Why don't my EGTs decrease when downshifting?
Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,458
Likes: 156
From: Sedalia, CO
Why don't my EGTs decrease when downshifting?
One of the general recommendations to reduce EGT's, particularly when towing, is to downshift. When I do that in the rig described in my signature, rpms obviously go up, boost increases, but EGTs either stay put on continue climbing, as if no downshift occurred. Why is that?
I've got bellowed up pipes and no discernible exhaust leaks, and no discernible boost leaks (can hit 25psi, which I think is about where my Turbo-Master wastegate controller is set). When Jody live-tuned my truck he noticed the issue, and mentioned that he'd seen it in one other truck, but didn't know if the owner had figured out why.
Any ideas? I'd love to figure this out, as it would greatly increase my ability to get up the passes around here.
Mark
I've got bellowed up pipes and no discernible exhaust leaks, and no discernible boost leaks (can hit 25psi, which I think is about where my Turbo-Master wastegate controller is set). When Jody live-tuned my truck he noticed the issue, and mentioned that he'd seen it in one other truck, but didn't know if the owner had figured out why.
Any ideas? I'd love to figure this out, as it would greatly increase my ability to get up the passes around here.
Mark
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
If you don't downshift, do temps keep rising?
Downshifting won't always reduce EGT's, but it can keep them from continuing to rise higher and higher, especially at high altitude.
For instance, if you make the exact same run twice - once with downshifting, and once without - and compare the end results for EGT's, which one ends up being higher?
Downshifting won't always reduce EGT's, but it can keep them from continuing to rise higher and higher, especially at high altitude.
For instance, if you make the exact same run twice - once with downshifting, and once without - and compare the end results for EGT's, which one ends up being higher?
Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,458
Likes: 156
From: Sedalia, CO
Hi Curtis. I was hoping you'd chime in...
Yes, they do. This thing has always run hotter EGTs than some of my friend's rigs, but they are all trucks and perhaps a little lighter. I can go well past 1400 when towing if I don't back out, and this is true whether it stays in OD, downshifts on it's own, or if I downshift manually.
My expectation, and perhaps you can tell me if it's realistic, is that a downshift to 3rd should generally stop the rise of EGTs, if not reduce them some, and least for a short time. That never happens.
I just thought of something: With a stock tranny and tuning, downshifting unlocks the torque converter, and most folks back out just a little 'till it locks up again, then ease back into it. (At least that's how I drove.) That behavior would reduce EGTs, for sure. With BTS and Jody's tunes, though, the TC doesn't unlock, so my pedal position no longer changes during and after a downshift. Could that be the sole reason for what I'm seeing? It still seems like EGTs should change some, as the combination of RPM increase and higher boost means there is suddenly a lot more exhaust is being created, but perhaps I'm not thinking about that right.
Mark
Yes, they do. This thing has always run hotter EGTs than some of my friend's rigs, but they are all trucks and perhaps a little lighter. I can go well past 1400 when towing if I don't back out, and this is true whether it stays in OD, downshifts on it's own, or if I downshift manually.
My expectation, and perhaps you can tell me if it's realistic, is that a downshift to 3rd should generally stop the rise of EGTs, if not reduce them some, and least for a short time. That never happens.
I just thought of something: With a stock tranny and tuning, downshifting unlocks the torque converter, and most folks back out just a little 'till it locks up again, then ease back into it. (At least that's how I drove.) That behavior would reduce EGTs, for sure. With BTS and Jody's tunes, though, the TC doesn't unlock, so my pedal position no longer changes during and after a downshift. Could that be the sole reason for what I'm seeing? It still seems like EGTs should change some, as the combination of RPM increase and higher boost means there is suddenly a lot more exhaust is being created, but perhaps I'm not thinking about that right.
Mark
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
Hi Curtis. I was hoping you'd chime in...
Yes, they do. This thing has always run hotter EGTs than some of my friend's rigs, but they are all trucks and perhaps a little lighter. I can go well past 1400 when towing if I don't back out, and this is true whether it stays in OD, downshifts on it's own, or if I downshift manually.
My expectation, and perhaps you can tell me if it's realistic, is that a downshift to 3rd should generally stop the rise of EGTs, if not reduce them some, and least for a short time. That never happens.
I just thought of something: With a stock tranny and tuning, downshifting unlocks the torque converter, and most folks back out just a little 'till it locks up again, then ease back into it. (At least that's how I drove.) That behavior would reduce EGTs, for sure. With BTS and Jody's tunes, though, the TC doesn't unlock, so my pedal position no longer changes during and after a downshift. Could that be the sole reason for what I'm seeing? It still seems like EGTs should change some, as the combination of RPM increase and higher boost means there is suddenly a lot more exhaust is being created, but perhaps I'm not thinking about that right.
