Home » The Nissan Variable Compression Ratio Engine Everyone Got Excited About Was Maybe Too Good To Be True

The Nissan Variable Compression Ratio Engine Everyone Got Excited About Was Maybe Too Good To Be True

Nissan Engine
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When Nissan unveiled the first mass-produced variable compression ratio engine back around 2016, there was a lot of buzz about what this engine could do. Cut to seven years later, and a few VC-Turbo engines are under NHTSA investigation for catastrophic mechanical failure. How did we get here?

For those familiar with the four-cycle internal combustion engine, the sequence of intake stroke, compression stroke, combustion stroke, and exhaust stroke should ring a bell. Today we’re honing in on that second stroke to give you a little more context on the how and why behind Nissan’s Rube Goldberg machine. An engine’s compression ratio is the ratio between combustion chamber volume when a piston’s at the bottom of its stroke versus at the top of its stroke. It’s also often one of the major keys to efficiency, power, and reliability.

Vidframe Min Top
Vidframe Min Bottom

A higher compression ratio typically increases thermal efficiency, though if compression ratio is too high, you can start to run into detonation issues when the fuel-air mixture ignites due to sheer compression before the spark plug lights it off. Needless to say, this is bad for your engine’s health.

When an engine is turbocharged, it’s not uncommon to see manufacturers lower compression to fight detonation, since a turbocharger is an air compressor itself. The downside? While at a steady cruise, turbocharged engines are typically out of boost, meaning a higher compression ratio under those conditions could theoretically boost efficiency.

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Cue Nissan working on a variable compression ratio engine for decades, and finally getting it into production in 2018. The KR20DDET two-liter turbocharged four-cylinder engine and its little brother, the KR15DDT 1.5-liter three-banger, are currently the only engines you can buy with a variable compression ratio ranging from 8:1 under full boost to 14:1 under exceptionally light load. How do these engines physically achieve that feat? Well, let’s take a look.

Nissan Vc Turbo Bottom End

Sure, the bottom end of this variable compression ratio engine may look massively different than what you’re used to seeing, but don’t panic. Think of what Nissan calls the “multi-link” as just a really fancy standalone big connecting rod end. After all, each one still sits on a crankshaft journal, and each one still uses traditional rod bearings. Because of this, each upper connecting rod, and therefore each piston, moves in the fairly normal reciprocating manner you’d expect from any engine with cylinders and pistons.

Sure, it might be visually confusing since the lower pivot point of the upper connecting rod isn’t centered above a bearing journal, but it technically doesn’t have to be, so long as it can still have a path of movement. When a VC-Turbo engine changes its compression ratio, it doesn’t physically move the crankshaft, it just rotates this diamond-shaped link by a few degrees.

Nissan Vc Turbo Actuation

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So, how is this link rotated? Well, it all starts in the bowels of the engine. Deep, deep down sits an electric motor with a gear reduction drive that pushes or pulls an arm. This arm rides on a shaft beneath the crankshaft, and when the arm moves, the shaft and all the lower connecting rods on it move as well. Lower connecting rods? Ah, yes, those connect up top to the aforementioned diamond-shaped links around the crankshaft, and that rocking motion changes the height of the pistons relative to the crankshaft, altering the compression ratio.

If this all sounds hideously complex, you aren’t wrong. There is a considerable quantity of moving parts involved in shifting a VC-Turbo engine from malaise-era-crank-up-the-boost compression to incredibly high compression, and in a brief on a safety investigation into engine failures, NHTSA claims that several technical changes have occurred throughout production due to potential failures of the variable compression ratio KR15DDT and KR20DDET engines:.

Based on an analysis of the VOQ and FR data, ODI has identified three (3) vehicle models with elevated variable compression engine failure rates. These includes 2021-2023 Nissan Rogue equipped with KR15DDT engine; 2019-2021 Nissan Altima; and 2019-2021 Infinity [sic] QX50, both equipped with the KR20DDET engine. During discussions with Nissan, ODI learned that they have attempted to address main bearing and L-link damage/seizures on the KR15DDT and KR20DDET engines by introducing multiple manufacturing processes changes over time.

Well, the Rogue is Nissan’s best-selling vehicle in America by a longshot, with almost 400,000 sold between the start of 2022 and the end of this September, when Nissan’s most recent quarterly sales report came out. The Altima is a hot seller too, although it came with two engines during the affected model years. As we previously wrote in The Morning Dump, a massive Nissan recall could be coming for these engines, and something of this scope certainly wouldn’t be cheap.

 Infiniti Qx50 006.jpg

Adding insult to injury, the fuel economy of the two-liter VC-Turbo four-banger doesn’t seem that good. Despite the advanced tech, an all-wheel-drive Infiniti QX50 only scores an extra single MPG combined over an all-wheel-drive four-cylinder BMW X3 or Lexus NX 350, and scores one MPG worse combined than an Audi Q5. I’ve personally seen disappointing figures, and Car And Driver took a much deeper dive into dissecting the middling fuel economy.

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One unexpected standout in the data: good old-fashioned rounding. To arrive at the integer values that are reported on the window stickers, both the Audi and the BMW round up to 25 mpg while the Infiniti rounds down to 26. The other main factor limiting the EPA rating of the Infiniti is the QX50’s lack of stop-start functionality.

Yeah, it seems like Infiniti could’ve reached desired EPA fuel economy targets with just automatic stop-start and some other vehicle-level or powertrain-level tweaks.

22 Nissan Rogue 18

In the end, Nissan’s VC-Turbo variable compression ratio engine technology is interesting, but it might be more headache than it’s worth. Although it’s not radically different from a standard piston-type internal combustion engine, it has just enough extra moving parts that failure, it seems, is an option.

