Dyno in 3rd?
- Thread starter 5uprahboy
- Start date
unplug ECT and manual shift to 3rd IIRR.........
If i'm wrong someone will correct me.
Or look up the gear table and look for 1:1
If i'm wrong someone will correct me.
Or look up the gear table and look for 1:1
Well I had previously dyno'd at 320rwhp in 4th with a 4.5:1 diff. Suprafest dyno guys put it in 3rd with my 3.9:1 diff and I only got 230rwhp. Drag racing the next day proved the car was not having issues, and the only thing I changed (other than getting some joiners removed and the joins welded up) was me washing and cleaning the car. I know it was in 3rd as I was crossing the line at 170kmph right a the end of 3rd gear, not the speed of the 2nd graph....
Here's the original dyno:
http://www.supras.co.nz/pics/ecu/finished/dyno.jpg
And here's the Suprafest dyno in 3rd:
http://www.supras.co.nz/pics/ecu/finished/SFdyno.jpg
Here's the original dyno:
http://www.supras.co.nz/pics/ecu/finished/dyno.jpg
And here's the Suprafest dyno in 3rd:
http://www.supras.co.nz/pics/ecu/finished/SFdyno.jpg
Technically speaking the power you make doesn't change based on gearing, only the final torque output, but since most Supras that dyno are turbocharged, higher load will result in more boost.
Power is calculated based on engine speed and torque, engine torque is calculated based on the torque applied to the dyno divided by the speed difference between the dyno and the engine.
Jeff
Power is calculated based on engine speed and torque, engine torque is calculated based on the torque applied to the dyno divided by the speed difference between the dyno and the engine.
Jeff
Zumtizzle;1051311 said:
Depends on the dyno and operator. No need to unplug ECT if they can load the tranny enough not to downshift. If its a good dyno and operator just putting it in drive and waiting for the shifts will be all you need to get a solid run out of it in 3rd.
had runs on two dyno's with different operators. 3rd gear auto did 326 vs 2nd gear run of 300.
Jeff Lange;1052339 said:
But look at the power curve. It just goes up and up and up and up until, no more revs. If only there was a way to make it last longer, like, oh I dunno, if they did it in 4th?
Also, you say power is based on engine speed and torque. Torque applied to the dyno will be different in 3rd. And if my tacho wasn't reading accurate, they wont have a solid base for the engine speed and therefore the other readings will be wrong?
Torque curve should be the same no matter what gear you're in. Torque applied to the dyno will be higher, but speed will be lower, hence making power the same. I doubt they go off of your tach to get an engine speed, they should be reading it directly from the engine.
My previous post didn't explain things all that well. Basically a dyno measures torque applied to it, this multiplied by the speed gives you power. Power doesn't change due to gearing, only torque and speed.
Let's say your engine puts out 400ft-lbs of torque at 5000rpm. (We'll forget about load, turbos and drivetrain loss for a second).
In 3rd gear, (1.31:1) with a 3.91:1 rear end, that results in 2048.84ft-lbs to the wheels, with the wheels spinning at 976.16rpm.
In 4th gear, (1.00:1) with a 3.91:1 rear end, that results in 1564.00ft-lbs to the wheels, with the wheels spinning at 1278.77rpm.
HP = (Torque X Speed) / 5252
So, at the engine:
HP = (400ft-lbs x 5000rpm) / 5252
HP = 380.81hp
In 3rd gear, at the wheels:
HP = (2048.84ft-lbs x 976.16rpm) / 5252
HP = 380.81hp
In 4th gear, at the wheels:
HP = (1564.00ft-lbs x 1278.77rpm) / 5252
HP = 380.81hp
Those figures apply only to the vehicle's rear axle. There is also a gear ratio between the size of the tires and the size of the dyno's roller, but like I said, ratios do not matter when calculating power. Power is calculated based on the speed and torque of the dyno's roller. Knowing the engine speed at that same time allows you to calculate the engine's torque. Note how none of those calculations require you to know any gearing information or tire size information for the vehicle.
Now, adding in a turbo and the fact that it will build more boost and faster based on load, as well as many other factors, make gearing a bit more of an issue, but you should still get a pretty close result in either 3rd or 4th. 5th might be a good idea as well, but may result in some bogging of the engine, but again that depends on the engine and the rear end gearing and tire size.
