The consensus on other websites, ie, RVnet.com, that it is pretty much impossible to create unsafe EGTs with a stock diesel, at least towing a reasonable load (in my case, "only" 6500 lbs) at freeway speeds.

Anyone have gauges on a completely stock LBZ that can confirm or deny this? I don't have gauges yet, and probably wont get them this year. But I have a long tow thru some mountains coming up in a few weeks, and I want to make sure I'm not likely getting anywhere near unsafe EGT territory.

Thanks in advance.

The consensus on other websites, ie, RVnet.com, that it is pretty much impossible to create unsafe EGTs with a stock diesel, at least towing a reasonable load (in my case, "only" 6500 lbs) at freeway speeds.

Anyone have gauges on a completely stock LBZ that can confirm or deny this? I don't have gauges yet, and probably wont get them this year. But I have a long tow thru some mountains coming up in a few weeks, and I want to make sure I'm not likely getting anywhere near unsafe EGT territory.

Thanks in advance.


Ya that consensus is correct, youve gotta look at it like this theses are work trucks that are ment to be worked and worked hard. And being that not every duramax owner is on the net trying to find out as much info on their truck as possible the factory isn't going to allow a tune that would ever see the truck into an unsafe EGT level. Heck the duramax engine won't even give you full power when the truck is cold just for the people who don't warm up their trucks. Egt only really becomes necessary when your running any type of tune because as you add fuel your EGT will rise. I typically run any where between 600-800F and thats a stock truck and my foot has gotta be in it good to crack a 1000F.
Hope this helps.

I don't agree. I've got a fairly stock truck in that there are no tunes just a little exhaust work and I hit 1325 F heading up the Coquihalla summit in British Columbia pulling my 2000lb boat. I was doing approx 75 miles/hr when I hit the top and didn't have my foot all the way into it but was actually surprised to see the EGTs that I was able to hit. Now this being said, it is a fairly long and steep grade (I estimate about 8% at the top) so that may have something to do with it.

I don't agree. I've got a fairly stock truck in that there are no tunes just a little exhaust work and I hit 1325 F heading up the Coquihalla summit in British Columbia pulling my 2000lb boat. I was doing approx 75 miles/hr when I hit the top and didn't have my foot all the way into it but was actually surprised to see the EGTs that I was able to hit. Now this being said, it is a fairly long and steep grade (I estimate about 8% at the top) so that may have something to do with it.

What gear was this in? Manual mode? Tow Haul mode? or full auto letting the truck do it's thing.
When towing in the mountains with my boat I like to use the Manual mode and select which gear I'm in. I can keep the rpm's up a little bit, which brings the egt's down. With my boat and truck full of camping gear I'm at 15,500 lbs total weight on a public Cat scale.

I have seen my "stock" LBZ hit 1450 numerious times.
Around that point the truck down shifts and EGT's drop.
LBZ's run hot in the mountains.

You can hit some nasty EGT's if you are not careful, even stock. Towing heavy can do it.

Ya that consensus is correct, youve gotta look at it like this theses are work trucks that are ment to be worked and worked hard. And being that not every duramax owner is on the net trying to find out as much info on their truck as possible the factory isn't going to allow a tune that would ever see the truck into an unsafe EGT level. Heck the duramax engine won't even give you full power when the truck is cold just for the people who don't warm up their trucks. Egt only really becomes necessary when your running any type of tune because as you add fuel your EGT will rise. I typically run any where between 600-800F and thats a stock truck and my foot has gotta be in it good to crack a 1000F.
Hope this helps.

Where did you hear that?

IMO, on a 100% stock truck, you won't hurt it immediately. You can cause long-term damage, after the warranty is long-gone(which GM wouldn't care about), but even then....think about the hundreds of thousands of clueless people who bought diesel trucks to tow their big travel trailers/horse trailers, who don't have a clue what EGT's are. There are a ton of them who don't have any problems, and have trucks that last a lot-o-miles. On the other hand, if it was my personal truck and I was going to be towing heavy, I would be putting gauges in......for the small amount it will cost, it will be cheap insurance. JMO though......

