Why don't my EGTs decrease when downshifting?
Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,456
Likes: 155
From: Sedalia, CO
What I am saying is not he has an issue with his tuner, there is something tweaked with his truck, trans or elsewhere. You should not have the issue he is having.
If I am going 65 in OD pulling and the EGT's are reaching 1300+*, I can hit the OD button and continue to pull at 65, with the EGT's dropping to 1100 or less.
If I am going 65 in OD pulling and the EGT's are reaching 1300+*, I can hit the OD button and continue to pull at 65, with the EGT's dropping to 1100 or less.
Assuming it really is a difference in our trucks, and further assuming your water injection is not it, what else could it be? I'm fairly well certain ICP stays up, at least now that I have a T500, as I've measured it. I have no idea what my fuel pressure is doing, and there's no way to know without installing a manual gauge, right?
I can, and will, drop down to less aggressive tune, but I suspect that will just allow me to to be a little less careful with the EGT's, but won't change the behavior I'm trying to diagnose.
Mark
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
Ahhh, this is exactly the issue I'm trying to figure out. Why does your truck behave this way, and mine does not? Does your TC unlock on this 4-3 downshift, and do you back off ever so slightly to get it to lock up again (and in so doing lower EGT's), or does it stay locked and the EGT's fall a bit without you changing pedal position? I'm trying to figure out if the difference is driving behavior, or actually in the hardware.
Assuming it really is a difference in our trucks, and further assuming your water injection is not it, what else could it be? I'm fairly well certain ICP stays up, at least now that I have a T500, as I've measured it. I have no idea what my fuel pressure is doing, and there's no way to know without installing a manual gauge, right?
I can, and will, drop down to less aggressive tune, but I suspect that will just allow me to to be a little less careful with the EGT's, but won't change the behavior I'm trying to diagnose.
Mark
Assuming it really is a difference in our trucks, and further assuming your water injection is not it, what else could it be? I'm fairly well certain ICP stays up, at least now that I have a T500, as I've measured it. I have no idea what my fuel pressure is doing, and there's no way to know without installing a manual gauge, right?
I can, and will, drop down to less aggressive tune, but I suspect that will just allow me to to be a little less careful with the EGT's, but won't change the behavior I'm trying to diagnose.
Mark
TC stays locked from about 32mph hour. You dont really have a 4th gear, you have 3rd and then OD.
When I get to that point where I have to down shift I will lift slightly, hit the od button, let her settle and hammer down.
you can't fix stupid!
Joined: Mar 2008
Posts: 1,906
Likes: 2
While I'm quite sure your Swamps tuner and your super-maintained and modded truck can take diesel and make the ultimate tow beast "out of thin air" (good job, by the way), I'd prefer to help AcladedDog solve the issue that this thread was started for. For some reason, his DP is making too much power to use in his configuration, so reduce power settings are being recommended.
Noramlly, I wouldn't want to interfere with anybody else's input - but you're telling him to just slow down more and like it. I find it interesting that your Swamps doesn't make too much power for the engine under real load. I thought all tuners had to back off for the big pull - but maybe there are some that have no need to back off. I learned something about Swamps.
Noramlly, I wouldn't want to interfere with anybody else's input - but you're telling him to just slow down more and like it. I find it interesting that your Swamps doesn't make too much power for the engine under real load. I thought all tuners had to back off for the big pull - but maybe there are some that have no need to back off. I learned something about Swamps.
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
My tuner or any tuner for that fact can be driven and tow in any setting you want and not have EGT issues, other then at WOT. My drag3 file makes X amount of hp at 40% of throttle... My hot street file makes that same X amount at 60%... and so on and so forth...
Way over simplified but you get what I am laying down?
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you can't fix stupid!
Joined: Mar 2008
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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
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
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.
Post Fiend
Joined: Feb 2002
Posts: 10,600
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From: Carhenge
I pretty much consider it to be a gear Per se.
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
I tow in my hot street file...
I control my EGT's with the shifter **** and my right foot. No issues towing anywhere in the country going as fast as I want...
Too many people get all caught up in the 20tow, 40tow, 60 tow... 315 tow, 7894tow...
Just throw it in a setting and tow. I could tow in the drag3b file without issue other then starting off would be a little smoky.
I control my EGT's with the shifter **** and my right foot. No issues towing anywhere in the country going as fast as I want...
