Question about black smoke at higher elevations in an HDJ81 (1 Viewer)

[shmukster]

Just got back from a 4400- mile trip to Colorado in my 1990 HDJ81. Trip notes here:

Notes on a 4400 mile trip in an HDJ81

The truck performed extremely well I couldn't have been happier with anything except maybe the brakes. I did note that at higher elevations when the transmission would downshift going uphill the truck would smoke black. Sometimes very heavily and I believe it can be said that the higher the elevation the blacker the smoke was. We did several high passes and it was first evident when going up Guanella Pass on the hard road. I didn't see any negative effects of this but just looking to see if this is common. Being very unfamiliar with and knowledgeable about diesels I'm looking for some explanation for this. Thanks!

 

[roma042987]

totally normal Gary. Mine did the same thing going up Guanella and Monarch last week. Its just that the turbo doesn't make enough boost because of the lower density of the air so it over fuels. Mine was like a freight train at times steadily leaving a dust trail hauling tail over the passes. It was nice to go over Monarch pass at 55mph passing a few modern vehicles, heck if it wasn't for the curves I could have gone even faster.

 

[RhinoRig]

It's unburnt fuel. Black smoke means you had too much skinny pedal applied. You were probably also heating up the head to about 1300F or more. That's the data I have from living at 8600ft and the EGT sensor. We drive by temp anymore instead of speedometer. "How fast are you going, honey?" "Oh, about 1050F." Which translates to about 65-70mph on the flats (not that we have much of that) but 40mph going up a steep grade, especially Vail pass or Eisenhower tunnel. It's the slow lane with the big diesels for me. Sure, I could pass everyone, but who wants a melted turbo?

Now, I think that she's running really hot based on what others have reported. The high alt compensator may not be working or the PO may have screwed with the fuel settings. I think it may be time to refurb the IP, as we've done everything else but that.

Here is a great tread about smoke.
Diesel smoke questions? Read this first!

 

[doug720]

As noted above - Black smoke is too much fuel, which makes too much heat, which melts pistons!

Buy and install an EGT gauge ASAP, preferably just before the turbo where all cylinders meet pre turbo location. Your engine will live longer!

 

[roma042987]

call me a skeptic but how often do you hear of someone melting pistons on a stock setup? How many miles of this mountain driving do you presume it will take to melt said pistons? Maybe on a engine that didn't originally come with a turbo or possibly one which someone upped the fuel but on a stock set up again I don't see any harm.

 

[AussieHJCruza]

My HDJ80 would have been running scary high EGTs with a stock tune under load. I didn't get an EGT gauge on it till I was intercooled, and even then, I could get EGTs out of the safe region without too much trouble.

When the truck was new and injectors and pump were all within spec, timed correctly and so-on, quite likely that EGTs would never have been an issue. But, 20+ years down the track, firstly, everything is starting to get a bit worn, pump wear affects the timing, injector spray pattens may not be correct, previous owner might have messed with stuff, IMHO, it's not worth the risk. If it's blowing black and it's a diesel, especially turbo, quite likely under sustained load, EGTs are getting unsafe.

My advice is, fit an EGT gauge with the sensor in the manifold, before the turbo. The results might be suprising. I have a mate who will agree with this, he destroyed a Nissan TD42 with excessive EGTs, and it wasn't a smoke machine either.

My truck showed no signs of fuel pump wear. Started easily, ran well, made decent power, didn't smoke excessively, got expected fuel economy, yet internally, it couldn't hold timing advance at higher revs and with a bit of right boot and load, would spin the EGT gauge like the tacho, or maybe even faster.

 

[doug720]

My engine is an Isuzu 4BD2 that is a factory turbo charged and inter-cooled diesel. When my set up was 100% stock, at elevations over 6000', I could get the pre-turbo EGT temps well over 1300f. I was pulling ok, blowing some black smoke - but not too bad.

A quick down shift to raise the rpm's up and it would drop 300f instantly. Elevation means less air, and the turbo can't keep up, so EGT goes up, fast.

I have changed turbos to blow more air, this helps a lot, but, as the elevations go up, especially on a warm day, if left in high gear, I can get the EGT's well over 1300f still. Black smoke is a warning, an EGT gauge is a confirmation...and a cheap one!, of potential problems.

