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Originally Posted by audioholic 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.