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Old 10th July 2014, 10:52   #136
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by humyum View Post
It'll go down in history as 'just another car'. JUST ANOTHER ENGINE. Ecoboost is out of the box, Revotron, really not.
The 1.2L engine in the Swift is, similarly, just another engine. Yet it sells. The Tata engine's turbo would make it infinitely more driveable than a NA engine. All the low end torque available would be enough for somebody who loves to drive to pick it up over any Maruti.

Last edited by Aditya : 15th July 2014 at 10:13. Reason: Editing in line with modifications to previous post
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Old 10th July 2014, 11:18   #137
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I am an Automotive Engineer, I know what 'driving modes' in a turbo charged 'can' do. You assumption if laughable that only because a F10 BMW M5 has it, it cannot be trivial. It is not that difficult.

With all due respects, i would like to know more about it. The last time i drove a car with this feature was a 528i and really wondered how the engine made so much of difference in these modes. Only thing i noticed was a difference in the engine rpm while up-shifting. What is the real technology behind it ?

Last edited by Aditya : 15th July 2014 at 10:14. Reason: Editing in line with modifications to previous post
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Old 10th July 2014, 11:26   #138
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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3) All cars will not do all things well. .
Exactly the point. Unfortunately here that is what the company promises of. Performance, economy, loads of features, best quality, space, less price and what not. How? No one knows. Just like how they promised a 1L rupee Nano. Of course its not their fault if material costs increase. However, why create a hype and then disappoint people? Promise that its going to be a 1L car, then start of with a slightly greater 'introductory' price, and slowly increase prices. After that even if they loaded it with features it wouldnt sell.

Here in this case, can the people who justify the conservative power output please tell me how much benefit it will give to FE? And can anyone how a Turbocharger will help better FE in a 'petrol' engine? AFAIK in case of a diesel engine it 'improves' combustion and prevents incomplete combustion of fuel. The power gain in a diesel engine is a result of complete combustion of the diesel fuel and a little bit of increased fuel flow as the speeds increase.
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Old 10th July 2014, 11:47   #139
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Here in this case, can the people who justify the conservative power output please tell me how much benefit it will give to FE? And can anyone how a Turbocharger will help better FE in a 'petrol' engine? AFAIK in case of a diesel engine it 'improves' combustion and prevents incomplete combustion of fuel. The power gain in a diesel engine is a result of complete combustion of the diesel fuel and a little bit of increased fuel flow as the speeds increase.
When you turbocharge a small engine, at low RPMs it is still a small engine as the turbo isn't compressing the inducted air. So the engine isn't using a lot of fuel when not required. Contrast that with a large NA engine which sucks fuel even while idling.
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Old 10th July 2014, 12:05   #140
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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When you turbocharge a small engine, at low RPMs it is still a small engine as the turbo isn't compressing the inducted air. So the engine isn't using a lot of fuel when not required. Contrast that with a large NA engine which sucks fuel even while idling.
That is known friend, but compare it to a NA 1.2l engine and point out the benefit it offers apart from the torque, wrt fuel economy(since it is expected that the engine will be highly efficient). The justification you gave is apt for an engine like the ecoboost compared to a 1.6L NA petrol giving out the same power output. My simple question is, what benefit will a 1.2TC engine give in comparison with a 1.2L NA engine?
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Old 10th July 2014, 12:17   #141
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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That is known friend, but compare it to a NA 1.2l engine and point out the benefit it offers apart from the torque, wrt fuel economy(since it is expected that the engine will be highly efficient). The justification you gave is apt for an engine like the ecoboost compared to a 1.6L NA petrol giving out the same power output. My simple question is, what benefit will a 1.2TC engine give in comparison with a 1.2L NA engine?
I don't expect an increase in fuel efficiency, but as I wrote before, there would be a difference in driveability because of better torque being available at lower RPMs.
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Old 10th July 2014, 12:20   #142
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by audioholic View Post

Here in this case, can the people who justify the conservative power output please tell me how much benefit it will give to FE? And can anyone how a Turbocharger will help better FE in a 'petrol' engine?
Turbo does the same job on an engine regardless of fuel type and that is to inject more air at lower RPMs. Why would a petrol engine not benefit from this? It will make more power and torque at lower RPM thereby reducing the need to rev the engine, or frequent downshifting, thereby increasing FE. Of course, you can drive a turbo petrol spiritedly and loose that FE advantage easily. Diesel has higher combustion efficiency than petrol, but if you compare a petrol NA engine with a turbopetrol of the same size, the turbo one will enable a relaxed yet brisk drive.
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Old 10th July 2014, 12:46   #143
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by audioholic View Post
1) Exactly the point. Unfortunately here that is what the company promises of. Performance, economy, loads of features, best quality, space, less price and what not. How? No one knows. Just like how they promised a 1L rupee Nano. Of course its not their fault if material costs increase. However, why create a hype and then disappoint people?

