Tried to Dyno my car

[Itzkirb]

OK, so I tried to Dyno my Supercharged car today, but we had some problems. First off, has anyone with a Tiptronic dyno'd their car and if so how?

I brought it to the Dyno place, hooked it up and ran it. The results were terrible. It seems that with a Tiptronic there is a built in torque converter? Something was happening that did not allow my car to show it's full power. In fact the Dyno result came in lower than a stock C2 would have. I guess the car senses the front tires not moving and cuts some of the power for safety reasons?

I do not have PSM so that wasn't the issue. Does anyone know how to Dyno a Tip?

[jenner]

Every automatic car has a "built in torque converter." That said, plenty of automatic cars go on the dyno, so I doubt that is your problem.

I'm not familar with cars without PSM, but do you have a traction control switch that you can defeat? This is most likely what you need to do. Then the computer won't care bout the rears spinning more than the fronts and you can do your dyno.

It is something to do with the engine computer or traction control, not the automatic transmission.

[Loren]

Most engine mods are tested with the engine only type of dynos. Roller type dynos are not known to be very accurate and can cause damage to the car.

Here is an excerpt from a TT TSB on dynos:

If the vehicle is run on a two-wheel roller dynamometer, sufficient inner-cooling cannot be ensured. As a result, boost air temperatures reach excessive values. This will lead to loss of engine power and

damage to the engine due to overheating.

The considerable amount of heat generated may damage the transmission.

The significant amount of slip at the wheels caused by the high power output may lead to incorrect output measurements and damage the tires.

Note: Tire damage may not be immediately recognizable.

[CAFleming]

Most engine mods are tested with the engine only type of dynos. Roller type dynos are not known to be very accurate and can cause damage to the car.

From what limited knowledge I have, I would have to agree with Loren. Steve Dinan did an excellent "white paper" on dyno testing recently in which he gave a detailed analysis of why roller dynos are really pretty worthless, even for giving comparative results after mods. Unfortunately my link to this article doesn't work, but it convinced me that it's hard to have much faith in anything short of the very sophisticated (relative to roller dynos) methods that the manufacturers use--and even then, they've been shown to be wrong at times!

One of the major points that Dinan makes in his paper is that the fan used in most dyno test to simulate frontal air intake at speed, is totally inadequate, and can seriously affect intake charge and air fuel ratios, thereby skewing results. When manufacturers do dynos on an installed engine, they use a set-up that uses a huge wind-tunnel like fan to closely approximate frontal air charge. One must then carefully compare multiple runs under identical conditions to determine if any change in the engine set-up truly makes any difference, pro or con.

[jenner]

Isn't his question how to dyno his car not how accurate dynos are?

[ebaker]

Evidently Tips will not dyno correctly. At least on the 996TT, the torque convertor lock up clutch won't stay locked and it also forces upshifts before the power peak. The ECU seems to cut the engine power too. There are several threads on 6speed online about this. If the car is 4WD you MUST disconnect the front driveshaft or you'll destroy the front diff. Even a 4WD dyno with linked rollers will cause damage unless the driveshaft is disconnected.

[peterjoyce]

I have a non related question, can you dyno a 4wd car?

[jenner]

ebaker does what your wrote apply to the 4WD system in a Cayenne as well?

Peterhoyce you can dyno a 4WD car on a 4WD dyno. Audis, Subarus, Mits Evos ETC can all be dynoed on a 4WD dyno, so I don't understand why the 911 all wheel drive can't....