If you only see 600-800 you must baby your truck alot. i have a 5 inch exhaust and diamond eye down pipe, and i see 1250 plus on some hills in colorado and that is empty with a trailer on it can hit 1500 very easy if you arent careful. put the gauges in and you will be amazed at how hot it can actually get

From the looks of things its pretty hard to hurt these engines EGT wise. one user on here was doing a burnout and had the uppipes GLOWING orange. and the coolant temp gauge pegged! and he drove it home, and it was still running untill some electrical problems stopped it a few weeks back. it was a LLY.

I got over 1300+ in my stock LBZ pulling a civic on a car trailer (not tow dolly) at 70 going up a slight hill. Also, climbing a mountain with 8% grade I was in 4th and had to slow down to 40- 45 to keep EGTs under 1300.

No Gauges = Ignorant Bliss
Gauges = Informed hauler

It is possible, and easy to hit excessive EGT's with a stock truck. All you have to do is add some weight and lug the engine. Climbing a hill is typically where you will see this, IF YOU HAVE GAUGES. I was completely astounded at the temps my truck got to, after I intalled gauges. Before that I was oblivious as to the extreme temps it was actually getting to. I have had mine to 1500* with the gauge, and I have done the same haul before the gauges. I know that I have had to had higher than that before the EGT gauge was installed. I can also hit that temp empty with my foot buried for a while too.

I got over 1300+ in my stock LBZ pulling a civic on a car trailer (not tow dolly) at 70 going up a slight hill. Also, climbing a mountain with 8% grade I was in 4th and had to slow down to 40- 45 to keep EGTs under 1300.


I admittedly don't know a ton about these trucks like many of the fellas here...but doesn't this seem a bit embarrasing? Having this manly diesel powered, do anything, anytime, pickup and have to nurse it to 40-45 MHP to do any kind of hauling? Again, what do i know, but I would think these trucks should be able to pull 2k up a 8% grade like they were going downhill or something.

That said...I am in the same boat...I see 1200+ regularly just trying to pass someone on the freeway; and I don't have a lead foot. :confused: It's emabrrasing to watch a toyota Corolla pass me on any sort of grade because my EGT's are entering the 1300+ range and I have to milk it along.

I admittedly don't know a ton about these trucks like many of the fellas here...but doesn't this seem a bit embarrasing? Having this manly diesel powered, do anything, anytime, pickup and have to nurse it to 40-45 MHP to do any kind of hauling? Again, what do i know, but I would think these trucks should be able to pull 2k up a 8% grade like they were going downhill or something.

That said...I am in the same boat...I see 1200+ regularly just trying to pass someone on the freeway; and I don't have a lead foot. :confused: It's emabrrasing to watch a toyota Corolla pass me on any sort of grade because my EGT's are entering the 1300+ range and I have to milk it along.

2 things......try downshifting, you will see the lowest EGT's if you are around 2200-2800 rpm, the EGT's will go WAY up if your in 6th gear lugging the engine. The other thing, you probably could keep going 70 mph(keeping up with the corolla!!!), if you ignore the gauge, and you will most likely be fine(on a stock tune of course). On the other hand, it is possible to hurt it, so why bother. And also, you might not necessarily cause immediate damage, but down the road, you might need new pistons and/or turbo.

ive peged out my ppe egt gauge to 2000 many many times!!

2 things......try downshifting, you will see the lowest EGT's if you are around 2200-2800 rpm, the EGT's will go WAY up if your in 6th gear lugging the engine. The other thing, you probably could keep going 70 mph(keeping up with the corolla!!!), if you ignore the gauge, and you will most likely be fine(on a stock tune of course). On the other hand, it is possible to hurt it, so why bother. And also, you might not necessarily cause immediate damage, but down the road, you might need new pistons and/or turbo.

