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+--- Thread: Exhaust manifold temperature...clarification please (/showthread.php?tid=1773)
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Exhaust manifold temperature...clarification please - JMBT - 05-19-2017
So, I am watching my exhaust manifold temp gauge like a hawk while climbing. With a typical load, not super heavy or super light, on the big TX hills, and its 96 degrees outiside today, I can either:
A) Hold my speed steady to the top with no gear drop, at top temp is about 930, as I back out of it, and kick on my manual fan switch to cool down.
B) Hold top gear until RPM's drop off a bit then hit my fan switch and grab a lower gear. I'll top the hill about 8 mph off my starting speed, and temps about 830- 850
C) Flip manual fan switch at bottom, drop gears and speed in succession, to keep manifold temp gauge in the 700's and RPM's high.
So, conventional wisdom says the cooler the exhaust temp the better on the engine right? However, I have also seen on posts where it was stated that in a high torque application, if manifold temp is too low too much heat may be staying in cylinders, and damaging them?? Did I read that correct? Just trying to figure out how best to run the motor that will extend the life as much as possible. Any help will be appreciated! Thanks.
RE: Exhaust manifold temperature...clarification please - Pete379 - 05-19-2017
I'm not sure what your particular set up is but i measure both manifold temp(clamped on like Rawze shows in his guage install video) and post turbo inside exhaust pipe. A cm870 with hx60 turbo and member tuned to around 675 at the wheels I believe and even running fully loaded up a 20 mile incline running hard(65-70) I have never seen outside manifold temp that high.. I think I hit 750 possibly on the manifold in 92 degree temps and ac on today but that's ma and would have only been for a moment or two before it starts dropping again.
It's my experience that temps that high would be caused by a boost leak or air restriction somewhere but to your question i don't think by the numbers that you posted that you need to worry about heat staying inside the cylinders but should concentrate more on keeping the heat soak down...
I'm sure there are others on here that are more knowledgable in this particular area but I hope this helps you get the answer you are looking for
RE: Exhaust manifold temperature...clarification please - Rig Wrench - 05-19-2017
(05-19-2017 )JMBT Wrote: So, I am watching my exhaust manifold temp gauge like a hawk while climbing. With a typical load, not super heavy or super light, on the big TX hills, and its 96 degrees outiside today, I can either:
A) Hold my speed steady to the top with no gear drop, at top temp is about 930, as I back out of it, and kick on my manual fan switch to cool down.
B) Hold top gear until RPM's drop off a bit then hit my fan switch and grab a lower gear. I'll top the hill about 8 mph off my starting speed, and temps about 830- 850
C) Flip manual fan switch at bottom, drop gears and speed in succession, to keep manifold temp gauge in the 700's and RPM's high.
So, conventional wisdom says the cooler the exhaust temp the better on the engine right? However, I have also seen on posts where it was stated that in a high torque application, if manifold temp is too low too much heat may be staying in cylinders, and damaging them?? Did I read that correct? Just trying to figure out how best to run the motor that will extend the life as much as possible. Any help will be appreciated! Thanks.
Sound ok post turbo in the pipe. On the manifold I'm not soo sure. If your a lower gear, using less pedal, the lower temps are fine. It's when your buried in the throttle and it stays too low that problems arise
RE: Exhaust manifold temperature...clarification please - JMBT - 05-19-2017
Ok, so buried in the throttle, if the temps stay low is when the damage occurs! Thanks for the clarification, that was the piece of the puzzle I was missing!
RE: Exhaust manifold temperature...clarification please - Mrkentee - 05-19-2017
(05-19-2017 )JMBT Wrote: So, I am watching my exhaust manifold temp gauge like a hawk while climbing. With a typical load, not super heavy or super light, on the big TX hills, and its 96 degrees outiside today, I can either:
A) Hold my speed steady to the top with no gear drop, at top temp is about 930, as I back out of it, and kick on my manual fan switch to cool down.
B) Hold top gear until RPM's drop off a bit then hit my fan switch and grab a lower gear. I'll top the hill about 8 mph off my starting speed, and temps about 830- 850
C) Flip manual fan switch at bottom, drop gears and speed in succession, to keep manifold temp gauge in the 700's and RPM's high.
