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Old 21st July 2010, 12:23   #1
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Default Common Rail : Why is cold start tougher at higher altitudes

MY travels take me to many places where overnight temp falls to around -5 and then by morning its a brisk 2 degree or so above zero.
What I have noticed is that when I am at a low altitude(10,000 feet or less), the Safari starts easily after couple of applications of glow plugs.
However at the same temperature at higher altitude, eg 14000-15000 feet etc., more cranks are required.
Infact, even when ambient temp is around 5 degree, it takes 2-3 applications of glow plugs.
In narkanda, the temp was -1 in the morning, and she started in first crank.
Any scientific explanation for that.
I am told even Scorpio Common rail suffers from this problem. At higher altitudes cold start is more difficult as compared to cold start at lower altitude, temperature being the same.
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Old 21st July 2010, 12:44   #2
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The first thing that comes to my mind is lack of Oxygen. Probably it takes a while for the ECU to understand that the surrounding has less Oxygen (from the usual setting) & adjust itself to make the mixture little lean. May be someone who's constantly living in high altitude does not experience this problem as the ECU is climatized to understand this. Again, this is a guess, appreciate someone to have explain this better.

Last edited by aargee : 21st July 2010 at 12:45.
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Old 21st July 2010, 12:56   #3
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But what if the car has been at that altitude for a few days, shouldn't the ECU have "learnt" by now
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Old 21st July 2010, 13:04   #4
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Tanveer, is this issue related to Safaris and Scorpios only, or do Innovas also face the same problem? And what about the Swifts/DZires etc. that travel to Ladakh?

Last edited by SS-Traveller : 21st July 2010 at 13:07.
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Old 21st July 2010, 13:24   #5
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Quote:
Originally Posted by tsk1979 View Post
But what if the car has been at that altitude for a few days, shouldn't the ECU have "learnt" by now
Yeah, I'd this thought during lunch. Again, I guess it depends upon the number of days spent on plains versus mountains. More number of days on plains, ECU accustoms to plains. Like SS-T Sir says, somebody should comment on Innova/Swift etc.

Probably Goandude can comment on Innova, if he has observed (Source - http://www.team-bhp.com/forum/travel...hotologue.html ("Innova"ted Ladakh: A photologue))

Edit - Had another thought that I couldn't dismiss - atmospheric pressure? Not necessary on the fuel & cylinders, but on various other components.

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Old 21st July 2010, 13:28   #6
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It has got nothing to do with the technology but with the Fuel characteristics i.e. Diesel.

Did you have the right mix of Diesel/ Kerosene ??

Were you using any Anti-caking/freeze additives ??

I am not sure if Oil companies supply winter diesel in these regions and therefore any of the above is required for instant start in a Diesel engine or as you did, heat it up.

Last edited by dadu : 21st July 2010 at 13:30.
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Old 21st July 2010, 13:32   #7
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I guess it might have something to do with the fuel also ?? The density might vary quite a lot & the amount of fuel travelled into the rail might differ due to it being colder, may be the pressure built up is also different which might cause a few cranks to get the reqd pressure.
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Old 21st July 2010, 13:33   #8
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Quote:
Originally Posted by SS-Traveller View Post
Tanveer, is this issue related to Safaris and Scorpios only, or do Innovas also face the same problem? And what about the Swifts/DZires etc. that travel to Ladakh?
I am talking about altitudes around 4200m and above.
In Leh, the swift at our hotel had erratic start, just like the safari.
In Hanle I had to park the safari in sun for 15 minutes, and then it started just fine. Night temp went down to -5, and in the morning it was around 5 degree C above zero
Speaking of scorpio, the absence of glow plugs in the 2.6 could be the cause, but I am not sure.
Quote:
Originally Posted by aargee View Post
Yeah, I'd this thought during lunch. Again, I guess it depends upon the number of days spent on plains versus mountains. More number of days on plains, ECU accustoms to plains. Like SS-T Sir says, somebody should comment on Innova/Swift etc.

