Dissapointing dyno results - Questions
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From: AZ
Dissapointing dyno results - Questions
I had my car dynoed a couple months ago and it rolled the numbers in my sig. This was in the middle of Summer in 95.78*, 28.64" with a 1.05 CF and minimal humidity (13-17%). I dynoed the car again today with the PCMforless tune, 95.56*, 28.79", 60% humidity with a 1.05 CF. All numbers are SAE. The car rolled 330.23 rwhp...the graph is near identical to the graph from a few months ago.
My question is...how does humidity affect barometric pressure, or vice versa? Does humidity get factored into the SAE corrections at all?
I'm not too worried about the lower numbers...track times are what I'm concerned with.
I know humidity will kill performance at the track etc., but curious if it is somehow figured into the SAE correction.
The main reason I dynoed the car again is to see how the A/F looked after the tune. Below is a graph of the A/F...the car was leaning out pretty bad up top with a max of 13.84:1. We hooked a F/P guage up to the car and it read ~ 32 psi @ idle....read 40 psi until ~ 4800 RPMs where it dropped to aorund 30 for the rest of the pull. I think I'm in need of a new fuel pump because I was having the same problem w/the lean condition last time I dynoed the car.
A/F Graph
Thanks.
My question is...how does humidity affect barometric pressure, or vice versa? Does humidity get factored into the SAE corrections at all?
I'm not too worried about the lower numbers...track times are what I'm concerned with.
I know humidity will kill performance at the track etc., but curious if it is somehow figured into the SAE correction.
The main reason I dynoed the car again is to see how the A/F looked after the tune. Below is a graph of the A/F...the car was leaning out pretty bad up top with a max of 13.84:1. We hooked a F/P guage up to the car and it read ~ 32 psi @ idle....read 40 psi until ~ 4800 RPMs where it dropped to aorund 30 for the rest of the pull. I think I'm in need of a new fuel pump because I was having the same problem w/the lean condition last time I dynoed the car.
A/F Graph
Thanks.
Last edited by 97bowtie; Aug 29, 2003 at 01:08 PM.
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Joined: Apr 2003
Posts: 1,591
From: PA
sorry to hear that.
As you know i am definitly no expert on this but........ Humidity can also be measure as the vapor pressure. The SAE correction uses the 'dry' barometric pressure. In my case it was 29.8 in Hg - .66" Hg vapor pressure. So basically it reduces the barometric pressure.
Exact same dyno i take it?
You can get variability between pulls due to the engine operating temp, i saw that in my first three pulls when i was stock.
-brent
As you know i am definitly no expert on this but........ Humidity can also be measure as the vapor pressure. The SAE correction uses the 'dry' barometric pressure. In my case it was 29.8 in Hg - .66" Hg vapor pressure. So basically it reduces the barometric pressure.
Exact same dyno i take it?
You can get variability between pulls due to the engine operating temp, i saw that in my first three pulls when i was stock.
-brent
Registered User
Joined: Apr 2003
Posts: 1,591
From: PA
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Joined: Oct 2000
Posts: 283
From: lhc, az
You might want to ask the place that dynoed your numbers. I know the newer superflow dynos factor everything in, including, BP, humidity, altitude, air density, etc. Can't say much about any other dynos, when i researched a some chassis dynos for a friend that was gonna purchase one I don't recall/remember any of them besides superflow factoring all of that in for SAE correction.
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