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YOUR RESEARCHAdded HP with cooler ambient temp
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Check math/memory please do
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Suggestion
If someone wants to check my math/memory please do.
Leading evidence: 'Check math/memory please do' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check math/memory please do' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Run slightly rich during acceleration or high torque applications
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Suggestion
The downstream oxygen sensor is used for this and since it can only detect the A/F ratio crossing point, oxygen content in the exhaust vs none, most systems run slightly RICH during acceleration or high torque applications and use the upstream MAF/IAT sensors to determine A/F mixture ratios.
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Suggestion
It's not a linear relationship, but above was a linear approximation for typical ambient temperatures using P=nVRT.
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Suggestion
The downstream oxygen sensor is used for this and since it can only detect the A/F ratio crossing point, oxygen content in the exhaust vs none, most systems run slightly RICH during acceleration or high torque applications and use the upstream MAF/IAT sensors to determine A/F mixture ratios.
Run slightly rich during acceleration or high torque applications
No successful repair reported for this finding.
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Reported fixes
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Read evidence and context
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0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Suggestion
The downstream oxygen sensor is used for this and since it can only detect the A/F ratio crossing point, oxygen content in the exhaust vs none, most systems run slightly RICH during acceleration or high torque applications and use the upstream MAF/IAT sensors to determine A/F mixture ratios.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
The downstream oxygen sensor is used for this and since it can only detect the A/F ratio crossing point, oxygen content in the exhaust vs none, most systems run slightly RICH during acceleration or high torque applications and use the upstream MAF/IAT sensors to determine A/F mixture ratios.
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I read a post somewhere in this forum not too long ago about the added HP that can be achieved with cooler ambient temperatures (resulting in cooler intake air temp) but didn't pay much attention to it.
I bought my 996C4 Cab this summer and now it has been in the mid 30's (Fahrenheit) and maybe I am just imagining this, but the seat of the pants dyno really seems to notice a difference in throttle respone and acceleration.
I do not race or track my car, so I wonder if I am just imagining this. I don't think I am, and it really makes me want to have more HP all the time. Has anyone else noticed this with cooler temperatures?
If I remember, I calculated once that 5 degrees F is about 1%, so let's just guess 50 degrees is on the order of 10%. You're not imagining things. If someone wants to check my math/memory please do. It's not a linear relationship, but above was a linear approximation for typical ambient temperatures using P=nVRT. I have a G-meter, and on some really cold days, it definitely pulls a lot harder; really hot days, a lot less.
Yup. Engine management systems optimize for Lambda, the stoichiometric ratio, about 14.7 to 1. As the air gets denser due to temperature, the system provides that much more fuel. Therefore, at a given throttle opening, more combustion components are available, and presto, more HP. That's why a cold air induction system gives you a few HP on some cars too.
Someone posted these links on another forum. Very interesting. I guess that being at about 1,500 ft. elevation doesn't help me either.
I imagine the CHAMP car race in Denver causes the engineers to make some adjustments.
Thanks everyone for your comments!
http://www.viperclub.org/faq/techtemp.html
http://wahiduddin.net/calc/calc_hp_dp.htm
It definitely makes a big difference, even more so in turbo cars.
Similar to the temp difference, 0-60 times at sea level can easily be 5% quicker than at a mile high due to the denser air.
Stoichiometric ratio only applies at relatively constant road speeds, cruising. The downstream oxygen sensor is used for this and since it can only detect the A/F ratio crossing point, oxygen content in the exhaust vs none, most systems run slightly RICH during acceleration or high torque applications and use the upstream MAF/IAT sensors to determine A/F mixture ratios.
That's why those MAF/IAT mods you can buy on Ebay sometimes actually work. Via modifying the IAT, Intake Air Temperature, signal they fool the engine mixture control system into "thinking" the intake airflow is cooler, densor, than it really is and that results in getting an even richer mixture for acceleration than the manufacturer intended.
This is a source reference. Confirm exact model applicability in the original material.