(Photo credits: Nissan, Infiniti)

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Eric Smith
Eric Smith
5 months ago

Great article explaining the complex/not-complex VC-Turbo in a manner even a fool like me can grok. Gotta say though, that last line is where I mentally said, “and that’s why I’m a proud subscriber and loud-mouthed about it”.

And just a general off-topic comment that I hope Jason is back to complain about some Nissan taillights in record time. With the segue complete and so now that I’m on that topic, if you haven’t already made a donation, please do. Finally, if any of you have any power in the USA to change it so we may live in a country where when we are #2 highest spent per-capita in tax-funded insurance on top of #1 spent on private insurance that our fellow Americans don’t have to start charity drives to cover the cost of care, etc, well if you have that power, it’d be awesome for you to exercise it and magic us into healthcare nirvana. Thank you all and apologies for the off-topic. I will endeavor to improve.

Last edited 5 months ago by Eric Smith
Manuel Verissimo
Manuel Verissimo
5 months ago
Reply to  Eric Smith

Alternative solution: ship Torch to France in a music instruments crate. I’ll deal with the paperwork so he has healthcare.

Angular Banjoes
Angular Banjoes
5 months ago

This was an interesting concept, but I still remember saying “no chance this is reliable” when I saw it for the first time. Too many bearings, too much linkage, just too many oily parts in general, and since this is Nissan, too many opportunities for disaster. Maybe Honda or Toyota could have made this work, but no way I’d trust a novel design like this from a company like Nissan.

Ron888
Ron888
5 months ago

This is the first i’m hearing of this.It’s a little surprising their fuel economy isnt great.
I wonder if it’s because turbos + variable valves (which several brands use) can be set up to achieve a similar end result?
Or maybe others have more tech overall? Adding different solutions together would give better results.Maybe Nissan are lagging there?

Captain Muppet
Captain Muppet
5 months ago
Reply to  Ron888

1% reduction in emissions is a big target for an engine technology improvement, from the viewpoint of an engine designer and/or an OEM. But it’s very hard for a customer to notice a 1% improvement.

Especially if your engine is carefully optimised for the government drive cycle that the owners completely ignore.

What we need is an eco driving mode that limits throttle and speeds to mimic the drive cycle, then everyone would get great mpg. Or everyone would turn it off like they do with stop/start because it turns out that while drivers like complaining about mpg they aren’t willing to sacrifice anything at all to improve it.

Manuel Verissimo
Manuel Verissimo
5 months ago
Reply to  Captain Muppet

I think most electronic throttles do limit transient speeds for better emissions. My 2004 BMW does at least, unless I use sport mode.

Captain Muppet
Captain Muppet
5 months ago

It limits the throttle enough to be annoying, but no where near enough to get performance down to WLTP levels.

Manuel Verissimo
Manuel Verissimo
5 months ago
Reply to  Captain Muppet

Fair enough

Aron9000
Aron9000
5 months ago

This is why I still subscribe to the big naturally aspirated V6 school of thought if you want more scoot in your family sedan or suv. Currently driving a 2014 Lexus ES350. 2GR-FE V6 in that car with the six speed automatic is such a sweethart combo. No turbo lag, good off the line torque yet it really pulls hard on the highway, its like a small V8 but with way better fuel economy. Would absolutely blow the doors off an Altima with the mickey mouse turbo 4 cylinder under recall. Around town Im getting 21 to 24. Straight highway is 31ish, did 33 when I kept it below 75.

If I cared that much about fuel economy and drove a lot of miles Id be thinking Prius instead, the normal 3 cylinder and 4 cylinder turbos dont give you that great of a bump in gas mileage to put up with all the shennanigans once they are out of warranty. Im talking pretty much any Hyundia/Kia 4 cylinder turbo built in the past 10 years blowing up at low miles(and then the dealer denying your warranty claim), this Nissan engine, honda’s turbo 4s have oil burning issues as well.

Its like we have completely regressed in reliabilty/durability to cheat the epa test for an extra 2mpg. Same thing with GM putting cylinder deactivation on all their v8s. Yeah that 2 extra mpg really saved you a bunch of money when you have a $6000 engine repair right after you just paid the damn loan off.

Tristan Hixon
Tristan Hixon
5 months ago
Reply to  Aron9000

The Altima with the turbo 2.0 has a 0-60 of 5.9s. Your ES350 with the V6 has a 0-60 of 6.5s. So, no.

That Guy with the Sunbird
That Guy with the Sunbird
5 months ago
Reply to  Tristan Hixon

Damn. 5.9 seconds? No wonder the Altimas are causing such havoc.

VanGuy
VanGuy
5 months ago
Reply to  Tristan Hixon

You’d rather have an Altima than a Lexus, based solely on a 0.6 second difference in 0-60 time?

They’re both below 7 seconds; what does it matter at that point?

Tristan Hixon
Tristan Hixon
5 months ago
Reply to  VanGuy

I never said that. It was in response to his statement that his ES350 would blow the doors off of an Altima with the turbo four pot.

VanGuy
VanGuy
5 months ago
Reply to  Tristan Hixon

My bad. Misinterpreted.

Utherjorge
Utherjorge
5 months ago

Throw in the typical Nissan subprime crowd, where regular maintenance doesn’t happen, and yeee-hawwwww

Bradillac
Bradillac
5 months ago

Very good article. This is why I come to the site. Thanks.

Electronika
Electronika
5 months ago

First of all, very interesting story, I never knew what made the VC engine different so thanks for that.

