Altitude affect turbo performance??

Submitted: Thursday, Jun 14, 2007 at 13:33
ThreadID: 46650 Views:3808 Replies:13 FollowUps:5
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Have a neighbour took his turbo 80 series to the snow (Thredbo) last weekend. The vehicle had been recently tuned and set up at The 'Gong (sea level). He commented that it performed like a slug up in the mountains, but was OK when he got back home.
Would the altitude (I'm suggesting atmospheric pressure) have any effect on the boost of the turbo?? I understand they are set up at about 0.5 ATM (whatever that is in bars??).
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Reply By: Member - Roachie (SA) - Thursday, Jun 14, 2007 at 13:41

Thursday, Jun 14, 2007 at 13:41
I doubt the altitude in the Snowy's would have caused that effect. More likely to have been the diesel he had in his tank. They sell "special" diesel up there which waxes-up less than standard diesel does.

I know that a naturally aspirated diesel will be a slug in the mountains , but a turbo should have overcome that issue.
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Follow Up By: Member -Signman - Thursday, Jun 14, 2007 at 13:49

Thursday, Jun 14, 2007 at 13:49
Yup- that could be it. He had the tanks full- and it may be that the servo still had Summer blend !!!
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Reply By: zumzum - Thursday, Jun 14, 2007 at 13:47

Thursday, Jun 14, 2007 at 13:47
The altitude can do this .... I was on tour some time ago at Akaroola Sanctuary (Flinders Ranges) on th Top Ridge Traks. The guide said some time the troopy gos as a roket ... some time in very bad! It depend from the high/low pressure on the air ....

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Follow Up By: Member -Signman - Thursday, Jun 14, 2007 at 13:55

Thursday, Jun 14, 2007 at 13:55
OK on that Luca- but I don't think there would be a dramatic difference between Arkaroola 'base' and Sillers......
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Reply By: flappa - Thursday, Jun 14, 2007 at 13:55

Thursday, Jun 14, 2007 at 13:55
I would have thought it should have little effect on a Turbo Vehicle. It would suck the amount of air it required regardless.

I do know it can effect carby vehicles , even from the Coast to Canberra.
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Reply By: anleky - Thursday, Jun 14, 2007 at 13:58

Thursday, Jun 14, 2007 at 13:58
Altitude definitely as an effect on horse power, so does air temp and humidity.
The rule of thumb is for every 100m of altitude 1% of power loss.

Is it a factory or aftermarket turbo system?
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Follow Up By: Member -Signman - Thursday, Jun 14, 2007 at 14:09

Thursday, Jun 14, 2007 at 14:09
After market- Denco???
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Follow Up By: anleky - Thursday, Jun 14, 2007 at 20:48

Thursday, Jun 14, 2007 at 20:48
Was it fitted with an Aneroid or 'altitude compensation device'?
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Reply By: Paps - Thursday, Jun 14, 2007 at 14:08

Thursday, Jun 14, 2007 at 14:08
Oxygen deprivation has the same effect on engines as on humans, especially diesels that rely on an excess of air. I have had both diesels and petrol's in the Vic Alps regularly and both are affected by altitude, the diesels more so. Although, I'm not a scientist. Cheers Paps.
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Reply By: Member - extfilm (NSW) - Thursday, Jun 14, 2007 at 14:09

Thursday, Jun 14, 2007 at 14:09
I took one of the company work utes to the snow. Was a 98 Navara diesel and at the time was only 3 years old with 100 000ks on the clock.
Going up the steep hill to thredbo just before the Skitube I was pulled over by the boys and had the Ute Defected due to exsessive smoke coming from the exhaust and they informed me I should be putting my fuel in the ute from Jyndabyne for which I told them that this was the second tank from Jyndabyne.
Upon my return to Sydney I went to the workshop I used to work at and they undefected the ute without doing anything to it......
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Follow Up By: Paps - Friday, Jun 15, 2007 at 11:52

Friday, Jun 15, 2007 at 11:52
I believe the thing with the fuel aditive is to prevent the diesel from solidifying in freezing conditions. The excess smoke was probably due to partial burn of the fuel due to lack of oxygen??? It appears even computer controlled diesels can't adjust to all conditions.
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Reply By: Member - Karl - Thursday, Jun 14, 2007 at 15:10

Thursday, Jun 14, 2007 at 15:10
I lived in Canberra for a couple of years and it sits at 750m above sea level and did a few trips up to the snow etc and never had an issue with my Diesel with an aftermarket turbo. Personally I would think that is was more a diesel fuel issue rather than an oxygen issue, if it was alpine grade then it will start to freeze - a common problem.

