Dyno X in what gear?
- Thread starter AngleT
- Start date
AngleT
Always more tuning to do
HP reading will be different, right?
I understand that if you're just tuning the engine for the most HP, it doesn't matter what gear you're in, more is more. But, when we start comparing "my X dyno'ed at __ HP" The standard for comparing would be 3rd gear, right? If I dyno'ed my car in 2nd gear, it would have a higher HP than if I dyno'ed it in 4th, wouldn't it?
Was watching the video of my car on the dyno and noticed that he only went to 3rd gear (94hp). I've seen other videos of different cars (not X's) being dyno'ed and they went into 4th. What's the "rule-of-thumb" for the X?
Gear ratios for an 83+ X1/9
First 4.090
Second 2.235
Third 1.469
Fourth 1.043
Fifth 0.863
FYI... This is before I went to the B3 cam, removed the compression ring from the head and added the MSD ignition controller. Should be more HP now.
I understand that if you're just tuning the engine for the most HP, it doesn't matter what gear you're in, more is more. But, when we start comparing "my X dyno'ed at __ HP" The standard for comparing would be 3rd gear, right? If I dyno'ed my car in 2nd gear, it would have a higher HP than if I dyno'ed it in 4th, wouldn't it?
Was watching the video of my car on the dyno and noticed that he only went to 3rd gear (94hp). I've seen other videos of different cars (not X's) being dyno'ed and they went into 4th. What's the "rule-of-thumb" for the X?
Gear ratios for an 83+ X1/9
First 4.090
Second 2.235
Third 1.469
Fourth 1.043
Fifth 0.863
FYI... This is before I went to the B3 cam, removed the compression ring from the head and added the MSD ignition controller. Should be more HP now.
Theoretically? No.
Power is torque times RPM, and that's the same at the flywheel no matter what gear you're in, as long as the the throttle is wide open so you're getting all the torque there is and the RPMs are the same.
At the wheels: In second gear the wheels are turning more slowly for a given engine speed but are delivering more torque. In fourth they're turning faster but delivering less torque. That's why you can spin the wheels more easily in lower gears; the increased torque breaks the wheels loose more easily (well, not on a stock X, but you get the idea
)
The decrease in torque and the increase in wheel speed exactly cancel out, and you end up with the same power, namely what's at the flywheel less the drivetrain losses.
Power is torque times RPM, and that's the same at the flywheel no matter what gear you're in, as long as the the throttle is wide open so you're getting all the torque there is and the RPMs are the same.
At the wheels: In second gear the wheels are turning more slowly for a given engine speed but are delivering more torque. In fourth they're turning faster but delivering less torque. That's why you can spin the wheels more easily in lower gears; the increased torque breaks the wheels loose more easily (well, not on a stock X, but you get the idea
)The decrease in torque and the increase in wheel speed exactly cancel out, and you end up with the same power, namely what's at the flywheel less the drivetrain losses.