It seems to me that other then forced induction and direct injection, none of the “advanced” ideas to make it to market have done anything to really improve the ICE engine enough to really make things better.

They tried and tried to make the rotary work and yes Mazda and a couple of others including NSU and Suzuki did it but it never was the disrupter that it was supposed to be (I have hope for liquid piston but that won’t be a car engine), Mazda also tried the Miller cycle on the Millenia but that was a dead end too, They tried to make the sleeve valve engine work but it didn’t work, The Mazda Skyactive-X engine isn’t living up to its potential, Subaru’s flat engines are becoming a dead end too. Even Ducati’s desmo engines are too expensive and limited for wider adoption.

Turns out a simple 3 or 4cyl <= 2l DOHC Otto or Atkinson cycle engine with direct fuel injection and a turbo charger seems to be the best ICE engine for a simple every day family type vehicle. Is it fun? no! is it sexy? no. but it works and is fairly simple.

Last edited 5 months ago by Electronika
Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Electronika

That’s one way to look at it, but another is that all “advanced” technologies that make it to an acceptable level of refinement and reliability eventually become industry standard and are no longer considered advanced. Think electronic ignition and fuel control and self-adjusting hydraulic valve lifters – off the top of my head, probably the #1, 2, and 3 reasons people can get by treating cars made in the last 30 years as appliances.

On the way to electronic fuel injection, we tried mechanical fuel injection. Whoops.

Electronika
Electronika
5 months ago

but are things like hydraulic vale lifters and electronic fuel injection (I would include multiport fuel injection as well as it was a major evolutionary step from throttle body injection) major deviations from the basic formula? Lets take for example the GM Iron duke. it is an iron block and head, medium displacement, at least at is introduction carbureted, overhead valve, 4cyl engine and made about 80hp about as simple as can be. To compare to a typical engine of today Honda’s L15BE in the CRV and Accord (and many others around the world) is only 1.5l and features an alumnum head and block, DOHC VTEC engine with direct fuel injection and produces 190hp in the CRV.

To get from the Iron Duke to the L15BE there were a lot of evolutionary steps, including several you mentioned like mechanical fuel injection and hydraulic valve lifters. The old saying that we all stand on the shoulders of those who came before us. However, I don’t know if you can make the argument that in order to get from there to here you needed the Willis Silent Knight Sleeve Valve engine or that we needed the Miller cycle engine or many of the other dead ends like the compression ignition gas engine (Skyactive-X). You can also make the argument we didn’t need the Wankel either but without that we wouldn’t have the RX-7 and that would be a shame.. but I don’t think the billions that Mazda, NSU, GM, AMC, Chrysler, AM General, Suzuki and others spent on the 70’s and 80’s Wankel boondogle was worth the RX-7. Or at least it would have been better to have just been more honest and used it for a performance engine and not tried to make it everything to everyone.

But that isn’t what this story is about… This is about Nissan’s VC and I think that is destined to end up with the Silent Knight in the dustbin of automotive “interesting ideas” that were more trouble then they were worth.

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Electronika

I think we’re saying the same thing here: before you industrialize a tech and put in into mass production, it’s really hard to know which techs are going to be hydraulic lifters and which are going to be Willis Silent Knight Sleeve Valves (I had to look this one up. It’s pretty wild, thanks!). When HCCI and SCCI (as I recall, SkyactiveX is SCCI) went into commercial production, that was a “woah, we’re living in the future” moment for guys like me. It was a holy grail in the realm of science fiction for a really long time.

This article and comment section are a BIG nail in the coffin of Nissan’s VC tech because Nissan won’t continue to develop it if it becomes poisonous to their reputation, but what if Nissan had quietly eaten the costs, root-caused the failures, iterated a few new designs and then rolled out something that lasted 200k miles trouble-free? That happens. I know for a fact that other OEMs developed, built, and tested variable compression tech.

Tristan Hixon
Tristan Hixon
5 months ago

My 2010 car doesn’t have hydraulic valve lifters.

AC2DE
AC2DE
5 months ago
Reply to  Tristan Hixon

What car is that?!

Tristan Hixon
Tristan Hixon
5 months ago
Reply to  AC2DE

Honda Fit. I did a valve clearance adjustment about a year and a half ago now. Thankfully, it’s screw adjusters, and not shim and bucket.

Last edited 5 months ago by Tristan Hixon
AC2DE
AC2DE
5 months ago
Reply to  Tristan Hixon

Wow! Even Harley-Davidson (not exactly known for technological advances) had hydraulic lifters on their Evolution engines! (Maybe even earlier, but I don’t have any experience with them…)

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Tristan Hixon

My 1978 motorcycle feels your pain.

Cheap Bastard
Cheap Bastard
5 months ago

“On the way to electronic fuel injection, we tried mechanical fuel injection. Whoops”

I dunno what horrors you had with mechanical injection but FWIW Bosch K-Jetronic was probably the most reliable part of our early to mid 1980s German cars.

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Cheap Bastard

I have actually never owned or even worked on one, but the reputation of mechanical fuel injection suggests that experience isn’t typical.

Try to keep it going, because what you have is a piece of history.

Ron888
Ron888
5 months ago
Reply to  Electronika

In most cases it would be wrong to say dead ends.It’s just that there are many ways to improve IC engines,and many of them overlap in how they do that.VC for example can be replicated (in a fashion) by clever use of turbo and variable timing.
In the end some tech is cheaper to implement than others so it’s not surprising most are choosing the small engine+turbo+etc.It’s likely the best cost solution.

You dont think the skyactive X is very good?I havent heard a lot so far but the numbers seem to be great.Maybe i got some wrong info?

