Coasting and tranny ???

MR.K · 04-07-2008, 02:52 AM

When you shift back into Drive after coasting around 45-50 mph.....the motor ,if running, would be at an idle ..if not running ,stopped ....dose it jar the tranny or cause clutch wear ,Yea it's an automatic but it still has to have some type of clutch ? Has anyone did damage this way? ...Should you rev the motor a bit when shifting into D to keep the jarring down .....? I'd like to try this coasting thing ...just don't want to short"n the life of anything.....thanks.

**efusco** · 04-07-2008, 03:07 AM

Nope, no clutch. no risk of damage. All that happens from neutral is a change in the power flow.

Bill Merchant · 04-07-2008, 03:15 AM

The Prius has a Power Split Device, not a transmission like other cars. Although Toyota calls it an ECVT (Electronic Continuously Variable Transmission), it's a planetary gear set with MG1 driving the sun gear, MG2 driving the ring gear (coupled to the wheels), and the ICE driving the planetary carrier. The Prius is always in gear, even in N.

patsparks · 04-07-2008, 06:47 AM

I'd be more concerned about over spinning MG1.
If you accelerate from under 42mph to over 50 there is a posibility you will over spin MG1 ans damage it. This might happen going down hill.
Then again the ICE may fire up to protect MG1 while in neutral, I haven't a clue.

**efusco** · 04-07-2008, 07:33 AM

Quote:

Originally Posted by patsparks

I'd be more concerned about over spinning MG1.
If you accelerate from under 42mph to over 50 there is a posibility you will over spin MG1 ans damage it. This might happen going down hill.
Then again the ICE may fire up to protect MG1 while in neutral, I haven't a clue.

If you're in a ICE-off glide (under 41mph) and then go into a downhill acceleration you're safe from overspinning MG1 until you exceed 62mph....I do it every day on my commute.

Danny Hamilton · 04-07-2008, 11:49 AM

Quote:

Originally Posted by MR.K

....dose it jar the tranny or cause clutch wear. . . .

No, it does not.

Quote:

Originally Posted by MR.K

Yea it's an automatic but it still has to have some type of clutch ?

Nope, If the Internal Combustion Engine (ICE) is idling while you are coasting in Neutral, then one of the the electric motor/generator (MG1) spins up to take the load off the engine. When you shift back into Drive, MG1 slows down as the ICE speeds up to create a nice gentle smooth transition.

Quote:

Originally Posted by MR.K

. . . .Has anyone did damage this way?. . . .

Not the type of damage you are asking about (shock to the drivetrain). There is some concern about MG1 spinning too fast if you switch into Neutral when the ICE is off and then coast downhill to exceed 62 mph. On the other hand, I'm not familiar with any reports of that damage yet either.

Quote:

Originally Posted by MR.K

Should you rev the motor a bit when shifting into D to keep the jarring down .....?

First of all this would be entirely unnecessary. Additionally, I didn't think the car would "rev the engine" if you are in Neutral. I'll have to try this, but I thought that the ICE would continue at it's current rpm no matter how far you press the accelerator.

qbee42 · 04-07-2008, 12:14 PM

Quote:

Originally Posted by Danny Hamilton

First of all this would be entirely unnecessary. Additionally, I didn't think the car would "rev the engine" if you are in Neutral. I'll have to try this, but I thought that the ICE would continue at it's current rpm no matter how far you press the accelerator.

I don't think it will rev. As the driver of a Prius, you are just a voting member when it comes to engine speed. You push the pedal to register your vote to go faster, but the ECUs get to vote too. In this case I think the driver is overruled.

Tom

MR.K · 04-07-2008, 02:19 PM

Thanks everyone....so to get it right ...#1 ..what speed can you go to N when driving? #2 ..what speed can you go back to D after coasting?...#3 ..is there below 42mph and above 42mph rules?.....thanks

qbee42 · 04-07-2008, 04:22 PM

62 mph is the magic figure which causes MG1 to hit 10,000 rpm. Below that you can shift in and out of N anytime you want. Some Prius drivers do it at higher speeds without reporting damage, but you take a risk when you do.

Tom

zeeman · 04-07-2008, 04:38 PM

interesting discussion and it sure makes sense to me

one thing i cannot picture is how does engine engage so smoothly that you cannot feel even a small jerk?
and, does the M2/generator ever spin in opposite direction while car is moving forward and ICE kicks in?

i presume that M2/generator changes the speed really quick from say 5000 RPM to 3000 RPM and this causes the engine to start spinning from 0 RPM to say 1500 RPM if engine speed and load are under preset parameters.
but, does M2 ever changes the spin direction while driving forward?

