High altitude and no HAC on 2H = engine damage?

[Moodoo]

We are back from a great drive through the mountains. Once again thanks all for the advice, much appreciated, an interesting discussion.

The highest point was the Khardung La pass at 18,380ft. As recommended we ended up driving very slowly for all of it, a lot of the time second gear / 1250rpm / 18kph, and never over 40kph the whole time. I didn't try to adjust the fuel pump at all. Any time we saw black smoke i backed off or geared down. The scenery is so spectacular that going so slowly wasn't as frustrating as you would imagine.

Some observations:

• When going downhill at altitudes over 4500m, foot off the accelerator, letting the engine slow the car, a lot of blue/white smoke would blow out.
• Over 5000m the engine sounded painfully rough - a metallic clattering sound is the best way I can describe it.
• The tickover/idle rpm increased with altitude - from 650 to 1150

Judging by the amount of black smoke the local vehicles were kicking out, they aren't too bothered about high EGTs

FJn00b - we are heading over to Pakistan in a few days and may well head up the Karakorum Highway, if we do I'll let you know.

Cheers,

Andrew

 

[jaymundy]

What would an HAC look like? I've got an unidentified appendage on my injector pump and am wondering if that might be it.

 

[blis]

What would an HAC look like? I've got an unidentified appendage on my injector pump and am wondering if that might be it.

The hac is basicly just a diaphram with hose coming to other side and should be mechanical lever on otherside, going to pump...

 

[jaymundy]

The hac is basicly just a diaphram with hose coming to other side and should be mechanical lever on otherside, going to pump...

Sort of like the thing on the right side of the pic? I was never sure quite what it was, but assumed it was something to do with shutdown that a PO disconnected for some arcane reason.

 

[blis]

Yup, that should be it far as i can tell...

ps. Probaply nicest feature of hac is its self-throttling behavior, as in when the load increases it should increase fuel so you can crawl without hitting gas pedal at all (real usefull on wet snot/swamp/soft ground)

 

[o8ko8k]

This was a great read. I have a 2h diesel and i live in AZ where i could be at sea level or at 7000ft. i too have expereinced the soot monster while towing at 7000ft. I found this article on TDI club that i found facinating as well so i thought i would add it to this thread. I hope no one gets all hurt that i have added somthing to a thread thats been dead for 4 years now. I found myself thinking that rich meant cooler temps yet the Pyro doesnt lie so i did some googling and this is what i found...

From the words of the TDIMeister...
http://forums.tdiclub.com/showthread.php?t=140557

...Within the realm of Diesel engines, more fuel for a given amount of air results in increasing temperature. I will expound on this in a moment

I believe the confusion stems from the concept of stoichiometry and stratification.

A very basic observation in combustion is that, regardless of fuel, flame temperatures are at a maximum at a point very close to the stoichiometric air/fuel ratio. On fact, This peak occurs very slightly lean of stoichiometric, around Lambda = 1.1 for many hydrocarbon fuels. It its not entirely coincidence that NOx peaks also at the same Lambda value.

The second basic tenet one needs to understand is the difference between a homogeneneous charge and a stratified charge, because that is where gasoline and Diesel engines begin to diverge.

Gasoline engines (except specific stratified-charge designs) operate under a homogeneous charge, where fuel and air are pre-mixed at a uniform air-fuel ratio throughout the combustion chamber at the time of ignition.

In contrast, a Diesel engine, which injects the entire fuel charge within a short window in terms of crank angle, has a decidedly non-homogeneous, or stratified charge. This means that within the volume of the combustion chamber (i.e. the piston bowl), there are extremely lean and extremely rich regions, and everything in between. Combustion initiates at sites that are sufficiently hot and having air fuel ratios within the range of combustible limits, starting with the sites that are near stoichiometric.

Much research and development by engineers is focussed on making the mixing of fuel and air as rapidly and evenly as possible within this extremely short window of time, which has spurred the development of high-pressure fuel injection and injection rate shaping strategies, since the above-described stratification results in both unacceptable levels of NOx and soot emissions.

