Dyno Wheels
09-09-2005, 05:37 PM
#12
Senior Member
Join Date: Jan 2002
Location: CT
Posts: 1,345
4th gear is usully the best gear to use for most cars, it applies enouf engine load to produce an accurate measurment of hp at the wheels, it also lets a bigger turbo spool up faster, it is also easier to dyno a higher gear on the dyno since the car is smoother to drive with hihger gear as some people have trouble transitioning the throttle. like i said it really depends on the car and the setup to choose the proper gear. if the gear ratio is too high as in if you dyno the car in 1st gear sometimes it will not show a proper hp.
09-09-2005, 11:12 PM
#15
Junior Member
Join Date: May 2005
Posts: 25
It's been around since dynojets have existed, that higher gear ratios and smaller wheels will yield lower dyno numbers. You haven't proved why you think that's wrong besides 'the car is smoother to drive in higher gear'.
10-20-2005, 02:22 AM
#18
Senior Member
Join Date: Jan 2002
Location: CT
Posts: 1,345
Originally Posted by fc3s4utnv' post='769970' date='Oct 17 2005, 02:00 AM
Ill provide the dyno if you wish to test your theory Kahren. We took a freinds six speed S2000, between 3rd, 4th, and 5th, the car had almost 40 hp between the three
many new cars, output diffrent amount of horsepower in diffrent gears, because they are tuned to run more conservative in the higher gears.
i have tested many cars between the gears and they showed no diffrence. these were cars equipped with standalones.
10-21-2005, 05:39 PM
#19
Junior Member
Join Date: Oct 2005
Posts: 5
I know I'm new here, but here's my 2 cents:
I'm in no way an expert, but I have had multiple cars on the dyno and have put alot of thought into wy every car I've dyno'd put out less torque, but more horsepower in 4th gear versus 3rd gear. And why it's given more torque but less horsepower in 3rd gear versus 4th gear. If you measured the actual (uncorrected) amount of torque and horsepower in first gear, you would get a huge torque number, and a small horsepower number. And if you measured the actual (uncorrected) amount of torque in fifth gear, you would get a small torque number and a large horsepower number. To understand this, you have to look at the equation: horsepower=torque*rpm/5252. When you're in first gear the wheels are obviously spinning alot slower than in fifth gear. But people want to hear a standardized number when talking about power, so the dyno tries to compensate for gear ratio, accounting for tire diameter, trans gear ratio and differential ratio. The reason the dyno shows different number between different gears is because it’s not perfect. It tries to do it’s best to compensate, but it’s not perfect. If you dyno in first gear, it will try to compensate for the gearing, but it will still transfer over a larger torque value and smaller horsepower value. And in fifth gear it will transfer over a larger horsepower value and smaller torque value. If someone with more technical expertise could comment on this it would be much appreciated. Those are just my ramblings.
I'm in no way an expert, but I have had multiple cars on the dyno and have put alot of thought into wy every car I've dyno'd put out less torque, but more horsepower in 4th gear versus 3rd gear. And why it's given more torque but less horsepower in 3rd gear versus 4th gear. If you measured the actual (uncorrected) amount of torque and horsepower in first gear, you would get a huge torque number, and a small horsepower number. And if you measured the actual (uncorrected) amount of torque in fifth gear, you would get a small torque number and a large horsepower number. To understand this, you have to look at the equation: horsepower=torque*rpm/5252. When you're in first gear the wheels are obviously spinning alot slower than in fifth gear. But people want to hear a standardized number when talking about power, so the dyno tries to compensate for gear ratio, accounting for tire diameter, trans gear ratio and differential ratio. The reason the dyno shows different number between different gears is because it’s not perfect. It tries to do it’s best to compensate, but it’s not perfect. If you dyno in first gear, it will try to compensate for the gearing, but it will still transfer over a larger torque value and smaller horsepower value. And in fifth gear it will transfer over a larger horsepower value and smaller torque value. If someone with more technical expertise could comment on this it would be much appreciated. Those are just my ramblings.
11-01-2005, 12:42 AM
#20
Senior Member
Join Date: Jan 2005
Location: Greenwood AR
Posts: 831
Your half way right.
A dyno is dumb, persay, it only knows what input into it. You will get "off" readings when you change up the tire(and or wheel) sizes from stock. Hp and tq is calculated fromt he rate at which the drum is spun and the rpms of the car. If you change the "gearing" up alot it wil not read right. And of course their is always the argument dynos are off, oh its off, it didnt like my car. NO you car just didnt have what you though it did. The only way a dyno can produce number that are "wrong" is to grind weight off of the roller. And plus I have probably dyno and participated in tunning of a couple hundred cars, with about 20 of them being in the last two weeks.
A dyno is dumb, persay, it only knows what input into it. You will get "off" readings when you change up the tire(and or wheel) sizes from stock. Hp and tq is calculated fromt he rate at which the drum is spun and the rpms of the car. If you change the "gearing" up alot it wil not read right. And of course their is always the argument dynos are off, oh its off, it didnt like my car. NO you car just didnt have what you though it did. The only way a dyno can produce number that are "wrong" is to grind weight off of the roller. And plus I have probably dyno and participated in tunning of a couple hundred cars, with about 20 of them being in the last two weeks.