What Does This Car and Driver Comment Mean?

[DavidNJ]

http://www.caranddriver.com/var/ezf...lication/f87e985ed73b2f75dbaa3b6f22231ab6.pdf

 

[nearwater]

http://www.caranddriver.com/var/ezf...lication/f87e985ed73b2f75dbaa3b6f22231ab6.pdf

Looks like they're saying the car automatically upshifts once they reach that RPM (5500 when in 1st gear, 6200ish thereafter) even when they put it to manumatic shift mode.
Interesting.
I've never put the gear into manual mode before. It ain't a sports car, and never felt the need for it.

Dan

 

[DavidNJ]

Has someone noticed what happens when you floor it though the 1-2 and 2-3 shifts?

 

[ctrcbob]

In Manumatic, it stays in the selected gear, even if you lift your foot from the accelerator. If your RPM goes up to the listed RPM limits, yes it will shift to the next higher gear automaticly.

The difference is;
1. Except for when the RPM reaches the upper RPM limit, in Manumatic, the transmission will stay in the selected gear when easing off the accelerator. Only after it reaches the upper RPM limit, will it upshift by itself to the next higher gear, in order to keep the engine from over-revving. It will not downshift by itself unless the RPM drops so low as to cause drivability problems.
2. In Automatic, the transmission will upshift to the highest gear available when easing off the accelerator. Even an upper gear that you really don't want to be in. It will also downshift by itself at lower RPM just as normal automatics do.

This is why people have better control of their cars with a manual or the next best thing of Manumatic transmissions. You are always in the gear you want to be in, not the gear the transmission picks for you, which will always be one of the higher gears.

 

[DavidNJ]

But the question is does it take the engine to the redline or UPSHIFT automatically at 5500 1-2 and 6200 for 2-3 and the rest? Isn't the power peak 6500 and the redline 6750?

 

[ctrcbob]

But the question is does it take the engine to the redline or UPSHIFT automatically at 5500 1-2 and 6200 for 2-3 and the rest? Isn't the power peak 6500 and the redline 6750?

It must upshift at those RPM's automatically, even though in manumatic mode, in order to protect the engine.

Again, the advantage of Manumatic is that EXCEPT at VERY LOW, or VERY HIGH RPM's, the transmission stays in the gear you want it to be in, otherwise, in automatic, the transmission will always upshift to the highest gear available for the RPM. I.E. The gear the ECM/TCM wants the transmission to be in.

 

[DavidNJ]

What engine speed to the board members see their upshifts occur at in automatic and manual mode? The implication is that the V8 only has around 300hp before it shifts to second, dropping to around 220 or so. And further, in the other gears it shifts before it gets past 330-350hp.

Is that what owners are observing?

 

[QCTLG]

What engine speed to the board members see their upshifts occur at in automatic and manual mode? The implication is that the V8 only has around 300hp before it shifts to second, dropping to around 220 or so. And further, in the other gears it shifts before it gets past 330-350hp.

Is that what owners are observing?

Where do those numbers come from?

See this and you be the judge...
[nomedia="http://www.youtube.com/watch?v=xy2R1zGV3wc"]YouTube- 2009 Hyundai Genesis 4.6 0-60[/nomedia]

 

[DavidNJ]

I did a straight line approximation. 333ft-lb@3300rpm is 221 hp. It may be closer to 360 at 6300rpm. The 1-2 shift drops revs 45% (big gap). 6300rpm would be to 3500, 5500 would be to 3000.

The electronic gauges on modern street cars are fake. That is why BMW says it doesn't use many and why they are so stable. They might as well be warning lights. On a Honda S2000 the tach just lies about the revs after a 1-2 shift, maybe 500rpm too high. At least it says in the VTEC. The ECU actually has a delay which requires a combination of rev and throttle change to drop out of VTEC.

Note that 375hp@6500rpm is 301ft-lb of torque, so the torque curve is pretty flat and the straight line approximation is probably pretty good.

The video seemed to shift way short of the redline in each gear, about 6300, maybe 6200.

 

[JamesD]

There may be some other considerations that are not obvious. I have an Acura TL with a 5-speed "manumatic", but it only allows manual control in gears 2-5. Rolling away from a stop, the 1-2 shift occurs automatically, then you're on your own after that. The only exception is when you slow to a stop again; it drops back to first on its own at the right time.

Hyundai may do it for the same reason Honda does, be it emissions or limiting the amount of torque (or shaft speed) you can put through the tranny. One thought is that with heavy reduction, the output torque in low gear is off the charts, and that may exceed some limit in the ZF (or maybe the universal joints or rear end, who knows?).

I realize your overall point is about why these numbers aren't at redline. It might be interesting for somebody to run it wide open (in a safe place) in regular automatic mode and see if it upshifts at redline or short shifts in the lower gears...

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[DavidNJ]

If it is being done to limit power, it would explain an early 1-2 shift. However, the video didn't support that statement; C&D may have had a pre-production 2009.

It is common to limit power in first and sometimes second in front wheel drive cars to limit torque steer. However, it is usually done by juggling ignition timing not short shifting, which with the huge 1-2 gap puts you way out of the power band after the shift.

Does anyone know what the V6 does? This may explain the relatively small difference in 0-60 times.

 

[DavidNJ]

I found the transmission gearing. The V6 is shorter (higher numerical) and has closer spacing. What that means is that 6200 in first (the 290hp peak) occurs where the V8 is at 5900, where the V8 is at 345hp, not 375.

After the 1-2 shift, which occurs 2 mph earlier with the V6, the V6 is at 3650 rpm, maybe 195hp. The V8 is at 3500rpm, maybe 220hp. That is 30% smaller gap then at the same rpm, but they are not at the same rpm.

Second gear is also shorter. At 60mph the V6 is 6100, nearly its power peak, probably over 285hp. The V8 is at 5600rpm, 330hp, maybe a bit less. 45hp difference, not 85hp difference.

The higher torque peak in the V6 implies when foot to the floor redline shifting, the horsepower curve is fuller for the V6.

Add to that the V6 is 5% lighter. Using those 60mph numbers and 3900 and 4100 pounds, the ratios are 13.7 vs 12.4 lb/hp. Using 290hp and 375hp the numbers would be 13.4 vs. 10.9, a much bigger difference.

If you are on the Autobahn, foot to the floor from 55 to 130 soon as you get past a truck or out of a construction zone, the V8 can show its muscle. If you are in the US you would have to be foot to the floor to 75-90 to get that big a gap.

So the reason they are close in the foot to the floor tests is a combination of gearing and early shifting. If you have a US driving style where you virtually never use full throttle acceleration, the peaker V6 will seem weaker. If you are foot to the floor, the V6 will be tolerably close.

Does anyone disagree?

 

[DavidNJ]

One other point, the V8 is just at the 3-4 shift as it gets to the 1/4 mile, shifting just past it. That is one reason it is clocking those very fast times. The V6 eats the 3-4 shift just before the 1/4 mile mark and is way down on the power curve for those last few hundred feet.