Transmission being geared to 1.0:1 is only a small part of the puzzle.
Jeff
My previous post didn't explain things all that well. Basically a dyno measures torque applied to it, this multiplied by the speed gives you power. Power doesn't change due to gearing, only torque and speed.
Let's say your engine puts out 400ft-lbs of torque at 5000rpm. (We'll forget about load, turbos and drivetrain loss for a second).
In 3rd gear, (1.31:1) with a 3.91:1 rear end, that results in 2048.84ft-lbs to the wheels, with the wheels spinning at 976.16rpm.
In 4th gear, (1.00:1) with a 3.91:1 rear end, that results in 1564.00ft-lbs to the wheels, with the wheels spinning at 1278.77rpm.
HP = (Torque X Speed) / 5252
So, at the engine:
HP = (400ft-lbs x 5000rpm) / 5252
HP = 380.81hp
In 3rd gear, at the wheels:
HP = (2048.84ft-lbs x 976.16rpm) / 5252
HP = 380.81hp
In 4th gear, at the wheels:
HP = (1564.00ft-lbs x 1278.77rpm) / 5252
HP = 380.81hp
Those figures apply only to the vehicle's rear axle. There is also a gear ratio between the size of the tires and the size of the dyno's roller, but like I said, ratios do not matter when calculating power. Power is calculated based on the speed and torque of the dyno's roller. Knowing the engine speed at that same time allows you to calculate the engine's torque. Note how none of those calculations require you to know any gearing information or tire size information for the vehicle.
Now, adding in a turbo and the fact that it will build more boost and faster based on load, as well as many other factors, make gearing a bit more of an issue, but you should still get a pretty close result in either 3rd or 4th. 5th might be a good idea as well, but may result in some bogging of the engine, but again that depends on the engine and the rear end gearing and tire size.
Transmission being geared to 1.0:1 is only a small part of the puzzle.
Jeff
Jeff Lange;1052415 said:Torque curve should be the same no matter what gear you're in. Torque applied to the dyno will be higher, but speed will be lower, hence making power the same. I doubt they go off of your tach to get an engine speed, they should be reading it directly from the engine.
My previous post didn't explain things all that well. Basically a dyno measures torque applied to it, this multiplied by the speed gives you power. Power doesn't change due to gearing, only torque and speed.
Let's say your engine puts out 400ft-lbs of torque at 5000rpm. (We'll forget about load, turbos and drivetrain loss for a second).
In 3rd gear, (1.31:1) with a 3.91:1 rear end, that results in 2048.84ft-lbs to the wheels, with the wheels spinning at 976.16rpm.
In 4th gear, (1.00:1) with a 3.91:1 rear end, that results in 1564.00ft-lbs to the wheels, with the wheels spinning at 1278.77rpm.
HP = (Torque X Speed) / 5252
So, at the engine:
HP = (400ft-lbs x 5000rpm) / 5252
HP = 380.81hp
In 3rd gear, at the wheels:
HP = (2048.84ft-lbs x 976.16rpm) / 5252
HP = 380.81hp
In 4th gear, at the wheels:
HP = (1564.00ft-lbs x 1278.77rpm) / 5252
HP = 380.81hp
Those figures apply only to the vehicle's rear axle. There is also a gear ratio between the size of the tires and the size of the dyno's roller, but like I said, ratios do not matter when calculating power. Power is calculated based on the speed and torque of the dyno's roller. Knowing the engine speed at that same time allows you to calculate the engine's torque. Note how none of those calculations require you to know any gearing information or tire size information for the vehicle.
Now, adding in a turbo and the fact that it will build more boost and faster based on load, as well as many other factors, make gearing a bit more of an issue, but you should still get a pretty close result in either 3rd or 4th. 5th might be a good idea as well, but may result in some bogging of the engine, but again that depends on the engine and the rear end gearing and tire size.
Transmission being geared to 1.0:1 is only a small part of the puzzle.
Jeff
Thanks for your very decent reply! They didn't open the bonnet - the only way the would've got my engine revs is off my tacho, which isn't accurate.
I'm reading over your post again and again - making sure I've got everything right.
I love these sorts of posts
Then the dyno probably just read "Road Speed" instead of engine RPM. Do you have the graph to post?
Jeff
Jeff