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Old 4th April 2010, 23:59   #16
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Guys the figures posted above are wrong.
Attached is the figures for the D segment sedans
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Old 5th April 2010, 02:06   #17
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Originally Posted by holysmoke View Post
Guys the figures posted above are wrong.
Attached is the figures for the D segment sedans
Wow, now I know why you are gobsmacked. Accord's 11.76 to 100 is slow as hell. That is in entry level C-Segment territory. The Camry doesn't fare much better either.

Edmunds, a US car magazine known for its slowest performance times among the mainstream magazines, got a 9.1 second 0 - 96 kph and a 13.3 0 -120 kph time for the similar 177hp 5 speed automatic US Accord. 9 second 0 - 96 times are the norm for cars in that segment like the Accord, Camry, Malibu, Altima etc. We can't even accuse the ACI testers of not being able to shift because these are automatics.

I don't think ACI is lying. So, how is the Superb so much faster than the automatic Accord? I don't know, but it's got to be the transmission and the gearing.

DSG cars are typically slightly faster than their manual counterparts and if a previous poster's times are correct for the Manual Accord (9.19 to 100 which is practically the same as the DSG Superb), we can probably assume the DSG Accord, if it had existed, would be right up there with the Superb too.

Last edited by tacho : 5th April 2010 at 02:09.
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Old 5th April 2010, 11:56   #18
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Originally Posted by tacho View Post
Wow, now I know why you are gobsmacked.

I don't think ACI is lying. So, how is the Superb so much faster than the automatic Accord? I don't know, but it's got to be the transmission and the gearing.
Exactly. But does the transmission and gearing make SO much of a difference? The Accord has 10% more power and is lighter, and still the Superb literally smokes it in the times. What about the torque?
Does the fact that the engine is turbocharged make a difference? Could it be such that it shows x horsepower on paper but actual effective horsepower is more (since it is a turbo)?
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Old 5th April 2010, 12:06   #19
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While the power/torque output, gearbox affect the speed/acceleration, it also depends on the engine design itself.
Some engines can produce good peak power but do take time to get there (EX: Optra 1.8, Acceent 1.6) while some other engines may produce relatvely lesser peak power output but are revy and can get to the peak powerband pretty quickly (ex: Ford 1.6 ROCOM, OHC 1.5).
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Old 5th April 2010, 14:03   #20
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Can someone please clarify if you meant acceleration or top speed???

Lets just imagine theoretically an engine "A" of 1.6 ltr capacity produces 100bhp for a car with the lowest drag coeffecient and the least rolling resistance possible.

If you are after top speed you will need a tall final drive and well spaced gear ratios.
If you are after accceleration you will need a short final drive and well spaced gear ratios.

So as far I would think the final drive would be the most critical component.
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Old 5th April 2010, 14:12   #21
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Quote:
Lets just imagine theoretically an engine "A" of 1.6 ltr capacity produces 100bhp for a car with the lowest drag coeffecient and the least rolling resistance possible.

If you are after top speed you will need a tall final drive and well spaced gear ratios.
If you are after accceleration you will need a short final drive and well spaced gear ratios.
I think the right ratio would be the one that lets the car achieve its aerodynamic top speed close to its redline in top gear.

EG : The OHC VTEC maxes out around 185-190 (true speed) but the 5th gear @7100rpm is good for close to 250kmph.

Now if you change the final drive from 4.058 to 4.928, you will run out of gears at 207kmph (which is still above the top speed of the vehicle) but at the same time you benefit from a shorter overall gearing.

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Old 5th April 2010, 14:30   #22
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Put an 80kg driver in each car and the p/w difference is right down to around 25 hp/ton.

But I agree that 9.95 vs 10.8 is a huge difference. At those power levels, traction is a big issue and the Veyron's AWD helps immensely, and the Atom definitely lost a few tenths of a second on manual gear changes compared to the Veyron's ultrafast DSG (or some variation).
I've already mentioned that traction is also a factor. Even so, an AWD Atom would still find it difficult to beat 9.95 due to its lower torque to weight ratio, gearing, aerodynamics and lack of sheer power which comes into picture as the speed increases etc.

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But these are two cars on opposite ends of the spectrum. I was hoping you would come up with some 'normal' cars with similar drivetrains.
Exactly, you cannot judge a cars performance just based on its power to weight ratio. Which is why you're asking me to compare cars with similar drivetrain coz power to weight doesn't mean anything without help from all the other factors.

If power to weight was the ultimate factor, it should not make any diff, what car you're going up against as long as your ptwr is higher. But it doesn't work that way.

I've got another example for you. Verna 1.6 petrol vs Verna 1.5 diesel. I've got the file on the other system at home. Shall post the acc times later. You will be surprised to see the acc of the diesel even though it has a slightly lower power to weight ratio. The petrol doesn't even stand a chance.

Shan2nu

Last edited by Shan2nu : 5th April 2010 at 14:41.
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Old 5th April 2010, 14:36   #23
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Wow, now I know why you are gobsmacked. Accord's 11.76 to 100 is slow as hell. That is in entry level C-Segment territory. The Camry doesn't fare much better either.
Thats bcoz the Accord is a 5 speed regular automatic with tall gearing. The manual version does 100 in the low 9s or late 8s. The superb on the other hand is using the 7 speed DSG which is quicker than a manual and is using pretty short/close gear ratios. Hence the huge difference.

