Diesel mixture/overheating

Submitted: Wednesday, Aug 06, 2014 at 19:48
ThreadID: 109046 Views:2260 Replies:12 FollowUps:3
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Hello all,

I'm in Kazakhstan at the moment on an overland journey from London to Cape Town with a NSW registered troopy

We did a big hill climb the other day and seem to have problems with the engine getting hot.
We're a bit concerned because tomorrow we leave Kazakhstan for Kyrgyzstan to do the Pamir hwy, second highest road in the world with a 4655m pass.

We fooled around by removing the spotties and inter cooler.
We are driving a '94 1hZ troopy with dts turbo running 8psi. We're told by the bloke who rebuilt the engine that the top mount we have fitted will cause the combustion temp to increase because the cooler more dense air will burn hotter.
After removing the cooler and doing the spotties we noticed a slight improvement but still gets hot.

It's probably worth mentioning that our troopy has an auto out of an 80 series LC because I'm parra and can't drive manual. We have two transmission coolers fitted in front of the radiator. It is now AWD.
We also carry a fair bit of weight.

We have noticed on the long and gradual hill climbs the EGT hovers around 500-520.
If it remains on this temp for too long the engine starts to get hot.

I'm thinking of removing some diesel from the mixture to help cool the EGT down.

Does any one have any tips or advise. I know what I need to adjust, just unsure of how many turns and how sensitive it is.
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Reply By: The Bantam - Wednesday, Aug 06, 2014 at 20:08

Wednesday, Aug 06, 2014 at 20:08
Remember internal combustion engines are effected by altitude.

It is such a problem that in some high altitude countries they still use steam over diesel railway engines.

I don't know what the detail is or how it plays out with diesel. But many simple motors like snowmobiles and chainsaws run different jetting at altitude.

Its all to do with the air being thinner and there being less oxygen to mix with the fuel.

I cant give you a solution...but those are the problems I am aware of.

AnswerID: 537269

Reply By: Peter_n_Margaret - Wednesday, Aug 06, 2014 at 20:21

Wednesday, Aug 06, 2014 at 20:21
You can reduce the EGT temperature simply by not using full throttle.
Try it and see what difference it makes.

Not relative to your engine, but I run the EGT on the Perkins in the OKA up to 500/520 with a boost of up to 19psi without problems, but that is not at altitude.

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AnswerID: 537272

Reply By: Hoyks - Wednesday, Aug 06, 2014 at 20:25

Wednesday, Aug 06, 2014 at 20:25
The more fuel you pump into the cylinder the hotter it will burn. Because you are at altitude there is less available air, even though you have forced induction, so the fuel air ration is richer and will be making more heat.

Some diesels have a thing called an altitude compensator that backs off the fuel a bit when the atmospheric pressure is lower, I don't know if yours would though.

You could try backing off the fuel setting on the injection pump just a touch, but if you don't know what you are doing then it could get messy. Try 1/8 of a turn and keep track of what you have done. Refitting the intercooler might be a good idea as it will cool the incoming air charge and give you a bit more oxygen into the system.

Probably the easiest option is to run slower or a lower gear so the engine isn't working as hard and doesn't need as much fuel. What is a good tune for NSW isn't going to work real well at those altitudes though.

AnswerID: 537273

Reply By: Member - john y - Wednesday, Aug 06, 2014 at 20:27

Wednesday, Aug 06, 2014 at 20:27
Bottom 2-1/2 hose on dts turbos are prone to over expand and deteriorate under pressure I.e hill climbs. The walls of the elbow are too soft and the elbow constricts and this restricts the air input leading to poor fuel air mix hence overheating.worth a thought has happened to me twice over the life of my 80 series. Good luck
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AnswerID: 537274

Reply By: pop2jocem - Wednesday, Aug 06, 2014 at 20:36

Wednesday, Aug 06, 2014 at 20:36
Not familiar with the part of the world you are in at the moment but it sounds like you are getting to some pretty high altitudes. As I'm sure you have noticed the air is getting a bit thinner as in not as much flow rate. This will of course affect the efficiency of the combustion process. The fuel delivery may stay the same but the amount of oxygen available is less. This will raise the temperature of the internals of the engine and of course the exhaust gasses. By reducing the fuel you should reduce the temperatures as you have said. How much? Depends on local conditions but the fuel screw is quite sensitive. You shouldn't have to alter it much. From memory you will be looking at parts of a turn rather than how many turns. You will of course also notice a drop in performance as well. A better strategy would be to add more air but not as easy to do unless you have some way of altering waste gate settings if you have one.
I don't know if you have changed the radiator from standard but remember the Troopy was never engineered for an auto so the addition of the heat from the tranny coolers may be leaving it a bit short of capacity. The other factors to take into consideration are that I would think the air temps are probably dropping so should be to your advantage but keep in mind the radiator is using air flow to dissipate coolant heat. I'm just spit balling here but maybe thinner air doesn't conduct the heat as well??????? As in the fan may be working it's backside off but not shifting as much volume , same as the poor old turbo.
Not sure all that fits in just some thoughts.

