Prius FAQ: Snow and Ice vs Traction Control - Page 3 - GreenHybrid

wwest · #21 (**permalink**) 04-10-2008, 08:42 AM

Quote:

Originally Posted by Tideland Prius

I seem to be the only person that had experiences with both TRAC setups on the same car.

Here's the background info in case you haven't been following me on PriusChat:

2005 Prius bought in Oct 04.

The first winter, I got stuck pulling out of the curb. We had a good 10-15cm of snow. I decided to test the Prius' TRAC since it's the first winter and snow events around here (esp. with 10+cm) are few and far between (they usually melt within days). As expected (at the time), the wheels spun and the TRAC cut all power. No amount of prodding on the acccelerator would produce any forward movement at all (can't imagine rolling on momentum if the power was cut while making a left turn).

Anyway.. that was my one and only time with the TRAC cutting all power. Next year (winter 05/06), there was that ECU update. My Prius tech fried my engine ECU so my poor car was at the dealership for a week and a bit.

I found out the TRAC changed its behaviour by accident actually. I was backing into the garage (we're on a slope) and I noticed this weird sound... it was like the engine was revving up and down. I thought it was weird but figured it was the TRAC doing its thing. Then I noticed the blinking Slip Indicator. Ok, so it was TRAC. I had regained grip by then so I ignored it. I knew it was a bit icy in the alley. So I continued to back up and then it happened again. It was then it strucked me. The tyres were spinning! I stopped the car then intentionally tried to get the wheels to spin and it did. The engine was just revving up and down as the power was fed in pulses by the TRAC in an attempt to regain traction.

I posted my findings online and we couldn't figure out why I had the old "cut all power" TRAC behaviour before and now it was exhibiting the "slip and grip" behaviour. I thought it might have something to do with the ECU update but a wife of a Prius tech said her DH wasn't aware of any changes done to the TRAC.

I hope you can delve deep into this issue and maybe find out how I managed to get it changed and help those that have the old TRAC setup, update to the new one.

You appear to be making an "apples and oranges" comparison.

Forward traction, pulling away for the curb, vs reverse traction, backing uphill into your garage.

Since your Prius had no reverse gear it uses only the "electrics" for reverse drive and therefore there is no need for frictional braking to restrain wheelspin/slip. I would also suspect that the level of torque the electrics can produce for reverse "motion" is artificially restricted, certainly so once wheelspin develops in reverse. In any case the electrics cannot easily produce the level of torque for reverse motion as can be had with both the ICE and electrics providing "forward" torque.

Reverse drive torque controlled via the electrics, no need for braking control, no "threat" to rotor warpage from overheating, no engine dethrottling required.

Apples...and Oranges.

msantos · #22 (**permalink**) 04-10-2008, 08:55 AM

Quote:

Originally Posted by David Beale

Msantos, I think your company had better brake down and get some tires! Before someone is killed!

David, lets pull back a little here.

I use Michelin X-Ice tires on all my cars. While I am sure the Nokians you mentioned are a very fine winter tire, the Michelins remain one of the best. I have my own experience over a good number of years to vouch for it and they hit FE as much as they stick even in weeks worth of -40C weather.

With that said, I want to re-emphasize that it did not happen to me nearly as often as it happens to the owners of earlier models in my area. Jayman (also a local) may totally hate his and he even swears by studded tires. Frankly, I don't think studded tires are needed when we use good winter rubber instead, at least on the 2007 models. But what I am also saying is that it still happens to a minor but yet undeniable degree. I am not crazy and neither are some who own post 2006 models.

Cheers;

MSantos

Tideland Prius · #23 (**permalink**) 04-10-2008, 03:29 PM

Quote:

Originally Posted by wwest

You appear to be making an "apples and oranges" comparison.

Forward traction, pulling away for the curb, vs reverse traction, backing uphill into your garage.

Since your Prius had no reverse gear it uses only the "electrics" for reverse drive and therefore there is no need for frictional braking to restrain wheelspin/slip. I would also suspect that the level of torque the electrics can produce for reverse "motion" is artificially restricted, certainly so once wheelspin develops in reverse. In any case the electrics cannot easily produce the level of torque for reverse motion as can be had with both the ICE and electrics providing "forward" torque.

Reverse drive torque controlled via the electrics, no need for braking control, no "threat" to rotor warpage from overheating, no engine dethrottling required.

Apples...and Oranges.

It has done the slip/grip going forward too, what's your point?

wwest · #24 (**permalink**) 04-10-2008, 09:16 PM

My point...??

I was responding to/with the information you gave us. If that information was wrong or incomplete...

But, under the circumstances you described in your post my point was well made.

Tideland Prius · #25 (**permalink**) 04-13-2008, 10:44 PM

Fair enough... and now I've completed it. It acts in an identical manner forward or in reverse.