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You CAN tow with a Prius

Discussion in 'Gen 2 Prius Main Forum' started by Cory151, Feb 11, 2013.

  1. Cory151

    Cory151 Member

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    I normally bed haul 2-3 dirtbikes (260lbs a each) with a 2010 Supertduty F-250 Turbo diesel. No big deal as it get 16.2 mpg no matter whats in the truck, but it also dynos at 513 hp with nothing more than an H&S tuner and a DPF delete, so I can't hate on a truck that is not being used for hauling the thousands of pounds it was designed for.

    My roommates and I go riding about twice per week all over SoCal. We couldn't help but wonder if we'd be money ahead buy getting a trailer and using either his 3rd Gen or my 2nd Gen Prius to get us to riding locations.

    After doing some research on here and hearing everyone saying "you'd be crazy to try" or "the motor generators would burn out" and finally "the Prius wouldn't be able to slow the load" etc, we decided to find out for ourselves. We proceeded to find a well used Craigslist trailer for $175 redo some suspect welds, slap on some new tires and a fresh coat of Bedliner in a can and give it the old college try.

    In the last six months we have logged thousands of miles on both cars, going from San Diego to Lake Elsinore Motocross, Pine Valley OHV trail, Corral Canyon OHV trail, Pala Raceway etc. Standard load out is 2-3 bikes (260 lbs. each), three rail brakeless trailer (365 lbs.) Safety gear and tools/water/10 gallon jerry can of fuel for 2-3 riders 100 lbs, and finally 2-3 adults (average weight 180 lbs).

    Now it was no surprise to me that both cars managed this task with ease and without incident, what did amaze me though is that most of the trips the cars got between 39-45 mpg (hand calculated) as long as we set the cruise control to 55 (state law in California with trailers). In fact I still have a hard time figuring out how a car with such a small engine is able to pull an additional 1,000-1,500 lbs and get nearly the same MPGs as normally driving with no load at 70 mph?? The Prius was very stable at all times and it seemed as if the main batt would charge up faster upon stopping. Though this may be a perceived effect and was not measured in any way. Here is a pic on the way to lake Elsinore MX. Pleas ignore my roommates excited stance for this photo.

    IMG_4270.JPG
     

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  2. Cory151

    Cory151 Member

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    Oh and I forgot to mention the looks we get while towing are are priceless....
     
  3. PriusCamper

    PriusCamper Senior Member

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    Thanks for expanding our notion of what these cars are capable of! And it makes sense that regen braking is going to charge the battery faster, that's alot more rolling weight to slow. Most of all please follow up with a post if you ever have to do any major evasive maneuvers or hard braking... It'll be good to get details on how the Prius handles when it's pushed so far beyond its recommended load limits!
     
  4. xPETEx

    xPETEx Junior Member

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    Thanks for posting this, we're planning to tow small things with ours. This is very reassuring.
     
  5. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    I have hauled lots in the Prius and it does fine. A few hundred pounds of wood, 600+ pounds of slate tile, and this weekend 25qty of 55lb concrete bags ~1400pounds and 20 bags of pea gravel at about 40lbs a piece 800lbs for a total of 2200lbs in the hatch. The rear suspension was NOT happy but I still had clearance between the wheel and wheel wells on my 15in tires.

    I have not tried towing with a trailer but the same principles apply. The instant torque available from MG2 and the ICE together is pretty incredible.

    This is for a GenIII after the gearing at the output of the ring gear:

    [​IMG]

    So you get about 460ft-lbs of torque to the ground with the Prius compared to 600-ish with the big-a$$ truck? And with the Prius you get regen braking and friction braking. It is a truly remarkable vehicle.

    I would suggest if you are towing often, then you should monitor the MG temperatures on a scangauge or android app. On a long incline the inverter temp and MG temps will increase. It will auto-correct by power reduction if it gets too hot, but it is nice to have a warning if you need it.

    There is another member who has towed his airplane with the Prius...
     
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  6. Cory151

    Cory151 Member

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    Thanks for the input, we have to pull a pretty large grade going from sea level to 6,000 feet every time we go east and no issues up or down it thus far. Unfortunately our household is without any android based product so we will not be able to monitor MG temps. We've already agreed if a problem would arise wed simply take it to Toyota (hitch less) and have it warrantied. I have however changed the trans axle oil and it always looks the same towing or not.

    Why does that torque graph drop off after 25 mph, wouldn't torque in relation to RPM be a better example of engine capability? Just wondering because it feels as though torque drops off considerably at freeway speeds (must factor wind). As far as big trucks go, there is an unofficial diesel war taking place between the big three. Ford and Dodge (Cummins) do not currently manufacture a diesel pickup that makes less than 800 ft lbs, the simple application of a tuner allows them to easily surpass the 1,000 ft/lbs (and that torque is available at virtually any speed).

