Less oxygen per volume...

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Less oxygen per volume... Posted by John Williams [Email]

(#1982) [Profile/Gallery] (more from John Williams) on Sun, 2 Apr 2006 09:07:57

In Reply to: Re: how is boost measured?, Dean, Sat, 1 Apr 2006 15:36:25 Members do not see ads below this line. - Help Keep This Site Online - Signup

I am not exactly sure how it all works in technical terms, but its all about density altitude. If its hot and sticky at sea-level, I have seen some drag strips talking about the density altitude being at 1800'. That means the pressure and amound of oxygen per volume is less that day.
Think of a hot sticky day at 5000'??? When can see a density altitude of 9000'ams here in Denver. In the summer the air is super thin and performance drops off a ton. I still feel that if you pump x volume of air at sea-level through your turbo and into your engine and x volume of air in Denver, you will have more oxygen at sea level by pumping the same volume of air that contains less oxygen per volume up here a mile high. There is less oxygen per volume of air. Turbo works harder, makes more heat, ic cannot get rid of heat as efficiently, my ic company did some testing for an Evo in Denver, he established a 15% loss in ic efficiency. Then the exhaust manifolds do not get rid of heat as quickly in the less dense air. There are numerous factors that cause the limitation of hp at altitude. I have seen days that represent density altitude of 3400', good day for power, then on hot days in the summer as high at 9000', bad day.... Like Jak said, if you are maxed out at sea-level, I would think you will lose more hp at altitude than if you have say a stock Viggen with 20-30% head room:-) This car is able to increase boost as you climb in altitude and almost maintain sea-level performance. NOw if you maxed that viggen out to 550bhp and then brought it up to Denver, I would say you will lose around 10-15% hp.... My own car loses around 15% by sae and its just about 10-15% less than Jak's car and other stage 5 cars of similar make/model with smaller turbos. I make 250whp uncorrected here in Denver, Spoolin900 made 270whp with a 15t turbo, Jak made 280whp with jsp25/gt28r turbo. So for me to make 250whp with a larger turbo of T28/gt28R either means the 15% is actually the correct amount of power loss or my car is hurting and does not make much power.
After discussing with Nick the dyno shop owner that sees all kinds of Viggens, ng900s with many differnt tuners, he stated this was one of the best so far, so I am inclined to believe I really do have a 15% power loss from sea-level. Every racer, dyno shop owner, has told me we definetly lose power up here, even with forced induction cars. These are guys that go to sea-level and race, they state there is no question the cars run stronger at sea-level...
John

posted by 4.228.12...

Posts in this Thread:

how is boost measured?, LesH, Sat, 1 Apr 2006 14:22:01
- Power Loss at altitude, nikos, Sat, 1 Apr 2006 18:09:17
  - also intercoolers become less efficient, jak , Sat, 1 Apr 2006 21:22:51
    - keeping it simple, vigge, Sat, 1 Apr 2006 23:28:09
      - I would never argue how much is lost, jak , Sun, 2 Apr 2006 09:13:06
      - To add to the above, Vigge, Sun, 2 Apr 2006 08:32:25
    - Re: also intercoolers become less efficient, soneway, Sat, 1 Apr 2006 23:26:46
- Re: how is boost measured?, Dean, Sat, 1 Apr 2006 15:36:25
  - Less oxygen per volume..., John Williams , Sun, 2 Apr 2006 09:07:57 <-- Viewing This Message
  - Re: how is boost measured?, Vigge, Sun, 2 Apr 2006 03:23:34
    - Re: how is boost measured?, Dean, Mon, 3 Apr 2006 23:03:04
    - short overlap :-), jak , Sun, 2 Apr 2006 21:13:34
    - Re: how is boost measured?, vigge, Sun, 2 Apr 2006 08:28:04
      - thats a valid point on pre turbine exaust pressure, jak , Sun, 2 Apr 2006 11:57:31
        oops, jak , Sun, 2 Apr 2006 11:59:46
        A good link about this, SteveW, Sun, 2 Apr 2006 16:12:00
        02 not constant by volume..., John Williams , Mon, 3 Apr 2006 08:17:06
        Finally a way to understand this oxygen per volume., John Williams , Mon, 3 Apr 2006 08:55:40
        Re: Finally a way to understand this oxygen per volume., vigge, Mon, 3 Apr 2006 12:13:55
        do you have the slip on this viggen at 5000 feet?, jak , Mon, 3 Apr 2006 20:35:00
        Re: do you have the slip on this viggen at 5000 feet?, vigge, Mon, 3 Apr 2006 23:20:55
        yeah I asked back trhen but never got them, jak , Mon, 3 Apr 2006 23:28:52
        I dissagree, SteveW, Mon, 3 Apr 2006 14:24:49
        Re: I dissagree, Vigge, Mon, 3 Apr 2006 22:47:36
        Ok, SteveW, Mon, 3 Apr 2006 16:31:38
        Re: Ok, vigge, Mon, 3 Apr 2006 23:18:32
        Re: Finally a way to understand this oxygen per volume., John Williams , Mon, 3 Apr 2006 14:14:43
        Re: Finally a way to understand this oxygen per volume., vigge, Mon, 3 Apr 2006 23:26:31
        Ok Vigge, will you help me figure all this out?, John Williams , Tue, 4 Apr 2006 09:11:44
        Re: Ok Vigge, will you help me figure all this out?, Vigge, Tue, 4 Apr 2006 10:04:26
        Re: Ok Vigge, will you help me figure all this out?, John Williams , Tue, 4 Apr 2006 15:48:46
        Re: Ok Vigge, will you help me figure all this out?, vigge, Wed, 5 Apr 2006 13:35:56
        Re: Ok Vigge, will you help me figure all this out?, John Williams , Wed, 5 Apr 2006 14:07:39
        Re: Ok Vigge, will you help me figure all this out?, Vigge, Wed, 5 Apr 2006 14:20:01
        Well, I will say this, its hot!!!, John Williams , Fri, 7 Apr 2006 08:22:42
        Re: Well, I will say this, its hot!!!, vigge, Fri, 7 Apr 2006 12:23:30
        Re: Well, I will say this, its hot!!!, John Williams , Sat, 8 Apr 2006 06:07:04
        Re: Well, I will say this, its hot!!!, vigge, Sat, 8 Apr 2006 12:24:38
        Mid-way on delivery pipe is 142F, John Williams , Sun, 9 Apr 2006 13:03:59
  - absolute pressure, jak , Sat, 1 Apr 2006 21:11:16
    - Re: absolute pressure, TML , Mon, 3 Apr 2006 02:15:43
      - yeah I think you are rite pre98, jak , Mon, 3 Apr 2006 09:22:35

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