Kangarooing up road
22 August 2000, 09:34 AM
#1
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Techies Help required! 
When accelerating at night! (Or when outside air temperature is cold) I have flat areas in the acceleration through the rev range! So I accelerate then the power dies then i accelerate and power dies again this happens all the way up to the red line! Which is kind of like im kangarooing up the road!
When it is daylight (or when outside air temperature is warm) this problem is alleviated and sometimes even completely disappears!
The clutch is not slipping so it cant be that!!
No Subaru garage can fit me in for a week to have a look, as they need it overnight!! As if I visit during the day, outside air temp is up, and there’s virtually no problem to show them!
HELP
thanks in advance
DENZ
When accelerating at night! (Or when outside air temperature is cold) I have flat areas in the acceleration through the rev range! So I accelerate then the power dies then i accelerate and power dies again this happens all the way up to the red line! Which is kind of like im kangarooing up the road!
When it is daylight (or when outside air temperature is warm) this problem is alleviated and sometimes even completely disappears!
The clutch is not slipping so it cant be that!!
No Subaru garage can fit me in for a week to have a look, as they need it overnight!! As if I visit during the day, outside air temp is up, and there’s virtually no problem to show them!
HELP
thanks in advance
DENZ
22 August 2000, 01:18 PM
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It is all to do with your height.. you see pressure temperature and density all decrease with altitude- and with a higher altidude you get an increased True air speed or TAS (IAS calibrated for position manouvre and density, error - not to mention compressability but that is only above 300 knots 
). It is all todo with the density, as density goes down there are less air paritcles which means you need to increase speed to get the same number of particles as you would do at a low speed. You have to remember you Indicate Air Speed stays constant!!! 
Anyway as i was saying, with an increase in altitude your SFC (specific fuel consumption) goes down which makes your engine more efficient , but the higher you go, the more thrust you need which realively increases your SFC. You will in the end come to you absolute altitude (where rate of climb is zero) or sevice altidude (altitude of a defined measure). Well once this happens your engine cannot provide enough thrust that is needed to keep you at the altitude , and you will either descend or your engine may quit as it cannot provide the thrust/ SFC with mixture to air ratio. (15:1 , but generally 12:1)
While all this is going on you have to think about your drag, with induced drag and parasite drag (profile etc) Well as your speed is increased your form drag incrased and starts to move forward underneath your spoiler , we have to think about induced drag though, because... it does reduce with an increase in speed, it is relative to your weight... an increase in weight increased induced drag! Well once we have thought about this... with the consideration of what you had for lunch! , we can go on to think about other delightful things.
Ian
PS- Hope you get your car sorted!
PPS- We haven't even started on 1 engine innoperative!!! or V1 Vfe
[This message has been edited by Hos (edited 22 August 2000).]
). It is all todo with the density, as density goes down there are less air paritcles which means you need to increase speed to get the same number of particles as you would do at a low speed. You have to remember you Indicate Air Speed stays constant!!! Anyway as i was saying, with an increase in altitude your SFC (specific fuel consumption) goes down which makes your engine more efficient
, but the higher you go, the more thrust you need which realively increases your SFC. You will in the end come to you absolute altitude (where rate of climb is zero) or sevice altidude (altitude of a defined measure). Well once this happens your engine cannot provide enough thrust that is needed to keep you at the altitude , and you will either descend or your engine may quit as it cannot provide the thrust/ SFC with mixture to air ratio. (15:1 , but generally 12:1)While all this is going on you have to think about your drag, with induced drag and parasite drag (profile etc) Well as your speed is increased your form drag incrased and starts to move forward underneath your spoiler
, we have to think about induced drag though, because... it does reduce with an increase in speed, it is relative to your weight... an increase in weight increased induced drag! Well once we have thought about this... with the consideration of what you had for lunch! , we can go on to think about other delightful things. Ian
PS- Hope you get your car sorted!
PPS- We haven't even started on 1 engine innoperative!!! or V1 Vfe
[This message has been edited by Hos (edited 22 August 2000).]
22 August 2000, 02:06 PM
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Hos
Your a nutter!!!!
Will keep you all informed!!
SeanT,
it was after the exhaust was fitted but that could be a coincidence !! I hope so for my warranty’s sake!!
thanks
Denz
Your a nutter!!!!
Will keep you all informed!!
SeanT,
it was after the exhaust was fitted but that could be a coincidence !! I hope so for my warranty’s sake!!
thanks
Denz
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