12-14-2020, 06:11 PM | #1 |
Drives: 2019 Chevy Camaro ZL1 M6 Join Date: Jul 2019
Location: Sea level
Posts: 1,276
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Anyone knowledgeable on dyno at altitude?
With just a few bolt ons my car did 567/586 SAE (smoothing 5) at 5865ft altitude (pre-flex tune - 91 octane and factory tune). How different would the numbers be at sea level or near sea level if all other factors were the same (temp, DA humidity etc)? I guess what I’m asking is if there’s a formula for hp loss due to altitude on supercharged cars? I know they read lower at altitude, I’m just wondering if it can be determined how much.
Edit: I know full well that dynos are only a tool. And what matters is the after mod dyno results to measure gains. This question isnt about that. TIA Last edited by CW3SF; 12-14-2020 at 06:28 PM. |
12-14-2020, 07:20 PM | #2 | |
Drives: 2019 ZL1 Join Date: Mar 2019
Location: NJ
Posts: 1,535
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Quote:
You could lose up to 96bhp being 5000ft above sea level. |
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12-14-2020, 07:36 PM | #3 | |
Drives: 2019 Chevy Camaro ZL1 M6 Join Date: Jul 2019
Location: Sea level
Posts: 1,276
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Quote:
Appreciate the input. |
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12-14-2020, 07:37 PM | #4 |
Drives: 2019 ZL1 Crush Join Date: Jan 2019
Location: Colorado Springs
Posts: 564
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you lose about 3PSI up here compared to sea level. What that equals in HP, no clue. Part of the correction factor is accounting for altitude so that is probably what you make down @ sea level. I think uncorrected I was right below 600WHP
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2019 Crush A10
E-Force 2650 670WHP 615WTQ All besides the 2650 is bone stock down to the air filter. |
12-14-2020, 08:18 PM | #5 | |
Drives: 18 Tahoe RST, 19 Z06 Join Date: Apr 2017
Location: Colorado Springs, CO
Posts: 327
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Most dyno operators give you the corrected to sea level numbers unless you specifically ask for uncorrected numbers.
Those numbers probably are what your car would make at sea level. Quote:
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12-14-2020, 08:36 PM | #6 |
Drives: '20 ZLE Join Date: Jun 2020
Location: Mile High
Posts: 3,805
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Your dyno # should be corrected for altitude. Supercharged and turbos do not lose as much as NA, which can lose 20-25% up here depending on DA.
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'20 ZL1LE A10.
LME 390, E2650, FBO. 1116/967. 100 octane. 15" conversion/Weld/MT ET Street R 325/50R15. 1.35/9.25/151 at 3500 ft. (only one pass so far). Alky Twin 10+10 MAF, 100% meth. No dyno or ET. |
12-14-2020, 08:42 PM | #7 |
Drives: 2019 Chevy Camaro ZL1 M6 Join Date: Jul 2019
Location: Sea level
Posts: 1,276
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I appreciate the explanations. Just moved here last summer so this altitude stuff is new to me.
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12-14-2020, 08:45 PM | #8 |
Drives: '20 ZLE Join Date: Jun 2020
Location: Mile High
Posts: 3,805
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Denver has one of the lowest DA I've ever seen tonight - 3582 ft.
25F 25.19 merc 15F dew point
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'20 ZL1LE A10.
LME 390, E2650, FBO. 1116/967. 100 octane. 15" conversion/Weld/MT ET Street R 325/50R15. 1.35/9.25/151 at 3500 ft. (only one pass so far). Alky Twin 10+10 MAF, 100% meth. No dyno or ET. |
12-14-2020, 09:18 PM | #9 |
Drives: 2019 Chevy Camaro ZL1 M6 Join Date: Jul 2019
Location: Sea level
Posts: 1,276
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Nice. This thread brought out all the Colorado peeps.
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12-15-2020, 11:22 AM | #10 |
Drives: 2019 Chevy Camaro ZL1 M6 Join Date: Jul 2019
Location: Sea level
Posts: 1,276
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So just to revisit what was input from above and trying to make some sense of it.
567whp can’t be what it would make at level. Add back in ~12% drive train loss foe the M6 and that’s 635 crank hp. This car has intake, TB and exhaust so that doesn’t add up. The car came with 650. The post indicating that cars make 3psi of boost here would make sense. The car with those mods, but down 3psi of boost should be in the 567whp range. They dyno shop told me that all cars make less here SAE than they would at sea level. He just didn’t know what the formula was for computing the difference. |
12-15-2020, 11:56 AM | #11 | |
Account Suspended
Drives: '21 Wild Cherry ZL1 Join Date: Aug 2018
Location: WI
Posts: 2,082
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Quote:
It is, as a result to behavior of gasses & gravitational force, not a linear chart, it’s more of a gradient curve. I always used .5psi drop/ 1kft of elevation. That is a rough estimate. As air density is also attributed to other variables it changes slightly from day to day or throughout a day. Base calculations for sea-level are 101kpa/14.67psi, Denver is said to be 85kpa/12.32psi. Some reading, very basic, on the subject. https://flexbooks.ck12.org/cbook/ck-...altitude-ms-ps & a calculator. https://www.mide.com/air-pressure-at...ude-calculator Add: to answer your question as it applies to HP at atmospheric pressure, assuming a adiabatic quotient of approximately 1.4 (non ideal gas) if you double atmospheric pressure HP would double. In reality there is always adiabatic & parasitic losses, as seen in people’s referring to HP/ lb of manifold pressure, so as a very rough estimate 7.5psi is approximately 50%. 3.2psi would be 25% less. Last edited by gtfoxy; 12-15-2020 at 12:39 PM. |
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12-15-2020, 12:27 PM | #12 | |
Drives: '20 ZLE Join Date: Jun 2020
Location: Mile High
Posts: 3,805
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Quote:
So it looks to me that yours makes around stock hp adjusted to sea level.
__________________
'20 ZL1LE A10.
LME 390, E2650, FBO. 1116/967. 100 octane. 15" conversion/Weld/MT ET Street R 325/50R15. 1.35/9.25/151 at 3500 ft. (only one pass so far). Alky Twin 10+10 MAF, 100% meth. No dyno or ET. |
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12-15-2020, 12:37 PM | #13 |
Drives: 2017 1SS Hyper Blue Join Date: Apr 2017
Location: Wisconsin
Posts: 478
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I wonder, has anyone ever created a dyno "chamber", where you could dial in whatever altitude, temp, etc conditions you wanted?
That would be pretty cool. |
12-15-2020, 12:43 PM | #14 | |
Account Suspended
Drives: '21 Wild Cherry ZL1 Join Date: Aug 2018
Location: WI
Posts: 2,082
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Quote:
They exist primarily in the aerospace industry. Example. https://www.nap.edu/read/9088/chapter/6 |
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