Dyno Results In 3rd Or 4th Gear

[hrd-hr30]

3rd gear usually produces slightly less than 4th gear, say 2 to 3 kw. This is due to the more load on the engine in 4th and the slightly longer time to complete the run allowing the turbo to work a bit more.

We do a lot of NA holdens as well and with similar differences of 2 to 3 kw between gears.

Cheers,

Mike

its about the transfer (and loss) of torque through the gearbox. 4th 'gear' just directly connects the input and output shafts - basically no torque loss apart from internal friction from bearings and the constant mesh gears under no load. 3rd gear transfers the torque through 2 meshed helical gears to a lay-shaft then back to the output shaft by another set of meshed gears introducing side loads and higher meshing frictions of those gearsets under load, all of which means increased torque/drivetrain loss.

that's why you see the same results irrespective of wether they are turbo or NA.

[Thunderbolt]

Most operators put the intake temp sensor on the air filter. While I can understand where the fellow is coming from, but the pipe temperature that he is measuring can differ from the real intake temp. If everyone else is puting theirs on the air filter, then you have to ask who is the most correct?

[Sydneykid]

so you're saying the dyno operator made an error?

he had the inlet temp sensor where i've indicated in the photo...he was telling me how not many dyno operators do that, but how it gives the most accurate readout!

It’s an inlet AIR temperature sensor, not an inlet PIPE temperature sensor. By putting the sensor there he is measuring the temperature of the pipe itself, which is most certainly not the temperature of the air inside the pipe.

This is why MOST dyno operators place the inlet air temperature in the inlet air steam. The best place being at the air filter inlet. That way it is measuring the actual temperature of the air going into the inlet system. Shoot Out mode is designed to give equal power readings no matter what the ambient temperature of the day is (which also affects the inlet air temperature) and the intercooler efficiency.

Which is what happens in the “real world”, the power output of the car changes depending on the temperature of the inlet air and the ambient temperature.

Personally I am not a big fan of inlet air temp correction, if I have a good heat shield and ambient air feed, I won’t to know how effective it is (ie; how much more power I get). I don’t want the dyno correcting for poor shielding and air feed.

cheers

[dezz]

so, in conclusion, he made an error, and ripped me off

[stealth]

Hi stealth,

Was this a 4WD Dyno or a 2WD Dyno.?

We have the challenge of running a GTS4 AWD RB20DET car on a Dyno shortly this week, but I'd like to know of some differences between the two as well as the selected gear for the run. Car is an automatic.

Seems a grey area to me about the whole procedure.

Cheers

sorry for the late response - used up all my internet download space...slow as

- dyno at Bris Turbo is 2wd I think the APC is 4wd

- car is manual

- ecu is Power FC

- speed limiter has been disabled

- turbo is GT35/40R int waste gate, std manafold HPC coated