Good luck

AnswerID: 537277

Reply By: Member - Ups and Downs - Wednesday, Aug 06, 2014 at 20:46

Wednesday, Aug 06, 2014 at 20:46
I know stuff all about turbos and altitude but you could check a simple thing like the viscous clutch operation of the fan. I've had your problem with my non turbo Troopy ('94 model also) and it was the fan. Until I found that out, on a long climb I would have to back off, and use a lower gear until the temperature dropped off.

AnswerID: 537282

Reply By: Whirlwinder - Wednesday, Aug 06, 2014 at 20:51

Wednesday, Aug 06, 2014 at 20:51
Mate, I would be contacting a serious diesel mechanic like West End Diesels in Sydney or one south west of Sydney on the way to Narellen.
Your problem and your location deserves expert advice.
AnswerID: 537284

Reply By: Ross M - Wednesday, Aug 06, 2014 at 21:04

Wednesday, Aug 06, 2014 at 21:04
If all is OK in normal operation, still with hills but without the altitude then perhaps the following will apply.

Because the air is thinner and less oxygen content it will be overfuelling which will cause EGT to rise.
The replacement of the intercooler should add density to the air via being cooler, but the less oxygen is the problem. Too much air cannot heat the exhaust but too much fuel will.
Ideally a diesel works best with more air than it requires.
I agree to reduce the full fuel amount should assist and even though you have a turbo lower power will be experienced. It is at altitude after all.

Return fuel setting to normal when down at lower altitude.
All vehicles experience power loss at altitude.

Less air density means less air through radiator to carry heat away as the fan is also less efficient.
Less conduction from radiator to air and less being sucked through the radiator.
You are closer to trying to pump a vacuum ie, less air for same volume. with the fan than in normal density air.

AnswerID: 537287

Reply By: rb30e - Wednesday, Aug 06, 2014 at 21:24

Wednesday, Aug 06, 2014 at 21:24
The engine has been running really well at normal altitude up til now.
Where we begun noticing the overheating was on a climb from about 1000m-2500m.

It was starting to cook well before we got to 2500m and had to do it in three attempts after allowing the engine to cool.

I'm kind of confused though as the bloke who rebuilt the engine was certain that the intercooler would cause over heating problems. its been fine up to this point with the cooler on it. But surely at altitude where there is less oxygen in the air, cooling the charge with an intercooler and making it denser should be of assistance.

The radiator has been upgraded with a larger alloy job, although we have A/C fitted (which we wont be using) it will also be disrupting flow to the radiator and the auto coolers in front of that.

I have tested the viscous coupling and it seems to be properly, we have the Toyota viscous fluid with us just in case.

The other thing we have noticed is that the exhaust temps are much higher at low revs when the turbo is not creating boost. Because we had the pump and injectors calibrated for turbo applications I think it is running much richer off boost causing the temps to rise much quicker, these old diesels pretty much have one setting.
once we come onto boost, trying not to exceed 5psi and keep the RPM moderate the exhaust temp starts to drop.

I think my plan of attack will be to reduce the fuel mixture slightly to begin with and analyse the difference. If I cant get any joy reducing the exhaust temp I will try and get more airflow to the radiator by removing the A/C condenser and potentially repositioning the auto coolers.

AnswerID: 537288

Reply By: Peter_n_Margaret - Wednesday, Aug 06, 2014 at 22:10

Wednesday, Aug 06, 2014 at 22:10
I sent a link to this thread to a friend who recently completed this journey.
Below is his response.....

I recently traveled through Kazakhstan / Kyrgyzstan/Tibet in a 4wd Mitsubishi Canter. Around 4500kg with 3.9l turbo.

I'd had mild overheating problems in Turkey due to higher speeds, steeper (4th/3rd gear) longer hills, higher air temperatures, and eventually I had to replace the radiator cap. But real clue was a lower gear, less accelerator but higher revs, and take the hills slower (2nd gear). On long hills (half an hour of steep uphill) I could find the spot where engine temperature was a little high but not increasing. I wondered about dust clogging radiator but not much came out when I blew air through it.