Too many people get all caught up in the 20tow, 40tow, 60 tow... 315 tow, 7894tow...
Just throw it in a setting and tow. I could tow in the drag3b file without issue other then starting off would be a little smoky.
...No where in my previous post did I say anything about slowing down. Down shift and bring the RPM's up.
I'm rambling now, but my tuner has nothing to do with how my truck tows, I could (and did) take your DP tuner chip, run it on the hottest setting you have and pull my 24k load up any road or pass in the country without worry one bit. Shift... Shift... Shift.
I'm rambling now, but my tuner has nothing to do with how my truck tows, I could (and did) take your DP tuner chip, run it on the hottest setting you have and pull my 24k load up any road or pass in the country without worry one bit. Shift... Shift... Shift.
I wanted to make sure that our friend in Littleton CO (6000ft elevation and a climb up the pass from there) didn't equate his situation with that of CSIPSDs. I'm not trying to discredit CSIPSDs experience, but hammer down in 3rd on any hill in the country while in race tune stretches his credibility beyond my personal limit. Any one of the many people who tow with a turbodiesel in Colorado, Utah, and many other "hilly" states might take issue with this approach on an 8000ft pass (Mt Rose, NV 8500ft - open all year).
As for Swamps - if it can tackle a 6000-8000 ft pass in race tune while towing an estimated 5000-6000lb travel trailer, then I am forced to wonder how much power gain is really there. Power generates heat and big power generates big heat.
And lastly - If the Swamps is capable of doing all of this any where and any time - why did CSIPSD go through the expense and trouble of installing a water injection system?
I have no problem with bragging up on one's capabilities - you spent the money, you paid for the braggin' rights. Just please don't leave out the salient details and caveats - this could lead ScaldedDog or other readers into putting "the hammer down" and hope everything's "cool". It could also discourage them from finding a sensible and cost-effective solution when it's not.
Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,456
Likes: 155
From: Sedalia, CO
Allow me to mediate...
First, I have a choice of 80t, 60t and 40t tunes for towing. I have other tunes, but like the towing shift strategies when, well, towing. I've tended to use the 80t most of time because I'm an American and more is better, right.
I wouldn't use a race tune for towing if had one, just because I have better tools readily available.
Second, I do think CSIPSD has a point, at least within the towing tune category. The difference between the three tunes is "fuel" (the one word answer I got from Jody when I asked him that direct question). Given that, I assert there's some pedal position on the 80t tune that maps almost exactly to the floored position on the 40t. If I understand correctly, that's what CSIPSD is saying, at least with respect to my situation.
None of this answers my original question, necessarily, but I think I'm beginning to understand the real answer. It might be in this comment:
I think most good drivers trying to be nice to their tranny drive that way, and it's the slight lifting that's lowering EGT's, not the downshifting itself. I've gotten out of the habit of doing that since I got my BTS - I love that thing - and perhaps that's why my EGT's don't drop during a shift. Next time I tow I'll anticipate the downshifts like I used to with a stock trans and see if the behavior I seek doesn't magically appear.
Mark
First, I have a choice of 80t, 60t and 40t tunes for towing. I have other tunes, but like the towing shift strategies when, well, towing. I've tended to use the 80t most of time because I'm an American and more is better, right.
I wouldn't use a race tune for towing if had one, just because I have better tools readily available.Second, I do think CSIPSD has a point, at least within the towing tune category. The difference between the three tunes is "fuel" (the one word answer I got from Jody when I asked him that direct question). Given that, I assert there's some pedal position on the 80t tune that maps almost exactly to the floored position on the 40t. If I understand correctly, that's what CSIPSD is saying, at least with respect to my situation.
None of this answers my original question, necessarily, but I think I'm beginning to understand the real answer. It might be in this comment:
Originally Posted by CSIPSD
When I get to that point where I have to down shift I will lift slightly, hit the od button, let her settle and hammer down.
Mark
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Allow me to mediate...
First, I have a choice of 80t, 60t and 40t tunes for towing. I have other tunes, but like the towing shift strategies when, well, towing. I've tended to use the 80t most of time because I'm an American and more is better, right. I wouldn't use a race tune for towing if had one, just because I have better tools readily available.
