Draxx

New RL owner here... in case you didn't notice. LOL


I have driven a Bonneville for the last 10 years. When I would be going down a hill, even a small hill, I would coast - the car would coast - the car coasted very well.

This RL does not coast. If anything it starts to slow down while going down a hill and giving no gas. I want to coast down big hills.

If I put it in neutral it does coast down the hill like the Bonneville would coast while in gear.

Is this a "feature" or do I have a "problem" because everything else on the vehicle seems flawless.

Does your RL coast?

Draxx

Can't edit! ....

I want to coast down small hills too for that matter ... but its like ... It has a drag. It wants to go slower. I had 2 different Bonneville's in 10 years and they both coasted.

I also noticed 42mph is its happy speed where the transmission cruises in 4th but at 40mph it can't seem to make up its mind and jumps back and forth between 3rd and 4th depending on how much power I'm requesting from it.

I'm only mentioning this as perhaps the jumpy 40's is related to the coasting issue - or for all I know nobody's RL "coasts" and you all think I'm crazy for penny pinching my petrol with habitual coasting! LOL! ????

So does your RL coast well?

253RL

I just noticed my 05 does the exact same thing, however I am almost positive this is a new thing because when I first got it I was doing some digging on noises and what not and someone else brought this same thing up about his rl wanting to slow or stop even when going down hill so I paid attention to my car and it stayed at the same speed or sped up down hills now it for sure feels laggy almost like brakes being applied! So weird you posted this now as I was seriously just thinking about it tonight.. My RL will most def come to a hault down hill and will not coast at all! That's all I got but I'm in the same boat.. Maybe tranny fluid change time as I just hit 55k..?

oo7spy

Draxx, it's all good. The SH-AWD has roughly 30% loss in the drivertrain due to drag/friction compared to 15-20% in a normal 2WD car, and the RL does not have enough low end torque to overcome most coasting situations. My car does the exact same thing. 45 with the slightest slope will alow me to coast, but nothing else will. Kick it to neutral if it is that important to you. Nothing is wrong with your car.

We have heard one experience where the owner believes his light weight pulley helped this, but who knows how much.

getakey

^ Not sure what low end torque has to do with coasting. The torque converter locks up if you are off the gas. Thus, the engine is braking the car going downhill.

Mr Marco

HDC = hill descent control? Was this available in 2005?

getakey

I'm not aware of HDC in RLs. I know a lot of Audis have it as well as Land Rovers and other "off road" vehicles

oo7spy

When you aren't on the throttle, the RPMs are low. If you have enough low end torque, the car can overcome the resistances slowing it down. My dad's Cummins turbo diesel can cruise with the clutch out and no throttle because the low end torque is enough. If the torque at 1-1.5k RPMs was enough, the car could coast no problem. Same reason a V8 'vette can get 30 mpg on the highway.

Draxx

Yes that is exactly what it feels like. The engine is breaking.

At first I thought my breaks were stuck ... then when I could coast in neutral and it felt like I expected I figured it was maybe related to the transmission or the AWD ... since I have never had an AWD car before. Always front wheel drive here. I'll decide what I think about that after it snows. LOL!

mitchkramez

One thing i noticed when reading that manual, it says that cruising speed (cruise control) will be held even when going down hill, and it certainly does - So I agree that this is a feature, not an issue

oo7spy

getakey, I will admit that I don't know very much about torque converters, so go easy.

getakey

sorry - did not mean it as criticism

wackjum

What about the acceleration device unique to the RL's SH-AWD system? I know when I lifted off the gas in the RL, the power delivery icon would show something on the two rear wheels.

The RL doesn't "coast" very well. It is a heavy car and loses speed quickly. I think the factory recommended PSI for the tires is too low. I consistently ran mine at 35 PSI all around and experienced better economy, better handling, and no unusual tire wear. I had the stock 17" wheels.

oo7spy

No need for apologies. I tend to be an asshole, so my skin is pretty thick.

