my theory on lag... am I close? (for the confused newbie)
10-09-2002, 06:20 AM
#1
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my theory on lag... am I close? (for the confused newbie)
ok. so i noticed that weather and altitude are the biggest primary reasons for lag. (I know, I know duh... this info is more for the people new to turbos.) when it was hot and humid this summer my car felt like it was sufficating. no power, all lag. now that it is fall out, and the air is cool and crisp, my car is a rocket again! almost zero lag and accelerates like a rubber band. also I noticed that owners from higher altitudes have more lag problems then owners at or below sea level. I experienced this problem when I visited my brother in colorado last year. I had an UNBELIEVABLE lag in the mountains from dead stop and gos. I think the lag problem is primary these two obvious reasons, not anything a toggle on the DBW will fix, or turning off the ESP. (sorry guys and gals, but these "rumors" don't work for me. I think its all in your heads =^p sorry hehe.) seems the only way to solve it for real is to either chip, or go for the 4.2. hmmmmm 4.2......treerun if you get one I will too! hehe
10-09-2002, 06:28 AM
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Re: Heat and humidity
I second that. I noticed the car was far more sluggish in hot humid weather this summer, even at sea level--I definitely saw a correlation. I assume there are some engineers who can explain it.
10-09-2002, 07:02 AM
#4
There was a post regarding this a while ago.
If I remember correctly, there was a discussion of the relative density of cold vs. hot air (and it didn't have anything to do with some of our posters)and the fact that cold=dense=more oxygen=more combustion. I'm sure some of our more physics-oriented members can elucidate. I guess if we all move to Alaska or northern Canada or Scandinavia, we'll solve this annoying lag problem.
10-09-2002, 08:36 AM
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Engineers? You don't need no stinkin' engineers...
...What you need is a genuine Weather Guy.
To show these effects, I've posted a picture (Warning: Technical Content) of the <a href="http://pictureposter.audiworld.com/23312/relrho.jpg">Air Density</a> relative to that at freezing and sea level, from the Perfect Gas Law. This doesn't correct for water vapor (humidity), which correction is down at the 1% level (although water [vapor] is lighter than air, so it does decrease the density a little).
For reference, Sea Level is 1014 mb or so, and places like Denver and Santa Fe are in the 850-800 mb range.
What this says is that when it's high up and hot, you car can tbe sucking some 30% less air than low down and cold. A pressurized system (turbos or superchargers) will help, as we all know, relative to a normally-aspirated car, but, still, it just won't have as much air as it will at sea level on a cool day. HPH
To show these effects, I've posted a picture (Warning: Technical Content) of the <a href="http://pictureposter.audiworld.com/23312/relrho.jpg">Air Density</a> relative to that at freezing and sea level, from the Perfect Gas Law. This doesn't correct for water vapor (humidity), which correction is down at the 1% level (although water [vapor] is lighter than air, so it does decrease the density a little).
For reference, Sea Level is 1014 mb or so, and places like Denver and Santa Fe are in the 850-800 mb range.
What this says is that when it's high up and hot, you car can tbe sucking some 30% less air than low down and cold. A pressurized system (turbos or superchargers) will help, as we all know, relative to a normally-aspirated car, but, still, it just won't have as much air as it will at sea level on a cool day. HPH
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10-09-2002, 08:38 AM
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Yeah, me too...
..I wish I'd been patient enough to wait and order a 6-speed.
Anyway, see the post just above for the heat/altitude thing. There's also the TIP thing, of course, which is why I asked. HPH
Anyway, see the post just above for the heat/altitude thing. There's also the TIP thing, of course, which is why I asked. HPH
10-09-2002, 08:39 AM
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The problem with your theory is that 6spd owners have not reported any lag problems.........
Turbo motors are much better at compenstating for altitude and heat that n.a. motors. I think you have to point the finger at the tip for your lag.
10-09-2002, 08:39 AM
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density of the air?
When it's hot, 02 molecules are spread further apart? And as a result per given volumeo air being recycled by the turbo, there is less 02 to combust with the gas. I would think that's why intercoolers are effective, because they render a cooler and therefore denser charge, which equals more power.
I hope this is correct.
I hope this is correct.