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ISX

EGT Figures for Reference

24 posts in this topic

I got the wild idea to make a whole graph of my EGT's at different speeds, temperatures, and conditions. I can't exactly graph them all instantly though so if anyone wants to help, just get on level ground and go a constant speed at a constant throttle, record the factors like I have, let me know if it is the truck in your sig or list the truck specs it was on. I want to see how everything affects the EGT's and I am too stupid to remember what it was "last time" so I am going to start recording what I see. I am going to do all 5th gear driving so if you guys are in a gear other than O/D, just list it so we know.

These will all be unloaded tests, people may wonder if their EGT's are normal or not so I want to get nothing but unloaded results.

Thanks to anyone that helps!

Posted Image

If you guys want this thing to be bigger to read it a little easier since the site scales it down, just click here.http://www.mopar1973man.com//isx97/Excel/TruckEGT.JPG

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Today's run to town for propane and fuel... EGT: ~400-450*FSpeed: 55 MPHAmbient Temp: +3*FWeather Conditions: Cold, 81% RHYear: 2002Model: 2500Trans: NV4500Driveline: 4WDWinterfront: Yes (IAT Temp 48-54*F @ 195*F coolant)RPM: ~1600Boost: ~2 PSI Edit in the tidbits for ya... post-2-138698173019_thumb.jpg

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Perfect. I added IAT to it. I also am just averaging all your temps. I got to thinking a little more and exhaust, intake,... would all be a factor in this (especially HX or HY turbo) but I think I will overlook all of these other stats for now. If we end up having wildly different numbers out of someone then we might have to get a bit more technical. I think most of us know what EGT they are at at certain speeds including me, so if I see a result that looks a little skewed I will get some more details on it from them so we learn why they are hotter/colder than the normal. The way this chart works I just replace the file, so the 1st post results are going to be changing rather than reposting an updated spreadsheet every time. I might add some more factors to it, I know what most of you have done to your trucks so I will fill it in if I add more factors.

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Here's what I had today coming home from town. EGT-625Boost-5 psiSpeed-60 mphTemp,+8*FYear-2000Truck-2500, 47re trans with HX turbo

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Here's what I had today coming home from town. EGT-625 Boost-5 psi Speed-60 mph Temp,+8*F Year-2000 Truck-2500, 47re trans with HX turbo

Guess I need boost in there too :lol: Thanks Volkswagon!

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Got some more figures today. It's getting interesting now that we are starting to match speeds so we can compare. You can see how I am just barely over Mike's EGT at 55 but the ambient temp is 22F hotter on my run so he should have been in the 300F's being only 3F, but the winter front bumped it up for him. I am going to leave my winter front off for the sake of this thread and see what I get whenever it decides to hit 3F here. I am organizing the results by EGT temp. I would like to do something to make each users truck stand out a little so it is easier to tell the trucks apart (I am not big on reading the year and model for every EGT result, would rather my truck's stuff be in green, mikes be in red, something like that..).

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Here are some figures from my current setup. 50 mph, ~1500 rpms, 575°, ~1 psi of boost60 mph, ~1800 rpms, 650°, ~2 psi of boost70 mph, ~2100 rpms, 700°, ~3 psi of boost

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Here are some figures from my current setup. 50 mph, ~1500 rpms, 575°, ~1 psi of boost 60 mph, ~1800 rpms, 650°, ~2 psi of boost 70 mph, ~2100 rpms, 700°, ~3 psi of boost

Do you know the ambient temp?

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Add a summer time EGT for yeah... EGT: ~600-650*FSpeed: 55 MPHAmbient Temp: 104*FWeather Conditions: Hot, 15% RHYear: 2002Model: 2500Trans: NV4500Driveline: 4WDWinterfront: No (IAT Temp 128*F @ 195*F coolant)RPM: ~1600Boost: ~2 PSI Note: Yes. I'm using the actual IAT sensor and not the MPG fooler.

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Do you know the ambient temp?

EGTs are ±25° of that from 50-100° ambient. I think those were noted at the following, 70 @ 97°, 60 @ 83°, 50 at 75°. IAT's are +10 from the ambient.

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I just did a test today and found something interesting. On the way to work I hit a flat section and looked at all the gauges, then on the way back I hit the same section and looked at all the gauges again. Both were at 55mph, the only difference was ambient temp.

Morning Run

[*]EGT: 435F +/- 5

[*]Ambient Temp: 77F

[*]Humidity: 60%

[*]Boost: ~2-3psi

[*]Speed: 55mph

[*]RPM:1611

Afternoon Run

[*]EGT: 435F +/- 5

[*]Ambient Temp: 94F

[*]Humidity: 60%

[*]Boost: ~2-3psi

[*]Speed: 55mph

[*]RPM: 1611

As you can see, ambient temp seems to have no effect. From AH64's info, I notice he is finding the same thing out. If I look at my records from winter, I notice I have exactly the same reading on EGT's, among everything else. What is interesting is how Mike notices a 200F hike in the summer, yet I don't see anything change which is with a digital EGT gauge so I can see every single degree. Have to do some research on this.

