2005 Prius on my chassis Dyno!!

About a year ago I had the idea to use the facilities at my work where I usually tune high horsepower cars to see how much power the Prius would put out. I posted the results but when the PC server crashed a while back all of that data was lost.

Well I just found it and I know that there were a lot of people that were interested in looking at the data.

I have attached the actual dyno sheet that will show the HP, Torque and Air Fuel ratio. I remember that I had one hell of a time to be able to dyno this car!! I had to physically disconnect the VSS connectors on the rear wheels so that I would be able to let the front wheels turn the dyno rollers.

Remember this is the power that the car is making to the ground. Generally speaking an automatic transmission will show a 20 percent reduction in power however I have no idea what efficiency what a CVT would be. We normally would multiply the amount of power/torque by 20 percent for auto and 15 percent for manual transmissions for crank hp/torque figures.

At any rate here is the graph!!

 

No problem Pinto... Imagine if we could get into the PCM and richen up the A/F ratio!! Take a look and see how lean the car runs accross its entire RPM range.

I just finished tuning a 07 Z-06 tonight and the A/F ratio was 10.5-11.0:1 STOCK!!!





<div class='quotetop'>QUOTE(Pinto Girl @ Oct 20 2006, 08:38 PM) [snapback]335932[/snapback]</div>

 

Hello Hobbit... When I had the Prius on the dyno it was very interesting in that the car would INSTANTLY rev to 3k and this is the reason why there was no data on anything below this RPM.

The A/F ratio was meaaured on a calibrated Bosch wideband 02 and was VERY consitent 15:1 with a small spike around 4700 RPM. What was also interesting is that even though the HV battery level would drop the amout in affected the HP/Torque was not a huge amount. I did not however run the car with the very last 2 bars remaining so it would have been interesting to see what she would do on motor alone.

At any rate it was pretty fun to put the Prius up there!! Especially when I had 4 other C5's to work on and they were all in a row waiting for the Prius to get off their dyno!!




<div class='quotetop'>QUOTE(hobbit @ Oct 21 2006, 11:02 AM) [snapback]336078[/snapback]</div>

 

I did about 10 different runs and all of them varied by a small percentage. This was probably due to the state of charge of the HV battery, temperature of the engine, varying inlet air temperature and minor variations in the dyno itself.




<div class='quotetop'>QUOTE(Tideland Prius @ Oct 21 2006, 03:57 PM) [snapback]336154[/snapback]</div>

 

When I go back to the shop on Monday I will pull up all of the runs that I did that day and graph them all together. This way we could see the varying numbers due to the HV battery fluctuations.





<div class='quotetop'>QUOTE(Tideland Prius @ Oct 21 2006, 04:37 PM) [snapback]336163[/snapback]</div>

 

When I first strapped the Prius down on the dyno I knew that there would be a few "issues" to overcome. Since the front wheels were turning the drums and the rears were stationary the computer saw this as a slipping condition and the red triangle came up on the dash along with a reduction in power.

I tried everything that I knew to disable it. Since there is no manual over-ride mode I pulled all of the fuses that control the VSC but the damn thing still caused an error. I then thought that the only way the car knows that the rears are not moving is due to the speed sensors on each axle. I simply unplugged each sensor on the rears and we were IN BUSINESS!!

The only problem this caused afterwards is that the red triangle stayed on the dash until aproximately 50 miles of driving or so. I suppose that the computer has to see X amount of miles or time where there is no VSS error for it to extinguish the light from the dash.

At any rate it was a fun and informative day on the dyno!!


<div class='quotetop'>QUOTE(David Beale @ Oct 21 2006, 06:12 PM) [snapback]336192[/snapback]</div>

 

Let me try to answer your questions. Yes, the electric motor does produce the rated (295) ft/lbs of toque from 0-1200 RPM's. The problem is that when you go WOT (Wide Open throttle) the RPM's instantly jump to 3k RPM's so this is why you do not see any data below this engine speed. The rated torque of the electric motor is not lost but is only present at the low engine speeds not depicted in this graph.

All vehicles with a transmission (manual, automatic and now CVT) suffer from parisitic losses in the drivetrain caused by gears, viscosity of fluid, weight of rotational masses..etc..etc.. We generally subscribe to the fact that we lose aprox 12-15 percent of a given engines power with a manual transmission and 20 percent with an automatic. I have no idea where the CVT would fair and the only real way to know would be to take the engine out of the car and connect it to an engine dyno. Then one can compare the figures to what we are getting on the chassis dyno.

Regarding the power output when the HV battery is in different states of charge, yes it does impact the amount of power it generates. Like I mentioned before when I go back to the shop on Monday I will overlay all of the dyno runs on one sheet and upload it here. This way you can see the hp/tq over 4-5 runs and at the varying levels of the HV battery.



<div class='quotetop'>QUOTE(ekpolk @ Oct 21 2006, 08:24 PM) [snapback]336227[/snapback]</div>