I was also suspicious of the fuel in Turkey, I bought the cheapest diesel, but local warned me off it and the vehicle felt better for the more expensive.

In Kyrgyzstan we hit problems at around 4,500m climbing passes when the engine warning light came on. Low turbo boost pressure. Black smoke had been getting steadily worse as we climbed. With a bit of experimenting lower gear, less accelerator, higher revs, slower speed again. The red light didn't stay off completely, just reduced how long it was on. At one point I thought a full tank was better than an empty tank (possibly fuel pressure) but couldn't confirm. No overheating problems but I was being cautious.

In Tibet above 5,000m the red light was on for long periods of time. Terrain a bit different, not so steep hills and long good roads. Easing off the accelerator would often result in light off. I didn't have overheating problems. A bit of humour - the fault codes also said the engine was running backwards.

Noticeably less power at altitude but I had a bit in reserve to start with.

I didn't find a choice of fuel in Kazakhstan / Kyrgyzstan / Tibet but in Tibet we were sort of directed to the "reputable brand". Few and far between in the west though.

Black smoke and low turbo boost are normal at altitude for vehicles tuned at sea level. The atmospheric pressure is lower. Basically less air getting into the engine. I didn't see many turbos at altitude and the locals probably have their vehicles tuned at altitude. I thought about retuning, I found some instructions for reducing fuel flow (to match the reduced air flow and rid myself of the black smoke) but didn't bother as it would only be for a few weeks.

Another trick is after long slow drive in too high a gear we had to leave the engine ticking over for a bit lest it boil when we stopped. Made the mistake once in India and lost half our engine water. Mildly disconcerting until we figured out why and subsequently kept the revs up.

We met a few people in landcruisers in Nepal, some of whom had come through Kyrgyzstan but not much comment about altitude. Possibly because people had other more serious problems to contend with and talk about.

Probably not much help but basically black smoke is normal, overheating possible, lower gear, higher revs, lower speed, and ask about fuel. Assuming that there isn't an underlying problem with the engine but its too much of a coincidence that your problems started with altitude. My recollection of troopies is that the engines are fairly robust.

We thoroughly enjoyed ourselves, enjoy your trip.

Julian "

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AnswerID: 537293

Follow Up By: Peter_n_Margaret - Wednesday, Aug 06, 2014 at 22:29

Wednesday, Aug 06, 2014 at 22:29
This is a link to Julian's blog.

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Follow Up By: braggy - Thursday, Aug 07, 2014 at 14:13

Thursday, Aug 07, 2014 at 14:13
Good on you Peter for your effort,
and good your mate for the reply .

Plenty of good advise from him, like , lower gear, more revs, less throttle.

Cheers Ken

FollowupID: 821588

Reply By: Member - mechpete - Thursday, Aug 07, 2014 at 11:03

Thursday, Aug 07, 2014 at 11:03
the easiest thing to do is put some extra oil in the viscious fan hub ,
everyone knows that the viscious fan hub is a common problem on
AnswerID: 537313

Follow Up By: Parso - Thursday, Aug 07, 2014 at 20:44

Thursday, Aug 07, 2014 at 20:44
Are you sure tat 'everyone knows'. That comment is not helpful.
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Reply By: TONY F2 - Monday, Aug 11, 2014 at 01:21

Monday, Aug 11, 2014 at 01:21
Yep as others have alluded to it would be a good idea to hold the Auto in second or third gear whilst doing the hill climbs. Also add more viscous oil to the fan hub as this will assist the van to work better.

Another thing to make sure of is that the Cooling Fan shroud is all in tact so that all the air being drawn through the Radiator by the Fan is going though the Radiator and not bypassing around the edges.

The Dts Turbo will have a waste gate on it which is adjustable. you maybe able to adjust the stroke of waste gate actuator to get a bit more boost out of it using the fuel already being provided. If you can't get any more boost out of it then yes it may be a good idea to back the fuel off 1/8 of a turn at a time.

Another thing is that if your Automatic gearbox is working hard it will be producing heat which will be hopefully being got rid of by the two coolers on the front of the Radiator.Unfortunately that heat that comes from the Auto Tranny coolers now transfers onto the Radiator.
May pay to check the Auto transmission oil is not burn't as well or discoloured.

Check the air filter is also clean. Also check all of your Air intake pipework is not collapsing under suction. As the air intake pipework gets older and softer it may collapse or suck in and that will stop air getting though to the motor and will mean there is more fuel and less air which is not a good thing.
Safe travels.

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