Sound advice...thanks Ryan

I see 1500+ on the big hills pulling my enclose trailer. Never let out and never had any issues.

try downshifting, you will see the lowest EGT's if you are around 2200-2800 rpm, the EGT's will go WAY up if your in 6th gear lugging the engine.

X2. My LLY is a 5spd, but whenever my EGT's hit 1300 towing hills, I drop to 4th and they drop right away. RPM's are your friend when towing. I've never had to back off in 4th because of excessive EGT's. The highest they've gotten is 1250 in 4th and held there. That is running a tow tune also.

So what does high EGT's hurt?

high EGT's hurt the pistons, heads, and turbo. (someone correct me if im wrong). if they get too hot, you could blow a hole in a piston, or lose a headgasket, or ruin the turbocharger.

Ya that consensus is correct, youve gotta look at it like this theses are work trucks that are ment to be worked and worked hard. And being that not every duramax owner is on the net trying to find out as much info on their truck as possible the factory isn't going to allow a tune that would ever see the truck into an unsafe EGT level. Heck the duramax engine won't even give you full power when the truck is cold just for the people who don't warm up their trucks. Egt only really becomes necessary when your running any type of tune because as you add fuel your EGT will rise. I typically run any where between 600-800F and thats a stock truck and my foot has gotta be in it good to crack a 1000F.
Hope this helps.

I completely agree. The trucks dont have an EGT gauge from the factory because GM knows that even if they did, no one would even know (or care) what the damn thing reads. If GM found that with their stock tuning, EGT's were a problem when towing at max GCWR, then they would have some idiot light or warning that says "pull over", or, more likely, just have a secret table in the ECM that pulls fuel back a little bit when the EGT's got hot.

Just hook up your trailer, put it in drive, put it in tow/haul, drive it, dont give it a second thought, and be on your way.

For you guys who think you need an EGT gauge when its stock, do you have ANY frkin idea how many people buy these trucks, dont know what an internet forum is, dont know what a tuner is, and dont even know what gauges are or "what an EGT is"....they just drive them the way GM meant them to be driven...they tow the max loads the truck was rated for....they change the oil everytime the DIC says "change oil", and other than that they treat it like any other vehicle (gas or diesel) they've owned in the past.

and...guess what...they do that/run them [dmax's] like that for hundreds of thousands of miles and they dont have a single damn problem with the thing. Imagine that.

ben

Where did you hear that?

IMO, on a 100% stock truck, you won't hurt it immediately. You can cause long-term damage, after the warranty is long-gone(which GM wouldn't care about), but even then....think about the hundreds of thousands of clueless people who bought diesel trucks to tow their big travel trailers/horse trailers, who don't have a clue what EGT's are. There are a ton of them who don't have any problems, and have trucks that last a lot-o-miles. On the other hand, if it was my personal truck and I was going to be towing heavy, I would be putting gauges in......for the small amount it will cost, it will be cheap insurance. JMO though......


It was actually a forum on here, one of the memmbers who had EFI live was able to log it and coolent temp must reach a certain level before full power is is reached at leased thats what i herd? And me coming from a colder climate when it gets cold here im pretty sure i feel a little bit of a power restriction. But eh i could be wrong maybe someone can chime in and clear things up.

I agree with Ben you are not going to hurt the truck with the stock tune compared to a 6.5 the Duramax is a engineering marvel at the amount of abuse it will take without batting an eye

It was actually a forum on here, one of the memmbers who had EFI live was able to log it and coolent temp must reach a certain level before full power is is reached at leased thats what i herd? And me coming from a colder climate when it gets cold here im pretty sure i feel a little bit of a power restriction. But eh i could be wrong maybe someone can chime in and clear things up.

