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"Certified Hybrid Killer"
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I developed a custom Excel application that will auto plot about a zillion different things all by just entering in the dynos and basic specifications for two different cars. I decided to give it a test run on these two cars because I was curious about it myself.

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 to weight ratio 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.

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.....
 

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"Certified Hybrid Killer"
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Discussion Starter · #2 ·
Part 2 :D

Performance Analysis

Code:
[b][u]Time to Distance[/b][/u]

[u]Dist[/u]          [u]AV6[/u]                   [u]TL[/u]
60'   :  2.33 @ 30.55 mph     2.32 @ 30.77 mph
330'  :  6.31 @ 59.20 mph     6.28 @ 59.75 mph
1/8th :  9.62 @ 74.55 mph     9.55 @ 75.32 mph
1000ft: 12.51 @ 85.63 mph    12.41 @ 86.61 mph
[b]1/4m  : [color=red]14.94 @ 93.17 mph[/color]    [color=green]14.81 @ 94.49 mph[/color][/b]
1/2m  : 23.50 @ 113.22 mph   23.26 @ 113.90 mph
1 mile: 38.12 @ 131.11 mph   37.86 @ 131.45 mph

[b][u]Time to Speed[/b][/u]

[u]Speed[/u]     [u]AV6[/u]      [u]TL[/u]
0-30 :   2.28s   2.25s
0-60 :   6.44s   6.31s
0-100:  16.86s  16.20s
You may think those times for the AV6 are a bit fast, and they probably are. However, these times were calculated with 6800 rpm shifts and it seems as though the AV6's shift mapping has the engine shifting at only 6500 rpm instead of 6800 rpm like it ought to. Our resident 7th gen track whore, 03LXV6guy (Larry) has proven that if you manually shift at redline and precisely nail each of the shifts such that you don't spend any time bouncing off the rev limiter, you can pickup a tenth or slightly more on your ET. This is how he ran his 14.58 with intake only. On the same night his other runs were 14.7's and either autoshifting, or hitting the limiter. A host of other AV6ers have been able to run about 15-flat with auto shifting (apparently at 6500 rpm). If we reconfigure CarTest to shift at 6500 rpm also, we then get a 0-60 of 6.52s and a 1/4 mile of 15.06s @ 92.66 mph with the same 2.33 60' time. This is within a few hundredths of what other 7g owners have been able to accomplish while stock and verifies that our simulated times are accurate.

Furthermore, since CarTest will also give you speed in gear, acceleration curves in G's, and top speed estimates as well, I can then use the results from CarTest to cross-check my Excel application calculations. CarTest estimates a maximum acceleration of 0.55g's for the TL in 1st gear and 0.53g's for the AV6, which is almost exactly what I calculated here (0.56g and 0.54g). In 2nd gear it sees in the low 0.3g range for both which again is consistent. Maximum speed in gear calculations are accurate, and the top speed estimated in CarTest is actually a tad slower than my estimates. So my results here are skewed very slightly higher. This likely traces back to my tire drag calculation, which can be roughly estimated as a constant percentage of the vehicle weight. I used 1% here, when 1.5-2.0% is probably a little more honest, especially at higher speeds. Changing the spot where I calculated this in Excel to 2% brings my estimates back in line with the proven CarTest software, and then CarTest and my Excel app are then in agreement. However, since this variable was held constant between the two cars, both are still on a level playing field to each other. Every tiny little thing has a small effect no matter how insignificant it may seem. And when multiple little things are added up, they can all combine to make significant difference in performance. Oh yeah, you have to add in the driver weight for the cars also, otherwise your results will be skewed even higher. I used 160 pound "test drivers" for each car. ;)

Now, on to analysis of the numbers. :cool:

From our time to distance and time to speed results, we can see that the TL just steadily inches away from the AV6 but again, will never get very far. The powerband and general torque curve shape is similar, as is gearing, and aerodynamics, so there really isn't much to report on since Honda tends to design their cars the same way. The TL is just very slightly faster but otherwise performs very similiarly and with similar characteristics to the AV6. In 1st gear the TL is able to accelerate about 0.05g's harder which would probably barely register on the butt-dyno. After the low-end of 1st gear, there is not much more than a few hundredths of a G of acceleration difference between the TL and the AV6 with the advantage going to the TL all the way up to high-speeds. It should steadily inch away from the AV6 all the way down the track, but will never really get very far.

It's actually much more interesting to look at different types of cars with these tools that I've developed because then you get to see the different design philosophies and priorites that other manufacturers have and see how they perform against each other and what works and what does not. It's amazing what you can learn, but the real challenge comes in getting that message out to others to share what you've discovered. For that, you just need to keep improving your tools. ;)



SUMMARY

Although the Accord V6 is not quite as quick or fast as the TL, it's damn close, and the difference in performance is not nearly as great as the 30 "rated" horsepower difference would lead you to believe. Can't forget about that 200 pounds of extra weight, now can we. The difference calculated here of one to two-tenths in the 1/4 mile is roughly only a single car-length. What this means is that the better driver will win. What this also means is that you only need an intake on your Accord V6 to truly equal or even beat the performance of the new 270hp TL.