I wish Mazda had gone ahead with the liquid piston engine.Sadly it’s too late now.
Even if it was simple to complete the development and throw it in a car, the end result would be no more efficient than a basic car engine(but with some other minor benefits).
Even highly efficient car engines are facing an uncertain future,so a low efficiency engine is dead in the water.

Hey did you see what happened to Mazda’s rotary powered range extender?From the numbers ive read it’s economy seems to be terrible.Pretty much what you’d expect from an inefficient engine.What were they thinking??

Electronika
Electronika
5 months ago
Reply to  Ron888

Ya everything I have seen with the rotary range extender seems terrible. I don’t know what they were thinking. Rotary for the sake of interesting technology seems like a waste. I wish they would jump on board with Liquid Piston’s technology it seems amazing. I think we will more and more of it once the DOD and DARPA approve it for military generators and drones. That will be the turning point I think.

As far as Skyactive-X I waited and waited when I had my 2015 Mazda 3. I loved that car and planed to buy a replacement when they were talking about it. I thought it was fantastic technology but they put it off and delayed it and then they released the next gen 3 with the same old under powered Skyactive-G series engines. Then I started getting bad reviews in the other limited markets. Now they have no plans to release it in the US. So I went in multiple other directions and didn’t look back.

If it were meeting expectations it would have taken hold by now.

I do agree with you. There are lots of little steps to increase efficiency and we have seen those evolutionary changes, things like variable valve timing, direct injection, the Atkinson cycle, electronic ignition, hydraulic valve lifters and the modern electronic controlled engines. They all have helped.

I think my main point was the VC engine was complicated for the sake of being complicated with minimal return on investment. And for companies tasked with making pedestrian people movers sold to people with poor credit that can’t afford or can’t be bothered with basic maintenance, it isn’t the best idea. Its one thing for a Koenigsegg Gemera to use exotic methods and technology to hit 1400 hp from a 3 cyl engine but you can also count on their buyers to be able to take care of them. It another thing for someone with BAE (Big Altima Energy) to be able to maintain one of these faberge eggs

Ron888
Ron888
5 months ago
Reply to  Electronika

Interesting,I didnt think of the military angle.You’re right,there’s almost certainly a long term market for a power dense engine.

Scottingham
Scottingham
5 months ago
Reply to  Electronika

The problem as I see it with the Liquid Piston engine is that they chew themselves apart way too quickly. For a military drone operation, that’s not a big deal since it’s likely a one way trip. For anything consumer grade, it’s a non-starter and why you don’t seem them now.

Last I looked, they were in the tens of hours range before needing a full rebuild.

Considering the lack of press between then and now, it’s still likely the same issue.

Electronika
Electronika
5 months ago
Reply to  Scottingham

That’s not what I have heard. At least in my aviation circle. From what I hear the army is about to order a stationary generator with the liquid piston engine and there are several aviation examples that both the USAF and DARPA are looking. One is a simple drone and the other is a reconnaissance drone.

I found this article
https://www.hartfordbusiness.com/article/liquid-piston-signs-deal-to-advance-us-armys-power-generation-capacit
Looks like they got at least one contract. But just looking at google results they have something with USAF too.

https://www.globenewswire.com/news-release/2023/10/05/2755430/0/en/LIQUIDPISTON-Hybrid-Power-System-Technology-Awarded-35M-U-S-Air-Force-Contract.html

Captain Muppet
Captain Muppet
5 months ago
Reply to  Ron888

Range extenders in EVs don’t have to get good mpg, they are there to allow you to make infrequent longer trips without having to plug in to recharge. If you’re using the range extender all the time you’ve bought the wrong car for your use case.

The Wankel range extender is smaller and lighter, reducing the impact of lugging around an engine you rarely use. It’s a benefit optimised for a mostly short range use case.

Lally Singh
Lally Singh
5 months ago
Reply to  Electronika

I think the problem is that they’ve added a bunch of stuff exposed to the power stroke of the motor. And that stuff is off angle and spinning at high rates. That’s instead of different parts sitting on an immobile head, which seem to live comparatively happy and safe lives.

Toobs-N-Stuff
Toobs-N-Stuff
5 months ago
Reply to  Electronika

whatever did happen with skyactive-x? I was really excited by the early talk, then it just seemed to disappear…

the idea of a gasoline engine with diesel efficiency at cruise and gasoline HP when needed seems like exactly what is needed (although in reality, the pseudo-Atkinson/hybrid Prius solution seems to be about the best option out there for overall MPG/performance tradeoff.)

Scottingham
Scottingham
5 months ago
Reply to  Toobs-N-Stuff

“Mazda has dropped the pricey SkyActiv-X powertrain variant and all mild hybrid grades from its Mazda3 small car range as part of a model year update that ushers in tech upgrades and a more streamlined model range.”

Soo, too complex/expensive for the rounding error improvements I guess.

Ron888
Ron888
5 months ago
Reply to  Toobs-N-Stuff

I happened to be reading about this last night.It was a surprisingly frustrating exercise!
These were normal car reviews so the efficiency part wasnt talked about a lot.Some said 55mpg was easy,another said a best of 65mpg.Someone amusingly mentioned that it refused to do worse than 50mpg no matter what. IIRC these were mostly UK websites so adjust numbers accordingly.
In the end i gave up finding solid usable comparison numbers.I’m sure it’s possible with more effort.

I cant help but think this was the last gasp for (purely gas driven) economy engines,and that’s sad.
I dont know every technical aspect ,but for sure they’re achieving the holy grail of clean burning ultra lean mixtures.I think the other main factors are also present- low pumping losses and so forth.
They could likely optimize it further but surely those would be small percentages.Its very likely this is the last.

