4 Speed Automatic vs 5 or 7 Speed

[Jchuacl]

U misunderstand me, I'm just adding another dimension into the discussion. This is a car forum isn't it, we should be discussing more on car stuffs rather than non car related matters.

 

My reasoning is very simple, it is how the engine/gearbox work hand in hand, and not just specifically focusing on the number of gears only.

 

 

i think you are getting out of point, just for the sake of replying.

we should take for example, comparing Mark X (4-spd vs 7-spd) or Euro R (4-spd vs 7-spd).

you are not apple-to-apple comparison, instead you are comparing engine to engine when the topic is discussing about gears.

i think i will stop here.

 

[20G]

u desperately burn mid night oil searching internet articles on how to drive car wanting to prove others wrong then come here trying to best others with ur monkey know how ? go sign up a class3 course before sprouting nonsense boy

 

sorry im not like u, u pathetic lil' arse. i dun need to search into the internet. i can AFFORD to buy a car and try out diff tunings.

 

i think u misunderstood me when i ask u to read up more. i did not get my info fr the net. i TRY them out physically.

 

the reason why i asked u to READ more is because i dun think u can afford a decent enough car to experience ecutek race rom or flat foot shifting.

 

abt the thing 'i cant drive'. think ur still squating by the drain watching guppies swim when i got my lic.

 

u replies certainly tells ur a TOTAL NOOB when it comes to car.

 

try harder, troll.

 

 

Edited April 3, 2012 by 20G

[Ooosh]

Mind enlighting me what's the difference in performance?

 

I assume the rx8 you are talking about have the exact same specs and the only difference is the gearbox.

 

As far as i can remember 4speed feels like the engine is very lethargic but 6speed feels like the engine has been treated with steroids

 

One is 06 reg and the other 07 reg engine specs same no mod

Edited April 3, 2012 by Ooosh

[Happily1986]

U misunderstand me, I'm just adding another dimension into the discussion. This is a car forum isn't it, we should be discussing more on car stuffs rather than non car related matters.

 

My reasoning is very simple, it is how the engine/gearbox work hand in hand, and not just specifically focusing on the number of gears only.

 

i have been thinking about your statement. You feel that cars with torque curves available at relatively lower revs tend to benefit more from gearboxes geared towards (pun intended) shorter ratio. I am picking something in your statement, i just can't put a finger on it now. If possible, do elaborate on your PoV. Thanks

[ER-3682]

Bro.. Sorry to say.. Many people are claiming the DSG gearbox is problematic.. Is it true?

Today newspaper said V.W. S'pore is recalling 8000 cars to retify the DSG.

[Wishcumstrue]

Next time at the top of Sheares bridge to Rochor, slow to 50 km/h at the top (I am sure your Wish will auto downshift), then let your Wish cruise down the slope without braking. Tell me as your Wish gain speed going down, does it upshift.

 

Here's what I can share based on my ride's behavior:

 

1) On down-ward slope at 50kph, the old Wish AT will remain in D or lockup when brake is not touched.

 

2) Only down-shift to 3rd when brake is applied momentarily.

 

3) As it gains speed downslope, AT will up-shift again to final drive on down-slope if no brake is applied for further 4 sec.

 

4) If tap brake, AT will go to 2.

 

 

 

 

[Pokyman]

Mine is the 7 spd wish, does it harm the GB when i always manually down the gear in order to accelrate harder?

[VellfireS]

Today newspaper said V.W. S'pore is recalling 8000 cars to retify the DSG.

According to them , it's a software upgrade.. Seems like our case of water ponding.. Hmmm.... [rolleyes]

[Victorco]

the DSG recall is for firmware upgrade so that when the MU Fail it wont prevent the car from moving off, so that the owner can drive back at Gear2 to workshop for fix at least better then stuck and wait for VW to tow back.

 

as for gearing, more dont = better, less dont = good.

 

is all about your engine and the ratio of your final drive.

 

if yours is a honda type-r engine you will wan a close ratio gear box to maintain high RPM each upshift.

if yours is a conti or normal engine you will wan a high ratio gear box to maintain low rpm each upshift.

 

so different engine diff box type.

 

as for manual if you are good in your shift you can practically shift without clutching in. that call rev match gear shift. basically it wont damage your gearbox nor your engine.