Probably Goandude can comment on Innova, if he has observed (Source - http://www.team-bhp.com/forum/travel...hotologue.html ("Innova"ted Ladakh: A photologue))

Edit - Had another thought that I couldn't dismiss - atmospheric pressure? Not necessary on the fuel & cylinders, but on various other components.
Well it depends whether he spent the night above 4200, and did temp drop below zero at night.
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Originally Posted by dadu View Post
It has got nothing to do with the technology but with the Fuel characteristics i.e. Diesel.

Did you have the right mix of Diesel/ Kerosene ??

Were you using any Anti-caking additives ??

I am not sure if Oil companies supply winter diesel in these regions and therefore any of the above is required for instant start in a Diesel engine or as you did, heat it up.
No additives, just normal diesel. However, in Narkanda, with lot of overnight snowfall, and -1 in the morning, she started on first crank.
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Old 21st July 2010, 13:41   #9
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Quote:
Originally Posted by tsk1979 View Post
No additives, just normal diesel. However, in Narkanda, with lot of overnight snowfall, and -1 in the morning, she started on first crank.
I can confidently say that's the reason, since you travel frequently to cold areas, try using BG Diesel Thaw or Bardhal Diesel Antifreeze next time.
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Old 21st July 2010, 13:47   #10
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Tanveer

I don;t think so that problem is w.r.t CRDI engine,
It is same with most of the diesel engine in cold weather.I remember that my palio 1.3 had glow plug issue - i i did start without cranking in cold temperature.

Please refer to Diesel engine - Wikipedia, the free encyclopedia

Cold start section for details regarding Diesel engine start up.

Thanks & Regards
Anupam00
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Old 21st July 2010, 14:32   #11
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Quote:
Originally Posted by tsk1979 View Post
Infact, even when ambient temp is around 5 degree, it takes 2-3 applications of glow plugs.

I am told even Scorpio Common rail suffers from this problem. At higher altitudes cold start is more difficult as compared to cold start at lower altitude, temperature being the same.
The ECU uses inputs from various sensors to do correction for high altitude conditions namely HFM sensor, Fuel Temperature sensor, Coolant temperature sensor. Once this input is obtained the appropriate "Density correction" is made. The ECU learns things from these sensors and this is a real time activity, which means if a vehicle from high altitude goes to a lower altitude the fueling will change in accordance to the inputs given by the sensor. This is a closed loop system.

Quote:
Originally Posted by aargee View Post
The first thing that comes to my mind is lack of Oxygen. Probably it takes a while for the ECU to understand that the surrounding has less Oxygen (from the usual setting) & adjust itself to make the mixture little lean.
Fuel quality also has a significant role.

Spike

PS- Tanveer which Scorpio model are you talking about? Does it have a glow plug?
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Old 21st July 2010, 17:04   #12
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Quote:
Originally Posted by dadu View Post
I can confidently say that's the reason, since you travel frequently to cold areas, try using BG Diesel Thaw or Bardhal Diesel Antifreeze next time.
Well at same temperatures, at lower altitude no problem, at higher altitude, problem..
Quote:
Originally Posted by anupam00 View Post
Tanveer

I don;t think so that problem is w.r.t CRDI engine,
It is same with most of the diesel engine in cold weather.I remember that my palio 1.3 had glow plug issue - i i did start without cranking in cold temperature.

Please refer to Diesel engine - Wikipedia, the free encyclopedia

Cold start section for details regarding Diesel engine start up.

Thanks & Regards
Anupam00
Glow plugs are fine, got them checked. I never face any problem on lower altitudes. Even at higher altitudes its not really a problem like the scorpios faced, but start is tougher than at lower altitudes
Quote:
Originally Posted by SPIKE ARRESTOR View Post
The ECU uses inputs from various sensors to do correction for high altitude conditions namely HFM sensor, Fuel Temperature sensor, Coolant temperature sensor. Once this input is obtained the appropriate "Density correction" is made. The ECU learns things from these sensors and this is a real time activity, which means if a vehicle from high altitude goes to a lower altitude the fueling will change in accordance to the inputs given by the sensor. This is a closed loop system.