Limiting our discussion to Diesel engines, we first have to distinguish a global, or overall, air-fuel ratio, as well as a local one. A Diesel engine ALWAYS operates at a globally lean air-fuel ratio; the engine would reach a limit of unacceptable smoke emissions around 18:1. When an engine is idling or operating at low load, the global A/F ratio can be much higher, like 100:1.

Regardless, even through the engine is operating globally lean, there are sites as said before that are extremely lean and extremely rich. The interface of the flame with the rich regions are sites of soot production and the locale of combustion in the stoichiometric and lean-of stoichiometric regions generate much of the NOx.

The only time when combustion temperatures can go down in a relatively rich mixture in a Diesel engine is when the engine is grossly overfuelled, such that the extremely-rich sites I described above dominate in the entire combustion chamber, which is manifested by extreme smoking.

It is important here to note that, whether Diesel engine or gasoline, EGT cannot be taken as a direct, 1:1, relationship with flame temperature nor peak cycle temperature. A very lean-burning gasoline engine will have low peak cycle temps but soaring EGT. Similar analogies can be made for Diesel engines.

Take home message #1 is that you need to understand basic concepts of stoichiometry and how flame temperature is a function of this stoichiometry; how they are different between Diesel and gasoline engines; the difference between a homogeneous charge and a stratified-charge; and the difference between global- and local stoichiometry.

The take home message #2 is that within the normal range of air-fuel ratios seen in a Diesel engine, more fuel = more heat = higher combustion temperature.

Take home message #3 is that EGT does not tell the full story about peak combustion temperature.

I never understood diesel combustion to this level b4. I thought i would share. BTW i have a pyro on order

 

[Dougal]

You are never going to melt pistons on a non turbo diesel without first being severely embarassed by the smoke.

Drive to limit the smoke and you'll be fine. It's turbocharged diesels which need to monitor EGT.

 

[cruiser_guy]

You are never going to melt pistons on a non turbo diesel without first being severely embarassed by the smoke.

Drive to limit the smoke and you'll be fine. It's turbocharged diesels which need to monitor EGT.

Not going to start an argument here but my BJ60 is turbocharged and will not exceed about 1200F on the pyro when pulling a hill.

There have been times when the hose between the turbo and the intake manifold has popped off and then it is essentially a non-turbo-charged engine. Immediately when the hose pops off the EGT's climb to 1500F and higher! I take my foot off as soon as I feel the reduced power and/or hear the slight pop of the hose coming off. Granted, I have not looked to see how much smoke I'm putting out at the same time as all that going on but all I am saying is that it's easier to get high EGT's without a turbo.

My injection pump fuel delivery is all factory set. I have NOT increased fuel due to the turbo.

 

[o8ko8k]

I don't see that as an argument bit a good comment. Besides the thread is 4 years old. I just wanted to add some detail to what the thread established. The original post is moot, the guy did the trip already.

 

[canucksafari]

I don't see that as an argument bit a good comment. Besides the thread is 4 years old. I just wanted to add some detail to what the thread established. The original post is moot, the guy did the trip already.

What the thread established - and is not moot in any sense - is if you want to regularly drive high altitude you are going to be doing other things besides redesigning an engine. If you go NA, you are going to reduce the load by gearing down and reducing the fuel by less eager use of the skinny pedal. If you want to go faster without risking the high EGTs and engine damage, then you need to compensate for the thinner air with a high altitude compensator (as the Indonesians call them). We call them turbochargers. All still good practical diesel driving advice now and well into the future.

 

[Dougal]

Not going to start an argument here but my BJ60 is turbocharged and will not exceed about 1200F on the pyro when pulling a hill.

Because of this:

My injection pump fuel delivery is all factory set. I have NOT increased fuel due to the turbo.

With a turbo and no fuelling increase, of course you've got cooler EGT.
Those who tune to a maximum safe EGT limits at lower altitudes though will need to watch EGT as they climb.

There have been times when the hose between the turbo and the intake manifold has popped off and then it is essentially a non-turbo-charged engine. Immediately when the hose pops off the EGT's climb to 1500F and higher! I take my foot off as soon as I feel the reduced power and/or hear the slight pop of the hose coming off. Granted, I have not looked to see how much smoke I'm putting out at the same time as all that going on but all I am saying is that it's easier to get high EGT's without a turbo.