Second, I do think CSIPSD has a point, at least within the towing tune category. The difference between the three tunes is "fuel" (the one word answer I got from Jody when I asked him that direct question). Given that, I assert there's some pedal position on the 80t tune that maps almost exactly to the floored position on the 40t. If I understand correctly, that's what CSIPSD is saying, at least with respect to my situation.
None of this answers my original question, necessarily, but I think I'm beginning to understand the real answer. It might be in this comment:
I think most good drivers trying to be nice to their tranny drive that way, and it's the slight lifting that's lowering EGT's, not the downshifting itself. I've gotten out of the habit of doing that since I got my BTS - I love that thing - and perhaps that's why my EGT's don't drop during a shift. Next time I tow I'll anticipate the downshifts like I used to with a stock trans and see if the behavior I seek doesn't magically appear.
Mark
First, I have a choice of 80t, 60t and 40t tunes for towing. I have other tunes, but like the towing shift strategies when, well, towing. I've tended to use the 80t most of time because I'm an American and more is better, right.
I wouldn't use a race tune for towing if had one, just because I have better tools readily available.Second, I do think CSIPSD has a point, at least within the towing tune category. The difference between the three tunes is "fuel" (the one word answer I got from Jody when I asked him that direct question). Given that, I assert there's some pedal position on the 80t tune that maps almost exactly to the floored position on the 40t. If I understand correctly, that's what CSIPSD is saying, at least with respect to my situation.
None of this answers my original question, necessarily, but I think I'm beginning to understand the real answer. It might be in this comment:
I think most good drivers trying to be nice to their tranny drive that way, and it's the slight lifting that's lowering EGT's, not the downshifting itself. I've gotten out of the habit of doing that since I got my BTS - I love that thing - and perhaps that's why my EGT's don't drop during a shift. Next time I tow I'll anticipate the downshifts like I used to with a stock trans and see if the behavior I seek doesn't magically appear.
Mark
There is also the PW strategy to factor in. High pressure with a narrow PW or low pressure with wide PW can deliver the same amount of fuel, but in a different form - one is atomized better. I don't profess to completely grasp thermodynamics or diesel tuning, I am just very experienced at learning that things are not always simple. To that end, I stand by the suggestion to give the other tune a try and see what happens.
AE data would be very interesting in your situation. If you DO see any difference in EGTs between the two tunes, I'd be curious to see the difference in RPM, MPH, ICP, and FIPW.
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
Sorry it took so long to reply, had to wait until a work break. I debated on even throwing that last bit in because I'm not a big fan being direspectful.
I wanted to make sure that our friend in Littleton CO (6000ft elevation and a climb up the pass from there) didn't equate his situation with that of CSIPSDs. I'm not trying to discredit CSIPSDs experience, but hammer down in 3rd on any hill in the country while in race tune stretches his credibility beyond my personal limit. Any one of the many people who tow with a turbodiesel in Colorado, Utah, and many other "hilly" states might take issue with this approach on an 8000ft pass (Mt Rose, NV 8500ft - open all year).
As for Swamps - if it can tackle a 6000-8000 ft pass in race tune while towing an estimated 5000-6000lb travel trailer, then I am forced to wonder how much power gain is really there. Power generates heat and big power generates big heat.
And lastly - If the Swamps is capable of doing all of this any where and any time - why did CSIPSD go through the expense and trouble of installing a water injection system?
I have no problem with bragging up on one's capabilities - you spent the money, you paid for the braggin' rights. Just please don't leave out the salient details and caveats - this could lead ScaldedDog or other readers into putting "the hammer down" and hope everything's "cool". It could also discourage them from finding a sensible and cost-effective solution when it's not.
I wanted to make sure that our friend in Littleton CO (6000ft elevation and a climb up the pass from there) didn't equate his situation with that of CSIPSDs. I'm not trying to discredit CSIPSDs experience, but hammer down in 3rd on any hill in the country while in race tune stretches his credibility beyond my personal limit. Any one of the many people who tow with a turbodiesel in Colorado, Utah, and many other "hilly" states might take issue with this approach on an 8000ft pass (Mt Rose, NV 8500ft - open all year).
As for Swamps - if it can tackle a 6000-8000 ft pass in race tune while towing an estimated 5000-6000lb travel trailer, then I am forced to wonder how much power gain is really there. Power generates heat and big power generates big heat.
And lastly - If the Swamps is capable of doing all of this any where and any time - why did CSIPSD go through the expense and trouble of installing a water injection system?
