Went back to the dragstrip again, with a properly working 104 program...
12-12-2005, 08:23 PM
#102
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You are maybe confusing two different functions. Turbo spool and change in engine rpm over time
aren't the same thing. Saying that an engine revs quicker in a lower gear than it does in a higher gear doesn't mean the turbo spools slower in a higher gear. In fact, the 1.8t revs so quickly in 1 and second one is hard pressed to make full boost in those gears.
Going WOT in fourth gear on a 1.8t (especially uphill) loads the engine more than doing so in 3rd. Revs build slower in the higher gear which gives the exhaust gases more time to build pressure on the wheel of the turbo over a given rev range.
When one looks at merely a RPM vs boost pressure graph the 4th gear pull will necessarily show more boost at a lower rpm than will the third gear pull. The turbo simply has more time to build pressure with the slower rate of rev change.
This is one of the reasons a 4th gear dyno pull (on a 1.8t A4 5 speed) will show more power over a wider rev band than will the same car pulling in 3rd. Similarly, a 2nd gear pull will show less than the 3rd gear pull.
Physics is funny that way. It doesn't have a hard on for anyone in particular.
Going WOT in fourth gear on a 1.8t (especially uphill) loads the engine more than doing so in 3rd. Revs build slower in the higher gear which gives the exhaust gases more time to build pressure on the wheel of the turbo over a given rev range.
When one looks at merely a RPM vs boost pressure graph the 4th gear pull will necessarily show more boost at a lower rpm than will the third gear pull. The turbo simply has more time to build pressure with the slower rate of rev change.
This is one of the reasons a 4th gear dyno pull (on a 1.8t A4 5 speed) will show more power over a wider rev band than will the same car pulling in 3rd. Similarly, a 2nd gear pull will show less than the 3rd gear pull.
Physics is funny that way. It doesn't have a hard on for anyone in particular.
12-12-2005, 09:45 PM
#106
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Looks like the car wasn't asked for boost until after 3100 rpm. 3100+ rpm in fourth isn't near
<center><img src="http://i13.photobucket.com/albums/a275/zemun2/donrdyno.jpg"></center><p>
the load as one would see going WOT in 4th down around 2000 rpm as in this graph. I don't see the requested boost here. I'd imagine requested occurred before 2000 rpm since there will be some lag between requested and boost actually beginning to build.
Also, it looks to me like full boost (on the graph in your post above this one) is closer to 4000 rpm than to 4200 rpm.
the load as one would see going WOT in 4th down around 2000 rpm as in this graph. I don't see the requested boost here. I'd imagine requested occurred before 2000 rpm since there will be some lag between requested and boost actually beginning to build.
Also, it looks to me like full boost (on the graph in your post above this one) is closer to 4000 rpm than to 4200 rpm.
12-13-2005, 02:35 AM
#107
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ofcourse it will, i have, im agreeing with you, what was the point you were trying to make?
load and gear were not in question...your post said "this is what colder air can do to the same car..." but you just confirmed its really do to gear and load so i was just wondering if i missed the real point of your post
