Pyro probe location
06-04-2004, 06:43 PM
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Pyro probe location
I know how every thread on this topic says to mount the probe before the turbo. This raises a few questions in my mind.
1 Which 3 cylinders do you monitor? what about the other 3?
2 Why does EVERY Cummins manual say to put it in the turbo exit pipe within 6 inches of the turbo? Why is it there when done at the factory?
I have two trucks, one was before, now both after.
Flame away!
1 Which 3 cylinders do you monitor? what about the other 3?
2 Why does EVERY Cummins manual say to put it in the turbo exit pipe within 6 inches of the turbo? Why is it there when done at the factory?
I have two trucks, one was before, now both after.
Flame away!
06-04-2004, 09:28 PM
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no flame- but this has been run into the ground b4.......so the short ans. is b4 the turbo- it gives you a much more accurate reading NOW, and it is the law of avgs- as far as what the the cyl. are doing.......they can"t be doing much more or less if the eng. is running 1/2 way right.
As a side pt so far i have not herd of anyones probe letting loose and going thrue the turbo as of yet-it usd to be a concern.
As a side pt so far i have not herd of anyones probe letting loose and going thrue the turbo as of yet-it usd to be a concern.
06-05-2004, 12:05 AM
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This one has been hashed out a bit before, but let me try to answer your questions.
First, the most calss 8 rigs have a post-turbo location because they are worried more about monitoring the turbo than EGTs. Also, class 8 rigs tend to be either loafing or wide open, so it's easier to use a post-turbo location then. Finally, some of the early probes were known to occasionally take out the turbo when the fell iN!
Pre is now the way to go. The thinking is that you want to measure EGT as soon as you can to minimize the cooling effect of the manifolding. Heck, if you wanted to play it really safe, just put the pyro in #6 exhaust since that cylinder runs the hottest.
I had my pyro in the post-turbo location for a little while, then moved it. The results were radically different. With the post-location, the needle was very slow to move; while the pre location made the gauge VERY responsive. Also, there is no set difference-- i noted sometimes it was less then 100 degrees-- other times is was OVER 500 DEGREES! That's enough of a difference to mislead you and cause a meltdown when you think you're safe!
Don't be afraid to go PRE--- you can see a picture of the proper location (imho) in my member's photo gallery. I monitor cylinders 4,5,&6, since they run a little hotter.
Justin
First, the most calss 8 rigs have a post-turbo location because they are worried more about monitoring the turbo than EGTs. Also, class 8 rigs tend to be either loafing or wide open, so it's easier to use a post-turbo location then. Finally, some of the early probes were known to occasionally take out the turbo when the fell iN!
Pre is now the way to go. The thinking is that you want to measure EGT as soon as you can to minimize the cooling effect of the manifolding. Heck, if you wanted to play it really safe, just put the pyro in #6 exhaust since that cylinder runs the hottest.
I had my pyro in the post-turbo location for a little while, then moved it. The results were radically different. With the post-location, the needle was very slow to move; while the pre location made the gauge VERY responsive. Also, there is no set difference-- i noted sometimes it was less then 100 degrees-- other times is was OVER 500 DEGREES! That's enough of a difference to mislead you and cause a meltdown when you think you're safe!
Don't be afraid to go PRE--- you can see a picture of the proper location (imho) in my member's photo gallery. I monitor cylinders 4,5,&6, since they run a little hotter.
Justin
06-05-2004, 12:19 AM
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This one has been hashed out a bit before, but let me try to answer your questions.
First, the most calss 8 rigs have a post-turbo location because they are worried more about monitoring the turbo than EGTs. Also, class 8 rigs tend to be either loafing or wide open, so it's easier to use a post-turbo location then. Finally, some of the early probes were known to occasionally take out the turbo when the fell iN!
Pre is now the way to go. The thinking is that you want to measure EGT as soon as you can to minimize the cooling effect of the manifolding. Heck, if you wanted to play it really safe, just put the pyro in #6 exhaust since that cylinder runs the hottest.
