Infiniti's variable compression, thoughts?

[carbonBLUE]

http://www.roadandtrack.com/new-cars...ression-turbo/

​Infiniti's new turbo gasoline engine can change its compression between 8:1 and 14:1, offering diesel power and efficiency without the emissions.

thought this was really cool but since it is a new tech, i question reliablity

[00NissanNinja]

I'll be patiently waiting for there reveal at the paris auto show. Sounds very interesting to me. I'd love to see it in practice. There are a lot more parts and bearings which means more points of failure, plus more controls that an ecu will handle. Sounds interesting though. Nissan usually makes pretty reliable engines from my experience (but the things hooking into the engine not so much).

[mulekr1]

I don't like Nissan at all (Not SR, RB NOTHING ) but this is so cool holy shit.
To bad its only for 4 cylinders but still this is sick.

[themadscientist]

Just more moving parts to break. No thanks. I'll take my FJ20 or my RB26 before I mess with that crazy thing.

[fang_gt86]

Add this with a CVT tranny and you get the ultimate seamless power delivery?

[rice_classic]

I'm usually hopeful that new/better technology will prove out and be reliable.

The VC-T, if executed well and proves to be highly reliable and effective, could put gasoline engines in direct competition with power of diesel engines but without the drawbacks.

[reni]

How long before "VC-T just kicked in yo"

[Teseo]

Too soon junior

[krayzie]

Someone's gonna install a VC-T controller that will keep the engine fixed at 14:1.

[themadscientist]

Who would do such a terrible subversive and secretly awesome thing?

[chaoskaze]

I just saw a video of infiniti's Q45 in Japan with active suspension that came right after it was banned in F1 (1991??) Lol Quess what everyone said about that car in turns of reliability.

The video also included the celica with active suspension...& driver said it was faster then All Trac, forget the time thou.


That being said they are saying that they might unban active suspension in the coming years for F1.... So maybe we will see a light on that again.


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[themadscientist]

Complex things have more failure points; there's no way around that. Great engineering can mitigate failure through optimal tolerances, quality materials and thorough failure analysis and corrective action, but the more parts the more problems.


In an effort to increase some metric, be it fuel economy, max power or better power profile, etc, fine, but I prefer reliability over peak bragging numbers. My 33 year old Skyline's engine is still working. The turbo needs to be replaced and the 8-bit engine management system is getting tore out, but the engine itself is still tight after all these years.


It was pretty cutting edge in its day, but nothing like the Ubertech things under the hoods of modern cars and is greatly overengineered as far as strength. Things are getting lighter and shaved down to just strong enough these days and while that can lower weight and reduce cost it hurts reliability.

[krayzie]

Originally Posted by chaoskaze

I just saw a video of infiniti's Q45 in Japan with active suspension that came right after it was banned in F1 (1991??) Lol Quess what everyone said about that car in turns of reliability.

The video also included the celica with active suspension...& driver said it was faster then All Trac, forget the time thou.


That being said they are saying that they might unban active suspension in the coming years for F1.... So maybe we will see a light on that again.


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Just before the Japanese stock market crashed, the glory days...

[ame="https://www.youtube.com/watch?v=uXUN6dkvwz0"]1989 消���イテク アクティブサスペンション - YouTube[/ame]

[serialk11r]

This adds 2 extra bearings to the reciprocating assembly, which I don't really like.

My feeling is that this is kind of a silly direction to develop an engine, because the point is that you can run more boost at the lower compression ratio, except you can just simulate lower compression ratio with virtual Atkinson cycle and crank the boost up with some good intercooling to increase power. 265hp is not groundbreaking, this thing probably doesn't even hit 1 atmosphere boost.

On the economy side, 14 or even 15:1 compression ratio has already been done by Mazda, and while the Skyactiv engines get good fuel economy, I don't think it's a big enough step up to be worth this system.

If it were up to me, a 2L engine was the target for fuel consumption reasons and 265hp is the horsepower goal, I would give it a static 14:1 compression ratio and Nissan's existing VVEL system, with a big turbo pushing close to 2 bar boost. The engine prevents knock by reducing load once the turbo spools. A VVEL engine at 60% VE with 1.8 bar boost should be getting 330ish Nm of torque which is more than enough.

Alternatively you can drop the compression ratio down to 12:1 and have more power than the Subaru FA20DIT, or match the Subaru's compression ratio of 10:1 and run even more boost. The second you bring boost into the picture the options widen a lot, and these variable displacement, variable compression ratio things become less useful.