What you can learn from an egt-pyrometer

[imnprsd]

Last week I installed an EGT (with a pyrometer-K style probe) in my ISC-350HP/420HP and now that I have completed a 1500 mile trip I can share some findings with you.

You should also know I installed an Ag-Diesel Power Module in my ISC-350-CAPS and I now get 420HP and 1086 lb-ft of torque (on the dyno). So while your stock ISC-350 will have different EGT values, I suspect you will reach the same conclusions as I did.

[COLOR="Red"]Note: I was surprised how easy it is to exceed 1350F under a variety of load conditions. [COLOR="Red"](See Chart on how NOT to exceed 1350.) And now that I have an EGT I can tell you that I am driving my coach much differently than I did before.

Therefore, I highly recommend you install an EGT gauge and Pyrometer (K-probe) in your exhaust… just before the turbo. I will post how I did this in another thread but for know I can tell you that I highly recommend you get a digital EGT so you don't have to work hard at readlng the old-style, analog type, neddle EGT gauges.

I chose this one because it matched my fuel pressure indicator and the wiring was the same.

When you review the attached chart you will see that I even took measurement up an 8% grade and a 15% grade. And if you are wondering where I found a 15% grade… I came across 1 in The Big Bend National Park, TX last week (June-2020).

I also encountered a second 15% grade on HWY-170 when I left the park, so if you travel this route, I highly recommend you have a HP/Weight ratio of over 0.0131! …And frankly, I don’t think you can get to these limits unless you have increased your HP by installing an Ag-Diesel Power Module.

At this point I can’t tell you if the Ag-Diesel Power Module increases EGT values, because I did not have an EGT installed in my coach when I was running it as a stock ISC-350. But regardless of this, in my opinion, it’s likely you too will need to change the way you drive your coach to keep your EGT values within acceptable limits!

What is an acceptable EGT limit? …That’s a good question. It would appear that most people set this limit at 1250F, but I think that’s a holdover spec set by Bank’s Power on 250HP-ISB engines? Still, I was able to keep my ISC-350/420HP EGT limits in the 1250F range by constantly down-shifting whenever I found my RPMs to drop under 1800 or on 4% and higher grades I would keep my RPMs at 2000.

Personally, I will tell you that I see no reason why you can’t run up at 1350F for 15 seconds when you need the power to merge on to a freeway; or even 1400F for 10 seconds or less, but I would really try to avoid these very high EGT levels.

After 30 years of RV driving, this is my 5th RV and I'm shocked that I am now re-calibrating my driving habits. I.e. it's no wonder these RV manufactures DO NOT include an EGT with every RV they sell! ...Because they don't want you to know you are always running close to "red line" and probably are over shooting that point often! ...Think about it: How many RV would you be able to sell if you established a red-line of 1350F for 15 seconds and your customer found themselves easily exceeding 1400F in every day driving?

Further, this is interesting: When I accelerate from a dead stop up to about 35MPH at WOT you will not exceed 1250F on your EGT. However, when you attempt to accelerate from 35-60+ MPH at WOT you will exceed 1250F!!! …And this is the upper speed range you will encounter when merging on to a freeway.

Therefore, having an EGT gauge will help you monitor your driving habits and it will force you to adjust them. In fact, as I said above, with an EGT it’s likely you will change your driving style if you care about babying your engine while at the same time what to take full advantage of all the HP and torque available.

IT ALL COMES DOWN TO HP, TORQUE, AND WEIGHT

I have a 32,000 CWGR, 2004 Itasca “Horizon” 40AD; with a 3000MH Allison deep-pan transmission; and a Meritor #RS-19-144; with 275x80x22.5” tires and wheels… and I am towing a 3700 Lb. Saturn Aura, which makes a big difference on my EGT gauge. Plus I have an Ag-Diesel Power Module that delivers 420HP on the dyno.)

…And WHY are all this factors important? Well, it’s because all your EGT numbers (and for that matter your Manifold Pressure readings too) are based on gear ratios and that includes the size of your tires!

Remember, HP means nothing if you can’t produce rotational torque.

Note: I have not yet installed a “boost fooler” and I’m not sure I will based on another RV owner’s evaluation -- who said that $12 part on Amazon did NOTHING to lower his EGT and only raised his MP by 1-2 PSI. However, I’m still looking into other recommendations that you can better adjust your manifold pressure by installing a 1/4” ball valve to cut-off or reduce the PSI to the turbo actuator. And with this method the idea is to increase MP to 30 PSI for the expressed purpose of lowering your EGT. (TBD)

PARADIGM SHIFTS TO HELP YOU MANAGE EGT

* You can maintain your EGTs (mostly) under 1250F when traveling with your cruise control “ON” if:

A) You maintain cruising speeds under 65 MPH on typical freeway terrains or you are willing to travel at 70MPH. Why this is so I am not sure, but I think it has something to do with your coach’s momentum that enables you to travel over that small hill faster and therefore your engine does not spend as much time climbing that hill vs. the time it would take if you were traveling at 55MPH.