I also noticed (via scan gauge) that above 42 MPH engine engages (spins) at lower RPM without fuel consumption.
I presume this is so that M2 does not go in very high revs as that could potentially damage it at very high rotational speeds?!

does anyone knows of any good animation that would show what happens with ICE, M1 and M2 at various loads and various vehicle speeds?

04-07-2008, 06:47 AM	#4
patsparks An Aussie perspective Join Date: Jul 2007 Location: Adelaide South Australia Posts: 9,223 My Car: 2004 Prius Model: N/A Package: Base Thanks: 124 Thanked 180 Times in 138 Posts Friends: 33	Re: Coasting and tranny ??? I'd be more concerned about over spinning MG1. If you accelerate from under 42mph to over 50 there is a posibility you will over spin MG1 ans damage it. This might happen going down hill. Then again the ICE may fire up to protect MG1 while in neutral, I haven't a clue.

04-07-2008, 02:19 PM	#8
MR.K Member Join Date: Mar 2008 Location: Idaho Posts: 83 My Car: 2008 Prius Model: Package: #2 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 0	Re: Coasting and tranny ??? Thanks everyone....so to get it right ...#1 ..what speed can you go to N when driving? #2 ..what speed can you go back to D after coasting?...#3 ..is there below 42mph and above 42mph rules?.....thanks

04-07-2008, 04:22 PM	#9
qbee42 Senior Member Join Date: Mar 2006 Location: Northern Michigan Posts: 10,474 My Car: 2006 Prius Model: Package: #7 Thanks: 94 Thanked 387 Times in 289 Posts Friends: 10	Re: Coasting and tranny ??? 62 mph is the magic figure which causes MG1 to hit 10,000 rpm. Below that you can shift in and out of N anytime you want. Some Prius drivers do it at higher speeds without reporting damage, but you take a risk when you do. Tom

04-07-2008, 04:38 PM	#10
zeeman Senior Member Join Date: Mar 2008 Location: California Posts: 201 My Car: 2008 Prius Model: Package: #2 Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Re: Coasting and tranny ??? interesting discussion and it sure makes sense to me one thing i cannot picture is how does engine engage so smoothly that you cannot feel even a small jerk? and, does the M2/generator ever spin in opposite direction while car is moving forward and ICE kicks in? i presume that M2/generator changes the speed really quick from say 5000 RPM to 3000 RPM and this causes the engine to start spinning from 0 RPM to say 1500 RPM if engine speed and load are under preset parameters. but, does M2 ever changes the spin direction while driving forward? I also noticed (via scan gauge) that above 42 MPH engine engages (spins) at lower RPM without fuel consumption. I presume this is so that M2 does not go in very high revs as that could potentially damage it at very high rotational speeds?! does anyone knows of any good animation that would show what happens with ICE, M1 and M2 at various loads and various vehicle speeds?

04-07-2008, 02:52 AM	#1
MR.K Member Join Date: Mar 2008 Location: Idaho Posts: 83 My Car: 2008 Prius Model: Package: #2 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 0	Coasting and tranny ??? When you shift back into Drive after coasting around 45-50 mph.....the motor ,if running, would be at an idle ..if not running ,stopped ....dose it jar the tranny or cause clutch wear ,Yea it's an automatic but it still has to have some type of clutch ? Has anyone did damage this way? ...Should you rev the motor a bit when shifting into D to keep the jarring down .....? I'd like to try this coasting thing ...just don't want to short"n the life of anything.....thanks.

04-07-2008, 03:07 AM	#2
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,231 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	Re: Coasting and tranny ??? Nope, no clutch. no risk of damage. All that happens from neutral is a change in the power flow.

04-07-2008, 03:15 AM	#3
Bill Merchant absit invidia Join Date: May 2005 Location: USA \| Oregon \| Portland area \| 97004 \| Posts: 4,100 My Car: 2007 Prius Model: Package: #5 Thanks: 18 Thanked 10 Times in 8 Posts Friends: 60	Re: Coasting and tranny ??? The Prius has a Power Split Device, not a transmission like other cars. Although Toyota calls it an ECVT (Electronic Continuously Variable Transmission), it's a planetary gear set with MG1 driving the sun gear, MG2 driving the ring gear (coupled to the wheels), and the ICE driving the planetary carrier. The Prius is always in gear, even in N. Last edited by Bill Merchant; 04-07-2008 at 03:16 AM. Reason: This is my post 3200.