We spend many weeks a year staying at our place at 7200'. We make near daily trips up to 9500' plus, with occasional trips to well over 12000'. So we see experience this often.

Buy an EGT and see what happens. A diesel engine is a terrible thing to waste!

 

[OGBeno]

Using gearing with a turbo'ed diesel is key.

And backing off if necessary. This is smart.

 

[Greg_B]

It is scary how fast one can get into the danger zone in stock trim and not know it. And you will likely be fine...for a while. Maybe a long while. Maybe not.

As has been suggested, install gauges. Then you can drive to the gauges using your foot and gearing to find the efficient and safe zone. And you need gauges to tune it anyway.

I don't have a pyro on my BJ42, but I do have a mechanical coolant temp gauge. I've had it where I have had to feather the throttle to keep the coolant temps happy when fighting a headwind in Wyoming heading west. That feathering happened to be where there was little to no black smoke out the tail pipe. It was rather slow for the USA highways though.

On my BJ74 I was amazed as how quickly I could get post 1000f (pyro post turbo) on regular jaunts around home. A 2.5" exhaust helped considerably. As did upping the boost to 12 psi or so. Now I have to work it hard on a long hill on a hot summers day to get it up to 1000f. I feel better about that.

Same on my HDJ80 (FZJ converted with 1HD-T) with 2.5" exhaust and mild tune. I too was driving to the pyro and it was amazing how quick I could get past 1250f (pre-turbo on this one) if I did not know better. Before the g-turbo and intercooler I was backing out of many hills, and or dropping a gear and feathering the throttle to keep thing happy.

hth's
gb

 

[Dougal]

A better turbo will help considerably. So will a good intercooler.

At high altitude you've got thinner air, so the engine runs richer and hotter, it's also harder for the turbo to make boost. So you've got three things all working to spike your EGT.

An EGT or A/F guage will show you when to change down and unload the engine to avoid the smoke and high temps. But you'll get a feel for it just by watching smoke.

 

[mudgudgeon]

call me a skeptic but how often do you hear of someone melting pistons on a stock setup?

There's plenty of examples of "stock" set-up running really high EGTs not evident until a pyro is fitted.
But, yeah, I agree, melting pistons would be quite an achievement.

IMO, safe EGTs quoted by most are generally very conservative. At 1050f, there's a lot left on the table.

 

[OGBeno]

There's plenty of examples of "stock" set-up running really high EGTs not evident until a pyro is fitted.
But, yeah, I agree, melting pistons would be quite an achievement.

IMO, safe EGTs quoted by most are generally very conservative. At 1050f, there's a lot left on the table.

On a 3B w/ turbo, 1200-1500 are acceptable to me knowing what I know about my rig.


That said, I run 3rd very hard.

 

[Dougal]

IMO, safe EGTs quoted by most are generally very conservative. At 1050f, there's a lot left on the table.

Indeed. But measurement error also needs to be factored in. Many EGT probes are too short and/or in cold locations to give false safe readings.
I routinely run to 750C (1380F) sustained on my Isuzu but I know the EGT probe is getting a good reading and the engine has piston squirters and alfin pistons.

My 2.0tdi has a factory EGT probe. I've measured 800C from that.

 

[Greg_B]

There's plenty of examples of "stock" set-up running really high EGTs not evident until a pyro is fitted.
But, yeah, I agree, melting pistons would be quite an achievement.

IMO, safe EGTs quoted by most are generally very conservative. At 1050f, there's a lot left on the table.

Yup, pick your tolerance and set it there.

The 13BT pyro is not the best location as it is post turbo. It's slower to react both ways and after being run fairly hard takes a long time to come down below 400f (204.5C) at idle, due to heat sink effect of the turbo I would guess. Due to the remote location I bet in some situations my limit of 1000f (537.8C) is pushing it.

The 1HD-T is pre-turbo, reacts much faster and I am most comfortable with my warning buzzer set to 1250f (676.7C) . I have not reached it yet, since the turbo and FMIC. Of course, that means I have more tune available. Not much though, as I have seen 1180f on sustained pulls on long grade.