I was referring to your future response to my diesel/manual analogy. Like I said, I don't know very much about torque converters, but I would be surprised if the car didn't allow more power transfer through during a coast than at a stop. It seems like if the car had more power, it could overcome the resistances of the drive train like it can at 45 mph.

getakey

I believe that power delivery to the rear wheels is actually showing the "negative" torque being applied due to the engine braking. I may be wrong.

Matt W

I read the same post about the light weight crank helping the car "dragging" down hill, when I got my lightweight crank there might have been a small difference but I can still notice it dragging when going down a hill so its normal.

db22

Rolling down a hill with the car in neutral will cost you a transmission and possibly more. The manual states that it is not recommended to tow this car, it should be on a flatbed because of the lubrication system in the trans and diffs. If the trans is not engaged then the system will burn up.

And a lightweight pulley may allow you to roll about an extra foot coasting from 100mph (it is insignificant to the other obstacles involved in rolling resistance).

steve807

I've read somewhere that the torque converter can lock in 3rd and 4th as well as in 5th.
Unusual compared to most other cars.
The only possible reason to lock in 3rd and 4th is to get some engine braking for downhill brake saving and cruise control setpoint holding. The lock up in 5th is to enhance fuel economy. (but everyone agrees with that)

getakey

^ it definitely locks in 3rd and 4th and I agree with what you say is the reason

only trouble is at 35 to 40 mph it tends to "hunt" in and out of lockup

oo7spy

EL19

iTrader: (4)

My sentiments exactly. You dont tow this car because its AWD and towing it can ruin the diffs but that has nothing to do with it being in neutral.

Also the car doesn't "coast" because this car (and every Acura I've had) has logic in the computer that causes it to engine brake while coasting to keep the car from speeding up. If you want to coast, you will need to be in neutral. I also find that soemtimes if I want to coast I can just manually go to the 5th gear and it coasts fine.

GizmoPDX

I believe you are referring to the Grade Logic Control. I like it when driving down steeper slopes. I can give gas to the 40mph speed I want and then let off the gas pedal. The grade logic control holds the speed through engine braking to I don't have to constantly adjust my downhill speed by manual braking.

This was found on the Honda website.
Grade Logic Control alters the 5-speed automatic's shift schedule when traveling uphill or downhill, reducing shift frequency, and improving speed control. Throttle position, vehicle speed and acceleration/deceleration are continuously measured, then compared with a map stored in the transmission computer. The Grade Logic Control System then determines when the car is on a hill; if this is the case, the shift schedule is adjusted to automatically hold the transmission in a lower gear for better climbing power or increased downhill engine braking.

oo7spy

The problem isn't that the car doesn't speed up down a hill. The problem is that the RL slows down when descending all but the most steep grades. I should not have to press the gas or the brake to keep a constant speed down a hill. I imagine whatever is the reason is also what keeps me at a 19-20 mpg average.

oo7spy

You are thinking of the RLX demos. A mechanical differential cannot reverse direction until it is fully stopped. What would happen if you threw the car into reverse while moving forward?

However, an electric motor can apply an opposite force because the force applied by the stator to turn the rotor is not created by contact, but by electromagnetic fields with space between the stator and rotor. If there were contact like in a traditional clutch/differential and an opposite force were applied, carnage would ensue.

IanVS

There can still be a torque opposite to the direction you're going. Torque is just a force, not a direction.

I'm still somewhat suspicious that this is what the MID is showing, but maybe. I've wondered about it myself.

oo7spy

How do you suppose two gears locked together can move in opposite directions? Are are you suggesting the differential has a way to brake the axles?

Again, what would happen if you threw your car into reverse while it was moving forward?

IanVS

I'm saying getakey never said anything about going backwards or changing direction. He said "negative torque" from engine braking, which is just a force applied in the opposite direction from the spin of the wheels. Braking applies such a torque. Doesn't mean the wheels start going the other way.

getakey

Yes, exactly. The torque differential from left to right on the rear wheels works in both acceleration and deceleration.

oo7spy

So you are suggesting the engine actively applies a retarding force other than that caused by the vacuum generated from a closed throttle? Or are you suggesting the car measures the natural response in some sense and tries to relay the concept through the MID?

