Would appreciate any general or specific tips for manual shifting.
When to make shift..... should you release from accelerator during
shift.... is the car "receptive" when you stretch out to red-line.... any
specific do's and don'ts?

Thanks in advance


What a great car!!!

 

I have found that if you shift up at about 5500rpm, the split second that it takes to shift means that the shift happens at close to 6000 rpm which seems to maximize acceleration. If you try to shift at the redline, the slight delay makes you hit the rev limiter which slows you down. I haven't experimented a lot with this since I only have 2400 miles on my RL, but the times I tried it the acceleration was incredible. I think that this is why the car magazines have reported 0 - 60 times for the RL that range from 7.3 seconds down to 6.5 seconds. The difference in acceleration when you time the paddle shifts just right and of course the difference in acceleration when the A/C is on may account for this wide range.

 

IIRC, under wide open throttle (WOT), the air compressor will automatically turn off until normal throttle occurs. I seem to have felt it kick off on the RL and, without a doubt, on my M3 and previous Miata.

 

Interesting, thanks for the information DCD.

 

I don't pretend to know a lot about this topic ... But from years past, I thought the best place to shift was where the horsepower and torque curves crossed paths. Is that still true for this type vehicle?

If so, this chart may be of some assistance:
(Or maybe not ... What readingz are they showing?)

 

I am not sure what this chart is trying to depict

 

I could be mistaken (wouldn't be the first time), but I think ...

Horsepower:
300PS /6,200rpm = 300 bhp @ 6200 rpm

Torque:
36.0kg /5,000rpm = 260 lbs-ft @ 5000 rpm

 

HP and Torque always cross at 5250 RPM.....as a nature of how HP is caculated...


Maximum acceleration is going to be felt at peak torque, or 5000 RPM....

From 5000 RPM on the rate of acceleration is actually going to decrease, even though horsepower is still rising.

From that point on you would have to look at gearing....

 

I agree with LegendC. Horsepower is not measured directly, but is calcultated from torque, and is defined as 1 lb-ft of torque for 1 rpm = 1/5,252 HP. Example for 200 lb-ft of torque at 5000 rpm, the horsepower would be 200 X 5000/5252 = 190 HP. As you can see in this equation, if the rpm is 5252, if will cancel itself out, and will be equal to the torque. I have seen torque curves that do not cross at this point, but if they don't, they are bogus.

As far as shift points, I think this could best be determined by trial and error. As LegendC stated, the acceleration will probably descreases at 5000 rpm, but when you shift to a higher gear, the torque and horsepower will both decrease, and hence, acceleration will also decrease. The ideal shift point depends on the gear spacing.

 

I don't mean to correct anyone, but just about everybody misunderstands this topic. Please take my words with the utmost respect for others. I am here to educate. Nothing else. I think the RL forum is one of the nicest places to be, and I feel comfortable sharing here.


First off, many have addressed this issue of when to shift. I myself also wrote a series of articles to help address the issue. I haven't written one specifically for the RL, but it should apply to all vehicles.

The general concept goes like this.


Torque is a measurement of the motor's maximum output at any given engine speed. This point, made above, is true. Torque is measure in foot-pounds (force) in the Imperial system. Engine speed is measured in revolutions per minute (RPM).

For our purposes, we can effectively ignore the power curve. Give me the torque curve, and I can derive the power curve for you. The power curve gives some interesting statistics about the engine, but none of it is useful for determining the optimal shift points.


Before you can determine when to shift gears, you must understand what gears do. Gears are relationships between two rotating objects. You use gearing to adjust the relationship between the input shaft and the output shaft. For a car, the gearbox adjusts the relationship between the engine and the wheels. It helps provide mechanical advantage as needed to keep the engine working efficiently.

The engine has a normal operating speed. Imagine yourself on a 12-speed mountain bike. If you try to start in top gear from a stop, you'll be straining and most likely not go anywhere. You have to start in a lower gear. Likewise, if you want to go faster, you need to use higher gears. Otherwise you'll get stuck pedaling yourself to death without gaining any speed. Everybody who can ride a bike understands this.

