why do evos dyno in 3rd gear and not 4th?
Aug 31, 2006, 06:43 PM
#31
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I don't really understand what the big deal is with dynoing in a different gear, especially if you input the gear ratio into the dyno. The dyno will correct itself if you input the gearing, so I think that it doesn't really matter whether you use the 3rd or 4th gear. maybe someone can explain this better. 
Aug 31, 2006, 07:19 PM
#32
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does anyone read?
chassis dynos do NOT read torque!@!!! they read POWER and RPM. with those two values it calculates torque. it does NOT matter what gear you are in, except for the few reasons you wouldn't dyno in first/second, you go through the revs so fast a wideband will not give you readings that you can tune with, and like jbrennen said, you go through the revs faster then the turbo can spool. for 4th 5th and 6th gear you have high driveline losses thus your results will be scewed and appear to be low. chassis dynos CAN read torque, but the results do NOT tell you anything useful... because tire size, gear ratios, the deflection of the tire due to the tiedowns and all that stuff will effect the gear ratios (and thus torque), which would then have to be entered into the dyno. thats why you don't do that.
if you have ever done a dyno run where the thing wouldn't pick up the tach signal, you will notice that they readout in ground speed and HP. you can simply convert the speed to RPM if you know what gear it was done in. with RPM, you can calculate the torque with the HP graph.
chassis dynos do NOT read torque!@!!! they read POWER and RPM. with those two values it calculates torque. it does NOT matter what gear you are in, except for the few reasons you wouldn't dyno in first/second, you go through the revs so fast a wideband will not give you readings that you can tune with, and like jbrennen said, you go through the revs faster then the turbo can spool. for 4th 5th and 6th gear you have high driveline losses thus your results will be scewed and appear to be low. chassis dynos CAN read torque, but the results do NOT tell you anything useful... because tire size, gear ratios, the deflection of the tire due to the tiedowns and all that stuff will effect the gear ratios (and thus torque), which would then have to be entered into the dyno. thats why you don't do that.
if you have ever done a dyno run where the thing wouldn't pick up the tach signal, you will notice that they readout in ground speed and HP. you can simply convert the speed to RPM if you know what gear it was done in. with RPM, you can calculate the torque with the HP graph.
Aug 31, 2006, 07:22 PM
#33
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Originally Posted by onefast4dr
I don't really understand what the big deal is with dynoing in a different gear, especially if you input the gear ratio into the dyno. The dyno will correct itself if you input the gearing, so I think that it doesn't really matter whether you use the 3rd or 4th gear. maybe someone can explain this better.
3rd gear typically has higher power loss inside the gearbox (because it's further from the 1:1 ratio which minimizes power loss).
In 4th gear, the car reaches max boost sooner in the RPM curve.
In 4th gear, frictional and inertial losses between the gearbox and the wheels are higher, because all of the driveshafts, axles, diffs, wheels, tires, brake rotors, etc., are all spinning faster.
Aug 31, 2006, 07:23 PM
#34
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Originally Posted by ApexVIII
because it is a direct drive. the would be no increase in torque due to gearing . its the amount of torque the motor makes
It has nothing to do with torque for the reasons mentioned in KevinD's post above.
-shiv
Aug 31, 2006, 08:45 PM
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Originally Posted by shiv@vishnu
The reason that some have recommended the 1:1 gear is so that there is minimal loss in the transmission. Unfortunately, using a tall 1:1 gear will result in excessively high wheel speed which will also result in unusually high losses (this time, frictional losses between the tires/rollers).
It has nothing to do with torque for the reasons mentioned in KevinD's post above.
-shiv
It has nothing to do with torque for the reasons mentioned in KevinD's post above.
-shiv
Sep 1, 2006, 10:28 AM
#38
Originally Posted by Borti
Not true.
STi's 5th gear tops out at 137 mph. The heatsoak from that would cause unreliable numbers.
STi's 5th gear tops out at 137 mph. The heatsoak from that would cause unreliable numbers.
EVOlutionary
Sep 1, 2006, 11:35 AM
#40
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Originally Posted by EVOlutionary
Not true. The heatsoak from that would approximate real world racing conditions. I'd hate to get the car tuned in 3rd gear, then go out road racing and blow the engine up because there is more load and heat put on it in 4th gear.
EVOlutionary
EVOlutionary
Then again the turbo itself does not actually recieve any of the airflow.
Sep 1, 2006, 04:35 PM
#43
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Originally Posted by boomn29
+1.
MR's and STi's are supposed to dyno in 5th.
MR's and STi's are supposed to dyno in 5th.
3rd gear is fine.
Sep 1, 2006, 04:49 PM
#44
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Originally Posted by KevinD
does anyone read?
chassis dynos do NOT read torque!@!!! they read POWER and RPM. with those two values it calculates torque. it does NOT matter what gear you are in, except for the few reasons you wouldn't dyno in first/second, you go through the revs so fast a wideband will not give you readings that you can tune with, and like jbrennen said, you go through the revs faster then the turbo can spool. for 4th 5th and 6th gear you have high driveline losses thus your results will be scewed and appear to be low. chassis dynos CAN read torque, but the results do NOT tell you anything useful... because tire size, gear ratios, the deflection of the tire due to the tiedowns and all that stuff will effect the gear ratios (and thus torque), which would then have to be entered into the dyno. thats why you don't do that.
if you have ever done a dyno run where the thing wouldn't pick up the tach signal, you will notice that they readout in ground speed and HP. you can simply convert the speed to RPM if you know what gear it was done in. with RPM, you can calculate the torque with the HP graph.
chassis dynos do NOT read torque!@!!! they read POWER and RPM. with those two values it calculates torque. it does NOT matter what gear you are in, except for the few reasons you wouldn't dyno in first/second, you go through the revs so fast a wideband will not give you readings that you can tune with, and like jbrennen said, you go through the revs faster then the turbo can spool. for 4th 5th and 6th gear you have high driveline losses thus your results will be scewed and appear to be low. chassis dynos CAN read torque, but the results do NOT tell you anything useful... because tire size, gear ratios, the deflection of the tire due to the tiedowns and all that stuff will effect the gear ratios (and thus torque), which would then have to be entered into the dyno. thats why you don't do that.
if you have ever done a dyno run where the thing wouldn't pick up the tach signal, you will notice that they readout in ground speed and HP. you can simply convert the speed to RPM if you know what gear it was done in. with RPM, you can calculate the torque with the HP graph.
Chassis dynos read TORQUE/RPM. Horsepower is a number calculated from TQ & RPM.
HP is the result of Torque x RPM / 5252
Not sure where you heard "Horsepower" or "Power" is measured...