[Jchuacl]

It's all about driveability.

 

For my own car, if I were to slow down from 100-70km at 6th gear, I'll need to skip 1 gear to 4th in order accelerate again. Imagine for a car with automatic gear, it would probably would not have the

intelligence to drop 2-3 gears immediately and would be caught with flat footed.

 

For a car with high torque at low revs, 1 gear down would be sufficient to get decent pick up.

 

 

i have been thinking about your statement. You feel that cars with torque curves available at relatively lower revs tend to benefit more from gearboxes geared towards (pun intended) shorter ratio. I am picking something in your statement, i just can't put a finger on it now. If possible, do elaborate on your PoV. Thanks

 

[Happily1986]

It's all about driveability.

 

For my own car, if I were to slow down from 100-70km at 6th gear, I'll need to skip 1 gear to 4th in order accelerate again. Imagine for a car with automatic gear, it would probably would not have the

intelligence to drop 2-3 gears immediately and would be caught with flat footed.

 

For a car with high torque at low revs, 1 gear down would be sufficient to get decent pick up.

 

i would like to hear your piece on gear ratios. particularly the part where you say that short gear ratios benefit cars with early torque bands more.

[Jchuacl]

I rem that I mentioned close ratio would be needed for high rev engines so that engine speed will be at the optimal torque range.

 

i would like to hear your piece on gear ratios. particularly the part where you say that short gear ratios benefit cars with early torque bands more.

 

[Calm]

Interesting debates I'm reading here. I have no idea about all this technical stuff. All I know is 7 speed SHOULD be better than 5 or 4.. in terms of FC n performance.. Isn't it?

 

How about giving some examples of which car is 4 spd, 5 spd, 6 spd and 7 spd. Share your experience on why that particular car is good or no good. I believe a lot of readers with no car knowledge will really appreciate that.

 

Just my two cents worth.

 

: )

[Happily1986]

I rem that I mentioned close ratio would be needed for high rev engines so that engine speed will be at the optimal torque range.

 

ok, i think we need to make something clear first. Different engines will require different shift points because as you have mentioned before, different engine have different power curves. For e.g. old school VTECs tend to unleash most of their horses at very high rpm which is not true for some other cars (peak of power curve is realised at much lower rpm point) At the point, i would like to stress that shift point is also dependent on the way the driver operate the throttle as well. If you become heavy footed (short of doing a kick down), for sure your gearbox will drag gear and delay the shift point. So, both the high rev and non high revving engines will have delayed shift points. Conversely, if you try to feather the throttle, the shift points of almost engines will be advanced.

 

My point is, regardless of whether the peak of the power curve occurs early or late, the shift point has everything to do with the manner the driver controls the throttle, not the gear ratio.

 

As i mentioned before, the gear ratio is most easily observed on the tachometer. A short gear ratio is one such that, the tachometer needle falls by a short rpm range after shifting, thereby still confining the operation of the engine in the optimal rev range. A long gear ratio is one such that, the tachometer needle falls by a noticeably longer rpm range. The engine is no longer in the optimal rev range and there is some lethargy because the engine needs to work itself up before getting back into the optimal rev range.

 

 

Lets look at the above dyno chart taken from a B20 block. It is clear that this is a high revving engine as the peak of the power curve is realised very late at 8000 rpm. Assuming the redline is 9000 rpm, with short gear ratio, you will expect that the gear will reach say 8000 rpm and then drop to 6000 rpm (or higher/lower depending on short the gear ratio it is) The B20 is still in the peak region of its power curve.

 

 

This is a dyno chart from a 1.4 TSI Twin Charged. It is obviously not as high revving as it realises it peak power at 5500rpm, nowhere as stratopheric as the B20's. if you incorporate a short gear ratio on this same engine, it will probably reach shift point at 5500 rpm on hard driving granted that redline is probably at 6500 rpm. The tachometer needle drop says to about 4000 rpm or by the same rpm range if you incorporate the same gear ratio as that for the B20 in our academic discussion. Where the shift points are attained and to which exact rpm the needle drops to are different for the two engines but the extent of drop is the same. Both are still close ratio and both did the job of keeping the power plants running in the peak power region(s).

 

So why should you say that only high revving engines will benefit more from close gear ratios and by extension, better throttle response and pickup?