Michael Beranek
Michael Beranek
5 months ago

I’ve always suspected that this idea was too cute by half. It’s hard enough making a bottom end that doesn’t give up the ghost; making it articulated and complicated sure is a path to failure.

Captain Muppet
Captain Muppet
5 months ago

Counterpoint: it’s easy to make a durable bottom end, as long as you don’t make all the bearings as small and narrow as possible because you’re chasing another 0.2% efficiency.

Michael Beranek
Michael Beranek
5 months ago
Reply to  Captain Muppet

I agree with that. Like a start/stop system that chases a small percentage.

Shooting Brake
Shooting Brake
5 months ago

I’ve waiting for this since Nissan unveiled these engines. Super cool idea but Nissan can’t even build a cvt right and they’ve had more practice than just about anyone as they started out pretty early.

Eric Moody
Eric Moody
5 months ago
Reply to  Shooting Brake

Me too. Cool idea, but I knew that it was going to be problematic once implemented. Between this and the Jatco CVT I doubt many will make it much past 100k miles.

Needles Balloon
Needles Balloon
5 months ago

The Nissan Rogue with the VC engine easily has the best fuel economy in its class (non-hybrid compact crossovers) at 33mpg combined; the best anything else gets is 30mpg combined (CR-V 1.5T, Escape 1.5T, RAV4 2.5L), and the class average is ~28.5mpg (FWD models using the most fuel efficient engines). I would consider 10-15% better fuel economy for CAFE purposes than the competition, without having to divert battery capacity or engineering costs for a hybrid model to be a corporate win.

What isn’t a corparate win is having to recall these for possibly expensive repairs, especially after delaying the launch by a year, resulting in worse reviews of the new generation.

I would expect these MPG numbers to hold up better in the real world better than standard downsized turbos, I wonder what owners have been getting.

Ron888
Ron888
5 months ago

Very interesting.
I’ve run into similar issues when trying to find economy numbers for other cars with interesting tech. There don’t seem to be many apples to apples comparisons.

Daniel MacDonald
Daniel MacDonald
5 months ago

Not even a little bit surprised by this, sadly. Maybe if it had been Toyota or Honda, I might have seen it. But this always seemed overly complicated-and for not enough gain-from a company that as near as I can tell has had pretty subpar quality post 2000.

Cerberus
Cerberus
5 months ago

As expected when I first learned they were building them—not just failures (even if it wasn’t Nissan, this is a dumb idea that should never have left a proof-of-concept phase at most, but we’re talking about Nissan here, so there was even less hope it wouldn’t be a disaster), but the little to no real world driving benefit.

Rust Buckets
Rust Buckets
5 months ago
Reply to  Cerberus

Little to no real world driving benefit? Of course it depends on how they program it, but being able to switch from 8:1 all the way to 14:1 on the fly introduces huge fuel economy and horsepower potential.

Utherjorge
Utherjorge
5 months ago
Reply to  Rust Buckets

but did you read the article

Cerberus
Cerberus
5 months ago
Reply to  Rust Buckets

Just running a fairly high CR does nearly everything this stupid VC idea does all on its own thanks to DI. Size the turbo and intercooler right for the CR—like most other OEMs have been doing—and there’s almost no reason for VC. Yeah, you can get a little more efficiency off boost (which isn’t as often as it should be with an undersized 1.5 in a fat vehicle) and run a little larger turbo for some slightly better relative efficiency under boost, but for those small real world benefits, they’re employing an incredibly stupid set of major fail points on the critical bottom end of the engine. Adding weight and complexity to parts that already have to move at such extreme speeds—changing direction twice every revolution (movement which is asymmetric)—with varying loads throughout its travel is not an intelligent idea and I find it funny that there’s a question about that under an article about what a failure this has been.

Doctor Nine
Doctor Nine
5 months ago
Reply to  Cerberus

Mazda’s SKYACTIV-X SPCCI tech is a better solution to this problem:

https://www.youtube.com/watch?v=T48cdqxt364

Arch Duke Maxyenko
Arch Duke Maxyenko
5 months ago

LOL, called that shit way back on the old German Lighting Site when Nissan first announced the VC shit.

Captain Muppet
Captain Muppet
5 months ago

I said it would be fine.

I’ve learned my lesson: never underestimate Nissan’s utter disregard for the future success of Nissan.

Lockleaf
Lockleaf
5 months ago

I had high hopes for this tech mostly because it seemed interesting and fun. By high hopes, I mean, I hoped they would be reliable and show up in junkyards for me to play with for little money. But alas, my fears have been confirmed and they are underwhelming and prone to failure. Sad day.

Chronometric
Chronometric
5 months ago

Nissan has just announced a recall. All VC-Turbo engines will be getting Tommy John surgery to repair their overstressed elbows.

Mr Sarcastic
Mr Sarcastic
5 months ago

All this BS would not be a problem if established mpg was a clear test on a set track. But no government inflates mpg and reduces mpg from real life values based on its own who is sucking my cick. Just test it and release it

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Mr Sarcastic

…username relevant? The MPG test cycles are very well established and clear – there just aren’t very many people under the age of 80 who drive that way anymore.

Mr Sarcastic
Mr Sarcastic
5 months ago

Granted if you spend a few weeks investigating you can figure out the real mpg. I think my tax money is better spent on just documenting the real mpg instead of asking busy or uneducated consumers to figure put their real costs without the bias of government putting a point spread on it. And I would bet a vote from any non car manufacturers poll would get a response consumers want factual data not government mafia daya.