So, conventional wisdom says the cooler the exhaust temp the better on the engine right? However, I have also seen on posts where it was stated that in a high torque application, if manifold temp is too low too much heat may be staying in cylinders, and damaging them?? Did I read that correct? Just trying to figure out how best to run the motor that will extend the life as much as possible. Any help will be appreciated! Thanks.
I pick 'C', except for the fan. I only use it if I have to. Those numbers sound like mine. But I've barely ever been over 800, by using my foot and rpm. 20 lbs of boost, rpm above 1300, manifold temp in the lower 7's (if possible) and take whatever speed you get, depending on the grade.
Of course, hammering up the hill is fun, but not worth it.
RE: Exhaust manifold temperature...clarification please - Old Driver - 05-19-2017
I'll climb cabbage and not using fan keep my temp heat soak at 650ish. 700 is very high for me and I'm always 80000 pounds. Oil can get up to 235 maybe 239. Turbo I keep about 13 psi maybe 15 psi if I'm in a hurry. Coolant can sometimes get up to 205.
This is on a day when it's about 55 - 60 degrees out.
RE: Exhaust manifold temperature...clarification please - Rawze - 05-19-2017
(05-19-2017 )JMBT Wrote: ...
I have also seen on posts where it was stated that in a high torque application, if manifold temp is too low too much heat may be staying in cylinders, and damaging them??
...
You have comepletely mis-understood something there very badly!
===
What you have read was a discussion on what a custom tuner would look for when testing a truck -- AND HAS NOTHING WHATSOEVER ANYTHING TO DO WITH WHAT YOU LOOK FOR WHILE DRIVING IT!!!
if someone is adjusting parameters like boost, timing, fueling, etc... and they see too low of exhaust temps when its making 600-hp output,.. that is a bad sign of possible detonation.
---
How you drive the truck and where you keep your pyro temps during a hill climb if it has been set correctly has nothing whatsoever do do with that conversation !!!!!!
========
For driving it ---- Always keep pyro and boost as low as necessary to perform the task at hand with whatever method you have come up with. It is as simple at that. So, whatever trick or method you use, the lower the overall pyro temps and boost pressure you can maintain while performing a task, the less energy you are using and the more efficient the operation is. It has nothing whatsoever to do with pressing your foot down harder to make your pyro go up because it makes you feel better. -- Less temps and less boost = less strain on the equipment !!!! -- Energy in = energy out, and the higher you keep temps and boost etc... The more strain on your engine while driving it! --- It is as simple as that!!!
Don't try to over-complicate things. --- Your brain has somehow confused tuning discussions with driving habits. You have cross-wired some tuning info with how you are trying to drive it and that is incorrect. It is like trying to take someone's conversation about apples and apply it to potatoes! -- separate the 2 and it becomes more clear.
RE: Exhaust manifold temperature...clarification please - JMBT - 05-19-2017
Thanks all who responded! I feel I have a better understanding of the exhaust manifold temp now. Much appreciated!!
I had a teacher & coach one time tell me, "there are no stupid questions, just people who remain ignorant on a given subject if they don't ask the questions" -r.i.p. Coach
RE: Exhaust manifold temperature...clarification please - Rawze - 05-19-2017
(05-19-2017 )JMBT Wrote: So, I am watching my exhaust manifold temp gauge like a hawk while climbing. With a typical load, not super heavy or super light, on the big TX hills, and its 96 degrees outiside today, I can either:
A) Hold my speed steady to the top with no gear drop, at top temp is about 930, as I back out of it, and kick on my manual fan switch to cool down.
B) Hold top gear until RPM's drop off a bit then hit my fan switch and grab a lower gear. I'll top the hill about 8 mph off my starting speed, and temps about 830- 850
C) Flip manual fan switch at bottom, drop gears and speed in succession, to keep manifold temp gauge in the 700's and RPM's high.
I do none of the above. My truck gets 8+ mpg, even when loaded 80,000 lbs gross for a reason.
I drive by my boost gauge and never let it go above about 12-lbs boost or so. When i get to a hill, I down-shift early and climb it in the gear that allows me to keep boost low and a steady slow speed with 1600 RPM or so. -- If the hill is big enough for the pyro to start to get to 900+, I kick the engine fan on and keep going. -- I always let the super-truckers pass me, let them tear up and wear out their equipment,.. I am in it for sheer long term profit I can keep, and not have to use to fix my truck with all the damn time.