    I hope this helped ease the minds of people concerned about towing small loads with a Prius, heck..had I known what I know now, I might have never bought that truck to begin with. Either way if anything changes on these daily drivers/ tow pigs I will update this thread accordingly.
     
  7. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    You can't really make a graph based on RPM, because you have 3 RPMS, MG1, MG2, and the ICE.

    The few times you need to tow 1000ft/lbs at high speeds, a rental is way more cost effective.
     
  8. sorka

    sorka Active Member

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    There are no android apps that can monitor the mg2 temps through an elm327 as that is not part of OBDII. You'll need a ScanGuage for that which is the most economical consumer device for that purpose.


    Depending on the grade, you may need to use the engine brake "B" mode in order to reduce the load you put on the MG1 through the PSD.

    The MG2 won't care.
     
  9. ewxlt66

    ewxlt66 Active Member

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    What hitch are you guys using?
     
  10. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    My hardware monitors everything available on the CAN network including the Prius specific codes and is readable from any bluetooth device. Or via USB in a PC, or generally I just have the OLED screen showing battery pack voltage and then current in/out to maximize regeneration.
     
  11. stevemcelroy

    stevemcelroy Active Member

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    I tow my 17' sailboat and have not had issues. Just like with towing in any vehicle you need to be alert and watch traffic so you can take it slow and easy. I was totally amazed - the one long highway trip that I took with it (about 200 miles) I was able to get mileage in the mid 30's.
     
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  12. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

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    What about adding an extra cooler? Maybe a GenI inverter radiator plumbed into the system?
     
  13. maestro8

    maestro8 Nouveau Member

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    What's all the hub-bub about? Camping in the Prius | Page 3 | PriusChat

    My trailer's about 750# and braking distances are probably 3-4x what they are unloaded. There's no other way to put it... the Prius's brakes are crap.

    I'd hate to think about trying to brake with double the weight.
     
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  14. edthefox5

    edthefox5 Senior Member

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    460 lbs of torque to the ground? Thats big block Chevy territory. Truly a magical car lol....
     
  15. edthefox5

    edthefox5 Senior Member

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    Like Maestro says the scary part of towing is the brakes suck and it takes 3x longer to stop.
    And get an android and monitor mg temps as thats how the trans is going to fail. Your going to overheat the windings of the mg's.

    Easy way to tell right now how bad your stressing the trans and the trans cooling system is go to Home D and buy an IR Thermometer and take measurements of the Inverter and the reservoir and the trans body itself. Would love to see those numbers. Take it at the top of that 6000 foot hill.

    But its a pretty tough little car. Right up to the point it throws a CEL.
     
  16. Kyle401

    Kyle401 New Member

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    While I think that my Prius is a very good vehicle and don't doubt that you can use it for light towing, this statement isn't accurate. You are comparing torque after multiplication through the PSD to engine torque for the "big-a$$ truck."

    A more accurate comparison would be output torque from the truck's transmission. Most small block gas V8's would be around 1500 ft lbs while diesels would be around 3000 ft lbs depending on gearing and engine torque. If you account for final drive (differential) ratios the disparity between the Prius and the trucks gets even greater.
     
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  17. PriusCamper

    PriusCamper Senior Member

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    It's a good point that torque is a function of drivetrain just as much, if not more, than a function of the motor(s). I used to be a treeplanter and we'd drive around in forestry trucks that were designed for the most impossible terrain. Those things have the craziest low low granny gears ever. You could redline the engine and the wheels would barely be spinning. Now that's torque! Ain't no way a Prius could ever come close to that!
     
  18. xs650

    xs650 Senior Member

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    Something doesn't compute. That chart looks like MG2 torque at the ring gear at 106 mph is the same at ICE torque at the ring gear at that speed. If that's the claim, then the HP is also the same. The ICE HP is 98 hp and MG2 as installed and controlled MG net output in the Prius is about 40 HP.

    The chart also shows MG2 with 8 times the torque as the ICE at 0 mph. If that were true it would be difficult to tell MG2 only acceleration from ICE plus MG2 acceleration.

    The chart is a great idea, but need some refinement. It probably assumes that MG2 actually puts out its full rated torque under real world conditions.

    I know I'm over simplifying things, but the chart still doesn't look right. Would you run through the numbers for a couple of speeds?

    I'm off to Central America for close to 3 weeks, will report any Prius sightings.
     
  19. roflwaffle

    roflwaffle Member

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    Fool around with this and you'll see why.
    http://ecomodder.com/forum/tool-aero-rolling-resistance.php
    Any increase in energy required by a higher drag coefficient and more weight from the trailer is made up for by the lower speed.
     
  20. James BlueWolf

    James BlueWolf New Member

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    Did you just have a stock Prius tow package put on?