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Need 85D volunteer in Sacramento area for a dyno test......
- Thread starter sorka
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LargeHamCollider
Battery cells != scalable
It's a good thing you are testing with Dynojet instead Mustang. None of the Mustang AWD dynos can measure an 85D (or any Tesla D model) correctly because they take input only on one side. However Dynojet AWD dyno uses 2 independent dynos, one for each side. There is this unfortunate P85D video on youtube where they used a Mustang. They ended up measuring 413HP which is less than P85 that was measured in other videos at 428 and 436 HP.
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That dynojet model *could* be used to measure hp of an AWD Tesla but only if it has the optional Linx system which physically links both drums together with a belt. You can't dyno an AWD Tesla and have each axle spin at different speeds because the traction control system will kill it. I called Dynojet and had a 14 minute discussion with an engineer there about the suitability of using the 424xlc2 and it would need the optional Linx system in order to use it on an AWD Tesla. Most 424xlc2 have this system because you can't dyno most modern AWD cars without throwing errors and triggering the traction control.
The Mustang MD-AWD-500 already synchronizes both drums with a belt. The front roller is not a dummy roller:
AWD DYNAMOMETERS | Mustang Dynamometer Home: Chassis Dynamometer and Engine Dyno Experts; Dyno and Dynamometer Manufacturer
"To achieve this, Mustang’s AWD-500 Series incorporates an internal drive system that synchronizes the front and back rollers to simulate a flat, dry road condition. Synchronization, or linkage, insures that the front and rear rollers are always spinning at precisely the same road speed. This process eliminates the possibility of activating a vehicle’s traction control system and also insures that a vehicle’s torque management system is operating under the assumption that the vehicle is not skidding, turning or slipping."
I spoke with an engineer at Mustang Dyno for 8 minutes on this subject and the suitability for using this model of dyno to measure an AWD Tesla. You can also use the AWD-500 to test a front wheel drive or rear wheel drive car as well and is the right way to do it if you don't want to pull fuses or disable traction control systems.
The *one* dyno of a P85D showing only 413hp seems very suspect. My own VBOX runs are showing closer to 500hp. The P85 run you quoted was on a Dynojet. It's pretty well known that Dynojets tend to report high and Mustang dynos tend to report low. However, the P85 you quoted was done on a Dynojet. Dynojets and Mustang dynos are well know to produce different results with Dynojets measuring high and Mustang Dynos measuring low. I've experienced this myself with a tuned 300zx Twin Turbo going from a Mustang Dyno to a Dynojet on the same and seeing a 10% difference between the two running the same boost.
That said, I plan to do this with both brands of dynos. The one 424xlc2 in Sacramento was at Wyotech, but they're now closed. There are 3 more in southern California, but I need to call the facilities that own them and make sure they're willing to do AWD Teslas before I call for a volunteer down there.
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The front rollers are dummy because all they do is spin on their own without any power from the front wheels. If you put a rear wheel drive car to that dyno, those dummy rollers would still spin. If nothing touched them, they would still spin as long as the rear roller spins. This image explains the Mustang belt system (click to enlarge). This is from a different Mustang AWD dyno, not the MD-AWD-500 but the belt system is the same. I picked this photo because you can see the belt clearer. Why does this belt exist? It is not there to take power input from the front and transfer to the rear. It operates the other way around. It takes power from the rear and turns the small front rollers. In the first video below you can see all 4 front rollers spinning even though 2 of them don't touch the wheels.
Watch the first video where they used Mustang MD-AWD-500 to test P85D. They achieved 413HP but even the P85 scores more than that as you can see in the other two videos.
413 HP P85D Tesla P85D Shocks the Dyno with 864 ft-lbs of torque to the wheels - YouTube
428 HP P85: https://www.youtube.com/watch?v=xVmdr5nUArQ
436 HP P85: https://www.youtube.com/watch?v=Gqlttrv7kds
These Mustang dynos with a belt are suitable for all other AWD cars (except Tesla D models) because they have a single engine. You can measure 100% power from rear wheels only. You don't need front rollers. But in AWD cars front wheels turn too. Therefore you need dummy rollers. So why do they put the belt then if dummy rollers would do? Because the moment the front wheels start spinning, they push against those dummy rollers until they catch up. This can damage the center differential. Therefore with this belt they pre spin the front rollers to further reduce resistance. The Mustang dyno will completely ignore power input from the front motor. You need to use Dynojet for an accurate test. You will get low scores with Mustang.
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The MW-AWD-500's front and rear rollers are linked together with a toothed belt so they act as a single unit as if it were the ground. The PAU doesn't care how much force is applied to each roller. It could be front wheel only, rear wheel only, or AWD.