I had my pyro in the post-turbo location for a little while, then moved it. The results were radically different. With the post-location, the needle was very slow to move; while the pre location made the gauge VERY responsive. Also, there is no set difference-- i noted sometimes it was less then 100 degrees-- other times is was OVER 500 DEGREES! That's enough of a difference to mislead you and cause a meltdown when you think you're safe!
Don't be afraid to go PRE--- you can see a picture of the proper location (imho) in my member's photo gallery. I monitor cylinders 4,5,&6, since they run a little hotter.
Justin
First, the most calss 8 rigs have a post-turbo location because they are worried more about monitoring the turbo than EGTs. Also, class 8 rigs tend to be either loafing or wide open, so it's easier to use a post-turbo location then. Finally, some of the early probes were known to occasionally take out the turbo when the fell iN!
Pre is now the way to go. The thinking is that you want to measure EGT as soon as you can to minimize the cooling effect of the manifolding. Heck, if you wanted to play it really safe, just put the pyro in #6 exhaust since that cylinder runs the hottest.
I had my pyro in the post-turbo location for a little while, then moved it. The results were radically different. With the post-location, the needle was very slow to move; while the pre location made the gauge VERY responsive. Also, there is no set difference-- i noted sometimes it was less then 100 degrees-- other times is was OVER 500 DEGREES! That's enough of a difference to mislead you and cause a meltdown when you think you're safe!
Don't be afraid to go PRE--- you can see a picture of the proper location (imho) in my member's photo gallery. I monitor cylinders 4,5,&6, since they run a little hotter.
Justin
06-11-2004, 09:50 PM
#5
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pyro
I work for freightliner tmp ,and every truck that we build with a pyro is on the turbo down pipe. 1 it is alot easier to put it there as far as drilling etc. 2 the temp difference between manifold & down pipe is not that great. If it was I am sure that these trucking companies would it moved. These truck take alot more abuse than what we are driving. Just my 2cents.
06-11-2004, 10:42 PM
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Re: pyro
Originally posted by ftltmp
I work for freightliner tmp ,and every truck that we build with a pyro is on the turbo down pipe. 1 it is alot easier to put it there as far as drilling etc. 2 the temp difference between manifold & down pipe is not that great. If it was I am sure that these trucking companies would it moved. These truck take alot more abuse than what we are driving. Just my 2cents.
I work for freightliner tmp ,and every truck that we build with a pyro is on the turbo down pipe. 1 it is alot easier to put it there as far as drilling etc. 2 the temp difference between manifold & down pipe is not that great. If it was I am sure that these trucking companies would it moved. These truck take alot more abuse than what we are driving. Just my 2cents.
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06-12-2004, 04:26 AM
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I can confirm this. I USED to run it in the post-turbo location. I have seen anywhere from 100 to 550° difference!! I'd say the "temp difference between the two CAN BE quite substantial."
NONE of the CTD performance vendors recommends going with a post-pyro location.
If you want to base your readings (and the health of your engine) on the apples-to-oranges comparisons to big rigs, and IGNORE th advice of the most knowledgeable Dodge Diesel Vendors-- fine.
But I wouldn't recommend it.
Justin
NONE of the CTD performance vendors recommends going with a post-pyro location.
If you want to base your readings (and the health of your engine) on the apples-to-oranges comparisons to big rigs, and IGNORE th advice of the most knowledgeable Dodge Diesel Vendors-- fine.
But I wouldn't recommend it.
Justin
06-12-2004, 06:22 AM
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So i am to ignore what the creator of my engine says to listen to what the aftermarketeers are saying? You dont think Cummins knows what the temperature difference is between the two locations? Get any Cummins manual and read for yourself, they want probes within 6 inches of turbo exit.
Got napalm?
Got napalm?