2) Here in this case, can the people who justify the conservative power output please tell me how much benefit it will give to FE? And can anyone how a Turbocharger will help better FE in a 'petrol' engine? AFAIK in case of a diesel engine it 'improves' combustion and prevents incomplete combustion of fuel. The power gain in a diesel engine is a result of complete combustion of the diesel fuel and a little bit of increased fuel flow as the speeds increase.
1) They did it with Indica and even Safari. Nano was a different case altogether. Started off with a very tough target and the engineering challenges were many considering the final cost they were targeting. This was one reason for delay.
Look at what they have done this time, offering a tech which almost nobody else has in small car segment. Already the cars were spacious, had NVH better than most of current competition. May be I am expecting a bit too much, but almost all cars are claimed to be doing too much without being actually good at it. E.G. Duster is sold as an SUV !!! A car based on an old platform. It seems we are over expecting from Tata ( or may be I am in an appreciation mood for Tata! )

2) Lower relative power output (for turbocharged motors ) resulting from lower boost/small turbo gives the flexibility to offer benefits in low end torque and in mid range. This is applicable to petrol and diesel engines. The gains are actually helpful in day to day drives and improves driveability. This improved driveability coupled with smart gearing results in relatively less gearshifts improving FE and ease of drive. Smart, optimized gear ratios are required as tall gearing can blunt the available performance and short ratios will result into too many gear changes. The basic advantage of Turbo is similar for petrol or diesel motors.

Last edited by aaggoswami : 10th July 2014 at 12:49.
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Old 10th July 2014, 13:17   #144
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by blacksport View Post
Contrast that with a large NA engine which sucks fuel even while idling.
From experience, Turbo petrols aren't really all that efficient at idle. I feel that a turbo charged engine, when off boost drinks the same amount of gas. Its only when you get moving and when you are at optimum rpm, the efficiency benefits of a turbo over naturally aspirated are seen.

I can't think of a better example than the Mitsubishi Cedia. A 2l block thats incredibly efficient. Owners have reported consistent city cycle numbers of 10-11kmpl. Off course, its not so great on the highway but still good for the size of the block.

As for small turbo petrol engines available to us, Fiat's T Jet is no great shakes and the same story with the Ford Ecoboost. VW's TSI seems to be the most efficient.

I have managed to exceed the Arai fuel economy claim on my car but boy did it require some careful driving. Really defeats the purpose of buying a turbo petrol.

I once thought this whole turbo petrol revolution will end economy concerns. I don't feel anything has changed.

I really look forward to this Revotron engine. I hope the "felt" power exceeds the claim.

Last edited by sandeepmohan : 10th July 2014 at 13:21.
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Old 10th July 2014, 13:23   #145
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

Just waiting for the official review on this particular engine as they claim three state of tunes for performance. Hope there is a perceivable difference in the 3 modes given.

Hope they have plans to boost up this engine to larger capacities and install in their other portfolio rather than pasting the same.

Anurag.
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Old 10th July 2014, 13:43   #146
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by anandpadhye View Post
Turbo does the same job on an engine regardless of fuel type and that is to inject more air at lower RPMs. .
Yes sir, it injects more air into the engine. What is not being talked about is fuel Just injecting more air will not do. The engine should maintain the AFR ain't it? Thats the only thing I was asking. In case of diesels, a NA diesel engine can take in more air and fuel to give you power, and in lower Rpms it can offer better FE also. Thats not the case with a petrol engine. Though the TC does the same work, the result is different.

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Originally Posted by blacksport View Post
I don't expect an increase in fuel efficiency, but as I wrote before, there would be a difference in driveability because of better torque being available at lower RPMs.
Okay I have no further questions in this regard!


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Originally Posted by sandeepmohan View Post
From experience, Turbo petrols aren't really all that efficient at idle. I feel that a turbo charged engine, when off boost drinks the same amount of gas. Its only when you get moving and when you are at optimum rpm, the efficiency benefits of a turbo over naturally aspirated are seen..
.
Exactly what I am doubtful about. Indeed a turbo petrol will be a wonderful performer, but I doubt it will be anywhere that efficient. Let the ARAI figures come out.
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Old 10th July 2014, 13:49   #147
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by a4anurag View Post
Hope they have plans to boost up this engine to larger capacities and install in their other portfolio rather than pasting the same.

