Are V6-Engined Midsize Sedans Way Over The Top?

[trollbait]

Originally Posted by SteveMak

Porsche's 718 base has a 2.0L turbo flat four, delivers 300 hp and 280 ft-lbs of torque that comes on early and stays pretty flat. Reviewer rave about how good it is... without needing to qualify it, as in "this is a GREAT engine... for a 2-liter, I mean."

The torque response of turbos is different than that of a naturally aspirated engine, and this results in a different feel to the driver, which some prefer.

Turbos can be fun, and they can be fuel efficient for those willing to drive them in such a manner. But my main point is that they can get good fuel economy ratings is because the official tests use light acceleration that doesn't ramp up the turbo boost. The way most people drive will ramp up that boost, and they won't see much improvement in fuel economy over a larger NA engine.

In other words, a 2L turbo gets good fuel economy on the test, because the test cycle drives the car as if it has only half the accelerator pedal travel. Which results in the engine only being driven like a 2L without a turbo.

[SteveMak]

trollbait: I agree that driving style make a colossal difference in fuel economy. I also don't put much faith in EPA fuel economy numbers. I look at Fuelly's reports to see what others are getting in real-world economy.

What I think you're saying, is that a turbo, in and of itself, does not save fuel. I agree. In fact, putting a turbocharger on an engine will always burn more fuel (assuming the same engine, with and without turbo)! The only way to get a turbo to save fuel, is to make the engine smaller so that it burns less fuel when it doesn't need a lot of power -- that is, when the turbo's boost is minimal or nil. Once the turbo kicks in and the boost (turbo-induced inlet pressure) goes up, then so does the power and the fuel consumption.

I suspect you already know all this. I'm just using more words to clarify possible misunderstanding other readers might have.

[Draigflag]

Turbo's are mainly for performance gains, but that doesn't mean they can't be good on fuel, it's nice to have a choice. Acceleration can still be brisk, using low end torque and early gear changes, engine doing very little work. Then the Brutal acceleration is just a pedal away when you want some fun.

Having an engine with no turbo is just dull, very frustrating and tiring having to rev the engine to make progress, and tiring having to change gear more often rather than just increasing boost by applying more throttle.

And back to the op, are V6 engines overkill in sedans? I've sort of changed my mind thanks to Alfa, 2.9 V6 biturbo with an epic 510 bhp. Oh boy...

[trollbait]

Originally Posted by SteveMak

trollbait: I agree that driving style make a colossal difference in fuel economy. I also don't put much faith in EPA fuel economy numbers. I look at Fuelly's reports to see what others are getting in real-world economy.

What I think you're saying, is that a turbo, in and of itself, does not save fuel. I agree. In fact, putting a turbocharger on an engine will always burn more fuel (assuming the same engine, with and without turbo)! The only way to get a turbo to save fuel, is to make the engine smaller so that it burns less fuel when it doesn't need a lot of power -- that is, when the turbo's boost is minimal or nil. Once the turbo kicks in and the boost (turbo-induced inlet pressure) goes up, then so does the power and the fuel consumption.

I suspect you already know all this. I'm just using more words to clarify possible misunderstanding other readers might have.

Of the official n rating systems out there, the EPA comes closest to predicting real world results. The average MPG reported on Fuelly is really close to EPA combined for most models.

Agree on the rest.

Originally Posted by Draigflag

Turbo's are mainly for performance gains, but that doesn't mean they can't be good on fuel, it's nice to have a choice. Acceleration can still be brisk, using low end torque and early gear changes, engine doing very little work. Then the Brutal acceleration is just a pedal away when you want some fun.

Having an engine with no turbo is just dull, very frustrating and tiring having to rev the engine to make progress, and tiring having to change gear more often rather than just increasing boost by applying more throttle.

And back to the op, are V6 engines overkill in sedans? I've sort of changed my mind thanks to Alfa, 2.9 V6 biturbo with an epic 510 bhp. Oh boy...

Let you in on a secret, the Prius gets most of its efficiency gains through engine downsizing. The electric side helps, but its main job is to overcome the smaller engine's lack of performance so people will buy the car.

A turbo or super charger can be used to also down size the engine while keeping performance at an acceptable level for buyers. The issue, at least in the US, is that most have never driven a turbo before. Coming from a V6 or even a larger 4 cylinder, they don't realize the turbo can be sucking down more fuel for the same level of acceleration.

With higher fuel prices, turbocharging has been more common in the EU, and most drivers likely understand how to drive a turbo for efficiency.