kevo3030

I want to dyno my 2019 A4 Quattro but the shop said to research whether or not it can be put in dyno mode. I guess Audi AWD have specifics about them that aren't like S3, TTRS so they don't know if they can hook it up. Anybody know if your can dyno mode A4 Quattro?

SMac770

I don't know how to respond to this because I have no idea what they are asking. Do they not know how to put an AWD car on an AWD dyno and test it? Are these people some kind of Tesla fanboys? Because a google search for "dyno mode" is a bunch of Tesla bs that essentially puts the car into unsafe mode.

kevo3030

I thought their response was odd too. Like you are the shop who does dyno...how do you not know what cars you can and can't, and how to do it? Why do I need to research something to know if you can do your job? I just figured every car can be dyno'd...it's just 4 wheels turning on spindles?

SMac770

Copying 142's post here, so people finding this thread by its title will also find an answer:
https://www.audiworld.com/forums/a4-.../#post25730036

Appears to do the same thing as in the Tesla search hits, turn off traction control, etc.

Apparently, dyno mode on the VW clones disables the Haldex so only the front wheels are driven. That's different than real quattro cars using Torsen. But a B9 A model with quattro ultra; no idea if dyno mode on that disables the rear wheel engagement.

More on the subject, but seems mostly about Torsen cars: https://www.audizine.com/forum/showt...into-Dyno-Mode

142 guy

Vehicles that can shift power delivery between the axles may create an interesting problem in terms of the calculation of horsepower. As demonstrated by Audi's implementation of the Ultra system, power losses in the drive system are the lowest when you you are in front wheel drive only mode (assuming traction is not a limitation). If you want the true / maximum / whatever you want to call it horsepower measurement you probably get the best (highest) results if you are in pure front wheel drive.

I have never set my eyeballs on a 4 wheel drive vehicle being dyno tested, just 2 wheel drive vehicles. The 2 wheel torque measurement and horsepower calculation is straight forward (with the exception of the black magic correction factors that seem to get applied to the actual measurements). Measuring the output from a 4 wheel drive vehicle where the center differential is locked should also be relatively easy. Vehicles that can actively shift the torque back and forth between axles based upon speed differences could create interesting problems. For an AWD vehicle like an Audi would you allow the rear axle dyno to coast, driven by the rear axle in which case the vehicles traction control would determine the rear axle speed? I can see that as creating the potential to get speed differences and oscillations between the front and back axles during the test. Or do you actively drive the rear dyno so that it speed matches what the front is doing? Even with driving the rear rollers getting a perfect speed match between axles will be difficult leading to a messy torque measurement.

Conceptually it would be much simpler to treat it like a FWD vehicle.

kevo3030

Then I guess that goes to the original question this shop had for me if they are asking if it can be put in dyno mode, if dyno mode means that puts it in FWD and takes off AWD.

But then why are there dynos made for AWD vehicles? Why would they dyno them if they wouldn't create accurate results? That wouldn't make any sense. How does Audi come up with specs for HP and TQ if there isn't a way to pinpoint it because of AWD?

SMac770

Audi makes the engine, they're doing the tests with the engine on a stand, not in a car. That's why it's crank power vs wheel power.

And not all AWD cars can be made to operate in just 2WD, for example every Torsen based Audi (which is all of them except the VW clones until quattro "ultra" came along).

142 guy

As SMac770 stated, Audi and probably every other vehicle manufacturer does engine testing and torque measurements on a dyno stand, not a chassis dyno. Audi Engineering probably has rolling road / chassis [size=13px]dynamometer[/size] for testing vehicles, the purpose being probably to test and confirm tail pipe [size=13px]emissions. Initial brake system testing and other drivetrain testing would also be likely uses[/size]. There are some ancient SAE recommended practises on how to use a chassis dyno on really big vehicles for wheel torque measurements. That is a recommended practise, not a standard and there appear to be no RPs or standards for light vehicle chassis dyno testing to determine power output.

There are SAE, ISO and JIS standards for measuring engine torque on a test stand and these include standards for the correction factors for standard testing conditions (temp and barro). Chassis dynos appear to be the wild west. These days most chassis dynos are retail businesses and I expect that there are absolutely zero regulations requiring those retail dyno guys to comply with any standards or to have their equipment calibrated and tested to confirm that it is accurate. Just because a vendor says that they can dyno test an AWD vehicle doesn't mean they can give you an accurate power measurement. If you want truth in advertising, just ask the vendor for their NIST certificate or when was the last time that the dyno was calibrated.

In the US there is legislation called Title 40 Protection of Environment and it does have a subsection Part 1066 which sets out some very rigid requirements for chassis dynos including NIST traceability. But that is for [size=13px]emission[/size] testing and I expect none of the retail dyno dudes are doing emission testing. They can probably tell you whatever they want because nobody is checking. Dyno shopping is a really common phenomena. Don't like the results that you get from one dyno shop, head someplace else to get bigger numbers and bragging rights.

If there is some kind of 'dyno mode' that puts the Audi into FWD only, a 2WD dyno probably has a better chance of giving you an accurate number and it will be a larger number because it reduces the power losses in the drive train.