I have no problem with bragging up on one's capabilities - you spent the money, you paid for the braggin' rights. Just please don't leave out the salient details and caveats - this could lead ScaldedDog or other readers into putting "the hammer down" and hope everything's "cool". It could also discourage them from finding a sensible and cost-effective solution when it's not.
I'll reply further when I get back to work tonight...
Allow me to mediate...
First, I have a choice of 80t, 60t and 40t tunes for towing. I have other tunes, but like the towing shift strategies when, well, towing. I've tended to use the 80t most of time because I'm an American and more is better, right. I wouldn't use a race tune for towing if had one, just because I have better tools readily available.
Second, I do think CSIPSD has a point, at least within the towing tune category. The difference between the three tunes is "fuel" (the one word answer I got from Jody when I asked him that direct question). Given that, I assert there's some pedal position on the 80t tune that maps almost exactly to the floored position on the 40t. If I understand correctly, that's what CSIPSD is saying, at least with respect to my situation.
None of this answers my original question, necessarily, but I think I'm beginning to understand the real answer. It might be in this comment:
I think most good drivers trying to be nice to their tranny drive that way, and it's the slight lifting that's lowering EGT's, not the downshifting itself. I've gotten out of the habit of doing that since I got my BTS - I love that thing - and perhaps that's why my EGT's don't drop during a shift. Next time I tow I'll anticipate the downshifts like I used to with a stock trans and see if the behavior I seek doesn't magically appear.
Mark
First, I have a choice of 80t, 60t and 40t tunes for towing. I have other tunes, but like the towing shift strategies when, well, towing. I've tended to use the 80t most of time because I'm an American and more is better, right.
I wouldn't use a race tune for towing if had one, just because I have better tools readily available.Second, I do think CSIPSD has a point, at least within the towing tune category. The difference between the three tunes is "fuel" (the one word answer I got from Jody when I asked him that direct question). Given that, I assert there's some pedal position on the 80t tune that maps almost exactly to the floored position on the 40t. If I understand correctly, that's what CSIPSD is saying, at least with respect to my situation.
None of this answers my original question, necessarily, but I think I'm beginning to understand the real answer. It might be in this comment:
I think most good drivers trying to be nice to their tranny drive that way, and it's the slight lifting that's lowering EGT's, not the downshifting itself. I've gotten out of the habit of doing that since I got my BTS - I love that thing - and perhaps that's why my EGT's don't drop during a shift. Next time I tow I'll anticipate the downshifts like I used to with a stock trans and see if the behavior I seek doesn't magically appear.
Mark
It is 100% the shifting that lowers the EGT's... Comes down to one simple thing...
AIR FLOW... You downshift and bring up the RPM's you have just doubled the amount of air your turbo is ingesting, IC is processing, and motor is exhaling. These trucks simply love RPM's (within reason) and lugging kills you on EGT's.
There is nothing wrong with towing for hours on end at 2500-2700 RPM's.
That's a well thought-out answer, and I offer this up just for additional consideration: There's also a sensitivity factor. I've looked at enough AE data to see some interesting things - like why my cruise control has a rough time settling down sometimes. The cruise control programming had XYZ throttle response in mind, but the 80e tune blows past that anticipated throttle response. The cruise control has some hunting to do before things settle down. Apply that same principle to your foot and it could be quite easy to overcorrect for changing slopes/speed. Maybe not.
There is also the PW strategy to factor in. High pressure with a narrow PW or low pressure with wide PW can deliver the same amount of fuel, but in a different form - one is atomized better. I don't profess to completely grasp thermodynamics or diesel tuning, I am just very experienced at learning that things are not always simple. To that end, I stand by the suggestion to give the other tune a try and see what happens.
AE data would be very interesting in your situation. If you DO see any difference in EGTs between the two tunes, I'd be curious to see the difference in RPM, MPH, ICP, and FIPW.
There is also the PW strategy to factor in. High pressure with a narrow PW or low pressure with wide PW can deliver the same amount of fuel, but in a different form - one is atomized better. I don't profess to completely grasp thermodynamics or diesel tuning, I am just very experienced at learning that things are not always simple. To that end, I stand by the suggestion to give the other tune a try and see what happens.
AE data would be very interesting in your situation. If you DO see any difference in EGTs between the two tunes, I'd be curious to see the difference in RPM, MPH, ICP, and FIPW.
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound