I would much rather have the mid rpm performance of the VQ than high rpm performance like my hondas.

 

Haha! That's cool Clint. I was working on a similar area under the curve analysis myself.

This one was for the Import Tuner Magazine MREV2 test.
This is based on a different data set but is a similar kind of analysis showing the average power per gear.

These plots show the pre/post power effects of MREV2 on 1/4 mile racing and a hypothetial race to the speed limiter @ 162MPH.

They are not done yet but they show interesting results.

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Ever hear the expression "torque wins races, horsepower sells cars"

Torque is whats important. Torque is power. Horsepower is a measure of torque over a period of time.
What was mentioned about shifting at redline so the next gear drops down in the torque curve is usually correct. But sometimes there is no torque to be had at the upper rpm band and power falls off. So sometimes its better to shift before redline to avoid this.
I haven't looked at all the stats yet.. but being a DOHC engine.. I would bet the torque peak is high.. but this engine with its variable valve systems allows for a wider torque curve.. so running it up to redline might not be necessary all the time.

 

Is that for the 2007 or another year?

 

That was a different year engine. With a different dyno/calibration.

Probably a bit OT.

 

This is true to a point but only if the acceleration measurement was measured in one gear or if you define it as TQ as applied to the asphalt.

The gears change the TQ as applied to the asphalt and this is where HP is important.

Since there is a range of curves and RPMs possible, it ends up that HP is the determining factor because of gear shifting requirements.

See the attached image for data on the transmission and final drive gear ratios.
As an example:
third gear drive ratio is 5.736
fourth gear ratio drive is 4.484

Peak HP is important because the TQ applied to the asphalt at 3RD gear redline is higher than the TQ applied to the asphalt at the bottom 4th gear.

Revup engine TQ at redline is ~165 ft/lb
The TQ to the asphalt in 3rd gear is 165*5.736 gear ratio = 946 ft/lb

Vs

Revup engine TQ at the entrance to 4th gear is 5472 RPM or ~200 ft/lb
The TQ to the asphalt in the bottom of 4th gear is 200*4.484 gear ratio = 896 ft/lb

So as you can see, the high RPM engine TQ in 3rd redline gear puts more TQ to the asphalt than the higher engine TQ level when in 4th gear.

This means you want to spin it up in the high RPM range as much as possible. Where the highest HP occurs...

The car accelerates faster at high RPM in third gear than it does at mid RPM in 4th gear.

In conclusion, its not engine TQ that wins races, its wheel TQ that wins races. And that means we need to consider both the engine curve along with the gears.

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If you going to use that example of multiplied torque, don't you have to take all the other variables into account too, like the fact that your moving at a greater speed requiring slightly less torque to continue momentum. There might be 50 ft/lbs less torque at the bottom of 4th then at the top of 3rd, but it should be just as easy to accelerate at the same rate do to the fact that you have increased momentum that requires less torque. Up until the point were drag takes over that is. That's why higher redlines are a good thing right. I'm prob talking out of my rear end but I'm just trying to get the head juices flowing. Bear with me.

 

If you going to use that example of multiplied torque, don't you have to take all the other variables into account too, like the fact that your moving at a greater speed requiring slightly less torque to continue momentum.
No. The speed at the top of 3rd Vs the botom of 4th are exactly identical.
The difference is that 3rd still has a higher TQ capability and this means it has a higher acceleration capability.

There might be 50 ft/lbs less torque at the bottom of 4th then at the top of 3rd, but it should be just as easy to accelerate at the same rate do to the fact that you have increased momentum that requires less torque.
No. Momentum has nothing to do with acceleration. They are exclusively independant variables. Momentum is the factor of mass and velocity.
Acceleration is force (or TQ) applied to the mass.

And regardless of the engine RPM, on this car, 3rd gear will always accelerate faster than when it is in 4th gear.

Drag is another exclusive and independant variable. TQ doesn't affect drag. Drag is only determined by velocity, cross section and drag coefficent.
Its not really relavent to a comparison of 3rd Vs 4th.

