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.

 

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.

 

Several differences...

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.

 

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

 

there needs to be a standard, a basis of comparison. 1:1 is as good as any, decent load on the engine, without excessive wheel speed and parasitic drag. What would you recommend if not 1:1?

 

With the IXs, the first 4 in the 5sp are the same as the first 4 in the 6sp.

 

Should I be retuned using 3rd gear instead of 4th then?

 

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

 

Nope.

 

I am not so sure that a dyno simulates the amount of airflow you would recieve on the street. It seems there would be less heatsoak because of the extra cooling.

Then again the turbo itself does not actually recieve any of the airflow.

 

I have also wondered why my car was dynoed in 3rd. Now i have some reasons! Thankx guys.

 

Cool because my ish mobs...!!!

 

That's crazy. So by the time you reach full spool you'll have a car that's basically going well over 130 gyrating on a dyno and giving you screwy readings as opposed to a car doing about 80-85 more firmly planted.

3rd gear is fine.

 

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...

 

Try this link KevinD
http://madscientistmatt.blogspot.com...eter-does.html