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Old 4th December 2015, 10:16   #3451
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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Originally Posted by sachinchavan View Post
No. Turbocharging and cylinder direct injection are distinct technologies. We are used to seeing them as a combined technology because the modern Diesel engines have both. Please note that Diesel engines are by default direct injection.

However direct injection is relatively new in gasoline (petrol) engines. Turbo charging is too, but not as new. While turbocharging is essentially using the heat of the exhaust gases, direct injection makes the turbo more effective (see below) beyond many other benefits.

To quote from the article linked below, "When the fuel is sprayed in, the hot air vaporizes the fuel and the process actually reduces the temperature of the mixed charge in much the same way water injection did. The result is that modern GTDI engines can run with higher levels of turbo boost and higher compression ratios with less risk of knock. More boost and compression mean higher torque output from the engine. Thus, smaller displacement engines can produce more torque at lower rpms resulting in better drivability. With this kind of engine behavior, drivers feel less need to rev the engine to get the performance they expect and fuel efficiency is improved. Direct injection also has an immediate impact on efficiency and emissions by more precisely metering fuel and leaving less unburned fuel going out the exhaust."

You can read here for more on it: http://www.autoblog.com/2009/05/28/g...ected-engines/


Wikipedia page on Gasolene direct injection explains it in lot more technical details. It says, "Direct injection may also be accompanied by other engine technologies such as turbocharging or supercharging, variable valve timing (VVT) or continuous variable cam phasing, and tuned/multi path or variable length intake manifolding (VLIM, or VIM)."


Coming to Tata's Revotron, it is turbocharged but does not Direct injected It has the conventional Multipoint fuel injection (MPFI). Source: http://m.overdrive.in/features/tata-...ine-explained/

I think it's the same with Linea's T-Jet. The Ford Ecoboost however, is a direct injection engine.
Ok, thanks for sharing these. Could you also explain the need for the traction on/off button in GT TSI. Why is it given and why there is no on/off for ESP?
When should we switch off the traction control? and how does it help?
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Old 4th December 2015, 10:28   #3452
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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Ok, thanks for sharing these. Could you also explain the need for the traction on/off button in GT TSI. Why is it given and why there is no on/off for ESP?
When should we switch off the traction control? and how does it help?
From my limited knowledge with using TC (other members please correct me if I am wrong)

Say one of the wheels is stuck in snow or a ditch or something line that. With TC switched ON the ECU will cut back on power if it finds the wheel/wheels is/are "spinning".

The way to get out of this mess is to switch between D and R quickly so that the rocking motion can get the wheel unstuck. Usually the shift lock prevents the gears to be changed from D to R. But at very low speeds (car is stuck so negligible speed) the shifter will move from D to R and R to D to give that rocking motion to get out of the mess.

So trick if to turn off TC and use repeated D-R and R-D with a gentle push of the Gas pedal.
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Old 4th December 2015, 10:39   #3453
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Default Re: Polo 1.2L GT TSI in Jaipur

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Why have they given an option to switch off traction control and then why not ESP? Why and when should we switch off traction control?
Absolutely no idea! I just found the differences - I am not aware of all the whys/hows.

I think someone else has tried to answer this - in this or other thread - I do not remember.

I can guess (Experts - please correct me if I am wrong) as and when you feel that having traction control will actually make the tyres turn in un-desirable way, you can put it OFF. I am not able to give an example. I think someone had mentioned that the car had started to spin or the tyres had started to spin and the driver put OFF the traction control to get back control!

See how confused I am! Sorry!
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Old 4th December 2015, 10:42   #3454
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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Originally Posted by freedom View Post
From my limited knowledge with using TC (other members please correct me if I am wrong)

Say one of the wheels is stuck in snow or a ditch or something line that. With TC switched ON the ECU will cut back on power if it finds the wheel/wheels is/are "spinning".

The way to get out of this mess is to switch between D and R quickly so that the rocking motion can get the wheel unstuck. Usually the shift lock prevents the gears to be changed from D to R. But at very low speeds (car is stuck so negligible speed) the shifter will move from D to R and R to D to give that rocking motion to get out of the mess.

So trick if to turn off TC and use repeated D-R and R-D with a gentle push of the Gas pedal.
Oh ok, I was under the impression that it has to be switched off for driving in tracks if you need some noise from the tyres.

Ok so my understanding of the three terminologies in a single liner -

1)ABS - activates only at the time of braking, reduce the wheels getting locked by pressing and releasing the brake calipers/piston for may be like 50 times in a second.?

2) ESP - Active always (not just at the time of braking like ABS), any skid/wheel lock up will be reduced by applying varying pressure of brakes in different wheels individually automatically.?

3) TC - Activates at the time the tyres lose traction and it cuts off the power to that tyre making it inactive? So its a feature which will take in charge once the ESP cannot control the car when slipped?

All seems a bit interlinked and confusing. Anyone pl clear the above doubts.
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Old 4th December 2015, 10:49   #3455
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

One more doubt I have been having is that in automatic cars, if the battery dies off, can we start the car by pushing it in neutral and then suddenly shifting it to D mode while moving?

Will it start the car ?
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Old 4th December 2015, 12:31   #3456
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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One more doubt I have been having is that in automatic cars, if the battery dies off, can we start the car by pushing it in neutral and then suddenly shifting it to D mode while moving?

Will it start the car ?
DSG and AMT are manual boxes with addon hardware and software so theoretically this should work.
That said, DSG is an expensive piece of equipment, I would not want to risk unless in an emergency.

