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__2003 Honda Accord V6 Sedan 5AT vs 2004 Acura TL 5AT__So we start off with the two stock dynos for the Accord V6 5AT and the new 04 TL 5AT from VTEC.net and dump them into Excel. Power is nice, but the power

**is what really matters because a heavier car needs more power to accelerate it at the same rate as a lighter car. Basic F=ma physics. So that gives us the two plots below.**

*to weight ratio*AV6 and TL dyno: www.vtec.net

AV6 and TL weight: 3360 lb vs 3575 lb, www.hondanews.com

__Dyno Comparison and Power-to-Weight Analysis__So as you can see here, while the TL does have a steady overall power advantage, much of that is taken away by its heftier curb weight. Yes, 200 pounds

**does**matter. Also, you can see that the TL does have noticeably better low-end response thanks to its variable intake manifold which the AV6 lacks. Low-end response is critical in heavy automatic cars since you are locked to low-revs by the torque converter (2000-ish rpm) on launch and don't have the option of revving up higher to start off with like you do with a manual. So the TL should be stronger off the line.

__Gearing & Thrust Analysis__I previously have never gone so far as to actually look at gearing in these write-ups. If you're just trying to keep things as

*simple as possible and easy to understand*for people then a quick and dirty power to weight analysis is going to tell you pretty much everything you need to know with a good accuracy. However, some of my previous work has come under some very harsh criticism (particularly when it involves another manufacturer starting with the letter "N") and have claimed that I understand nothing about cars or gearing when in reality I truly do have a very intimate understanding of such things. Therefore, I will go the extra mile and start posting thrust and gearing analysis charts for various cars as well. Yes, it's entirely possible that a more powerful overall engine that is hobbled by overly tall gearing can still get beaten by a less powerful engine with more aggressive gearing. This is what the thrust curves look at.

By multiplying the engine's torque output vs RPM by the gear ratio and final drive and then dividing by the rolling radius (in feet) of the tire, we can translate the engine's torque (in pound-feet) to a thrust in a unit of just pounds, and the results are below. The overall gearing on 1-3 is pretty much identical and there isn't much to see, but there is on 4th and 5th gear where the AV6's gearing is actually shorter (numerically higher, more torque multiplication) than the Acura's. For simplicity, I will omit 5th since that's strictly just a cruising gear in both cars and not an acceleration gear. Also, since gearing can vary between cars, we also need to convert the X-axis of our plots from engine RPM to MPH. You can do this by relating the overall tire diameter to a distance, calculation how quickly the tire travels per "1 RPM" and then multiplying that speed by the axle RPM.

So the TL's thrust advantage from the intial dyno holds steady in the first 3 gears because they are pretty much identical. But the AV6's 4th gear is 9% shorter, and this all but negates the TL's thrust advantage.

However, thrust is not what we

**really**need because thrust is just a force. You apply the force that you have to a

**mass**and then that is what determines your rate of acceleration, so this is what we need to calculate next.

__Gear by Gear Acceleration Analysis__We already know the force (in pounds) that the engine and gearing create, and then you simply need to apply that force against your mass (also in pounds) and you can easily get the acceleration rate (in G's), but it's not quite that simple. There are forces that act against the car as it moves, and the biggest of those are drag from the tires, and also wind resistance. By knowing the dimensions of the car you can do a basic frontal area calcultation, and then combine that with the coefficient of drag (Cd) of the car to get the drag force (in pounds) vs a speed in mph and we can then subtract this out of the thrust. Also, tire drag can be roughly approximated as a constant of 1% of the vehicle's mass. With these now taken into account, we can plot the accleration curves and also get a realistic estimate of the top-speed.

Without these calculations, the gear/acceleration analysis will simply show each car accelerating to infinity which is not realistic at all. Since I am already going the extra mile, what's another mile further? Therefore, I have incorporated such calculations into these plots. Looking at the specs on www.hondanews.com, a basic frontal area calculation shows that the TL is slightly larger, but has a slightly more streamlined body (0.29 Cd vs 0.30Cd) so aerodynamics are about a wash.

Notice how the 1st and 2nd gear plots are relatively flat and follow the torque curves of the engines, but then how the top of 3rd gear beings sloping downwards, and how 4th gear really goes downwards. This is because aerodynamic drag is a function of your velocity

*squared*and increases exponentially. This shows that assuming no electronic limiting, the AV6 should be able to hit nearly 150 mph, but the TL should be able to hit about 155 mph. Also interesting to note is that the analysis shows that an AV6 in 4th gear may actually be able to pull on the TL a little bit when at high speeds on the highway (try at your own risk).

It also helps to be able to see all gears and all speeds at the same time on the same chart, so we can do that as well.

Here we can also see the very tall 5th gear, and this is proof positive that it's

**only**for crusing and fuel economy. The gears provide so little thrust that top speed actually occurs in 4th gear, not 5th gear. Both of these cars can only manage to get to the mid-130's in 5th, but can reach or exceed 150 mph in 4th gear.

__Powerband Analysis__Just as important as "how much" peak horsepower or torque you have is "where" exactly it is made. Although this can be seen in the main dyno comparison chart, there is also an 0.2L displacement difference here, so what we can do is normalize the torque output vs RPM of the engines to a percentage of their maximum and then plot over all RPM. The result is below.

Now it's much easier to see the advantage of the TL's variable intake manifold since this shows that the TL is able to produce a higher percentage of its peak torque over a wider range than the AV6 can. Again, this is especially important for initial off the line acceleration.

__So What are The Numbers?__My Excel application does a pretty good job of creating lots of comparison charts and various analysis' relative to the two cars. But to get hard numbers,

**CarTest Software**is still the best option. My application basically derived the "core" of CarTest and allowed me more flexibility to make different types of analysis'. But CarTest does many more things. By feeding it all of the same specs and chassis dyno data and calculating itself what I did here, it will then take that data and also estimate weight transfer and launch traction (60' times), torque converter multiplying effects, shift times, and then it can finally give you the "hard" numbers that you're looking for, and that is as follows.

continued in next post.....