B) When climbing steeper grades 3% or more, then you need to downshift your transmission to keep your RPM’s above 1800; and on 4%+ grades you need to keep your engine RPM above 2000 RPM in order to keep your EGT under 1250F. (See chart.)

* Stop using your foot pedal to maintain driving speed.

This is especially true when using “cruise control” because much of the time your engine will have enough torque to avoid downshifting the transmission, but this is a major problem, because it will lead to your RPMs dropping under 1800 on a minor grade of 3% or less, by adding more fuel, that will cause your EGT to rocket over 1400F without you knowing it!

è If the hill you are trying to climb gets steeper, you need to manually downshift your transmission. Fist to 5th gear… and then to 4th gear… or even to 3rd gear to keep your RPM’s over 1800… and on steeper grades above 4% you probably will need to downshift your transmission as necessary to keep your RPM’s over 2000… and then your EGT numbers will mostly remain under 1250. …And then you MPH is whatever it is!

è Don’t worry about MPH if you care about your engine. Drive your coach according to RPM and all your temperatures will be lower than if you over fuel or lug your engine.

Specifically, you should stop worrying about climbing that hill at 55 or 45 or even 35MPH. IT DOES NOT MATTER, because that grade is only a few miles long anyhow.

...What matters is how you treat your engine; and if you don’t have an EGT I hope the chart I created will help you accept what I am sharing with you.

HOW TO CONTROL YOUR EGTs WHILE CLIMBING A GRADE

I compiled this chart after taking a lot of measurements; and what I came to realize is that my EGT is a function of gearing and RPM when traveling on the highway with 2-3% grades and/or when getting into steeper grades like 4%-6%. ...And in all cases, if you don’t have your RPMs above 1800 you will experience high EGT values that may exceed your acceptable limits. ...Whatever that is? ...I'm still trying to verify you can operate your ISC safely at a constant 1350F, but I'm having trouble find an authority on this subject.

[Mlfiedler]

Man, you put together some impressive sets of numbers!

It is a shame those of us without the Ag-Diesel add on are pressed to compare how our vehicle may have responded in the same circumstances. I wonder, is the “plug-and-play” capability of the A-D unit a feature that would allow you to expand that data set, by dropping the A-D unit out of the circuit?

If I understand correctly, wouldn’t that allow your ECM to meter in fuel like most our not-yet-upgraded ISC350’s, and make the effects of RPM and the ups and downs of the roadway on tracking your EGT all the easier to understand? Just a thought.

Love that you have real world experience to tell us about!

[imnprsd]

Mlfiedler: Yes, the AG-Diesel module can be easily unplugged, but I'm not going to do it because I have to take apart my bedroom floor in my Freightliner Chassis to get to the top of the engine.

My hope is that someone with a stock ISC-350-CAPS or HPCR or HPFR coach in the 40' or 32,000 lb weight class, who tows a car, will install an EGT and then creates a chart like did so we can compare EGT numbers.

NOTE: Thread by VANWILL also talk about lower EGT values by preventing the turbo waste gate from opening. This increases boost from 24 to 32 PSI and forces more air into the combustion chamber, but without enough fuel to burn the additional air creates a leaner burn, which lowers EGT in a diesel engine.

So my next step is to bypass the turbo-actuator air line by adding a boost fooler or 1/4 ball valve. Then I will recreate my chart to see if this method will lower my EGT.

I realize my Ag-Diesel Performance Module skews the EGT numbers some, but by how much I do not know. My guess is that your stock ISC-350 will reach exceeding high EGT numbers anytime you are climbing any type of grade (2%-4% and steeper) and your RPM is not above 1800 and 2000 for the steeper grades.

I found it interesting that I could climb an 8% grade and a 15% grade at 2000 and still keep my EGTs inline with acceptable limits. HOW? BY DOWN-SHIFTING TO LOWER GEARS!

...And I bet that 95% of RV owners don't down-shift to lower gears often or fast enough. ...But now that I have an EGT I do it faithfully and I don't think it's because I installed the Ag-Diesel Power Module.

One think I know for sure: I'm not going to give up my Ag-Diesel Power Module, because without it my 350HP/32,000 RV, towing a car, is a DOG!!! So I just have to be careful when calling on those extra ponies!

My message to everyone with a stock ISC-350 or ISL-400 is this: When accelerating from 35-60 you need to back off your foot pedal and let the engine keep pace with our fuel delivery; and when climbing a hill or grade of any type, you need to keep your RPMs over 1800 (or 2000 for 4%+ grades) if you want to treat your engine nice!

