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Dyno numbers air temp question...

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Old 07-23-2006, 02:46 PM
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Default Dyno numbers air temp question...

I know there has always been high rwhp cars that have been questioned. How many of you guys have checked the IAT temps vs the shop temps?
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Old 07-23-2006, 03:00 PM
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How about simply the correction factors that no one seems to include anymore?
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Old 07-23-2006, 03:11 PM
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Since most dyno with the hoods open, IATs tend to follow ambient temps. Whether ambient temps mimick what's entered into the correction factor is always a point to debate though.
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Old 07-27-2006, 07:00 PM
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The reason I as is, we recently had a car dynoed locally that dynoed @ at a shop who is known for big dyno numbers. The car dynoed close to 500rwhp and 440rwtq when the package was built less than a couple of months ago. When the car goes on the rollers here, it lays down a less than exciting 458/401. The owner was pissed but IMO they are strong numbers. Either the car lost 40/40, which the owner says it runs the same as before or the dyno correction factors can be manipulated.
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Old 07-27-2006, 08:05 PM
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Originally Posted by Phil99vette
The reason I as is, we recently had a car dynoed locally that dynoed @ at a shop who is known for big dyno numbers. The car dynoed close to 500rwhp and 440rwtq when the package was built less than a couple of months ago. When the car goes on the rollers here, it lays down a less than exciting 458/401. The owner was pissed but IMO they are strong numbers. Either the car lost 40/40, which the owner says it runs the same as before or the dyno correction factors can be manipulated.
Was this at Tempest Phil? I don't think the correction factors work real well, when its real hot and humid like it has been here lately. What were the weather conditions when you made the first dyno pulls?

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Old 07-27-2006, 10:57 PM
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This wasn't my car, it was one from a couple states north. I'll talk to you more about it this week. Give me a call when you get a chance.
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Old 07-28-2006, 08:49 AM
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Our dyno is located in an area where we probably have as much of a variation in atmospheric conditions as anywhere, yet our atmospheric correction factors seem to be amazingly accurate on NA cars. With boost applications, the higher corrections on a hot, steamy day seem to help their numbers because they create their own atmosphere to some degree, but not using corrections at all make it worse even less accurate.

A vehicles measured IATs usually run slightly higher then ambient due to engine proximity and heat soak. One thing that we do to help keep correction factors more accurate is to keep our weather station close to the car's engine compartment. During a long multi Hr tuning session, we often see a 5% increase in the correction factor due to the outside and in-shop temps climbing plus other atmosphere changes. When you're monitoring slight HP/TQ changes based off of tuning changes, it would be impossible to provide a good tune not using corr factors.
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Old 07-28-2006, 11:27 AM
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Originally Posted by Phil99vette
The reason I as is, we recently had a car dynoed locally that dynoed @ at a shop who is known for big dyno numbers. The car dynoed close to 500rwhp and 440rwtq when the package was built less than a couple of months ago. When the car goes on the rollers here, it lays down a less than exciting 458/401. The owner was pissed but IMO they are strong numbers. Either the car lost 40/40, which the owner says it runs the same as before or the dyno correction factors can be manipulated.
Correction factors can be heavily manipulated or just plain mis-used. But they do work and work well when used correctly.

I was reading an article the other day where the same car was dyno'd with the same mods/setup on the same dyno just under different atmospheric conditions (i.e. on different days).

In STD form there was a 20rwhp difference. Once corrected to SAE there was less than 0.5rwhp (yes you did read it correctly) variance between the runs.
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Old 07-28-2006, 12:01 PM
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I've seen many high hp cars on this forum show some strange correction factors when they dyno...like barometric pressure of 28.70 or 29.20 when it was actually close to 30.0...or high ambient temperatures inputed on a cool day.
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