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Re: Dyno #s... (archive)
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Posted by Rob Anderson on March 21, 2001 at 23:57:35:

In Reply to: Dyno #s... posted by JamesM on March 21, 2001 at 11:02:12:

Trust me it will show up as more torque, because remember what torque is. And you also need to remember that you have a driveline loss. There will be an increase in HP and torque because remember hp is a function of torque and RPM. The lightened flywheel will increase rear axle torque because it reduces reciprocating mass in the driveline, which then in turn allows the motor to work more because it has less resistance. This all has to do with angular momentum and angular velocity. If you want a technical explination of how it all works in math terms let me know. Oh, and BTW, I was going to have my car dynoed at Steve D's dyno, but he could not get it to work properly so I was not able to do it. Maybe over the summer I might be able to meet up with him and dyno the car.


Rob
M535i SIG Chief Technical Advisor
www.m535i.org


I don't think a lighter drivetrain and flywheel will show up on a steady-state dyno. If you bring the engine up to speed, then load it with the dyno, you're only looking at its actual torque output. Chassis dynos and even most engine dynos measure steady-state torque output and calculate power from torque and RPM. They just do it in many steps.

Transient dynos will show a torque increase when used to test acceleration. F1 teams (all the well-funded ones, at least) use transient dynos to fine tune their engines. Static torque output is fine, but it won't show you how an engine will accelerate coming out of a turn. Transient dynos are much more effective when tuning fuel and ignition maps, too.

Steve D'Gerolamo is a distributor for some nifty dynos that hook to the drive wheel hubs (2 or 4 wheel drive). They have many different capabilities, including transient dyno operation. You can give the dyno a constant load, and have the engine accelerate against that load. Read the website. It's pretty cool, but really expensive. If I were to start a race team or pro shop, I'd use one of those puppies!

James
james_535@yahoo.com




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