Of course, the TL does offer other things as well. Does it handle better? Yes. Is it more refined and does it have a nicer interior and offer more luxury features and gizmos? Certainly. However, it is not significantly faster than the Accord V6 when both are equipped with automatics. Counterpoint: And if the Accord buyer so chooses, they can take the $7000-8000 price differential between the Accord and TL and either pocket the money and use it for other things, or modify their cars (as many Accord owners love to do) to their own liking such that it does everything the TL will and more, and possibly even better.

No doubt the TL is a "better" car, but once you reach a certain point, even small improvements in either refinement or performance end up coming at great expense. The TL and its other luxury brand competitors are all fine examples of that. For the money, you simply cannot beat cars like the Accord.

Thanks for reading. :cool:
 

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Good write up Steve-o. You couldn't make it any shorter could you? :laugh:
 

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Yes Steve, this is why we love you. ;)

I am really shocked though about the numbers between the two
cars. I assumed the TL would be substantially faster than the
Accord. So much for assuming.
 

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Nice write-up! With regards to modding the Accord to make it faster or almost as fast as the TL, I dunno folks, maybe I'm getting old, but I'm leaving my my wife's Accord totally stock. Aside from the obvious fact that I don't want to sleep on the couch for messing around with my wife's brand-new car, I'm beginning to wish that I had left my Altima stock (for noise reasons, mostly). Yeah, I know, I know, it's sacrileage :)
 

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Yeah but the TL looks better. :p

Put that into excel and calculate how the ladies will respond to the TL compared to the Accord. It seems to be able to calculate everything.
 

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To me, the main deficit of the Accord is in handling, not straight-line performance. And that may be correctable with antisways and better shocks and tires.

In the US, the difference between a car that can top out at 155 versus 150 just isn't particularly important...
 

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I agree with your power numbers - when looking at the Accord vs the TL, I immediatlely figured that the TL's higher power output would be negated by its weight.

Let me add some of my own thoughts comparing an Accord 6MT to the TL 6MT. In this case, the power numbers you give are still valid. However, the TL gives you more than just refinment and luxury for your $7000. You get:

- LSD in the transmission
- HID
- 4 piston Brembos up front, larger (but still crappy) solid disks in the back
- Wider tires (235s vs the AV6's 215's)
- Noticably tighter suspension.
- Much better stereo & speakers, w/ a sub (Acura uses Bose)
- Two more doors ;)

I bought the AV6, but there have been a few I times have regretted not buying the TL - mostly when I've needed to transport 4 adults around. The styling is a matter of personal taste, and I admit I like the AV6 coupe better than the TL.

If you can do the work yourself, you can probably raid the TL parts bin and add all of the above for ~ $4k - $6k. Having done that, you'll have a car with all the power of a TL, but that will handle and brake better because of the lack of 200lbs. However, you'll never have the resale that the TL will have, because you never get your money out of mods. Its a tough choice.
 

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Nice writeup steve! I love reading analysis like this... Lol!

If you have time, maybe you can also analyze the 6speeds?
 

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Newbie question, so does this mean the TL and the Accord are built on the same platform?
 

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Short and sweet! LOL

Nice in depth analysis. So SteVTEC, are you going to allow this spreadsheet into the wild so others can play Car God? ;)
 

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well 2 things steven

1. lxv6guy is not our "veteran track whore"! that title belongs to me, "torquie" the first person on here to run a 14.7 @ 97mph by letting the tranny shift at 6,500rpms! :eek:

2. I'm curious to see you do the same analysis with the 6spd accord vtec dynos vs the '04tl 6mt. 217whp vs 223whp, but will weight, and limited slip differential play a crucial role? hmmmm......
 

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Excellent unbiased report Steve. Well done! As others have mentioned I'd love to see the 6MT's compared- how do you take those wider tires and LSD into account? I was considering (when my warranty goes out) putting the TL LSD into my car, I'm hoping it'll be worth it (maybe they'll be a better aftermarket option by then).
 

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Mag racing taken to a higher level

Not to crap on this thread or anything but I can't believe you actually think this means anything in the real world. For the "zillion" factors your software takes into account there are a zillion more that would apply in the real world. Very nice and tidy results for mag racers to talk about though. Unfortunately they don't mean anything when you take it to the track.
 

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Re: Mag racing taken to a higher level

cibalom said:
Not to crap on this thread or anything but I can't believe you actually think this means anything in the real world. For the "zillion" factors your software takes into account there are a zillion more that would apply in the real world. Very nice and tidy results for mag racers to talk about though. Unfortunately they don't mean anything when you take it to the track.
yeah, your right. those are best-case-sinario-cold-weather/low humidity times.
 
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