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Here are some figures from my current setup. 50 mph, ~1500 rpms, 575°, ~1 psi of boost 60 mph, ~1800 rpms, 650°, ~2 psi of boost 70 mph, ~2100 rpms, 700°, ~3 psi of boost

i dont have all the extra info yall have but these #'s are consistant with my truck 90* +or- 5* in 6th gear level ground. they have been pretty consistant for the past 1.5 years since i started payin attention.

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As you can see, ambient temp seems to have no effect. From AH64's info, I notice he is finding the same thing out. If I look at my records from winter, I notice I have exactly the same reading on EGT's, among everything else. What is interesting is how Mike notices a 200F hike in the summer, yet I don't see anything change which is with a digital EGT gauge so I can see every single degree. Have to do some research on this.

Interesting, I would have expected your static timing to have had more change with ambient and the dynamic timing of VP's and CR's to have kept it more similar.

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Interesting, I would have expected your static timing to have had more change with ambient and the dynamic timing of VP's and CR's to have kept it more similar.

There is a lot of folklore concerning dynamic timing. The one thing that can never be produced is the actual timing that those things are running. I'm sure somebody knows it but I haven't seen any info on any truck with a computer concerning what the timing actually is. How do we know it isn't going in between 2* and that's it? Maybe it's going between 10*. Nobody knows. One very interesting thing is that the VP44 trucks knock like crazy. When I park next to one that is running, I think my truck is falling apart until I figure out their truck is running. Now when Mike ran that IAT fooler, it quieted the engine down, seemingly retarding timing. Here's where it gets sketchy. I cannot produce the kind of knock that the 24V's produce, no matter how high I set my timing. Why is that? Is it from the higher pop pressure? 12V's have more compression so it would seem they would knock louder. But now lets look at the 6.7's that maximize pop pressure, yet they hardly knock at all. So between a 12V, VP44, and 6.7, the results are scattered and apparently timing cannot be judged by amount of knock. I can advance the timing on my truck and it knocks more, but only when you step on it, idling it sounds the same, not this incredible rattle the vp44's make idling. It seems to me that timing is only part of the equation of the rattle scenario's. I'll throw this out there as well. When my timing was advanced a good bit, it would start at 50F like it started at -10F with stock timing.. It was horrible. I think it was advanced a little much, maybe 18-20*. I lost a ton of low end power, gained a bunch up higher, EGT's didn't seem any different. MPG's weren't any different. That is why I have the hardest time understanding how a chip on a vp44 truck can make it get any more mpg's when I can swing a long ways with timing and never see a difference.

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The reason the 6.7 runs so quiet is the controlled pilot injection event, its also why HPCR 5.9's are so quiet. VP trucks are loud for sure, and I am not sure why they are so loud relative to a 12V, they both only use 1 injection event.

The "pop" pressure on a HPCR actually isn't pop as they injectors are electronically opened. The pressure also varies greatly from about 7K at idle to 23K max on my truck. EFILive is out for the 06-07's, and you can see how much the timing varies! Long read, but there are some good graphs and charts in here talking about the stock tuning, which is essentially the same from 04.5-07. http://www.competitiondiesel.com/forums/showthread.php?t=104594&highlight=stock+timing+tables

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The reason the 6.7 runs so quiet is the controlled pilot injection event, its also why HPCR 5.9's are so quiet. VP trucks are loud for sure, and I am not sure why they are so loud relative to a 12V, they both only use 1 injection event.

The "pop" pressure on a HPCR actually isn't pop as they injectors are electronically opened. The pressure also varies greatly from about 7K at idle to 23K max on my truck. EFILive is out for the 06-07's, and you can see how much the timing varies! Long read, but there are some good graphs and charts in here talking about the stock tuning, which is essentially the same from 04.5-07. http://www.competitiondiesel.com/forums/showthread.php?t=104594&highlight=stock+timing+tables
I forgot all about that. Hmm, we still need someone to figure out timing on those things. 13.5 years and we still have nothing lol.

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I should make a section for hills, cept that seems like it has too many varying factors. I went towards branson yesterday and measured the grade and came up with 6%. Made a video of it because it always sounds neat going up them, of course driving faster helps strain it :pant: Was 91F out. It starts recording at the bottom of the hill before I start getting into the throttle. No I don't drive like that all the time, I got 24.5mpg on that tank (went 800 miles!) so you know how I drive the rest of the time :thumb1:

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Well I got to admit ISX is right stay in 4th gear 1:1 ratio set the cruise for 53 MPH (2K RPM's) towing the Jayco and made new record 13.1 MPG when I got home... That climbing a 6% grade with tight corners (25 MPH) in 3rd Gear. Towing a Travel Trailer (GCWR ~15,000) EGT: 600-800*FAmbient Temp: 85FHumidity: 12%Boost: 2-15psiSpeed: 53mphRPM:2000 IAT Was locked at 140*F...