Fuel quality also has a significant role.

Spike

PS- Tanveer which Scorpio model are you talking about? Does it have a glow plug?
Spike, scorpio 2.6 CRDE does not have glow plugs. All 2.6 owners I have spoken to face some problem above 4000m above sea level.
Fuel quality in ladakh is very bad. I think that could be the problem, rather than altitude.

To explain a bit more, I gave three applications of glow plugs, and then started her in the morning. the engine started and then died.
I checked the primer pump, it had gone soft. I manually pumped the bulb till it was hard, and then again cranked engine.
Engine starts, and then dies. Again primer has gone soft.
So it seems fuel from tank is unable to come to the engine.

Then we pushed the car into sun with tank facing sun. After 15 minutes, she started fine. Erratic idle at first, with lots of smoke, and then smoother.

After that it was normal. I guess the fuel return line was returning warm diesel to tank.
My guess is that at night the diesel in the filter next to tank got gelled up, and needed direct heat from sun to thaw.
Could be due to ice crystals too.
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Old 21st July 2010, 17:23   #13
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Quote:
Originally Posted by tsk1979 View Post
Well at same temperatures, at lower altitude no problem, at higher altitude, problem..
The statement doesnt seem right, usually Altitude is inversly proportional to Air pressure, temperate and Density of Air. These are the standard values for pressure, temperature and density (ignoring the slight effect of humidity) at altitudes from sea level to 16,000 feet (about 4900 m).

Name:  AltitudeTemp.gif
Views: 6109
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  • 1 ft (foot) = 0.3048 m
  • 1 in mercury (Hg) = 3,376.8 N/m2 (Pa)= 0.49 lb/in2 (psi) = 12.8 in water
  • T(oC) = 5/9[T(oF) - 32]
Air density also affects the performance of automobiles, with lower density decreasing performance, as there is less Oxygen in the Air. Turbocharger is one way of increasing the density of the air going into an engine but doesnt help in starting.
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Old 21st July 2010, 21:19   #14
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Quote:
Originally Posted by tsk1979 View Post
I am talking about altitudes around 4200m and above.
In Leh, the swift at our hotel had erratic start, just like the safari.
In Hanle I had to park the safari in sun for 15 minutes, and then it started just fine.
What about Innovas? Any that you found struggling to start?
Quote:
Originally Posted by tsk1979 View Post
No additives, just normal diesel. However, in Narkanda, with lot of overnight snowfall, and -1 in the morning, she started on first crank.
Just curious - you carry your diesel in cans from Delhi/Noida, or fill up your extra storage from Leh? Could it be that the diesel from the plains is causing this issue?
Quote:
Originally Posted by dadu View Post
I can confidently say that's the reason, since you travel frequently to cold areas, try using BG Diesel Thaw or Bardhal Diesel Antifreeze next time.
We discussed the issue of adding diesel antigel to the tank in an earlier thread too, where Spike mentioned about antigel going into the tanks of export models. That thread was pretty much inconclusive - hope something positive results from this one.

BTW, dadu, where in India does one freely source BG Diesel Thaw or Bardahl Diesel Antifreeze? or any of the other brands?
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Old 21st July 2010, 21:57   #15
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Quote:
Originally Posted by tsk1979 View Post
But what if the car has been at that altitude for a few days, shouldn't the ECU have "learnt" by now
It mentioned in a similar fashion in many threads but ECU does not have artificial intelligence. It operates on different inputs it gets from sensors.

Problem is definitely due to lower air density. Its a common problem in hills.

WHat you should do is, Heat the glow plug, and crank the engine atleast thrice with no intention of starting.
On fourth try try to start the engine.

While driving in hills try to keep the rpm as high as possible. third and lower works best.
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