by a gauge, and most people dont have that sort of knowledge. I am only saying that putting a guage post turbo and running the EGTs within the range determined to be acceptable to the engine (regardless of mods, after all, parts don't know if you are modified or not, they only know tolerance levels of their respective materials), you will not gain what i believe to be a greatly enhanced benefit to run the pyro pre turbo aside from getting to see the needle move faster and farther. We all have friends that run their trucks with lots of mods and pre and post turbo. The only difference from my perspective is if you run it pre-turbo you assume a certain level of risk in installation and in operation. That level of risk, like you point out, is very minimal in some cases, and with a lack of experience or education, greater in other cases - such as shavings in turbo by misinstallation.
If I moved my pyro to preturbo, i would see greater response and higher temps more accurate to the piston. But it would not help my operation one bit. I already run what I run and it would not limit me more so and it would also not give me more room to go. If I ran the motor hotter, i am kidding myself about reliability, and it certainly is not going to run cooler (after recalculating for pre versus post turbo numbers).
I actually had a friend of mine say something very interesting once. He said, "pyro gauges are worthless". In hind sight, he maybe right with a reasonable tuned engine. He has a plate, intake, exhaust and Injectors. And he laughs when he is asked what his pyro numbers are. He said he used to watch them all the time for a couple of years. Then he realized he had no reason unless the vehicle started acting weird. It then became a diagnostic tool rather than a safety tool. I am more and more starting to agree with that. I guess the exception would be drag racers, but then again, like you said, a badly tuned or very agressively tuned engine will blow up anyway and the guage becomes useless, kind of like my friends said.
Hey, you did a great write up. Very intelligible.
Thanks,
V/R
Steve
10-29-2007, 04:18 PM
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The member who lost the piston was running excessive timing that I can't see being duplicated on a computerized CTD (12V= all mechanical, static timing).
A pre-turbo pyro wouldn't help your application because you are running modest amounts of fuel. I think a post-turbo pyro for you would work just fine.
Aggressively tuned engines aren't necessarily ticking time bombs. There are smart ways and dumb ways to operate the same engine, with corresponding consequences.
An interesting factoid that's counterintuitive: bore wear actually goes DOWN with piston operating temperature. Right up to the point where the piston actually seizes in the bore from having all the clearance taken up. That's why you often see that the longest lasting CTD engines are the ones that have been hitched to a trailer. The higher piston temps and greater load actually improve engine life as the pistons run a little tighter in their bores.
The interesting conclusion here is that a mildy more aggressively tuned truck with warmer running pistons can actually have LESS wear in the bores than a stock truck. Obviously, there are limits to this.
The Cummins specs for engine clearance assume that the engine is being worked and loaded, and a little more engine load can actually be a good thing.
Justin
A pre-turbo pyro wouldn't help your application because you are running modest amounts of fuel. I think a post-turbo pyro for you would work just fine.
Aggressively tuned engines aren't necessarily ticking time bombs. There are smart ways and dumb ways to operate the same engine, with corresponding consequences.
An interesting factoid that's counterintuitive: bore wear actually goes DOWN with piston operating temperature. Right up to the point where the piston actually seizes in the bore from having all the clearance taken up. That's why you often see that the longest lasting CTD engines are the ones that have been hitched to a trailer. The higher piston temps and greater load actually improve engine life as the pistons run a little tighter in their bores.
The interesting conclusion here is that a mildy more aggressively tuned truck with warmer running pistons can actually have LESS wear in the bores than a stock truck. Obviously, there are limits to this.
The Cummins specs for engine clearance assume that the engine is being worked and loaded, and a little more engine load can actually be a good thing.
Justin
10-29-2007, 04:28 PM
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HOHN I think this thread needs some of your super advice regarding egt's
https://www.dieseltruckresource.com/...d.php?t=175657
https://www.dieseltruckresource.com/...d.php?t=175657
10-29-2007, 08:56 PM
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Steven,
If you like post turbo, that's fine. Sounds like you know enough to watch your engine anyway. I think an EGT gauge is like any other gauge - most of the time, you don't need to look at it, but it is useful to have. A fuel gauge is of use because you can help predict when you will run out of fuel. An oil pressure gauge is of use because you can tell when your engine has insufficient oil pressure, and thus insufficient lubrication, and can hopefully shutdown before large $ damage occurs. An air reservoir pressure gauge helps a commercial trucker know his air system is functioning, and that he'll be able to stop his rig...
An EGT gauge can help prevent you from running the engine in danger areas. The danger on our engines is primarily the temperature pre-turbo hurting pre-turbo parts, so I favour a pre-turbo EGT gauge. My probe is relatively small, and I can't possibly imagine it is actually taking 10% of the area in the manifold passage, but I don't know how much space your probe might take. I'm quite confident mine doesn't go that far into the manifold - although I don't know how far exactly - in any event, length X width/diameter is relatively small in mine.
There are risks both ways... post turbo generally is associated with the risk of having less information (lower quality information).
But, either way, I'd argue it is still better than no EGT gauge. And I don't care to try to push my truck to 1600oF. Hell, it's been 4 years and I haven't even plated it yet...
If you like post turbo, that's fine. Sounds like you know enough to watch your engine anyway. I think an EGT gauge is like any other gauge - most of the time, you don't need to look at it, but it is useful to have. A fuel gauge is of use because you can help predict when you will run out of fuel. An oil pressure gauge is of use because you can tell when your engine has insufficient oil pressure, and thus insufficient lubrication, and can hopefully shutdown before large $ damage occurs. An air reservoir pressure gauge helps a commercial trucker know his air system is functioning, and that he'll be able to stop his rig...
An EGT gauge can help prevent you from running the engine in danger areas. The danger on our engines is primarily the temperature pre-turbo hurting pre-turbo parts, so I favour a pre-turbo EGT gauge. My probe is relatively small, and I can't possibly imagine it is actually taking 10% of the area in the manifold passage, but I don't know how much space your probe might take. I'm quite confident mine doesn't go that far into the manifold - although I don't know how far exactly - in any event, length X width/diameter is relatively small in mine.
There are risks both ways... post turbo generally is associated with the risk of having less information (lower quality information).
But, either way, I'd argue it is still better than no EGT gauge. And I don't care to try to push my truck to 1600oF. Hell, it's been 4 years and I haven't even plated it yet...
10-29-2007, 09:53 PM
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When you go PRE turbo you are still only guessing as to what the temp of the important parts are. I feel strongly that Pre is the way to go, but it is NOT a "piston temp guage".
After all, we don't really care about the the EGTs-- we care about the temps of the metal parts that can melt or fail. We hope and pray that EGTs correlate closely enough to draw meaningful conclusions. If not, I doubt Cummins would quote EGT specs either pre or post turbo.
JMO
After all, we don't really care about the the EGTs-- we care about the temps of the metal parts that can melt or fail. We hope and pray that EGTs correlate closely enough to draw meaningful conclusions. If not, I doubt Cummins would quote EGT specs either pre or post turbo.
JMO