Here's the digital EGT gauge I installed, which I like very much since it's a digital readout: ($130 on Amazon)

https://www.amazon.com/MaxTow-Double...s%2C606&sr=8-3

And if you do install a FASS or AirDog I would recommend this Fuel Pressure Gage:

https://www.amazon.com/MaxTow-Double...3751066&sr=8-1

And this dual gauge holder:
https://www.amazon.com/HOTSYSTEM-Uni...7N69GPZB1XBN8J

Note: You will need 3 wires for the Fuel Pressure Gauge; and 2 wires for the K-Probe Pyrometer to EGT gauge. So if you can find 50 feet of 18-gauge, 5-wire, speaker wire that will allow you to run 1 wire to both the EGT and the Fuel Pressure Sending Unit.

[MountainMike]

Great post and info on EGT. I too have installed a EGT and fuel pressure gauge in one instrument ( I used a VEI dual function gauge) I wonder if the overheating on the manifold could be a cause of the manifold cracking as well. Imnprsd, I am thinking of installing a 3way 12volt solenoid valve on the turbo-actuator so at anytime I can dump the pressure control and increase the boost (at the drivers seat) from the turbo and then return to normal boost control. Further note I did followed your post and installed a FASS pump and filter system.

[Ray,IN]

IMNPRSD, Aluminum alloy(pistons) begin to melt at 1,240°F.

ref: https://www.engineersedge.com/materi...ures_13214.htm

[imnprsd]

Exactly... So I am asking if anyone out there who has a stock ISC-350, 32,000 lb RV, and a tow car... Will answer these questions:

(NO SPECULATIONS PLEASE)

1) Comment on their EGT numbers when accelerating from a dead stop to ~35 MPG?

2) Comment on their EGT numbers when accelerating from ~35 MPG to 60 MPH?

3) Build a chart that is like the one I put together showing various power configurations when climbing a grade?

4) And I want to know from both ISC and ISL owners how often they push their stock engine to 1350F or even 1400F for some period of time (usually by mistake, because their cruise control is on and the highway just went from 2% to 3% uphill and the drive did not downshift.

My guess is that all ISC and ISL are capable of running at 1350 safely for a period of time. WHY?

My other guess is that EVERYONE (most everyone) is making the mistake of comparing the very hot EGT numbers at the exhaust manifold to the temperature inside the cylinder on the piston!!! ...And so we have yet another paradigm shift to think about.

This thread is mostly about getting everyone to down-shift their transmission when climbing any type of grade; and to be more careful when setting the cruise control. ...And for the rest of the Motor Heads out there, maybe someone with exceptional knowledge in this area will chime-in and square all these assumptions away.

IMO, I have not heard from anyone who did not get their EGT advice from a third party who got it from their dad or some other qualified individual.

What I want to do is separate story from theory from truth; and I hope in the end we all know how to SAFELY OPERATE OUR ENGINES... STOCK OR MODIFIED LIKE MY ENGINE IS NOW.

===

Further, I theorize that a single "K" probe pyrometer, installed in the exhaust manifold, just before the turbo is will show hotter temperatures in the 1350F range (and hotter)... because you are combining heat sources from 3 cylinders... where the pyrometer is installed. (See Picture.)

WHY IS THIS THE CASE? IDK, but maybe someone WITH ample qualification can confirm or denounce this theory. My exhaust manifold is a twin scroll (T-4) type exhaust (I think) and each side of the exhaust chamber is collecting heat from 3 cylinders.

And if I am right, then the real question about comparing EGT numbers to the aluminium alloy of a piston, or valves for that matter, is a mistake. Because the question you really should be asking yourself is: HOW MUCH HEAT CAN MY TURBO HANDLE ON A REGULAR BASIS?

Which reminds me: Another good practice I am now following is to give my engine more time to "cool down" before I turn the key off. ...And yes, this is because I also want to treat my turbo right!!!

[Mlfiedler]

Yeah, I wouldn’t want to tear up the floor, either.

I think you mentioned the A-D system allowing an owner to ‘set’ the power boost, at 0, 10%, 20%, or 30% . . . . Is that control accessible only through the floor?

(I’m way behind you, still addressing the fuel feed to the CAPS pump!)

Mike
.

[Maik]

You are correct to drive based on EGT and boost values. I bought my old coach with the two gauges installed. I drive based on EGT and try not to exceed 1200F on a regular basis. I will sometimes push it to 1300F but only in rare circumstances passing or getting around a truck on a hill.