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Last edited by Shan2nu : 5th April 2010 at 14:39.
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Old 5th April 2010, 16:20   #24
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Quote:
Originally Posted by holysmoke View Post
Exactly. But does the transmission and gearing make SO much of a difference? The Accord has 10% more power and is lighter, and still the Superb literally smokes it in the times. What about the torque?
Does the fact that the engine is turbocharged make a difference? Could it be such that it shows x horsepower on paper but actual effective horsepower is more (since it is a turbo)?
I think you should find an Accord in your town and run your car against it. I am more interested in why the manual Accord is so much faster than its automatic counterpart. Does anyone really believe the AT Accord is only as fast as a Fiesta 1.6? I have driven the Ikon and a Jetta Diesel DSG in India (both 11.xx times to 100) according to ACI and the AT Accord in the US. The Accord felt much faster.

Quote:
Originally Posted by Psycho View Post
Can someone please clarify if you meant acceleration or top speed???

Lets just imagine theoretically an engine "A" of 1.6 ltr capacity produces 100bhp for a car with the lowest drag coeffecient and the least rolling resistance possible.

If you are after top speed you will need a tall final drive and well spaced gear ratios.
If you are after accceleration you will need a short final drive and well spaced gear ratios.
Don't know what you mean by well-spaced gear ratios but one well-geared gear is enough to hit top speed.

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So as far I would think the final drive would be the most critical component.

Hey Shan2unu, so you are not going to take him apart for calling the final drive the most critical for top speed? J/K

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Originally Posted by Shan2nu View Post
If power to weight was the ultimate factor, it should not make any diff, what car you're going up against as long as your ptwr is higher. But it doesn't work that way.

I've got another example for you. Verna 1.6 petrol vs Verna 1.5 diesel. I've got the file on the other system at home. Shall post the acc times later. You will be surprised to see the acc of the diesel even though it has a slightly lower power to weight ratio. The petrol doesn't even stand a chance.

Shan2nu
Looks like the only thing we disagree about is the definition of the words 'most important factor'. I already explained what I meant by it.


Quote:
Originally Posted by Shan2nu View Post
Thats bcoz the Accord is a 5 speed regular automatic with tall gearing. The manual version does 100 in the low 9s or late 8s. The superb on the other hand is using the 7 speed DSG which is quicker than a manual and is using pretty short/close gear ratios. Hence the huge difference.

Shan2nu
A manual Accord is in Superb TSI DSG territory. An automatic Accord is in Fiesta, Palio 1.6, Esteem 1.3, Ikon 1.6 territory. You don't have a problem with that?
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Old 5th April 2010, 16:46   #25
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Hey Shan2unu, so you are not going to take him apart for calling the final drive the most critical for top speed? J/K
He was only talking about performance wrt gearing alone and not overall. So to achieve a given top speed, you do need a certain amount of tallness to the gear (depending on the car), or else you will end up with a car capable of doing 200kmph but runs out of revvs in top gear at 180kmph.

But there is a limit to how tall you can make the gearing, which is why i used the OHC VTEC example that is geared to do 250kmph@7100 in 5th but maxes out at 185-190kmph since it doesn't have the power or aerodynamic properties to overcome the resistances beyond those speed.

When you compare the stock 4.058 FD to the aftermarket 4.928 FD, the 4.928 is more complete wrt performance as it lets you hit your top speed while improving acceleration. You could also keep the FD stock and alter the gear ratios to achieve the same results (maybe make the gears closer as well, so that the engine never drops too low when you shift)

The only drawback with a shorter gearing is that it will affect your fuel economy as you will be driving at a relatively higher rpm at a given cruising speed.

Quote:
Looks like the only thing we disagree about is the definition of the words 'most important factor'. I already explained what I meant by it.
Yup, i never said ptwr doesn't help. Its just that i give equal importance to all the factors affecting performance.

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A manual Accord is in Superb TSI DSG territory. An automatic Accord is in Fiesta, Palio 1.6, Esteem 1.3, Ikon 1.6 territory. You don't have a problem with that?
No i dont, bcoz i know the Accord's A/T transmission is not efficient. The gearing is too tall for it to gain an advatnage over the manual, and the less you talk about the shifting time, the better.

If the Accord had a DSG box and was still doing 11.7, that would be something to worry about.

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Old 5th April 2010, 16:53   #26
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Anyway, this is ACI's test of the Honda Civic 5 speed AT. Not sure how tall the Civic's gearing is
Honda Civic Petrol Review

0 - 100 9.59 (Accord 11.76)
0 - 140 18.58 (Accord 23.69)

It's not even funny
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Old 5th April 2010, 17:08   #27
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0-100 in 9.5 is not the A/T, its the M/T. Thats a typo. You can check the timings for the M/T.

In the data page, they've mentioned weight as 1210kgs (which is the M/T), the A/T is 1240kgs. They've just typed "Automatic" where it should have read "Manual".

http://www.hondacarindia.com/civic/Specifications.html

I've test driven the manual as well as the auto versions of the Civic and the drop in performance is evident when you drive.

Shan2nu

Last edited by Shan2nu : 5th April 2010 at 17:26.
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Old 5th April 2010, 18:14   #28
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Quote:
Originally Posted by Shan2nu View Post
0-100 in 9.5 is not the A/T, its the M/T. Thats a typo. You can check the timings for the M/T.

In the data page, they've mentioned weight as 1210kgs (which is the M/T), the A/T is 1240kgs. They've just typed "Automatic" where it should have read "Manual".

Honda Car India :: Civic

I've test driven the manual as well as the auto versions of the Civic and the drop in performance is evident when you drive.

Shan2nu
Well, that makes sense then
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