You'll be smoking significantly at 1500F. Drive by the smoke and you'll be fine. With no turbo you don't need an EGT gauge.

It is also very very difficult to melt pistons on an IDI non turbo engine. The flat tops make it hard for the heat to get in. Unlike direct injection pistons which have a combustion bowl soaking heat directly into the piston core.

This is how those Scandanavian drifters are running those old mercs so rich and smokey without melting pistons. They are idi.

 

[o8ko8k]

What the thread established - and is not moot in any sense - is if you want to regularly drive high altitude you are going to be doing other things besides redesigning an engine. If you go NA, you are going to reduce the load by gearing down and reducing the fuel by less eager use of the skinny pedal. If you want to go faster without risking the high EGTs and engine damage, then you need to compensate for the thinner air with a high altitude compensator (as the Indonesians call them). We call them turbochargers. All still good practical diesel driving advice now and well into the future.

agreed, so let me clarify. the moot part is the trip the guy made years ago, not the advice about High alt driving. totaly agree.

 

[o8ko8k]

Drive by the smoke and you'll be fine. With no turbo you don't need an EGT gauge..

You may be right but I want one anyway

It is also very very difficult to melt pistons on an IDI non turbo engine. The flat tops make it hard for the heat to get in. Unlike direct injection pistons which have a combustion bowl soaking heat directly into the piston core.

This is how those Scandanavian drifters are running those old mercs so rich and smokey without melting pistons. They are idi.

i will consider my pistons not meltable.

 

[canucksafari]

You may be right but I want one anyway



i will consider my pistons not meltable.

Even if your pistons will not melt, the high EGTs will make its way into your cooling system. If it can't handle the increased heat, then you'll still be tearing things apart to fix them. I agree with you, an EGT gauge is a good piece of equipment to have in your rig. One of our club members picked up a digital one off of ebay for a very good price. IIRC, it will work on 12V or 24V systems.

 

[o8ko8k]

Even if your pistons will not melt, the high EGTs will make its way into your cooling system. If it can't handle the increased heat, then you'll still be tearing things apart to fix them. I agree with you, an EGT gauge is a good piece of equipment to have in your rig. One of our club members picked up a digital one off of ebay for a very good price. IIRC, it will work on 12V or 24V systems.

I cant learn about this stuff fast enough! Love it! Love it! Love it! I just had a crash course in battery charging! Anyways back to topic...

This corelates to the wild fluxuations in water temps im seing with my stock gauge right about the time folks are disapearing out of my rearview mirror in a cloud of black smoke. I'm hoping my combo Water/EGT gauge will help me track this better. I thought it a good start b4 I pony up for a new radiator.

 

[BreckenridgeCruiser]

In case anyone looks at this thread looking for HAC info, the Toyota HACs from this era only adjust for between sea level and ~4000 feet above sea level. Not really much help for those of us that start at 5 and drive up to 14,000 here in CO.

 

[Dougal]

As Canuck said. High EGT (high meaning past 1400F or 750C) still takes it's toll on your head, precombustion cups and cooling system.
But if you drive by smoke you'll be fine.

I ran an EGT gauge on my non turbo work car for a few weeks. It was direct injection but I couldn't get EGT past 500C without smoke.
The probe was about a foot down the manifold, so it could have been 550-600 at the ports. But still completely safe temperatures at the point it starts to smoke.

 

[Slowerthanu]

So, should I be adjusting fueling on my n/a 2h that does not have a HAC? This vehicle came from Japan and now lives at 4300 ft and higher. The bolt on the back of the pump still has the wire attached.

I turn this IN to decrease fuel correct?

 

[o8ko8k]

clockwise provides less fuel,
counter clockwise provides more fuel.

adjust in 1/4 or 1/2 in increments, test, and repeat.
u can test with a pyro for actual EGT (limit max temp to 1200F or less)
OR
u can watch out the back for black smoke.
I would reccomend the pyro

there are zillions of threads on this too