dynohead ?
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
dynohead ?
i have a question for you dynoheads. how accurate would the results be if a vehicle was driven in rain - lt/rain for 60 minutes. allowing one of the open element filters to be exposed to road spray and other vehicle mist for the complete hour, resulting in a filter that has absorbed water but does not appear to have passed any, maybe humid air but not lots of water, then dyno'd
the pull was performed during the conditions of:
High Temperature: 59° F (at 11am)
Low Temperature: 52° F (at 5am)
Average Temperature: 56° F
Time Temp(°F) Rel.Hum. Press. Weather
1pm 57 93% 29.70 rain
the dyno sheet reports:
Time Temp(°F) Humidty Press. SAE
1:36 67.33 50% 29.20 1.0
at an elevation of 508 ft.
with two fans directed toward the front of the car. one large exhaust fan and one carpet fan.
will the results be mostly accurate or would the difference between the actual (outside) conditions and the (indoor) conditions measured by the dyno result in an inaccurate report ? yes, the pull was done indoors with the bay door open and an exhaust fan behind the car running (for one of the pulls).
sorry, if this a basic question but this is my first run in with this dyno.
the pull was performed during the conditions of:
High Temperature: 59° F (at 11am)
Low Temperature: 52° F (at 5am)
Average Temperature: 56° F
Time Temp(°F) Rel.Hum. Press. Weather
1pm 57 93% 29.70 rain
the dyno sheet reports:
Time Temp(°F) Humidty Press. SAE
1:36 67.33 50% 29.20 1.0
at an elevation of 508 ft.
with two fans directed toward the front of the car. one large exhaust fan and one carpet fan.
will the results be mostly accurate or would the difference between the actual (outside) conditions and the (indoor) conditions measured by the dyno result in an inaccurate report ? yes, the pull was done indoors with the bay door open and an exhaust fan behind the car running (for one of the pulls).
sorry, if this a basic question but this is my first run in with this dyno.
Le Mans Master
Joined: Aug 2000
Posts: 5,529
Likes: 1,943
From: Austin Texas
Basically you are asking is the conversion from dyno-read TQ and HP to corrected TQ and HP is a reasonable representation of reality. Yes--It is a reasonable formula.
But I suspect you are really asking, If I go back and dyno my car again will I get different numbers? The answer here is yes!
If you go to a dyno with a full tank of gas, arrange for sufficient cooling to prevent overheating (lots more than generally used), and make 200 to 300 pulls on that dyno, you will get variations as big as 12HP (maybe even 20HP) even when the air, humidity, pressures,... are all the same! Some of this comes from the inherent accuracy of the dyno, and some of it comes from the engine computer trying to return the engine while it is in operation, some of it comes from tire traction variations with tire temperature, and some of it simply comes from the engine itself.
Will your engine give a number within 12-odd HP and TQ of its reading during the rain on a new day with more typical conditions (both corrected to STP)--there is about a 93%-95% chance that it will.
Will you ever know exactly what HP or TQ your engine produces--no, not to an accuracy of 2 HP or less; yes to an accuracy of 10HP or more.
But I suspect you are really asking, If I go back and dyno my car again will I get different numbers? The answer here is yes!
If you go to a dyno with a full tank of gas, arrange for sufficient cooling to prevent overheating (lots more than generally used), and make 200 to 300 pulls on that dyno, you will get variations as big as 12HP (maybe even 20HP) even when the air, humidity, pressures,... are all the same! Some of this comes from the inherent accuracy of the dyno, and some of it comes from the engine computer trying to return the engine while it is in operation, some of it comes from tire traction variations with tire temperature, and some of it simply comes from the engine itself.
Will your engine give a number within 12-odd HP and TQ of its reading during the rain on a new day with more typical conditions (both corrected to STP)--there is about a 93%-95% chance that it will.
Will you ever know exactly what HP or TQ your engine produces--no, not to an accuracy of 2 HP or less; yes to an accuracy of 10HP or more.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
more or less i'm asking is how much of an impact does a wet filter and rainy conditions have on a pull ? how would one confirm the correction factor ?