[Happily1986]

One more thing. For optimal throttle response, one should achieve gearing to keep oneself in the peak power region NOT the peak torque region. For the academic bla bla, read more about it here

 

bla bla bla

 

and another bla bla bla source. bla bla bla 2

Edited April 4, 2012 by Happily1986

[Jchuacl]

We are talking about driving on the road and not drag racing isn't it? If I were to drive in peak power region, then I'll only need 3 gears, 1-2-6. For automatic cars, the issue with pushing up to the peak power is the the transmission fluid temp will go up by about 3-4 degrees (based on what I used on a Toyota for a quick shift from 1-2-3). Do it again, and the temp will rise again. And this can lead to premature fluid lifetime degradation as every 10 degrees rise will decrease the lifespan by half.

 

For engines which have peak torque from low to mid revs, they don't really need to have close ratios for driveability on daily road conditions. Close ratios does come with a problem with high rpm at cruising speed which is not desirable for most cars as it's really noisy.

 

 

If you want to talk about racing, optimal gearing will depend on the engine, car's handling, and the track layout andd condition. If you look at 2011 Monza's F1 race where everyone use long gearing ratio for maximum top speed due to 2 long straights on the track, Vettel actually opted for close ratio gearing, sacrificed top speed , and still managed to get pole position , and win the race easily.

 

 

One more thing. For optimal throttle response, one should achieve gearing to keep oneself in the peak power region NOT the peak torque region. For the academic bla bla, read more about it here

 

bla bla bla

 

and another bla bla bla source. bla bla bla 2

 

[Happily1986]

We are talking about driving on the road and not drag racing isn't it? If I were to drive in peak power region, then I'll only need 3 gears, 1-2-6. For automatic cars, the issue with pushing up to the peak power is the the transmission fluid temp will go up by about 3-4 degrees (based on what I used on a Toyota for a quick shift from 1-2-3). Do it again, and the temp will rise again. And this can lead to premature fluid lifetime degradation as every 10 degrees rise will decrease the lifespan by half.

 

But gear ratio arguments are precisely either about fuel consumption or POWAAAAH isn't it? You can do with 3 gears but then you see, what about speed management? By sticking to 3 gears, either you compromise on top speed by cutting back on the final gear ratio or you are going to have 3 gear ratios to take care of the entire range of speeds. Not very feasible, is it?

 

For engines which have peak torque from low to mid revs, they don't really need to have close ratios for driveability on daily road conditions. Close ratios does come with a problem with high rpm at cruising speed which is not desirable for most cars as it's really noisy.

Thats why most gearbox offers a final gear ratio which is usually tall to save fuel. A tall gear ratio also implies that the crusing rpm will be low. How low again depends on how tall the gear ratio is.

 

If you want to talk about racing, optimal gearing will depend on the engine, car's handling, and the track layout and condition. If you look at 2011 Monza's F1 race where everyone use long gearing ratio for maximum top speed due to 2 long straights on the track, Vettel actually opted for close ratio gearing, sacrificed top speed , and still managed to get pole position , and win the race easily.

 

Definitely racing depends on alot more parameters than just gear ratio design/selection. Well since the thread is about gear ratios, i just confined the scope of discussion to gear ratio to make the discussion more constructive, thats all.

 

Honestly with reference to the winning of races, my philosophy is that the winner is likely to be the car/driver that maintain consistently the highest exit speeds. You may argue that the fella who can attain the highest speed(s) on the straights will be able to cut precious milliseconds but how much time does the average car spend in the straights as compared as in the bends? I feel this is a situation that calls for more than just scrutiny of the gear ratio employed. How fast you can take the corner depends on tire fatigue, tire wear rate, weight distribution (front/rear), camber angle, throttle control in the bend, corner entry speed and so on and so forth.

 

In a nutshell, i feel that because cars tend to slow down more in the bends, the actual residence time expended in the bends is substantially more than the residence time in the straights. Academically, if you want to win, you should reduce the residence time(s) in both the bends and the straights. There is a limited extent to how much time you can shave off in the straights (how tall can your final gear ratio go?) It is more prudent to milk and shave time spent in the bends. The car with the least residence time in the bend with distance being conserved (duh!) necessarily mandates that its average speed in the bends should be the highest.

Edited April 5, 2012 by Happily1986