Anurag.
The Revotron series comprises a total of 5 engines:

Quote:
Dr Tim Leverton, President and Head, Engineering Research Centre, mentioned how there were about five engines in totality that the Revotron family will cover, from small capacity engines to larger capacity engines for various different purposes. He also mentioned that these engines will power Tata’s current and future range of compact hatchbacks, compact saloons and midsize sedans in the next few years.
Quote:
This new engine family will offer a variety of engines in the coming months from a sub 1-litre engine to a speculative bigger sub 2.0-litre engine. The latter might also be used for export applications.
Source: http://www.zigwheels.com/news-featur...-engine/17711/
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Old 10th July 2014, 13:52   #148
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by audioholic View Post
Here in this case, can the people who justify the conservative power output please tell me how much benefit it will give to FE? And can anyone how a Turbocharger will help better FE in a 'petrol' engine? AFAIK in case of a diesel engine it 'improves' combustion and prevents incomplete combustion of fuel. The power gain in a diesel engine is a result of complete combustion of the diesel fuel and a little bit of increased fuel flow as the speeds increase.
First, I'm not going to justify the conservative power output. There is no need to justify anything here. According to the latest official specs, the engine makes 90PS@5000rpm and 140Nm@1750-3500rpm, at least in the Zest (the Bolt may have it's peak output restricted to 85PS, not sure).

It is indeed the second highest power and torque output (in its class) for a 1.2 lit. engine at the moment. It's true that the VW 1.2 TSI churns out 105PS and the smaller Ford 1.0 EcoBoost does even better with 125PS. However, the cars they power aren't in the same segment, unless VW decide to introduce a well priced manual version of the TSI. While Ford may (it's still "may") use the EcoBoost in competing cars in the future (next generation Figo/Ka and sub-4m Figo/Ka sedan), it would probably come in a detuned version that will produce less power (85 ~ 100 PS).

Two, the engine can indeed be tuned to produce more power. But the old TA-65 gearbox cannot safely handle any torque output more than 140 Nm. This is the reason why even the 1.4 DiCOR and it's improved version (1.4 CR4) have their torque limited to 140Nm, which has also restricted their power to 70PS, despite the DiCOR/CR4 featuring a 16 valve DOHC architecture with a VGT.

Compared to the 1.4 DiCOR/CR4, the 1.2 Revotron is a low tech engine. It's only an 8 valve SOHC design, and I believe it comes with an FGT. Not only that, the base engine is the Xeta's, which itself is derived from the geriatric 475DL block that powered the diesel Indica when it came out.

So churning out the power and torque figures it currently does is a fair achievement for the low tech Revotron, whose base is derived from an old diesel engine. It's not a high tech, cutting edge engineering masterpiece that rivals the Ford or Volkswagen engines. Neither does it pretend to be one, Tata's marketing efforts notwithstanding.

It can produce more power if necessary, but needs a new gearbox. Tata did indicate that the new 'boxes are under development, without giving a timeframe. So it's the company's lethargy on gearbox development that is to be primarily blamed for the "low" power output.

The "low" output notwithstanding (I type low within quotes because 2nd highest in its class isn't actually low), how many people are going to queue up for a high performance engine in a Tata car? Look at what happened to the 1.4 lit. 90PS Safire they plonked into the Vista. It flopped miserably and they had to discontinue it soon. Even the 90PS VGT Quadrajet version of the Vista failed to find enough takers, and they went back to a 75PS FGT version for the Vista Tech and now, Bolt.

A turbocharger "increases" fuel efficiency because it enables a lower capacity engine to produce similar torque (& power) as a higher capacity one (other factors remaining the same), whether the engine runs on petrol, diesel or any other fuel. And the torque curve is a particularly good indicator of fuel efficiency. A wide and flat torque curve starting from a low-ish rpm generally indicates good FE (in Indian conditions, at least).

The 1.2 Revotron's torque curve seems to be exactly that - wide and flat, despite being restricted to a peak of 140Nm because of the gearbox. Take the 1.4 CR4. It has the same low peak torque of 140, again because of the old gearbox. Even the 936cc Beat diesel has a better peak torque. But the wide and flat torque curve of the 1.4 CR4 gives the cars it powers a very useable torque band through most of the rev range, and hence excels at FE.