Cars work just like that. The engine, like you, has a certain range it can operate in. Every car is different, but the general concept is the same. Give it the incorrect
gear at the incorrect speed, and you will not get the optimal result: acceleration.

I'll avoid the physics for now.


The point is you have different, predetermined gear ratios to use. You measure acceleration by how much driving force you can put to the wheels at any given time. You try to maximise the driving force here because it wil net you better results.

When you change a gear, the relationship between the engine and wheels is also changed. How much it changes depending upon the type of gearing you have.

Generally, for maximum acceleration, at every discrete interval in time, you must consider this one simple question: can I put more driving force down by staying in this gear, or should I change up?

When you start out from a stop, obviously 1st gear gives you the most acceleration because it can put out more driving force. But as the vehicle speed increases, there will come a point where the engine will start running out of breath, and it needs to be changed up.

This point is determined by two (2) things:

1) The dynomometer, or dyno, plot of the engine torque characteristics.
2) The gear ratios themselves.


Give me a dyno readout and all the relevant gear ratios, and I can calculate precisely for you which RPM you should upshift in every gear for maximum acceleration. This is precise mathematical modeling. There is no need for inaccurate trial-and-error.


So I'll leave that there for now. If you would like additional details, you may review the series of articles I have written:
http://g6civcx.angryhosting.com/R6Me...hiftPoints.htm


It was written for motorbikes, but the conclusions are all the same. You need to determine when to change up.

I'll try to get a dyno run with my RL and write up an article like that for the RL. Stay tuned!

Have a great weekend.

 

g6civcx, That is indeed good stuff!

 

Thanks for the praise. I appreciate it.

It's also worth mentioning that hondamore brought up a very good point. The automatic shifts somewhat hesitantly under hard acceleration. So it takes a moment for it to change up after you have hit the gear stick lever or paddle.

Generally though, it is not correct to say that shifting at redline will net better acceleration. This may be true for 1st gear, but for other gears, it depends on factors I mentioned.

Sometimes, it's better to go pass redline into the overrev area because staying in gear will help with acceleration as opposed to changing up. Whether this is good for your engine or not is a different story.

Sometimes, you will have to shift well before redline because engine output drops off so much that the current gear can no longer provide mechanical advantage, and the next gear would be better.


Overall, it really depends on your specific engine output and gear ratios.


I'm trying to book a 4WD dyno session for my RL. I hope to be able to post up my findings for all to view.

Happying shifting ;p

 

Wow, you folkz are a lot smarter than moi and have some terrific info posted ... It is much appreciated. Not to sound even more stupid than I am, but I'd like to pose a question. PLEASE do not take this as a flamed response.

I mentioned the "old" method of shifting where the hp & torque curve cross (also indicated by LegendC as 5250rpm). He also mentioned that, "From 5000 RPM on the rate of acceleration is actually going to decrease, even though horsepower is still rising." (This seemz to be substantiated by the power curve image.) Sooo ... Am I correct or incorrect to think that the best "seat of the pantz" shifting would occur at this point?

People may have different gear ratios, but it seemz that the "sensation" of speed will increase until around 5200rpm ... Then you shift to the next gear. At that point, the RPM's drop ... But you will be back into the power curve with a sensation of increasing speed. Then you shift @ 5200 and it continues until you run out of gears or road.

BTW- I doubt this would be the optimal shifting point for timed runz, but strictly for simple "seat of the pantz" driving, would this be easy enough?

 

Driving force, or thrust, is a result of how much engine torque is transferred to the wheels. The more your engine makes, the more driving force you have pushing the car forward.

Look at the torque curve. You can see where torque peaks. At this point, you have the most driving force to the wheels.

Say you begin accelerating from idle all the way up to redline. You'll feel the most acceleration at torque peak. This is for one gear.


Shifting is a different story. When you change up, you reduce your mechanical advantage so that the engine can spin the wheels more quickly. Remember shifting up on your 12-speed bike to higher gears once you get going? You'll hit redline and you'll have to change up to speed up.

