Debugging slightly low boost
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
Well, I'm pretty sure Tugly will agree with me that the air intake part is looking normal. It is very common and expected that the filter minder portion on the AIS intake pulls 1/2 way down. That is why many folks swap out that one for the stock filter minder.
There has to be something going on with the air side to give u those elevated egt's.
There has to be something going on with the air side to give u those elevated egt's.
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More Turbo
Joined: Oct 2013
Posts: 584
Likes: 1
So the filter and minder seem ok.
The high EGTs indicate a problem on the intake side - so we're back to leak testing on the intake side (turbo to manifold, including the manifold)?
The chart above **might** be showing showing something else that I thought was strange. I recall reading that it's better to be in 3rd at higher RPMS vs OD at lower RPM.
I'm pretty sure that chart shows starting a hill in OD and then a downshift and higher RPMs and EGTs. I'm not sure how I could get a quick jump like that in any other way.
So, does that mean that if everything is perfect, then what I should see is a jump in RPM and the EGTs should go down instead of up?
The high EGTs indicate a problem on the intake side - so we're back to leak testing on the intake side (turbo to manifold, including the manifold)?
The chart above **might** be showing showing something else that I thought was strange. I recall reading that it's better to be in 3rd at higher RPMS vs OD at lower RPM.
I'm pretty sure that chart shows starting a hill in OD and then a downshift and higher RPMs and EGTs. I'm not sure how I could get a quick jump like that in any other way.
So, does that mean that if everything is perfect, then what I should see is a jump in RPM and the EGTs should go down instead of up?
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
Between 16 and 16.5, I see that although RPM goes up, Boost and MAP take a sharp drop.
If you were indeed WOT, not holding throttle at a set position, this shouldn't be.
Have you done a boost leak test? Checking your boots?
I won't speculate on too much, since you're getting help from folks who know more than I, rather pointing out this anomaly for opinions.
If you were indeed WOT, not holding throttle at a set position, this shouldn't be.
Have you done a boost leak test? Checking your boots?
I won't speculate on too much, since you're getting help from folks who know more than I, rather pointing out this anomaly for opinions.
Senior User
Joined: Sep 2014
Posts: 346
Likes: 0
Yes please let us know if you have checked the boots.
My filter minder melted off when my radiator kept spewing coolant all over the engine, it only left the very end on there. After I had just changed the dang antifreeze!!!
My filter minder melted off when my radiator kept spewing coolant all over the engine, it only left the very end on there. After I had just changed the dang antifreeze!!!
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More Turbo
Joined: Oct 2013
Posts: 584
Likes: 1
I don't know if it was WOT before the downshift and RPM jump. I suspect not.
What I did notice was that if I was going up a hill in od, every time that I paid attention to it, a downshift into 3rd always brought higher EGTs. I remember thinking that more RPMS was supposed to bring more cool air and EGTs should be going down.
I've done a number of boost leak tests. I've been asking about the filter and what not getting enought CFM through the turbo might look like lately because I've been grasping for other options to consider. It appears that we're pointing back toward the boost leak side again though.
If it's a boost leak, it must be something that presents itself only at higher pressure, higher than Ive been testing with.
What I did notice was that if I was going up a hill in od, every time that I paid attention to it, a downshift into 3rd always brought higher EGTs. I remember thinking that more RPMS was supposed to bring more cool air and EGTs should be going down.
I've done a number of boost leak tests. I've been asking about the filter and what not getting enought CFM through the turbo might look like lately because I've been grasping for other options to consider. It appears that we're pointing back toward the boost leak side again though.
If it's a boost leak, it must be something that presents itself only at higher pressure, higher than Ive been testing with.
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
The clamp was loose.
Boots can leak under pressure. How did you do the leak test?
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More Turbo
Joined: Oct 2013
Posts: 584
Likes: 1
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
How about smoke out the tailpipe? See and black clouds in the passenger mirror when towing?
Towing - You should see lower EGT's when going from low rpm's (1800ish) in OD to higher rpm's (2200 ish) in 3rd. The key to towing with these trucks is to keep the rpm's at or above 2K when running up grades.
Towing - You should see lower EGT's when going from low rpm's (1800ish) in OD to higher rpm's (2200 ish) in 3rd. The key to towing with these trucks is to keep the rpm's at or above 2K when running up grades.
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
I see those 10 PSI spikes on EBP, a good looking turbo, and wimpy boost with dips opposite of EBP spikes. The last time I saw that on Stinky, he had a leak at the intake plenum, near the CAC boot fitting.
A boost leak can show itself at low pressure, but you have to really look for it. I had about 5 PSI and the Simple Green bubbles out the intake plenum seal looked minor - but I can only speculate what it would have looked like if I had 20 or 30 PSI boost going on. I know for sure that the subtle bubbles were gone after replacing the plenums, and my boost/EBP/EGT numbers showed an obvious improvement.
A boost leak can show itself at low pressure, but you have to really look for it. I had about 5 PSI and the Simple Green bubbles out the intake plenum seal looked minor - but I can only speculate what it would have looked like if I had 20 or 30 PSI boost going on. I know for sure that the subtle bubbles were gone after replacing the plenums, and my boost/EBP/EGT numbers showed an obvious improvement.
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More Turbo
Joined: Oct 2013
Posts: 584
Likes: 1
Yes this is what I recall and why I thought it was strange when I saw higher EGT with higher RPMs.
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More Turbo
Joined: Oct 2013
Posts: 584
Likes: 1
It seems to pop up quickly and the plateau. I'll find an example later.