I don't think that the heights our alps get to is any cause for concern - you don't need a breathing apparatus to reach the summit of Mt Kosiosco, so I don't think an engine would be affected.

Anyway that's my opinion - based on my experience only.

AnswerID: 246792

Reply By: Axel [ the real one ] - Thursday, Jun 14, 2007 at 15:21

Thursday, Jun 14, 2007 at 15:21
Has / had to be a fuel problem as the turbo would actually love the cold thicker air , lovely cool air , what do you think an intercooler is actually for in a turbo engine ? yep ,cool it all down .
AnswerID: 246796

Reply By: Member - Duncs - Thursday, Jun 14, 2007 at 16:38

Thursday, Jun 14, 2007 at 16:38
I had a big problem with a lack of power in my MQ (normally aspirated diesel) on a summer trip through the Snowy years ago. I asked about a bit when I got home and the general opinion from a number of diesel mechanics I spoke to was that it would be the altitude. Thin air means less air.

I did a similar trip in my GQ TD42 with turbo and had no problems.

Again I had no problems with the GU TD42 factory turbo. I believe from talking with mechanics that the affect of the thin air is noticed by the turbo diesel but that it would not that it would be minimal and difficult for the driver to notice, instruments may show it.

The mechanic I trust most recommended getting diesels set up somewhere with a bit of altitude for this very reason.

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Reply By: Twinkles - Thursday, Jun 14, 2007 at 18:37

Thursday, Jun 14, 2007 at 18:37
back in the 80's when I had my first diesel we used to add something to the diesel when we went into the snow, kero or something(?)
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Reply By: Patrol22 - Thursday, Jun 14, 2007 at 19:13

Thursday, Jun 14, 2007 at 19:13
Guys just because air is colder it doesn't mean it is thicker (sic) - ie more dense. At a given altitude this would be the case. For example the air in Canberra on a warm day would be less dense than the air in Canberra on a cold day (like today:-)). But the higher one goes the less dense the air becomes and it could well affect a diesel engine turbo or naturally aspirated. This phenomenon is the reason that piston engined aircraft are ground boosted (or supercharged) to ensure that the fuel air mixture is not only in the same proportions but the same mass finds its way to the combustion chambers to retain the right power settings. If you had control over the amount of boost (and you were smart enough - that leave me out) then you would be about to retain the right boost to counter the effects of altitude. Hope this makes sense.
AnswerID: 246839

Reply By: Member - Stephen M (NSW) - Thursday, Jun 14, 2007 at 20:11

Thursday, Jun 14, 2007 at 20:11
Yep my old 2.8 lux was chooffing smoke and running warmer then it ever had when we left the high country and headed for the snowys due to the fires. Pulling up some hills was really annoying actually back in first on a couple of them and I had never seen the old girl choof smoke like I did those few days and it was running the fuel from the servo in Thredbo. Once we were headed out of the area it seemed to go good again and temp never ever moved prior or after that trip only while we were there. We were running aircon going into thredbo could have swarn it was 30+ degree's. We went to local coffee shop for a drink and I asked him what the temp was 16 degrees he said. So I reckon the height plus or minus, definately made a difference but I was not running turbo. Regards Steve M
AnswerID: 246852

Reply By: Wayne-o (Pilbara WA) - Thursday, Jun 14, 2007 at 23:25

Thursday, Jun 14, 2007 at 23:25
As altitude increases, the air gets less dense (for a number of reasons). Also the oxygen saturation of the air decreases.
This is mainly evident in a piston/non-turbo plane where power is a measure of manifold pressure in inches of mercury. At sea level, or standard atmosperic pressure of 1013 hpa, with the engine idling, MAP (manifold pressure) will read just under 29" of murcury. At full throttle, 27" of murcury: APPROX
At 10000 feet, with full throttle, the same engine may only recieve 15-19" of mercury MAP. this means that a 300 bhp engine at sea level, will only be producing approx 130-140 bhp at altitude.
The same will happen to any internal combustion engine, diesel or petrol, turbo or non-turbo.
The turbo being only driven by exhaust gasses, can only spin so fast, therefore cannot compensate for the loss in air density, and will spin at roughly the same speed, but produce less boost as it will compressing less dense air.
Turbo planes get around this by usind a turbo to MAINTAIN rated power. Meaning at sea level the waste gate is fully open, and no boost is provided. As the plane climbs, the air gets les dense, that waste gate begins to close, and boost is increased to MAINTAIN sea level power.
So the answer to the question is,
Any increase in altitude will decrease air density and decrease boost, and therefore horsepower.
Making the air colder, ie intercooling more etc, will reduce the serverity of the loss in power, but not to a noticable extent.
Hope this answers ya question pal,
AnswerID: 246931

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