If you were going to test a 4wd drive car, then you couldn't use this dyno. You'd have to use the Dynojet *without* the Linx system connected. 4wd drive cars lock their transfer cases and diffs to keep all 4 wheels synchronized, but slight differences in wheel/tire diameter would force them to be out of sync just slightly and you'd get massive skipping. This is why you can't drive a 4wd car in 4wd mode on dry pavement. In this case, you need two drums that are not linked each with their own PAU.
I asked the engineer I spoke to about this because I've seen this assertion made before. He said this was completely inaccurate. The drums are linked together like the ground is linked together. If what you said were true then the ground would also ignore the front wheels.
You have your scenarios when you can use a dual drum system not linked with their own PAUs vs a linked system with a single PAU backwards.
Also, if what you said were true, then an 85D will measure WAY less hp than the P85D on the same dyno. And I guess we'll just have to wait and see if that's true
I do plan to do this on both brands.
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Yes, I'm looking forward to Tesla results. My guess is Dynojet will score higher than Mustang. I'm not sure linkage is a good idea. With Tesla the wheels can be unsynchronized because it is just magnetic resistance in the motor. Therefore the problems that exist for other cars don't exist for Tesla. I think the person you spoke to at Dynojet maybe didn't understand that the car has two unlinked motors. I think without the linkage Dynojet would score even higher and would be even more accurate.
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Yes and that would be more accurate because you have two independent motors. Imagine a tandem bicycle with one strong and one weak cyclist on it. The strong cyclist pushes forward and is responsible for 100% power that turns the wheel. The week cyclist can not catch up and therefore all he does is turn the pedals. However imagine you separate rear wheels. You add one rear wheel for each cyclist and you add a gear to the weak cyclist. Now he is turning his own wheel and he has a gear to catch up to the rolling speed. His energy is not wasted. This is how the Tesla 85D works. The front and rear are not linked (maybe the engineer didn't understand that either). The front can apply power to the road because it is not linked.
If you link them you will ignore the front motor. The front motor is designed to be weaker than rear at high speeds. It can not catch up if you link them. But if you unlink them it will turn its own wheel and apply power to the road. When the rollers are unlinked, it replicates how the car works. If you link them, you are using the rear motor to turn the front wheels and the front motor is wasted.
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Yes and that would be more accurate because you have two independent motors. Imagine a tandem bicycle with one strong and one weak cyclist on it. The strong cyclist pushes forward and is responsible for 100% power that turns the wheel. The week cyclist can not catch up and therefore all he does is turn the pedals. However imagine you separate rear wheels. You add one rear wheel for each cyclist and you add a gear to the weak cyclist. Now he is turning his own wheel and he has a gear to catch up to the rolling speed. His energy is not wasted. This is how the Tesla 85D works. The front and rear are not linked (maybe the engineer didn't understand that either). The front can apply power to the road because it is not linked.
If you link them you will ignore the front motor. The front motor is designed to be weaker than rear at high speeds. It can not catch up if you link them. But if you unlink them it will turn its own wheel and apply power to the road. When the rollers are unlinked, it replicates how the car works. If you link them, you are using the rear motor to turn the front wheels and the front motor is wasted.
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Actually, even if the weaker cyclist adds any force, they will go faster than if that cyclist doesn't add force. Now if the front cyclist isn't willing to pedal as *fast* as the rear cyclist, then the front cyclist wouldn't be applying any force. If what you are saying is true, then the front wheels of the D would have to not be applying any force because the rear wheels are trying to turn faster than the front wheels are willing to. If what you said were true, then the ground would ignore the front wheels as well which we're pretty sure that isn't happening. Linking the two drums together is like driving on the ground. Riddle me this. If instead of two drums physically linked as one with a tooth belt we had a conveyer belt instead, do you think the front of the conveyor would ignore the front wheels??????
As far as the two brands measuring differently? Well that *is* likely because Mustang Dynos have a reputation for measuring lower than Dynojet dynos by about 10%.
As far as the two brands measuring differently? Well that *is* likely because Mustang Dynos have a reputation for measuring lower than Dynojet dynos by about 10%.
sorka, can you put a camera to record the dashboard during the test? It would be interesting to have that data. My guess:
Mustang: Will measure only rear motor
Dynojet linked: Will measure rear motor + 50% of front motor
Dynojet unlinked: Will measure rear motor and of front motor
Because the front and rear wheels in the car are not linked, the skipping you described can't happen with the Tesla. Therefore you can do the test unlinkage. It would be more accurate. If you don't do it, I hope somebody else will measure with unlinked Dynojet so we can see that indeed it shows more power.
Mustang: Will measure only rear motor
Dynojet linked: Will measure rear motor + 50% of front motor
Dynojet unlinked: Will measure rear motor and of front motor
Because the front and rear wheels in the car are not linked, the skipping you described can't happen with the Tesla. Therefore you can do the test unlinkage. It would be more accurate. If you don't do it, I hope somebody else will measure with unlinked Dynojet so we can see that indeed it shows more power.
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