The switchable power modes notwithstanding, I have a feeling the real surprise is going to be the 1.2 Revotron's real world FE figures. Tata petrol engines have been very poor on FE till now. I do know this, as we had a 1.2 Xeta for 7 years. The Revotron seems to be set to change all that.

On the topic of engine output, why is Tata being singled out here? There are other manufacturers whose engines produce ordinary outputs on paper. Toyota's 1.5 lit. petrol engine produces only 90PS, the same as the smaller 1.2 Revotron. I haven't seen anyone bash that engine solely on its numbers. That's not the only one. The famed manufacturers of driver's cars (Ford and Fiat), who have such a big fan following on Team-BHP, perform poorly when it comes to the output of their 1.2 petrols. The Ford 1.2 Duratec produces only 71PS, and the Fiat 1.2 Fire churns out a meager 68PS. Why is there not much criticism on those numbers, which make those relatively heavy driver's cars very sluggish to drive? Even Volkswagen and Nissan/Renault only give us 3-cylinder 1.2 petrols producing between 75 and 77 PS. No one bashes those solely on their outputs.

Yet, we have Tata presenting a 90PS 1.2 turbo-petrol with switchable modes in the same class, and people bring out the sledgehammer to demolish it even without getting behind the wheel. Why this kolaveri? Shouldn't one at least wait to try the engine before handing out its obituaries?

I don't understand the unduly harsh (and somewhat unnecessary) criticism of the Revotron's output here. I'm all for expressing oneself freely, and I have been quite a harsh critic of Tata Motors myself. But that was all constructive criticism, meant to make the lethargic folks at the company understand where they're falling short. They seem to be making a genuine effort at improving now, and I would give them the chance to do so, and wait and watch and hope they do improve. I wouldn't simply dismiss them outright, without even getting to experience the improved efforts they seem to be putting in place.

Last edited by RSR : 10th July 2014 at 14:05.
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Old 10th July 2014, 13:59   #149
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Yes sir, it injects more air into the engine. What is not being talked about is fuel Just injecting more air will not do. The engine should maintain the AFR ain't it? Thats the only thing I was asking. In case of diesels, a NA diesel engine can take in more air and fuel to give you power, and in lower Rpms it can offer better FE also. Thats not the case with a petrol engine. Though the TC does the same work, the result is different..
What AFR they want to maintain depends on if this is a regular indirect injection engine or a direct injection (e.g. the TSi) which can run lean. With turbo it will be a little easier to implement lean burn I think, though I am certainly open to learn if it's not the case.
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Old 10th July 2014, 14:01   #150
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Default Re: Tata Motors introduces 1.2L turbo-petrol Revotron engine

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Originally Posted by sandeepmohan View Post
From experience, Turbo petrols aren't really all that efficient at idle. I feel that a turbo charged engine, when off boost drinks the same amount of gas. Its only when you get moving and when you are at optimum rpm, the efficiency benefits of a turbo over naturally aspirated are seen.

I can't think of a better example than the Mitsubishi Cedia. A 2l block thats incredibly efficient. Owners have reported consistent city cycle numbers of 10-11kmpl. Off course, its not so great on the highway but still good for the size of the block.

As for small turbo petrol engines available to us, Fiat's T Jet is no great shakes and the same story with the Ford Ecoboost. VW's TSI seems to be the most efficient.

I have managed to exceed the Arai fuel economy claim on my car but boy did it require some careful driving. Really defeats the purpose of buying a turbo petrol.

I once thought this whole turbo petrol revolution will end economy concerns. I don't feel anything has changed.

I really look forward to this Revotron engine. I hope the "felt" power exceeds the claim.
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Originally Posted by audioholic View Post
Exactly what I am doubtful about. Indeed a turbo petrol will be a wonderful performer, but I doubt it will be anywhere that efficient. Let the ARAI figures come out.
The whole point of adding a turbocharger is not to get more power/torque/FE from the same engine. Adding a turbocharger, you can have a smaller engine instead of a larger one. See how a 1L Ecoboost engine replaced a 1.6L engine who would otherwise had done duty in the Ecosport. Now, this 1L Ecoboost engine gives a higher FE than the 1.5L NA engine in the same car. So you see what you get, right? More power, more torque and more FE than an "equivalent" NA engine. In essence a TA engine does not replace a NA engine of the same size, but a NA engine of a higher size.
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