[TR4]

imnprsd, from my bench test on the boost elbow, you will get more boost. The problem I found was that I couldn’t get it to regulate boost pressure to around 26 psi, a small increase over the 23 psi I had. It was basically like disconnecting the actuator. Installing a 1/4” ball valve to regulate the pressure won’t work, this will only slow the opening and closing of the waste gate. Now if you install this same valve on a T, on the hose from the turbo to the actuator, to regulate the “bleed off” pressure to the actuator this will work. You only need to bleed off a small amount of pressure.

I tried Vanwill’s method of removing the actuator, unstaking the actuator arm and shorting it by two turns. This improved my boost by a small amount. Before my max boost averaged around 23.3 with a high of 23.8 (on rare occasions). After adjusting the arm my max boost averaged around 24.5 psi with a high of 25 (on rare occasions).

I’m at around 34K, towing 4K
EGT before 1350
EGT after 1325
This is climbing many passes from SFO to Boise.

Although only a minimal decrease in EGT, I found I could maintain my speed longer without backing off the throttle. I’ve driven this route for the last six years. I also found that on certain grades I max out at 1200 F where as before I would be at 1325 F.

Since I’m on vacation, I don’t what to do anything radical and cause a breakdown. I will slowly adjust the actuator and hope for a maximum of 1250 F.

Bill

[CountryB]

Where are you getting the info about the "max exhaust temp" (1350)? I have not been able to find any manufacture's document stating a recommended max exhaust temp.
Is this published or common knowledge or ?

[Mlfiedler]

Originally Posted by CountryB

Where are you getting the info about the "max exhaust temp" (1350)? I have not been able to find any manufacture's document stating a recommended max exhaust temp.
Is this published or common knowledge or ?

I agree, Cummins certainly doesn't seem to hang it out there, as a number to guide us in tinkering with systems! I don't find any "Official" statement by any other engine maker, either.

Here's a pick-up truck world perspective on it: https://www.dieselhub.com/performance/egt.html

But if you Google the question, you get a fair number of replies that favor a range from 1250 to 1350, allowing for "spikes" as high as 1400. If you are dragging a sled for competition, you are going to see higher numbers, and be busy rebuilding engines!

[CountryB]

Thanks for that Link. I did some Googling on the subject and found this article (a really good read on the subject). The other sources I came up with agree.
Bottom line the 1250 to 1350 range is the maximum, as stated by OP and others.

https://official.bankspower.com/tech...-is-important/

[jcussen]

Originally Posted by CountryB

Thanks for that Link. I did some Googling on the subject and found this article (a really good read on the subject). The other sources I came up with agree.
Bottom line the 1250 to 1350 range is the maximum, as stated by OP and others.

https://official.bankspower.com/tech...-is-important/

That is the article I have always used as a reference. I have my pyro set to flash at 1300 F. and alarm at 1350 F. Once you get used to it, makes throttle and gear adjustments easy.

[imnprsd]

Today I plugged the turbo compressor side air line that connects to the actuator bellows, and now there is no air pressure to overcome the spring pressure that holds my waste gate closed.

My assumption is that the turbine would spin faster and drive the compressor wheel to deliver more air into the engine. And since diesels like to run lean my expectation was that my EGTs would all be lower.

The funny thing is: My MP gauge only reads +1PSI, but my EGT numbers are lower across the board, and I don't know why?

I understand that a faster spinning turbine will make the compressor side drive more air through the Charge Air Cooler (CAC) and that is supposed to result in high boost pressure (I was expecting 30-32 PSI) but I only got 26 PSI.

So on one hand, if my EGT number are lower, and they appear to be; and my MP gauge has barely inched-up 1-PSI to 26 PSI max at sea level, then maybe my boost pressure is actually higher than what is being displayed on my electric MP gauge? IDK, but I will try to find out why?

Can anyone tell me how and where my Freightliner electric Manifold Pressure (MP) gauge receives it's information?

A) Is is this information coming directly from the ECM? ...Or B) is there a MAP like sensor mounted somewhere on the cold air side and my gauge interprets that.

Note: Along with lower EGT numbers, I even think I have more horse power, but I will not be able to verify this until I can visit Ag-Diesel in Indiana.

So to recap:

* I installed an Ag-Diesel #12100 in my 2003-ISC-350-CAPS engine and now I get 420HP on the dyno...

* But my EGT numbers were very borderline (1350+) whenever my RPM dropped below 1800 when climbing most grades...

* Then I plugged the turbo actuator boost line to "choke-off" the air to the bellows inside the actuator, and now my waste gate does not open at all...[/B]

* And at this point I was expecting 30-32 PSI of boost pressure, but I only got 26 psi. However, my EGT number all appear to be under 1300... I.e., lower after I plugged the air line vs. before.

I'm thinking the ECM is being "fooled" somehow; only this time it the MP gauge that is not reading right?

Does anyone know how I can easily verify what my actual MP is? ... And if so, where do I check it?