Last edited 5 months ago by Mr Sarcastic
Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Mr Sarcastic

…Dude. I don’t even know where to start. Exactly how do you think label fuel economy numbers are measured?

Utherjorge
Utherjorge
5 months ago

he/she isn’t going to listen to you, but that doesn’t mean you’re wrong

Mr Sarcastic
Mr Sarcastic
5 months ago

Been checking my knowledge to prove my point. It seems my memory let me down. I would have sworn that some vehicle types were given inflated mpgs by the government but it appears I am wrong here.
Kudos to you for correction

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Mr Sarcastic

It happens, and you just handled it better than most… a while back I insisted publicly that between OHV and OHC, OHC was the older tech. It is not. I was wrong. I ate crow. I think that might be a “fact” that was once all over the internet though.

You may be thinking of some high profile examples of manufacturers inflating their numbers and trying to sneak it past the government, which verifies manufacturer numbers only in spot checks. They’ll always verify a newly released or redesigned vehicle, but will only pick a few examples to check among continuing models.

Rust Buckets
Rust Buckets
5 months ago

I mean it’s not the EPAs fault that many drivers nowadays drive like a bat out of hell at every stoplight.

I think people don’t even realize how hard they drive their cars, I think the high horsepower and exceptionally quiet engines on newer cars make it easy to beat the snot out of it without even noticing.

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  Rust Buckets

I think if today’s performance had been available in the 60s when the cycles were defined, people would have driven like this then, too. My own industry isn’t blameless, though. Even most turds that can’t get out of their own way get aggressive pedal mapping to make the cars feel peppier than they are, at least until you push into the pedal a bit more and find out it’s already given you all it’s got.

Last edited 5 months ago by Pit-Smoked Clutch
Alexander Moore
Alexander Moore
5 months ago

One of the big problems is MPG itself. Obviously the number of miles you get on a gallon of gas is going to change considerably based on the road conditions under which you use that gallon. Liters per 100 kms isn’t perfect, but it’s a much more conclusive and relevant metric that has a better chance of standing up in the real world.

MPG estimates have always been bullshit to me, I drive relatively normally (do the speed limit, accelerate modestly, coast wherever possible) but only suburban miles (no highway, usually) and always get 2 or 3 MPG short of the ‘City’ estimate regardless of what car I’m driving. If I do a long distance trip, it’s again 2 or 3 mpg short of the ‘Hwy’ estimate. I’m not saying the MPG test cycles aren’t scientifically achieved, but I do think they are pretty irrelevant in the real world and could really do with updating.

Cheap Bastard
Cheap Bastard
5 months ago

I drive as you do and easily match my car’s EPA numbers. Have you checked your tires?

VanGuy
VanGuy
5 months ago
Reply to  Cheap Bastard

With mostly highway miles, I usually get 39 miles per gallon on my 2012 Prius v. That’s with the original HV battery and a 1.5-inch lift.
The EPA rating is 44 city and 40 highway. I very rarely exceed 40, but still. It keeps me impressed.
I do lose 2-6 mpg in the winter months, but that’s expected.

Alexander Moore
Alexander Moore
5 months ago
Reply to  Cheap Bastard

Once a week. Maybe Volvos are just thirsty.

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago

The “city” estimate is (pretty much) based on the FTP75 test cycle, which covers 11 miles in a whopping 31 minutes at an average speed of 21 MPH with the AC off and the windows closed. There are 23 stops (ever wonder why everything has stop-start now?). The most aggressive acceleration is significantly more aggressive than all the others, and if it were extrapolated all the way to 60 MPH, would correspond to a 0-60 time of 19 seconds.

It produces FE numbers so absurdly high that there is a correction factor applied for the window sticker (but not for CAFE purposes, which is why the CAFE targets look insane), but for most people who use their AC, it isn’t quite enough. If you’re driving a car getting ~30 MPG or more, 2-3 MPG is a pretty reasonable amount to lose to just the AC compressor.

Alexander Moore
Alexander Moore
5 months ago

That’s probably a key part of it. I live in Tucson so the A/C compressor is running 24/7, and if not that then all the windows are wide open.

lastwraith
lastwraith
5 months ago

This is a complaint I have about my DD. It’s a 1.8 I4 but the pedal feel is incredibly aggressive on initial acceleration. Makes it very annoying to drive smoothly and even more annoying if there’s any traction issues or, you know, it’s winter.

Pit-Smoked Clutch
Pit-Smoked Clutch
5 months ago
Reply to  lastwraith

Ford?

lastwraith
lastwraith
4 months ago

2007 Vibe with the Toyota Corolla 1.8L

Pit-Smoked Clutch
Pit-Smoked Clutch
4 months ago
Reply to  lastwraith

If I remember right, that could have extra weirdness as that’s one of the first model years of electronic throttle control for the Corolla platform – unless it’s a GT.

I only know because I have an ’04 GT and it still has a cable, while the base engine got ETC. It’s also too aggressive on initial tip-in, but that’s an artifact of the huge throttle body they used to flow the air it needs at 8400 RPM. I wonder if someone at Toyota decided it would be a good idea to make the base engine feel like the GT/XRS?

lastwraith
lastwraith
4 months ago

NOT a GT, haha.
I don’t think mine is among the first but it’s definitely because of DBW programming, good recollection on your part. Sadly, I never found anything online about reprogramming a different Driver Demand Table, even via the dealer.