I'm not positive, but I'm 99.99% sure that isn't true.:confused:..........Ben, is it true???:)

I'm not positive, but I'm 99.99% sure that isn't true.:confused:..........Ben, is it true???:)

To some extent....there IS a table in EFILive that says "max fuel injected QTY when cold" (B0729)

HOWEVER...I have personally found that (at least on the LLY's), it doesnt seem to do anything??? :confused:

in a stock tune the table is maxed out to 120mm3.

ie, I have programmed it/configured the table to limit fuel to say 70mm3 when below the "cold/warm injection point" (162*)....but when the engine was cold (below 162*), I datalogged it and floored it, and the mm3 still went to 95mm3 (or whatever normal hot wide open throttle fuel rate is). Thats what confuses me.

It DOES change the main injection timing and pilot inj timing all around based on ECT...but as far as fueling, I dont know the exact answer to that.

Regardless, I think its safe to say that if you are running a stock tune, its safe/OK to drive it when its cold like any gasser, because GM specifically tuned it that way..with the intent that 99% of people buying these wouldnt know the 'specific do's and dont's" of diesel operation... (for example, its important to not run diesels hard until they warm up...we all know that, but most people who buy these trucks wouldnt know/care).

Obviously its better to wait before really hammering on it, but if the engine is cold and you suddenly have to merge with traffic or go WOT for some reason, I wouldnt worry too much about it. :)

JMO

ben

x2 big time w/ duratothemax, put it in tow/hual mode and go ,I see lots of old guys w/ stock trucks no gauges, and big trailers not giving a rats a** about exhust temps . If it blows up, go get a bigger truck.

What gear was this in? Manual mode? Tow Haul mode? or full auto letting the truck do it's thing.
When towing in the mountains with my boat I like to use the Manual mode and select which gear I'm in. I can keep the rpm's up a little bit, which brings the egt's down. With my boat and truck full of camping gear I'm at 15,500 lbs total weight on a public Cat scale.

Sorry for the late reply. I was using T/H in Auto. The truck kept the RPMs around the 1800 mark which I believe is max torque so I just played a bit with the throttle to make sure it was in that range.

I'm not positive, but I'm 99.99% sure that isn't true.:confused:..........Ben, is it true???:)

I'm not Ben;) But I'll throw in my $.02 anyways.

If I am reading the LMM tune correctly, it actually adds fuel to the "normal" amount whenever the ECT is below 32*F. This is likely to compensate for the lethargic feeling that older trucks can experience in cold temps.

Cold air charge = cold combustion temp = less combustion pressure = less power for the same throttle input. Hence, the lethargic feeling. That all adds up to the perception that the ECM is limiting power because it's cold.

Edit: LB7's & LLY's...no fuel modification based on cold ECT. Just looked at an LBZ tune and it does pull fuel...starting at +70*F to a max of 5% fuel @ -54*F and below. Dug deeper in the LMM tune and found that it pulls fuel in some areas (midrange) and adds fuel in others (lowrange) and no changes @ WOT....

Thanks everyone for the input. Ben's gentle reasoning is alway very much appreciated! I think I'm persuaded not to worry about it until/unless I put a mild tuner on the truck, at which will almost certainly include an EGT monitor (eg - Edge Evolution). That probably wont be until my 5 yr warranty expires next April.

Sorry for the late reply. I was using T/H in Auto. The truck kept the RPMs around the 1800 mark which I believe is max torque so I just played a bit with the throttle to make sure it was in that range.

Next time knock it down a gear and get the RPM above 2200 and the EGT will drop pretty quick.

Towing a double jetski trailer on the Hope Princeton with the stock tune I can hit 1300 deg plus with a heavy throttle and low RPMs.

x2 big time w/ duratothemax, put it in tow/hual mode and go ,I see lots of old guys w/ stock trucks no gauges, and big trailers not giving a rats a** about exhust temps . If it blows up, go get a bigger truck.

