Pr0PheT said:
You are obviously clueless. Manufacturers give times attained at sea level. Can you see this test was conducted at 1400m. You have a power loss of approx. 17 per cent at this level. A 125i is rated at 160kw sealevel. Up here minus 27kw therefore in the region of 133kw.Do you really think a car with 133kw can even get close to 6sec?
Personally i think the time is very impressive.
Not completely clueless; i have been known to get a clue on occassion. 17% loss of quoted figures is attributable to normally aspirated vehicles only.
Turbo/supercharging compensates for the losses incurred by engines due variations in atmospheric pressure.
And there's no accounting for your being impressed by 133kw.
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That part is actually not entirely correct, turbocharged cars do have a loss of power at altitude, however this is not in the region of 1.1% per 100m (15.4% at 1400m) like N/A engines.
Unlike Aircraft engines with turbochargers which keep their power constant up to 25000ft car engines start loosing power much earlier. The reason for this is that the car cant compensate for the difference in air pressure therefore the boost needs to be increased in order to have the same manifold pressure as at sea level because of the decrease in air pressure at altitude.
so example
ur boost is 5 at sealevel air pressure is 5 so manifold pressure = 10
ur boost is 5 at altitude airpressure is 2 so manifold pressure = 7
u lose power .. this is an extreme example as the ECU will compensate for this however there will still always be a loss in the region of 3 - 5%, there is a formula for it.
I might not be 100% on the facts but point is... forced induction also loses at altitude, FACT.... but its not a double digit precentage at 1400 - 1800m.
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Agreed - there would be a loss, though much smaller that on N/A cars. Also, I believe that twin turbo's (twin scroll?) were brought in to mitigate turbo lag; in theory then, a smaller turbo catches the slack on the lower end of the rev range.
phantom said:
Wow this thread sure livened up. First of all Derrick sorry i could have used more polite words.:sorry: Been in the game a long time and when i see cars being given times reserved for real performers i get a bit agitated. Please let me share some experience. In 1993 the Tarlton roadshow went down to Margate. I competed in my Toyota twincam turbo and in my same class was capri v6 n/A. At Tarlton the racing was close. Toyota ran 15.4 Capri ran 15.3. At Margate the Capri ran 14.6
and i won with a time of 13.8. I have also studied and know what the books say but at the end of the day its what happens in front of your eyes.So against what everyone thought the opposite happened.
Some of the guys i know with the fastest cars around have done it with experience and not books.:thumbs:
I would just like to give more food for thought.Although you do not lose the same amount of perfomance power as a n/a motor at highveld remember it is still n/a till the turbo starts spinning. On the log of the 125i the 0-100 was 7.45sec but if you take the logged time from 5-100 the time is only 7.0sec.I think this is why some magazines use this figure when testing so as to do away with gearbox lag,spooling of turbo and traction loss.Rule of thumb for us was to take 0,7sec off the time of a car going fom the highveld to the coast.Based on how they work in the USA this now gives this car a time of 6.3sec. I am sure that is enough to be impressed with.
There is nothing as contentious as dyno figures because there is a operator correction that gets entered into the software whereas satellites are where they are for everyone.
Dynos have their place if you want to modify because to go anywhere you have to know where you came from.Just use the same machine with the same correction figures.
There is no conspiracy so lets leave the FBI, CIA, NCIS, Scotland yard out of it.:roflol:
No worries, all's forgiven.