06-12-2004, 08:27 AM
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remember also that the creator of the engine doesn't intend on having their motor modified ...
they have the fuel system designed to specific standards, as far as they are concerned the post location is sufficient because they have already experimented to achieve the temps they feel ar neccassary ...
when we modify our fuel delivery then the factory specs go out the window ...
put it post .... modify and let the rest of us know how it works out
the FAA allows them to be installed pre in planes ...
put it where you want it ... you'll be the one that has to live with the consequences ... i've read dozens of posts from people who have regretted putting it post ... none who have regretted pre
good luck
they have the fuel system designed to specific standards, as far as they are concerned the post location is sufficient because they have already experimented to achieve the temps they feel ar neccassary ...
when we modify our fuel delivery then the factory specs go out the window ...
put it post .... modify and let the rest of us know how it works out
the FAA allows them to be installed pre in planes ...
put it where you want it ... you'll be the one that has to live with the consequences ... i've read dozens of posts from people who have regretted putting it post ... none who have regretted pre
good luck
06-12-2004, 10:23 AM
#11
I had mine post turbo for quite awile and just recently moved it pre. I had my "alarm" set for 850 on my gauge when it was post. The temp does come up quicker with it in the pre location, but judging from the readings I was doing fine with my pulling habits using the 800-850 rule for the post pyro reading.
06-12-2004, 09:31 PM
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I live in the shadow of the Cummins empire (Columbus In). There is no shortage of engineers around here. I run around with Test cell technicians. My buddy is a plant manager. The guy that wrenches on my trucks wrote service manuals for Cummins untill he retired. All that I have spoken to agree with the post application no matter what the engine, in whatever the application and no matter how much fuel etc. . I will not run mine pre turbo due to all the info straight from the mother Cummins. They all agree that I am safe to 1000f with a post probe. I guess if it goes to hell in a handbasket someday I will rally up the troops to fix it .
Maybee someday I can be one of those Test subjects.
Why do you want your pyro to dance like a boost gage?
Maybee someday I can be one of those Test subjects.
Why do you want your pyro to dance like a boost gage?
06-12-2004, 09:50 PM
#13
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I have worked in technical management capacities for over 30 years in the employ of a manufacturer of industrial engines (natural gas, diesel and dual-fuel), gas turbines, reciprocating and centrifugal compressors and turbochargers. The standard for larger industrial engines is to have a type K thermocouple in the exhaust elbow of each cylinder as well as a pre-turbo thermocouple. In addition, some of our engines also measure individual cylinder head combustion chamber deck temperatures. Unless the customer is doing thumbnail turbocharger performance calculations or is concerned with exhaust gas temperature entering downstream equipment (e.g., waste heat boiler or catalytic converter), we don't even provide a post-turbo thermocouple. The critical performance limiting factor on gas turbines is turbine inlet, NOT turbine outlet temperature.
As others have said, the recommendation to run post-turbo is based on the assumption that the fueling system has not been modified and therefore cannot generate dangerous cylinder or pre-turbo temperatures. That assumption is no longer valid for BOMBed trucks - we can seriously damage the engine (read, holed pistons or scuffed pistons/cylinders) if we don't monitor what's going on as closely to the power cylinder as possible when we're dragging our 13,500 lb 5th wheel RV up that 5 mile 7% grade. My EGT is measured pre-turbo. You can measure yours at the exhaust tip at the rear of the truck if you wish - it's your truck and your money.
Rusty
As others have said, the recommendation to run post-turbo is based on the assumption that the fueling system has not been modified and therefore cannot generate dangerous cylinder or pre-turbo temperatures. That assumption is no longer valid for BOMBed trucks - we can seriously damage the engine (read, holed pistons or scuffed pistons/cylinders) if we don't monitor what's going on as closely to the power cylinder as possible when we're dragging our 13,500 lb 5th wheel RV up that 5 mile 7% grade. My EGT is measured pre-turbo. You can measure yours at the exhaust tip at the rear of the truck if you wish - it's your truck and your money.
Rusty
06-12-2004, 10:00 PM
#14
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i will say this as nice as possible, there are countless trucks on the road with the pyro on the down pipe after the turbo towing 80,000# with million miles or better some dont even have pyros in them, you do the math.
06-12-2004, 10:12 PM
#15
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And I'll say this again. How many of them are running 50% to 80% or more above the OEM's stock BHP like my truck is while towing at their GCWR? A heavily BOMBed truck has different requirements. Additional fuel = additional heat. That additional heat has to be monitored and compensated for (i.e., knowing when to lift the right foot) if engine damage is to be avoided.
Rusty
Rusty