Engine/Transmission (1998.5 - 2002) Towing EGTs. Don't want to kill the pistons

[John - K5AWO]

I've got a 34' travel trailer that is 7800# empty. I figure that will easily go up 2,000# without even trying hard #ad


I'm not in any hurry on the road and will be trying to keep it below 2200 rpm. I've never pulled anything with this truck in its' current mod status, so don't have a history on the new setup yet. Also, it didn't have any gauges until last month. Now it has a full set, FP, EGT, Boost, cyl head temp and transmission pan temp (wish that were the output line. It's going to chg).

Before I got it, this truck was a full time hauler but don't know if it had any mods, when I got it, it was back to stock configuration.

City driving is pushing the EGTs up to 950-1000 on easy acceleration (10 psi) up to 45 mph and then it drops off to 600* at cruise level ground. Should it be pushing that high on light accceleration?

My biggest question is, what should the max temp be for the EGTs to keep from damaging the pistons and other stuff? I need to learn what I can get by with for a short burst to pass, but then what do I have to keept the EGTs under for a long steady pull up a grade that is a mile or six miles long?

The stock turbo is hitting 31 psi floor boarded.

 

[BILLVO]

You can run steady at around 1200 and not worry, anything over that I would down shift Short bursts can easily go to 1400. But at 31 psi on the stock HY35 turbo you are going to have a turbo failure at that pressure and your temps are going to be higher than if you went to a hybrid HX35 turbo.

 

[Gary - K7GLD]

You'll get varying info on that one - but for a pre-turbo EGT, it's generally accepted that extended temps at and above 1300* be avoided - you'll have to use your own best guess as to what "extended" means...



In my case, towing our 5er, I rarely see more than 1200* - and that's only when fully accelerating such as a passing situation - and usually EGT is 1000* or lower in mountain grades - about 600* on the flats as you are seeing...

 

[PC12Driver]

But at 31 psi on the stock HY35 turbo you are going to have a turbo failure at that pressure and your temps are going to be higher than if you went to a hybrid HX35 turbo.

I think the 98. 5 autos still used the HX35. Good for about 35 psi.



1000* on acceleration is perfectly normal. 1250* all day long is acceptable. You don't have anything to worry about.

 

[johncameron]

Van Aiken and RV275's should be a great towing combo. Keep it below 1300F and you are off to the races.

 

[NoSeeUm]

May sound funny to you, but 2200 rpm is really a nice place to be towing at if you are worried about EGT's. I try to pull most grades hanging at that rpm. With my set up I can do that all day long and not really go over 1000F EGT.



Not your question, sorry just my $. 02.



Jim

 

[DLane]

Remember especially in the summer here your temps may/will vary from what others consider the "norm" Part of the joy of living in the phx metro area right. there are two guys down here who's names you need if you have a diesel pickup and you may already know of them. Randy @ Reliable Diesel in Mesa and Fred @ Desert Diesel in Waddel. Both great mechanics and diesel powerup junkies

David

 

[John - K5AWO]

Thanks guys for ALL of the comments. I have met Randy at Reliable once, bought a used APPS from him a while back. Have PM'd with Fred a couple of years ago.

My selection for the mods was done after a lot of reading here on the TDR, but even so, that doesn't take the place of the "seat of the pants" for what you see when pushing the go pedal.

I will have to say, that after all of the mods were done (my son did it out in California for me) and I got the truck back, wow! that first drive was sure different than when I last drove the truck.

You have to know that when my boy took the truck home with him, the transmission was stock with a bad TC. He added all the mods for me and then brought it back home. Night and day... ... ... So, that is why I put this post out. I've got a "brand new" truck and wanted to know what to expect.

 

[Gary - K7GLD]

May sound funny to you, but 2200 rpm is really a nice place to be towing at if you are worried about EGT's. I try to pull most grades hanging at that rpm. With my set up I can do that all day long and not really go over 1000F EGT.



Not your question, sorry just my $. 02.



Jim

YUP - low RPM and heavy loads are what significantly aggravate EGT issues...

 

[Vaughn MacKenzie]

1250F can equal disaster

I think the 98. 5 autos still used the HX35. Good for about 35 psi.



1000* on acceleration is perfectly normal. 1250* all day long is acceptable. You don't have anything to worry about.

Try telling that to JNutter (aka Shooter). . . he fried #6 towing his TT up a grade with the gauge carefully held to the 1250F preturbo limit. About the time he crested the grade with his '00 (or '01?) it started knocking

There was another TDR member I read of who fried his at 1250 also . . . point is if you're going to push the limits, you gotta be sure your pyro is RIGHT. 1150 is the highest I go on my 12V, period. Not all CTDs can sustain the same temps. . . a 3rd Gen HO/600 series can withstand higher sustained EGTs than a SO 24v or 12 valve.



Vaughn

 

[ROADWARRIOR]

I think it was Cliffman who fried his motor pulling a grade with a trailer. If I remember right, it was either a bad pyro or excessive timing or a combination of both that caused his motor to burn up.



The way I understand it is that 1250 with stock timing is not the same as 1250 with advanced timing.



Dan

 

[BILLVO]

Try telling that to JNutter (aka Shooter). . . he fried #6 towing his TT up a grade with the gauge carefully held to the 1250F preturbo limit. About the time he crested the grade with his '00 (or '01?) it started knocking

There was another TDR member I read of who fried his at 1250 also . . . point is if you're going to push the limits, you gotta be sure your pyro is RIGHT. 1150 is the highest I go on my 12V, period. Not all CTDs can sustain the same temps. . . a 3rd Gen HO/600 series can withstand higher sustained EGTs than a SO 24v or 12 valve.