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Well I got to admit ISX is right stay in 4th gear 1:1 ratio set the cruise for 53 MPH (2K RPM's) towing the Jayco and made new record 13.1 MPG when I got home... That climbing a 6% grade with tight corners (25 MPH) in 3rd Gear. Towing a Travel Trailer (GCWR ~15,000) EGT: 600-800*F Ambient Temp: 85F Humidity: 12% Boost: 2-15psi Speed: 53mph RPM:2000 IAT Was locked at 140*F...

Right about what? All I can think of is I told you I go a lot faster when I pull the trailer so that I am never anywhere near lugging it :shrug: Works really good for me. Maybe you noticed your EGT's never become a worry when you do that. When I do 70 (2000RPM) I can hold it at 70 up any hill and am lucky to see anything over 900. I would do as you but 2000RPM in 4th on mine is not exactly moving lol.

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Hmmm... Playing with ISX idea... I went into town today and cruised 55 MPH and took my time EGT's hovered about 500-550*F downhill to Riggins, ID. Now once I was done came back home the same road set my cruise for 55 again but instead of 5th gear I grab 4th gear for the grade back up. This put me at about 2,100 RPM's but EGT's hover at 550-600*F for the trip home. But typically same rate of speed in 5th gear would turn out 800-850*F for the climb home.

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Hmmm... Playing with ISX idea... I went into town today and cruised 55 MPH and took my time EGT's hovered about 500-550*F downhill to Riggins, ID. Now once I was done came back home the same road set my cruise for 55 again but instead of 5th gear I grab 4th gear for the grade back up. This put me at about 2,100 RPM's but EGT's hover at 550-600*F for the trip home. But typically same rate of speed in 5th gear would turn out 800-850*F for the climb home.

Hook your TT on and do the same test... Without any real load the engine just ends up using more fuel to turn more RPM's since it isn't using any actual power to move the truck 55mph, just using fuel to turn the engine faster. The EGT's would be even higher but 4th gear has more leverage so it keeps them just a little over 5th gear's EGT's. The turnaround point comes when you hook on to a load.

When the truck is in 5th gear pulling 20k lbs (drastic to get the point across) up a 7% grade at 55mph, he is gonna be pulling maybe 1600RPM's, black smoking like crazy, melting pistons, everything, but the turbo will be maxed out at wastegate pressure. Exploring this deeper as to why his EGT's were high enough to melt the whole engine, we get to a simple formula that states that more air going into the engine means more air going out of the engine, which means more heat expelling out the exhaust. The other part of the formula states that fuel quantity does the opposite, raising the combustion temp as more is added. If we come up with a chart showing how much fuel it takes to move an unloaded truck a set speed at different RPM's, you will get a baseline. You will see engine turning horsepower is exponential, starting low and then getting steeper. Engine flow rate based on just cylinder displacement will increase linearly. Boost will be relatively low (remember we are talking constant RPM's, not acceleration). Because there is hardly any boost, the only way to remove heat is with RPM, but with no engine load (no TT), the engine isn't making much heat and therefore the effect is not seen much, if at all.

With this baseline, we can compare it with trailer towing and you will see something completely different. The engine turning HP (with TT and all) will look the same (though it will be higher numbers), the engine flow rate will be more because you are adding more fuel, more fuel means more heat which means more expansion and therefore more flow, why else would you get more power from more fuel. If you think of a steam engine it would be like putting a drop of water in or a cup of water, obviously the drop won't do anything but make you think someone let the air out of your tire. Because you get more flow, you get more boost, which loops around back to the intake and gives it more air to get hot and expand more and get even more flow until it all equalizes out. The boost will be much higher than baseline because of all the expanding air from the fuel combustion.

Now what does this mean for changing gears. The key here is engine flow.. The effect seen with an unloaded truck is reversed when loaded (though the principle is the same just not seen much, as I stated). In 5th gear the RPM's are low, so there isn't much heat removed solely from engine flow itself, the boost helps it out and allows that hot air to be shoved out. The fuel injected per power stroke is high. The high fuel and low engine flow can cause the black smoke if boost isn't there to make up for the loss in engine flow.

Stick it in 4th, now you have engine flow. The pistons are shoving all the hot air out, though boost isn't as much, it is overcompensated for by engine flow. The fuel injected per power stroke is lower, further helping the EGT's remain lower.

IF you were able to raise boost to the point of making up for the loss in engine flow, you could remain in 5th gear. Obviously as load increases, boost will need to increase, because you will be using more fuel so need more boost to compensate for....... Most of the issue is getting it to make boost during any situation/load. And so the VGT was born, the rest is history.

If I'm wrong let me know :lol:

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