Going back and re-reading his post, I see that he was clearly talking about the resistance from an engine brake and not an applied opposite force, but I don't think that is what the MID is indicating. When you let off the gas, the car still applies some forward power to the wheels. When you hit the brakes, it removes all power. I think the power to the rear wheels is a compensation for the drag because it is much more efficient to keep a speed than to stop power and then reapply it for acceleration. Letting off the gas doesn't always mean you want to slow.


The idea of using opposite forces in electric motors is pretty cool though. There definitely is a better way to recapture the potential energy of a moving mass than by blowing it all as heat through the brakes, and I think electric motors/induction has something to do with it.

getakey

When the car is going down hill, the weight of the car plus gravity is actually helping to turn the engine, which results in engine braking. Its just like trying to turn the engine over without starting it. It takes a lot of force to turn the engine. Think about it this way - if you had a manual transmission car and put the car on a lift, try turing the rear wheels to turn the engine. With the torqe converter locked, it is similar to a manual clutch engaged in the transmission. Even a simpler example, lift the rear wheel of your bicycle up and turn the wheel, it turns the petals.

What is displayed in the MID is this torque resulting from engine braking.

IanVS

I'm still not convinced that's what the MID is showing. What are you basing that conclusion on?

getakey

I believe there were some early threads (several years ago) discussing this. I'll see if I can find.

Why do you not believe that this is the case?

getakey

I found this article http://honda.co.nz/technology/engine/sh-awd/
and this quote:
"When cornering under deceleration (with the throttle closed), torque being applied to the outside rear wheel is varied to change the impact on the vehicles momentum from an inward yaw moment to an outward yaw moment, helping vehicle stability."

While not explicitly stating what is shown in the MID, it is stating that the SW-AWD does vary torque during deceleration. We know that it is not applying brakes, so the variable torque has to be achieved through the engine braking.

Edit - thinking more, perhaps I am wrong on this. If the MID display shows torque on outside wheel during deceleration and cornering then it would not be the eninge brake torque.

oo7spy

I believe that is still a forward power being applied to the outside wheel. Also, the indications that were are discussing here happen equally to both wheels and when coasting in a straight line.

getakey

Yes, got that. I was editing above when you posted.

As for the straight line downhill coasting, there is no forward acceleration being applied to the rear wheels, so what else could it be displaying?

getakey

Here's another explanation - my emphasis on "other". Would you interpret other to mean inside wheel?

"
Super Handling All-Wheel Drive creates cornering grip via electronic torque management. Normally, an AWD car transfers torque from the front to the rear as acceleration and spirited driving demands increased traction, but generally some power is always turning the front wheels. SH-AWD can transfer as much as 100 percent of the torque to the outside rear wheel alone. This "overdriving" effect helps the car turn in more quickly for optimum cornering ability. During hard deceleration through corners, torque is balanced to the other side to counteract oversteer."

Read more: http://www.hondatuningmagazine.com/n...#ixzz20Wm0Dfuq

oo7spy

Unless I am reading your posts wrong, I believe you are confused on the polarity of the the TC locking and unlocking. It is unlocked from a start through an acceleration until the turbine reaches 90% of the speed of the impeller at which point it locks, like a manual transmission, and the efficiency is improved for increased gas mileage during cruising. When you release the throttle, the TC will unlock.

Hard deceleration through a corner causing over-steer is a power slide. http://www.slate.com/articles/news_a...e_sucks.2.html

If you go into a corner and mash the brakes, the rear end will swing out. Applying torque to the inside wheel (the "other" wheel compared to an acceleration in a corner sending power to the outside for over-steer) will cause some under-steer and help to keep the rear end in line.

getakey

The TC in the RL is computer controlled. It does not unlock with a simple throttle release. Otherwise, it would coast better downhill.

oo7spy

Possibly, but you mentioned that the TC locks up when you release the gas suggesting that it was unlocked prior to the coast, and that is not the case.

getakey

To clarify, I meant that the TC will lock up once you stop accelerating which usually means release of throttle. There are more factors, but in general, the TC locks up when car goes from acceleration to "cruise".
So, in general, it would be locked immeadiately prior to coast and stay locked until you accelerate again. If you applied brakes, it would unlock when the transmission needs to downshift.