Vaughn

I agree totally about differences in pyro's I like to stay under 1200 for short distances and am more comfortable at 1100-1150.



The piston melt downs I know of were caused by a couple venders subpar injectors. People are tight lipped about it on this sight but are open about it on other sights. Do your research on the subject on other sights.



I am just throwing that in as a caution that egts are not the only reason for piston damage.

 

[NoSeeUm]

I think it was Cliffman who fried his motor pulling a grade with a trailer. If I remember right, it was either a bad pyro or excessive timing or a combination of both that caused his motor to burn up.



The way I understand it is that 1250 with stock timing is not the same as 1250 with advanced timing.



Dan

Yeah, every timing box almost always advertises "and lower EGT's", what they don't advertise is that along with that there is higher combustion temperatures. How much higher is the combustion temperatures, I don't know. That is an unkown for me, so I try not to go there very much.



For myself, I don't push the EGT on grades as a general rule. Unless it is for a short duration (a 20 count) and I am doing some testing. The difference in speed between pushing the EGT's in a higher gear as opposed to going a little slower in the next lower gear is not all that much. I am generally not in much of a hurry anyways. The time saved (or bragging rights) is not worth the risk of major engine work to me.



Jim

 

[Gary - K7GLD]

1000* on acceleration is perfectly normal. 1250* all day long is acceptable. You don't have anything to worry about

As far as I'm concerned, seeing how close you can come to the ragged edge of EGT limits makes about as much sense as seeing how close you can drive your rig to the edge of a cliff!



I'm perfectly happy to drop a gear, slow down, or whatever it take to stay well within EGT limits...



I value my engine too much to sacrifice it for the "bragging rights" mentioned furter above!

 

[John - K5AWO]

I don't have any interest in "bragging rights". And I won't be in a hurry either. i just wanted to know where the limit is for good common sense and if it goes over that, then drop a gear and take a few minutes longer going up the hill.

If one thinks about it, traveling up a 10 mile long hill at 45 mph will take 13. 3+ minutes; versus 70 mph in 8. 5 minutes. So, it takes me 5 extra minutes to top that long grade. Pretty cheap insurance I think to take the slow route. I doubt that I am going to be pulling the TT at 70 anyway unless it is on the level with zero wind or a tailwind.

Diesel just went up to $3. 03 today from $2. 87 in one fell swoop. So that really kind of puts the squash on trying for any speed runs loaded.

I really appreciate everyone's comments as my primary purpose in this thread is learning where to call calf rope on the EGTs for a long pull.

 

[klaybus]

1150 sustained pre-turbo max for me! Very short temporary 1200 bursts prior to taking it out of OD when necessary.



Clay

 

[Vaughn MacKenzie]

Diesel just went up to $3. 03 today from $2. 87 in one fell swoop. So that really kind of puts the squash on trying for any speed runs loaded.

You're lucky, the cheapest I've seen is $3. 19, our Flying J is $3. 34 which I believe is the highest ever for here. We've only had diesel under $3 for a total of about 4-6 weeks since Hurricane Katrina.

 

[BILLVO]

You're lucky, the cheapest I've seen is $3. 19, our Flying J is $3. 34 which I believe is the highest ever for here. We've only had diesel under $3 for a total of about 4-6 weeks since Hurricane Katrina.

It was on the news here locally in ND we hit a high for #2 at 3. 42 a gallon in Grand forks, locally it has been at 3. 29 for a few weeks already.

 

[John - K5AWO]

What seems to me to be unbalanced is the pricing on fuels around here. Diesel has not ever gone below $2. 87 for over a year. Yet gasolene has been down under $2. 25 most of the summer until about a week ago, but they continue to keep diesel at a fixed price.

Something is wrong with this picture. Diesel is the base stock for gasolene.

 

[John - K5AWO]

Just a follow up after the trip

Hi all, and thanks for all the previous bits of wisdom. I am happy to report that all went well on my first trip out towing.

Loaded up a 3/4 diesel Suburban on a car hauler. Also, the burb was loaded with full fuel, a spare diesel engine, jacks, tools, etc... Didn't weigh it but estimated the total load was probably over 7,000# easy enough.

Unfortunately, with all the extra stuff thrown in the back of the Suburban, that trailer was tail end heavy which I did not like at all. Had to throw some junk on top of the hitch and chain it down to get any weight at all on the tongue. With that extra weight in the back it would start swaying side to side at any speed above 55 mph, so the trip to San Diego was done at about 51 mph and 1600 rpm

The EGT ran at 800-950 with boost at 6-10 psi on the level. When I got to Alpine and started up that 6. 5% grade, I dropped it out of OD and she sat at 2200 rpm with the cruise locked on. Never bobbled an inch, passed other stuff that was really dogging down on that grade

Watched the EGTs when starting up the grade and when it hit 1250, that was when I kicked it out of OD. EGTs fell off 250-300* and the speed stayed the same. I'm impressed and happy

On the return trip, the car hauler had my Honda Goldwing loaded on it and nothing else. A tire was bouncing at 67 mph, so I just cruised along at 63 mph (GPS) with 1925 rpm and enjoyed the views on I-8 and thought maybe this would be a good trip to see what kind of mpg the new mods can get.

Very happy to report that according to the TRAX fuel management computer the truck consumed 10 gallons less fuel coming home than going out there. IF and that's a big 'if', the fuel gauges on the TRAX are even close, the truck consumed 22 gallons approx for a 400 mile trip. That's somewhere above 19 mpg. That is a number that is 4-5 mpg higher than I ever got before with this truck in stock mode- even by the rough number provided by the TRAX gauges.


Going to top the tanks off later so I shall see the real numbers then.