The first Gen ’03-’04 had cables and Gen 1.5 and up (’05+) got DBW, although maybe the ’05 AWD didn’t? No clue on the 2ZZ Yamaha though. Never found one of them in the wild that wasn’t beat =/

Last edited 4 months ago by lastwraith
Pit-Smoked Clutch
Pit-Smoked Clutch
4 months ago
Reply to  lastwraith

That engine controller was never cracked by the aftermarket, I believe. I looked into it because the 2ZZ BADLY needs its cam transition point moved down by a few hundred RPM – either to make the torque jump more dramatic at engagement or to keep it off the test cycles, it was set so high that there’s no way to avoid falling back to the fuel economy cam on the 1-2 and 2-3 upshifts. The 3-4 can stay on the hot cam, but it comes at 90 MPH – I only ever managed to execute that shift one time, and it was at a track day.

I got lucky finding my 2ZZ. Bought it from the original owner when it was 9 years old, who had covered the seats and steering wheel on day one and still had the original floor mats in their plastic wrappers in storage. They’re one of the better kept secrets, but they’re more compromised than the hotter hot hatches of a few years later. A Focus ST is heaver, but it’s got enough power to make that not matter much and it has non-garbage rear suspension to boot.

lastwraith
lastwraith
4 months ago

Well, that’s sad but at this point I’ve learned to live with my car’s “hot launch” behavior. It’s just a little challenging in the snow, which we get here. Definitely a big difference from my car and the wife’s 07 Forester. That thing doesn’t lose grip no matter what you do and mine is very easy to slip, even with the lawnmower 1.8L. However, I’d rather have the Vibe/Matrix than any Subaru product. Their AWD is top-notch but those engines are oil sieves on top of the head gasket issues. And now the modern ones are all CVTs….. gross.

That’s awesome on finding such a kept 2zz. I still see quite a few Vibes and Matrixes (Matrices?) where I am and a bunch of the awd variants in nearby snowier regions. Honestly, I don’t want any part of a manual here since traffic is ever-present but it would be fun to wind out a 2zz at the track. Thanks for the thorough response!

Alexk98
Alexk98
5 months ago

Only Nissan could make the case for a Hybrid being more mechanically simple than an ICE only vehicle

GreatFallsGreen
GreatFallsGreen
5 months ago

The Nissans using the tech saw good fuel economy ratings – the Altima was rated 25/34, better than a 2.0T Accord or V6 Camry, although the V6 Altima it replaced wasn’t really that much worse at 22/32. The Rogue is rated up to 30/37 which is about the highest in the segment for nonhybrids. But, not really enough still to justify the complexity and apparent failures.

The fraction of Altimas with the engine probably isn’t that great, and not like Infiniti has sold many vehicles with it either. But the fact that it’s in the very popular Rogue means it definitely can’t be ignored. Base Canadian Rogues still offer the old 2.5, as does its Outlander cousin, wonder if we’ll see them quietly reintroduce it to more trims.

Sensual Bugling Elk
Sensual Bugling Elk
5 months ago

I happened to be watching the SavageGeese Nissan Altima VC turbo review last night, and their only complaint was that the complex variable compression system was intrinsically more likely to fail and inevitably more complicated and expensive to fix.

They actually found the engine to be pretty characterful in use though. Well, until it was inevitably let down by the CVT.

Mr. Fusion
Mr. Fusion
5 months ago

The QX-50 was first out of the gate with this engine, and I remember reviews saying things like, “This may well be a very fun engine to drive, but we’ll never know because it is paired with an abysmal transmission.”

Anthony Magagnoli
Anthony Magagnoli
5 months ago

I actually didn’t realize they’d gone to market with the VC tech.

EmotionalSupportBMW
EmotionalSupportBMW
5 months ago

But why put they put the moving bit on the rotating assembly and not something stationary like IDK, the head. You probably would have to use a timing belt, and finding a gasket material that could be adjusted. But, still, seems easier then adding a moving part to a spinning thing in a volcanic death chamber.

Mr. Asa
Mr. Asa
5 months ago

and finding a gasket material that could be adjusted.

This. Never gonna happen. Never ever. Not with any degree of reliability long-term.

StillNotATony
StillNotATony
5 months ago
Reply to  Mr. Asa

Saab made one, but it GM killed it. Too expensive.

https://en.m.wikipedia.org/wiki/Saab_Variable_Compression_engine

PaysOutAllNight
PaysOutAllNight
5 months ago
Reply to  StillNotATony

The SAAB method was kind of weird, too. It involved pivoting the cylinder head over the block on a sort of hinge, with a bellows seal of some sort between the bottom of the cylinder skirt and the crankshaft.

Ron888
Ron888
5 months ago
Reply to  StillNotATony

I remember that one! The mechanical design looked weird but solid.I cant imagine those bellows lasted long though.

Tbird
Tbird
5 months ago
Reply to  Ron888

Blast from the past for me as well. The engineering seems much simpler and more solid on that one.

Ncbrit
Ncbrit
5 months ago

Overcomplicated engine internals turn out to not be that reliable. I’m shocked I tell ya.

Nsane In The MembraNe
Nsane In The MembraNe
5 months ago

I’ve been seeing this make the rounds and it’s definitely disappointing. I’m one of the folks who thinks the VC turbo technology is pretty neat. Turbo 4 bangers in general don’t actually offer serious fuel economy benefits until you’re at highway speeds. At that point, you can sit in a high gear off boost and essentially get regular 4 cylinder MPG.

But in actual city environments rather than the EPA’s bogus test cycle they’re as bad as anything else. My GTI consistently got 16-20 or so in real life city driving and my Kona N usually gets 13-17 or so. My lifetime fuel economy in my GTI was 23 and change and my Kona N is hovering at 20.5. Neither is good.