Mark
Yes, they do. This thing has always run hotter EGTs than some of my friend's rigs, but they are all trucks and perhaps a little lighter. I can go well past 1400 when towing if I don't back out, and this is true whether it stays in OD, downshifts on it's own, or if I downshift manually.
My expectation, and perhaps you can tell me if it's realistic, is that a downshift to 3rd should generally stop the rise of EGTs, if not reduce them some, and least for a short time. That never happens.
I just thought of something: With a stock tranny and tuning, downshifting unlocks the torque converter, and most folks back out just a little 'till it locks up again, then ease back into it. (At least that's how I drove.) That behavior would reduce EGTs, for sure. With BTS and Jody's tunes, though, the TC doesn't unlock, so my pedal position no longer changes during and after a downshift. Could that be the sole reason for what I'm seeing? It still seems like EGTs should change some, as the combination of RPM increase and higher boost means there is suddenly a lot more exhaust is being created, but perhaps I'm not thinking about that right.
Mark
1400 degrees towing is pretty high. Either you're actually hitting those temps, or your gauge is inaccurate. If you're really hitting those temps, then there are many reasons for that, ranging from engine issues to tuning.
Mark, if you'd like to get together sometime for me to look at your EX, let me know and I'll gladly help you out.
Postmaster
Joined: Jul 2006
Posts: 3,754
Likes: 1
From: Indianapolis
When I tow heavy (15-20k) I do my best to keep it under 1200*- if I start dozing it can hit 13+ no problem, but I just use my pyro instead of the speedo, especially on hills. Are you maybe pushing it too hard? What kinda injectors you running? Is your air filter clean? 25psi should be plenty, but I myself like being able to get a little more out of it, although the stock turbo is pretty much limited at about 24-25 psi before you get surge.
Lead Driver
Joined: May 2007
Posts: 5,613
Likes: 9
From: Flagstaff, Arizona
Hi Curtis. I was hoping you'd chime in...
Yes, they do. This thing has always run hotter EGTs than some of my friend's rigs, but they are all trucks and perhaps a little lighter. I can go well past 1400 when towing if I don't back out, and this is true whether it stays in OD, downshifts on it's own, or if I downshift manually.
My expectation, and perhaps you can tell me if it's realistic, is that a downshift to 3rd should generally stop the rise of EGTs, if not reduce them some, and least for a short time. That never happens.
I just thought of something: With a stock tranny and tuning, downshifting unlocks the torque converter, and most folks back out just a little 'till it locks up again, then ease back into it. (At least that's how I drove.) That behavior would reduce EGTs, for sure. With BTS and Jody's tunes, though, the TC doesn't unlock, so my pedal position no longer changes during and after a downshift. Could that be the sole reason for what I'm seeing? It still seems like EGTs should change some, as the combination of RPM increase and higher boost means there is suddenly a lot more exhaust is being created, but perhaps I'm not thinking about that right.
Mark
Yes, they do. This thing has always run hotter EGTs than some of my friend's rigs, but they are all trucks and perhaps a little lighter. I can go well past 1400 when towing if I don't back out, and this is true whether it stays in OD, downshifts on it's own, or if I downshift manually.
My expectation, and perhaps you can tell me if it's realistic, is that a downshift to 3rd should generally stop the rise of EGTs, if not reduce them some, and least for a short time. That never happens.
I just thought of something: With a stock tranny and tuning, downshifting unlocks the torque converter, and most folks back out just a little 'till it locks up again, then ease back into it. (At least that's how I drove.) That behavior would reduce EGTs, for sure. With BTS and Jody's tunes, though, the TC doesn't unlock, so my pedal position no longer changes during and after a downshift. Could that be the sole reason for what I'm seeing? It still seems like EGTs should change some, as the combination of RPM increase and higher boost means there is suddenly a lot more exhaust is being created, but perhaps I'm not thinking about that right.
Mark
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Post Fiend
Joined: Feb 2002
Posts: 10,600
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From: Carhenge
Downshifting alone isn't typically going to lower EGT's unless you back out of the go pedal some. The only time it will is if the higher RPM's allow you to back off the fuel.
The strategy I use is to downshift before I'm actually on the grade, which allows me to back out of the go pedal and lower EGT's before I'm on the hill and gives me more time before I'm up against my temperature limit. Once you're on the hill and get the temperatures up against your temperature limit, there's not a lot you can do except grab a gear and back out of the fuel.