Not everyone can ruin a $40k truck and buy a new one. That's why people with or without stock engines put gauges on to extend the life of the truck. I plan on keeping it for 20years if possible. It may not blow anything up immediatley, but over time, keeping the EGTs low and shutting the engine off when they are low may extend the life of turbo, pistons etc. And extend the life of the truck and save me money... Can't be too careful.

Sorry for the late reply. I was using T/H in Auto. The truck kept the RPMs around the 1800 mark which I believe is max torque so I just played a bit with the throttle to make sure it was in that range.

Next time try cruising that mountain at 2000-2100 (probably a one gear drop) and see what your EGT's do..........you will see it drop a lot.

OK fellas...I tried the manul downshifting with my EGT's sitting at about 1150....didn't see even a smidge of a drop in EGT's with the downshift. Nothing, nadda, zilch. Any ideas?

Also, if it can be explained easily, how do higher RPM's relate to lower EGTs? Seems the opposite would be true?

OK fellas...I tried the manul downshifting with my EGT's sitting at about 1150....didn't see even a smidge of a drop in EGT's with the downshift. Nothing, nadda, zilch. Any ideas?

Also, if it can be explained easily, how do higher RPM's relate to lower EGTs? Seems the opposite would be true?

What rpm were you at before the downshift? After?

I don't really know know to explain it, but think about a standard car....what is easier, starting in first gear(lower ratio) or starting in fourth gear(a lot higher ratio). This is obviously an exaggerated example, but it should help you understand. Same concept with pedaling a bike, is it easier on your legs to be in a higher gear, or lower gear while going up hills. The reason this concept relates to EGT's is because the engine doesn't have to work as hard to get the same amount of work done, therefore less fuel needs to be injected, which = lower EGT's. If that makes any sense!!;)

If less fuel is being injected, why don't you get better mileage with a lower gear?

Here's my theory on why downshifting lowers EGT's: more air is going through the motor to pull the heat out the exhaust pipe faster.

Airflow and turbo outlet temp....

Example:
WOT @ 2000 rpm you could see 45lb/min airflow
WOT @ 2800 rpm you could see 55lb/min airflow

You have the same amount of boost, but more airflow due to higher rpm. The additional air serves to lean the mixture, or another way to think of it, dilute the hot air with additional cold air. The higher airflow also brings the turbo closer to peak efficiency which lowers outlet temp, which lowers EGT.....in theory anyways. YMMV.

If less fuel is being injected, why don't you get better mileage with a lower gear?

Here's my theory on why downshifting lowers EGT's: more air is going through the motor to pull the heat out the exhaust pipe faster.

Yes more flow typically more RPM and HP and moving more air will typically cool things.

on the other thing if your at 1150 and drop it a gear then no it won't go down because that isn't even hot enough to worry about it.

If less fuel is being injected, why don't you get better mileage with a lower gear?

Here's my theory on why downshifting lowers EGT's: more air is going through the motor to pull the heat out the exhaust pipe faster.

It's about mechanical advantage. Drop a gear and the work load is spread more throughout the drivetrain rather than just the engine. It lowers your final drive ratio. It allows more energy to get to the ground rather than it being lost through heat production.

Remember, GM said the Duramax produces it's best torque at 1600-1800 rpm's but when they dyno an engine, the transmission is not attached. Go 1:1 (4th) if you're going to rely on the GM torque curve. Think about it, when you dyno a car they do not go past the 1:1 ratio.

What rpm were you at before the downshift? After?



I can't say for certain....I will do it again this afternoon and get back to you Ryan. Thanks for the help.

If less fuel is being injected, why don't you get better mileage with a lower gear?

You do.....when your towing. I don't really know how to explain it, but if you really think about it using common sense, you'll get it.

It's about mechanical advantage. Drop a gear and the work load is spread more throughout the drivetrain rather than just the engine. It lowers your final drive ratio. It allows more energy to get to the ground rather than it being lost through heat production.

Exactly. Instead of staying in OD and having to rely on brute engine torque, drop down to 4th and produce more torque at the wheels with less engine output through gear reduction.