It is incorrect to say you shift where peak torque is, or shift where torque meets power at 5,250 RPM, or shift so that the next gear will put you at peak torque. All of these are incorrect.

Your seat-of-the-pants feel is directly related to this. You feel acceleration force, not speed (bumps and vibration are caused by acceleration forces). A force acting on a mass results in acceleration. In order for maximum feel, always try to maximise driving force to the wheels.


Pretend that you only have 4 gears, and 2nd gear didn't exist. As you run to the top of 1st gear, the next gear up will lose so much driving force that it is better for you to stay in 1st for as long as possible, all the way up to the rev limiter. Once you hit 3rd, you'll lose so much mechanical advantage due to the numerical drop in gear reduction ratio.

Now imagine if you had a 2nd gear that is really close to 1st gear, and I mean really close. For this situation, shortly after hitting torque peak, you should change up to 2nd gear since you don't lose so much mechanical advantage.


So as you can see, it really depends on the ratios.


For my bike, it is not appropriate to change up at torque peak, and it is definitely not appropriate to change up at 5,250 RPM. It revs to 15,000 RPM with a 500 RPM overrev. Torque peak somewhere above 10,000 RPM. Take a peek at the spreadsheet in the link I posted and you'll understand.

 

Theorectially a contiuously variable transmission would allow the engine to always be delivering maximum torque. CVT is used in some cars, but there have been reliability problems. They seem to work better with smalller engines, but I did read somewhere that Nissian is putting a CVT with the 3.5 engine in the Murano. Maybe someday the CVT will be perfected.

 

Good link and very informative.

 

catsailr, thanks for the praise. And you are correct. The CVT continuously adjusts gear ratio to allow you to maximise torque output.

With the CVT, when you floor it the engine revs to torque peak and sits there. This is the because the engine can provide the most driving force to the flywheel at torque peak. The CVT continuously adjusts the gear ratio with a series of pulleys to provide maximum driving force tothe wheels.

 

There is a vast amount of great info here ... Thanx for attempting to educate me. Unfortunately, this old coot grew up on a one speed bike with no helmet (could be a factor in my brain damage). As a matter of fact, the brake was a foot pedal mounted on the right side of the cross-member frame.

Looking at your motorcycle stats, I can plainly see that shifting @ 5250 would not be correct ... But I think the original question had to deal with the current RL. Given the power curve posted and the gears that come standard ... I'm finding it difficult to understand where seat-of-the-pantz sensation would be dramatically better if one shifted outside of the 5250rpm range.

Again, I mean absolutely no disrespect with my comments above. Your knowledge in this topic is far superior to mine. Without going for all-out-racing stats (as your dyno info would conclude), would one get a decent seat-of-the-pantz feeling if you shifted the current RL @ 5250rpm?

 

427, thanks for the praise.

For street driving, you won't notice a 1/10 of a second difference. So therefore from your perspective, shifting between 5-6,000 RPM will still net you good acceleration.


Tell you what I'll do. I'll try to extract the torque values from the picture you posted.


Or if you want to help me out, see if you could approximate the torque reading for every 500 RPM from say 3,000 RPM up to 7,000 RPM. If you could give me those values, I could tell you exactly when to shift since we know the gear ratios on the 5-speed.


Maybe if there's a bigger picture. Where did you find that dyno plot from?

 

Also, I'll start another thread about torque and power later on. We use the Imperial system with horsepower and ft-lbs. The metric system uses different units, as you can see from the plot he posted above.

 

That pix came from the AcuraNews website: Click HERE
I increased the size a tad when I posted it, but I don't have access to the larger image. Does anyone have the full size image of this power curve?

 

I have driven the Murano (did last year) with the CVT...I didnt know it had a CVT until I went on the website and read it had it. I did realize something had to be up with its tranny as it was the smoothest tranny I have ever encountered. It is a very odd sensation though when intiially driving the CVT

CVTs rock and I would love to have one in the RL assuming reliability was fine.

 

I was going to try to get a dyno run on the RL yesterday, but unfortunately all the AWD slots were taken up by Mitsubishis and Subarus. Damn them

I'll try again next time.