Dyno for Dummies Questions
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Melting Slicks
Joined: Nov 2011
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From: Jacksonville FL
Dyno for Dummies Questions
1) I have seen lots of different styles of fans, sizes of fans and different positions used with dynos. Why is this? Is the main object to simulate airflow or control temp? What affect can this have on numbers?
2) What percentage +/- can a tuner's skills, style, etc. have on numbers? 1%? 2%? 0%?
In short, what is the overall range of +/- accuracy on output numbers? If a car dynos at 300whp, how much +/- could there be, speaking within reason of course?
2) What percentage +/- can a tuner's skills, style, etc. have on numbers? 1%? 2%? 0%?
In short, what is the overall range of +/- accuracy on output numbers? If a car dynos at 300whp, how much +/- could there be, speaking within reason of course?
Burning Brakes
Joined: Nov 2011
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From: Chandler, AZ
St. Jude Donor '12
I know there are lots more people on here with experience but here is what I know. The fans are used for temp control and airflow, mostly cooling while tuning on the dyno. I would say a basic tuner can do fine but someone who really knows what they are doing can get you 10 more HP on the same car. (just my guess)
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Melting Slicks
Joined: Nov 2011
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From: Jacksonville FL
Yes that was pretty much my understanding too. +/- 10 hp would seem to make sense.
Regarding the air flow of the fans though, would it not impact numbers if you did one pull with the fan blowing 50 mph and another pull with the fan blowing 10 mph?
Regarding the air flow of the fans though, would it not impact numbers if you did one pull with the fan blowing 50 mph and another pull with the fan blowing 10 mph?
Melting Slicks
Joined: Jul 2010
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
A dyno is a tool it is not magic. If you can get a baseline on your car before doing mods it will tell you how well the mod worked, and for that it is a great tool! Back to back pulls can very by as much as 1-5% on the same dyno, I have seen results very 20% or more from different dynos on different days etc. There is no national or international standard for dyno calibration! Again its just another tool in your toolbox!
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Melting Slicks
Joined: Nov 2011
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From: Jacksonville FL
A dyno is a tool it is not magic. If you can get a baseline on your car before doing mods it will tell you how well the mod worked, and for that it is a great tool! Back to back pulls can very by as much as 1-5% on the same dyno, I have seen results very 20% or more from different dynos on different days etc. There is no national or international standard for dyno calibration! Again its just another tool in your toolbox!
Seems to me that if there is that much variation then it is silly for us to even compare setups via dyno numbers.
I understand that the dyno "tool" is mainly of value for reference on the same dyno with the same tuner. My question I guess is more so how much variation there can be on the same dyno with the same tuner?
Melting Slicks
Joined: Jul 2010
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
Ambient temperature, air pressure, humidity, and engine temperature are just a few of the variables. Two of the most popular manufacturers of dynos usually very by 15%. My buddy owns a tuning shop and he can give your car 20% more horsepower on paper if you just want a piece of paper to impress your friends with. Unless you have pulls from the same dyno w/ the same tuner, corrected for atmospheric conditions any comparison between different pulls is basically meaningless! If you have a dyno sheet that shows you have 5% more horsepower then yours buddies car that was done on a different day, different dyno, different operator, then you don't really know who has more. When manufacturers such as Chevy or Ford rate their new models horsepower they use figures that are recognized by SAE and corrected for atmospheric conditions and they strive to be accurate. Your local tuner wants numbers that make him look good and keep his customers happy. None of what I am telling you is very well known, but it is all true!
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Melting Slicks
Joined: Nov 2011
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From: Jacksonville FL
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 2,789
Likes: 3
From: Jacksonville FL
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Thread Starter
Melting Slicks
Joined: Nov 2011
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From: Jacksonville FL
I think I asking how to correct for atmospheric conditions. That is kind of the same question as how much deviation there can be from pull to pull.
Melting Slicks
Joined: Jul 2010
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
To answer your question a meticulous operator on the same day allowing the car to cool to the exact same temperature can expect to get about 1-3% repeatibility on his machine. In other words a 300 HP car would repeat within 3 to 9 horsepower in a perfect world. A car will not repeat the exact same power each pull , plus you have the machine variances and weather is constantly changing. The dyno is still by far the best tool we have to measure changes but anyone who thinks the system is perfect is ill-informed and inexperienced !
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Melting Slicks
Joined: Nov 2011
Posts: 2,789
Likes: 3
From: Jacksonville FL
To answer your question a meticulous operator on the same day allowing the car to cool to the exact same temperature can expect to get about 1-3% repeatibility on his machine. In other words a 300 HP car would repeat within 3 to 9 horsepower in a perfect world. A car will not repeat the exact same power each pull , plus you have the machine variances and weather is constantly changing. The dyno is still by far the best tool we have to measure changes but anyone who thinks the system is perfect is ill-informed and inexperienced !
Since my last tune was on a hot and humid August Jacksonville day then i would not expect it was too far above the standard deviations.
1-3% sounds reasonable to me. So, our example of a 300hp car could be more accurately stated to be in the 291-309 range?
I am only interested in knowing accurate measurements, not about impressing anyone. My car's numbers aren't going to impress anyone here. Heck I could add a few hundred HP and I still wouldn't impress anyone here. There are tons of 700+ HP cars here...