Nissan to introduce gas engine as efficient as TDi

[TDI2000Zim]

Look Ma, no hybrids:

http://mobile.reuters.com/article/idUSKCN10P0IK

I still love diesel, but if they pull this off, I may fall in love with gas.

 

[VeeDubTDI]

That completely leaves regenerative braking off of the table. If I were to go back to gas, it would have to be a plug-in hybrid. Imagine if they combined this variable compression technology with a good hybrid system!

 

[GoFaster]

This probably isn't a great match to a hybrid powertrain because of the cost. The Toyota hybrids generally have been using an Atkinson cycle together with a fixed high compression ratio. They top up the acceleration using the hybrid system which means the engine doesn't have to do it and then there's no need for variable compression ratio.

Hybrids aren't the ultimate solution to everything, and this looks like a decent solution for non-hybrids. They could have picked a better application - They're going to put it in yet another CUV (yawn) tied to a CVT (yawn).

 

[turbobrick240]

Sounds interesting. I wouldn't want to own a gen. 1.

 

[Powder Hound]

From the article:

...The turbo-charged, 2-liter, four-cylinder VC-T engine averages 27 percent better fuel economy than the 3.5-liter V6 engine it replaces, with comparable power and torque...

So, definitely NOT an apples to apples comparison, not by any stretch of the imagination. You have to ask how much of the mileage increase is due to a smaller engine, and how much is due to turbocharging, and then see if there is any significant savings owing to variable compression. Then weigh just that portion against the cost (including future warranty costs, which are not known at this time).

Given the disparity of the two compared items, it sounds like a whole lotta hype for little direct gain to me. Nissan, go back and try it again. And give us the real numbers this time, not ones hidden in a lot of other clutter.

Cheers,

PH

 

[bhtooefr]

I'm under the impression that the variable compression is intended to increase low-load efficiency, while also allowing more boost to be crammed in at high-load.

However... what was wrong with approaches like Mazda's wide-authority VVT approach to this (Atkinsonizing, so expansion is maintained through the compression loss, although effective displacement is not), and just using some more displacement? Seems like the simpler approach that's more durable, and the turbocharging is all about improving part-load efficiency, which Atkinsonization can do too. Granted, looks like this engine also has some sort of VVT authority to Atkinsonize, but...

 

[GoFaster]

There's many ways to solve any given engineering problem.

The cam-timing-based Atkinson cycle but with a fixed mechanical compression ratio is still knock-limited at full load. Mazda's combustion system differs from others, which allowed that fixed compression ratio to be pretty high, but the original Skyactiv engines were not turbocharged, which limited their power output, and they've been criticised for that. There's a new one that is turbocharged but they're still going to be knock-limited at full load.

The Prius engine has a high mechanical compression ratio ... but that engine would be a lame duck without being attached to the hybrid system that it's designed for.