The strategy I use is to downshift before I'm actually on the grade, which allows me to back out of the go pedal and lower EGT's before I'm on the hill and gives me more time before I'm up against my temperature limit. Once you're on the hill and get the temperatures up against your temperature limit, there's not a lot you can do except grab a gear and back out of the fuel.
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Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
When I tow heavy (15-20k) I do my best to keep it under 1200*- if I start dozing it can hit 13+ no problem, but I just use my pyro instead of the speedo, especially on hills. Are you maybe pushing it too hard? What kinda injectors you running? Is your air filter clean? 25psi should be plenty, but I myself like being able to get a little more out of it, although the stock turbo is pretty much limited at about 24-25 psi before you get surge.
80e Tune 4in Exhaust.MP4 - YouTube
I don't suppose ScaldedDog knows somebody with AE. Hooking up and watching a number of things would provide a clue, since Jody spotted it right away.
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
according to your Sig, you haven't upgraded your intercooler yet. I am chose to go with the 6.0 IC, and with my setup, it drops my EGT's right around 220* when towing. I spent a total of $130 doing the upgrade, might be worth checking into for ya! Many will tell you on here the 6.0 isn't worth it, in my case....it produced REAL results, tested on the exact same hill, towing my boat.....before and after I swapped IC's
There is just not enough size differance to create that drop...
Lead Driver
Joined: May 2007
Posts: 5,613
Likes: 9
From: Flagstaff, Arizona
Judge for yourself if you think the 6.0 will work better then a 7.3 intercooler. Does the term "size matters" come to mind???
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
Over head shot... New is the 6.0, old is the 7.3...
Notice it is a narrower core...
Slightly thicker core...
In reality you have slightly LESS frontal area exposed to air flow... However the thicker core makes up for that...
Simply NOT a performance upgrade...
Lead Driver
Joined: May 2007
Posts: 5,613
Likes: 9
From: Flagstaff, Arizona
the rest of your post all I saw was Blah Blah Blah calling me a Liar (again)
if there wasn't NOTICEABLE results, then the thousands of people that have done it (and liked it) must be wrong according to you. I have never said the 6.0 intercooler is as good as an aftermarket Spearco, or Banks, or etc.......but it DOES work! (at 10% of the cost) If somebody is on a budget, and lots in this economy are, it's a very acceptable upgrade. So bash it all you want, you are in the minority. I sincerely apologize to the original poster for this rant
if there wasn't NOTICEABLE results, then the thousands of people that have done it (and liked it) must be wrong according to you. I have never said the 6.0 intercooler is as good as an aftermarket Spearco, or Banks, or etc.......but it DOES work! (at 10% of the cost) If somebody is on a budget, and lots in this economy are, it's a very acceptable upgrade. So bash it all you want, you are in the minority. I sincerely apologize to the original poster for this rant
Postmaster
Joined: Jul 2006
Posts: 3,754
Likes: 1
From: Indianapolis
As soon as I saw you post about the 6.0 core I KNEW the other would show up LOL... wow, and I used post # 3600 to cover this hehehe... too bad I can't find the popcorn eating smilie guy....
I'm kinda with clux- I usually have it in cruise, so when I start getting hot, I tap the brake to take it outta cruise, but keep my foot in it. At about 1100* I get outta the go pedal to take the load of the tranny, then throw it in 3rd, and after about a second or so, get back into the throttle. It used to slam the tranny with the heavy loads I drag, but now I'm good enough to where you don't notice the speed change, just an increase in rpms.
But we gotta face facts- us PSD owners keep asking more and more of our trucks. Hell for what I do I should be using at least a medium duty truck (F-550) to cover the RAWR, but it still won't be enough power. That's why you see some 3-4 car trailers being towed by a single axle tractor- they got the power you need to keep your foot in it no matter the terrain.
I'm kinda with clux- I usually have it in cruise, so when I start getting hot, I tap the brake to take it outta cruise, but keep my foot in it. At about 1100* I get outta the go pedal to take the load of the tranny, then throw it in 3rd, and after about a second or so, get back into the throttle. It used to slam the tranny with the heavy loads I drag, but now I'm good enough to where you don't notice the speed change, just an increase in rpms.
But we gotta face facts- us PSD owners keep asking more and more of our trucks. Hell for what I do I should be using at least a medium duty truck (F-550) to cover the RAWR, but it still won't be enough power. That's why you see some 3-4 car trailers being towed by a single axle tractor- they got the power you need to keep your foot in it no matter the terrain.