For Torque Converter type ATs there is a clear instruction in owner manual to not drive in Neutral as this can damage the transmission. I don't know why.. buts its clearly mentioed in i10 AT user maual

CVT - No clue what so ever.

Given a choice, I would jump start the car than try to push and get a rolling start.
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Old 4th December 2015, 13:08   #3457
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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You said combined. I meant pure city(with intense traffic). Yes I truly agree that once you show some long free stretches, it will be much better.
Uh, how about this? My GT TSi does roughly 50 kilometres every day. Through thick Mumbai traffic. I travel from Mulund to Andheri (that should give you an idea of the traffic. If not, the devil is called JVLR). In peak traffic, the mileage hovers around 11.5-12.

A couple of dashes to Pune and back, and I've got 21 to the litre both times. For the record, the car is at roughly 10k kms in 5 and a half months.

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Originally Posted by petrol_power View Post
....if the battery dies off, can we start the car by pushing it in neutral and then suddenly shifting it to D mode while moving?

Quote:
Originally Posted by freedom View Post
DSG and AMT are manual boxes with addon hardware and software so theoretically this should work..
NO! In no way should you attempt a dhakka start on a DSG. Read the manual. Rolling in Neutral is bad for the gearbox, especially when the car is switched off. Jumpstarting is the only option.


Cheers!
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Old 4th December 2015, 13:39   #3458
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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Originally Posted by petrol_power View Post
One more doubt I have been having is that in automatic cars, if the battery dies off, can we start the car by pushing it in neutral and then suddenly shifting it to D mode while moving?

Will it start the car ?
Quote:
Originally Posted by freedom View Post
DSG and AMT are manual boxes with addon hardware and software so theoretically this should work.
Both in the DSG and AMT, the gear shifting and clutch engaging has to be done by the mechatronics and AMT respectively. These require electricity to operate. Shifting from N to D mode will not put the gear box into a gear without a battery. So, the only way to start these cars is to jump start using an external battery.

Last edited by graaja : 4th December 2015 at 13:40.
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Old 4th December 2015, 15:08   #3459
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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Originally Posted by Cartman View Post
NO! In no way should you attempt a dhakka start on a DSG. Read the manual. Rolling in Neutral is bad for the gearbox, especially when the car is switched off. Jumpstarting is the only option.
Yes, bad practice to do a dhakka start.

Quote:
Originally Posted by graaja View Post
These require electricity to operate. Shifting from N to D mode will not put the gear box into a gear without a battery. So, the only way to start these cars is to jump start using an external battery.
Got it. Makes sense.
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Old 4th December 2015, 16:12   #3460
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

Since we are talking of gear shifts, I would like to share something which happened 2 days ago. My wife was driving the GT and decided to pull over to left. Don't know what went in her mind, but she changed the gear from D to P (D->N->R->P) while the car was slowing down. The car make the clinking sound (which I think is of the pin engaged in P mode) before coming to a halt. Now I have following doubts:

1. Why does the car allow gear shift gear from D to R when it is in forward movement? Can we do that at high speeds too (accidentally)?
2. Anything damaged? That moment I skipped a heartbeat. However the car is running fine from past 2 days and I am concluding that all is well.

I know very unlikely, but has anyone faced such an incident?

Last edited by manish84 : 4th December 2015 at 16:14.
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Old 4th December 2015, 18:37   #3461
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Originally Posted by manish84 View Post
Since we are talking of gear shifts, I would like to share something which happened 2 days ago. My wife was driving the GT and decided to pull over to left. Don't know what went in her mind, but she changed the gear from D to P (D->N->R->P) while the car was slowing down. The car make the clinking sound (which I think is of the pin engaged in P mode) before coming to a halt. Now I have following doubts:

1. Why does the car allow gear shift gear from D to R when it is in forward movement? Can we do that at high speeds too (accidentally)?
2. Anything damaged? That moment I skipped a heartbeat. However the car is running fine from past 2 days and I am concluding that all is well.

I know very unlikely, but has anyone faced such an incident?
I also had a similar incident few days back. Shifted from D to P while at around 5kmph. Heard a low metal clinging sound but the car came to a halt. I too was worried about the gear box but it is running smoothly (drove at least a 1000kms after that incident). So I too hope everything's fine.
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Old 6th December 2015, 07:52   #3462
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Yes, bad practice to do a dhakka start.


Got it. Makes sense.

So tell me, what happens when RTO tows your GT on a bad day
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Old 6th December 2015, 10:41   #3463
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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So tell me, what happens when RTO tows your GT on a bad day
Also after switching off the engine,I am unable to remove the key if not slotted in P mode. Also I cannot move from P to any other mode once the key is removed.! Is it an error or its the standard procedure? If so, in P mode, if they tows the car, won't the transmission go for a toss?

Someone pls guide.
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Old 6th December 2015, 10:45   #3464
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They don't tow automatic cars. Cars with automatic transmission are just clamped.
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Old 6th December 2015, 11:01   #3465
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Default Re: Volkswagen Polo 1.2L GT TSI : Official Review

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Also after switching off the engine,I am unable to remove the key if not slotted in P mode. Also I cannot move from P to any other mode once the key is removed.! Is it an error or its the standard procedure? If so, in P mode, if they tows the car, won't the transmission go for a toss?
Correct me if I am wrong.

Automatic cars comes with a shift lock button which allows to change from P to any other mode even when the car is not on. Using this shift lock button to shift from P to N allows automatic car to be towed as it brings the car into neutral. Some cars have a cap over this button which need to be removed before using this button while some have a direct access to this button.

Learned about it in a hard way when our automatic fortuner refused to start and had to be loaded in a flatbed.
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