 

Ah.. all this techno babble is making me think too hard.
I was raised on push rod V8 engines. Torque was king. Horsepower was for sissies. All we cared about was being nailed back into the seat. 7500 rpms was rare in race cars never-mind stock street machines.
Everything is changed.. but I still consider torque as the most important aspect of power. You hit the gas and it goes. not the wait for the 3500 rpm surge BS that most OHC engines provide.
When I test drove the G, I was expecting a weak hole shot and then the high pitched revving silky smooth power pull.
I was surprised to get nailed in the seat from the get go and was amazed at how it still pulled hard up high.
In everyday use.. its the instant torque that I depend on most. Aim and shoot.. the power needs to come on quick and move you when you see the open slot.
The G does this well .. and for a 6-cyl without push-rods..
I'm impressed!
All the explanations are fine.. but its torque that drives us and makes us smile

 

You talk about torque like it has no connection to horsepower. Anyway, bottom line is, rev these engines all the way out if you want the fastest acceleration.

 

Am I the only one that notices the Redline is closer to 7800 than 7500?

 

I do understand the connection... I'm sure I will get to appreciate the HP more when I get past the break-in period..

 

Some say 7600 is redline.. hard to tell with the way the tach is setup.
redline is usually a conservative number set by the factory... I wonder how many revs these engines can really handle..

 

Hydrazine, thanks for the insite, that's why I'm an electrical eng and not a physicist!

 

Yes I certainly have and for every time that expression is used a physicist and an engineer die in this world.

Torque is certainly an important element of the equation, but not the one to focus on when dealing with acceleration. Once again torque is NOT power. Get that out of your head. Horsepower is the measurement of power. This is straight out of physics 101.

In addition, torque is not simply a force either. It is a twisting tendency or "moment" as physicists termed it. Force alone cannot generate torque. Picture someone pushing a heavy crate. All that was involved is pure force. In order to generate torque, a force would need to be applied about a pivot point x-distance away (moment radius), not unlike a person’s feet acting on bicycle pedals. A better example of torque in the context of this discussion would be as follows,

The combustion inside a cylinder creates 50 lbs of explosive force and is exerted on the piston.
The piston linked to a 2-ft. crank arm (moment radius) in term generates 100 lbs-ft (or ft-lbs) of torque at the crank shaft.

Note ...
force [lbs] = explosive force from the combustion of the cylinder.
moment radius [ft] = length of the crank arm
torque [lbs-ft]= Force [lbs] x moment arm[ft]

finally,
power = torque x rotational speed x 2pi

which derives to …
horsepower [hp]= torque [ft-lbs] x rpm / 5252

Now that we have that cleared out of the way, let’s get to the beef of the discussion – the false notion that torque is what matters.

All that one can extrapolate from a torque plot is how much force an engine is capable of generating at a particular rpm. For that reason it is the go to chart when tuning and optimizing engine output. However, when dealing with non-static cases, such as vehicle acceleration (what everyone’s really after), torque plots simply don’t offer enough information for that purpose. Horsepower plot on the other hand spells it out very clearly. Why’s that you might ask?

Having gobs of torque is never a bad thing, but it’s the ability to apply it rapidly that ultimately matters … that loosely put is what we called work. Work over time is power or horsepower. Now let’s apply all this to the 5AT VQ35HR plot Tony attached in post #1,

4900 rpm, 255 ft-lbs / 239 hp (peak torque)
6700 rpm, 217 ft-lbs / 285 hp (peak horsepower)

Imagine if you would … two G35s traveling down the road perfectly lined next to each other. They are both traveling at the same velocity and in the same gear. Only one is sitting at @ 4900 rpm and the other @ 6700 rpm. There would be no up shifting for the sake of keeping this example simple. When given the signal to floor it, the G @ 6700 is going to easily out pace the other @ 4900 rpm. So what happened there? Last time I checked a 38 ft-lbs torque deficit was no laughing matter. Can you say Horsepower!

It’s all quite simple really. Albeit with only 217 ft-lbs of torque on tap, the G @ 6700 rpm was able to apply torque 36.7% faster than the other G with 255 ft-lbs of torque. The net result is more net power transmitted to the drivetrain which we perceive as acceleration. It is also important to note that with increasing rpm, less torque is needed to achieve the same power level. This is another reason why torque isn’t everything. I bet many people aren’t aware that an engine from the current top Formula-1 team only generate slightly above 200 ft-lbs of torque, despite making ~750hp and able to reach 19,000 rpm.




Almost but not quite. Again, one should be looking at the horsepower curve not torque curve and with the interest of maximizing the swept area under the hp curved for each gear. In this case, the VQ horsepower curve implies a clear advantage by shifting at redline through each gear. By your theory above (referencing the tq curve instead), you’d have to shifting at 5500 rpm. I’d challenge anyone to try that vs. redline shift at a drag strip.

Running it up to the redline for the VQ is necessary for maximum performance through each gear.