I was up at 10,947' (3337m) on the Bear Tooth Highway this summer and on initial throttle there was more black exhaust for sure, till the turbo spooled up. I do have to fine tune with the pin yet.

gb

 

[IanB]

call me a skeptic but how often do you hear of someone melting pistons on a stock setup? How many miles of this mountain driving do you presume it will take to melt said pistons? Maybe on a engine that didn't originally come with a turbo or possibly one which someone upped the fuel but on a stock set up again I don't see any harm.

I'll parrot the others here, you can get into EGT's that are in the red zone scary quick with a stock truck. I shudder to think what kind of abuse mine have seen driving them home from the coast with no gauges. Last summer I made a trip to the mountains with gauges, and it was a real eye opener.

 

[roma042987]

I'll parrot the others here, you can get into EGT's that are in the red zone scary quick with a stock truck. I shudder to think what kind of abuse mine have seen driving them home from the coast with no gauges. Last summer I made a trip to the mountains with gauges, and it was a real eye opener.

i understand everyone wants to be overly cautious with their "rare" and expensive Toyota turbo diesels but to each there own and everyone will have their own opinion. I haven't seen any publications from Toyota telling consumers how to drive their turbo diesels in the mountains or to install a pyro and monitor it. I'll drive my rebuilt 12ht with no regard to the egt's and we'll see how long it lasts. If it blows up in less than 100k miles or melts a piston i might install a pyro on the next one.

 

[Douglas S]

i understand everyone wants to be overly cautious with their "rare" and expensive Toyota turbo diesels but to each there own and everyone will have their own opinion. I haven't seen any publications from Toyota telling consumers how to drive their turbo diesels in the mountains or to install a pyro and monitor it. I'll drive my rebuilt 12ht with no regard to the egt's and we'll see how long it lasts. If it blows up in less than 100k miles or melts a piston i might install a pyro on the next one.

It's your own motor so do what you wish, but that's incredibly naïve. My truck was a stock as it gets when I bought it and I could easily push the EGT's far beyond the safe limit (unknowingly...until I installed an EGT gauge).

An EGT is what? $100? Compared to the cost of an engine rebuild it seems like a pretty easy decision. You would have trouble finding a modern diesel engine that doesn't have an EGT monitor built in right from factory; there's a reason why.

 

[stevebradford]

On the hill climbs I used to just use my gearing and just drive my cruiser enjoying the experience. Now that I installed an EGT gauge I find my self flogging it up the hills as fast as I can while trying to stay under 1100f...it's a sickness! I also have nightmares of cracked precups falling into the piston, never worried about things so much before.

Ignorance is bliss.

 

[brownbear]

There really isn't a set numerical value of what these engines can handle or not handle in regards to EGTS.

We kinda use 1300 as a limit I think based on what the domestic diesel crowd uses and internet facts and lore.

I'd say you are not going to kill it with heat (if stock) but you can hurt engines shutting them down hot, and that is in the manual for a turbo diesel, to idle to cool the engine.

Shock cooling is bad. I watch my EGT gauge till I am below 150 before shutting it off after pulling hard on a mountain pass or highway speeds.

Think of all those 3B's running around stock and naturally aspirated and probably hitting 1600 plus getting hot and no one knew better and they still make 400,000 kms or more without ever looking at an EGT gauge.

 

[mudgudgeon]

I understand everyone wants to be overly cautious with their "rare" and expensive Toyota turbo diesels

The rare part for me is the $5K to rebuild, or $8-10K to replace it, and that's in Aus, where they are far from rare.

I think most blindly follow the crowd and run conservative EGTs without full understanding of what's happening.

In a 1HD-T 1HD-FTE 1HZ etc you have oil squirters cooling the underside of the piston.
In any engine, you have a fresh air intake charge cooling the top of the piston and the head, you have water cooling the head.
At any given EGT, piston and head temperatures are far below the EGT. It takes sustained tuning at excessive combustion temps to heat soak everything.
Aluminum pistons, and inconel turbines have melting points of 750C?, 900C? Or higher? (can't remember, so Google it). Thermal expansion of pistons and having rings binding would be a concern to me before melting pistons

Tune so EGTs are limited to a max peak that you think is safe. Then driving to the EGT gauge is unnecessary, particularly if you understand that laboring the engine in too a gear is not good

I believe in aircraft engines, cylinder head temperature is measured at each cylinder, and is used to monitor critical combustion/engine conditions ahead of EGTs