This kind of seemed like something that could address that to an extent but alas, it isn’t. I really do question how much benefit continuing to downsize ICE engines is actually giving us, because once you factor in the additional maintenance and parts that high strung engines require I’m really not sure if the minuscule MPG and emissions benefits they provide will actually amount to anything at all.

It seems like the best solution we currently have is the mild hybrid systems integrated into the stop/start systems that German luxury manufacturers, Mazda, and Volvo are implementing. But then again, that’s also a convoluted solution. If we had another couple of years to keep developing ICE I’m sure there’d be some interesting solutions, but alas.

LarsVargas
LarsVargas
5 months ago

I’ve got a ’23 Hyundai Santa Cruz with the 2.5 liter turbo. It’s also AWD, weighs a hefty 4,200 pounds, and has an 8 speed DCT.

Around town, it might get 22 MPG, maybe a bit more. Not bad and a lot better than my Crown Vic got (roughly the same weight, larger displacement engine at 4.6 liter, RWD and less power, but 15MPG) on average. I realize it’s apples to oranges and 20 years of difference in model years, but interesting to see.

On the open road, however, the Santa Cruz is amazing. If I keep out of the loud pedal and speed around 70MPH with cruise on more or less flat roads, it’ll do 30-31 MPG easy. I’ve even hit 32 MPG on some trips. Even at higher speeds (we do have 85 MPH speed limits on some roads in TX) I can expect mileage in the mid to high 20s.

I got the vehicle exactly 1 year ago and it’s got 10,500 miles on it. Average (as reported by its computer) is 23.4 MPG in mixed driving. I’m pretty happy with that.

Mr Sarcastic
Mr Sarcastic
5 months ago
Reply to  LarsVargas

Wellman 2001 DD gets less than15 mpg. But I drive less than 10k miles a year. It will take a looooong time before 6 mpg pays for a $40,000 car and even then oil changes, maintenance, tires and repairs will require longer.

LarsVargas
LarsVargas
5 months ago
Reply to  Mr Sarcastic

Oh yeah. I didn’t get my new car specifically to save money on gas. But I am happy that it’s a lot more efficient than past cars while still being pretty fun to drive.

Mr Sarcastic
Mr Sarcastic
5 months ago
Reply to  LarsVargas

And if I buy a new car it won’t be based on mpg specifically but I would love actually knowing the real mpg instead of adter the government prize patrol lies.

LarsVargas
LarsVargas
5 months ago
Reply to  Mr Sarcastic

Overall I’m getting better than rated mileage with mine. But agree that the way gas milage is officially determined in the US needs some reworking.

Stacheface
Stacheface
5 months ago

I find it interesting how horrible mileage has not improved over the years. Or that smaller cars aren’t always that much better than something bigger. In my 02 Tahoe I get about 13-15 MPG, and “could” get a bit better with gentler driving. Though I did have a 90s Altima that got around 35 MPG, so there’s that end of the spectrum too

Drive By Commenter
Drive By Commenter
5 months ago
Reply to  Stacheface

MPG is an awful rating scale. Gallons/100 miles would be far more useful.

Instead of going “15 mpg to 20 mpg, what’s the fuss about”, saying 6.67 gallons/100 miles to 5 gallons/100 miles makes clear there’s a 1 and 2/3 gallon savings to be had. That math is why trucking fleets fight for tenths of a mile per gallon. 3 mpg (33.3gal/100mi) to 3.5 mpg (28.6gal/100mi) saves a lot of fuel!

VanGuy
VanGuy
5 months ago
Reply to  Stacheface

It was a shock to me around 2014 to find out that my 1997 conversion Econoline-150’s lived fuel economy of 12-17mpg was often similar or better than my friend’s Jeep Patriot.

They lived at the gas station with that thing since they had something like a 12- or 15-gallon tank, compared to my 33-gallon tank.

One of those two vehicles is slightly more practical for, well, everything.

Cerberus
Cerberus
5 months ago

The trick is to have a reasonable size engine that can move the vehicle off boost during regular driving in different conditions. I averaged 30 mpg from my Focus ST driving in a lot of Boston highway traffic. Lowest I ever got from a tank was about 25 and that was once, trying 87 octane (Ford said it was acceptable and I was doing a long highway drive and figured I’d save a few bucks. Nope. Also felt like I had three big dudes sitting in there.). Highest was about 32, IIRC. My manual Focus SE averaged 36, so for an extra 90 hp and 110 lbs ft, I didn’t think it was too bad, but that’s because it had the same size engine and what would have been a high CR for an MPFI N/A engine just a few years earlier.

Space
Space
5 months ago

I think you might be onto something, comparing my v8 2007 ford to my V6 2017 w/ a turbo both vehicles get exactly 20.4mpg. To be fair the 2017 is a 4×4 so we can assume it gets 1mpg better to make up for losses.
Is 1 mpg worth it? I can’t say for sure that’s like saving 250 gallons of gas every 100k miles.

Lokki
Lokki
5 months ago

For ways that are strange, and tricks that are odd,
the unfettered German Engineer is peculiar.
But he ain’t got nuthin’ on an unsupervised
Japanese engineer who got the fever for sumthin’ new:

Note: See Mazda

Dogisbadob
Dogisbadob
5 months ago
Reply to  Lokki

If Mazda did this VC shit, it wouldn’t matter because the car would rust before the VC problems have a chance to show up 😉

EVDesigner
EVDesigner
5 months ago

One of the other problems that people noted was the terrible engine response. If you were just cruising along and suddenly accelerated(overtaking for example) the engine would take a good 3 seconds to change behaviors, transmission took another second to kick down, and then 1 extra second for the turbo to actually spool up. By the time that happened you already lost your chance to overtake.

Utherjorge
Utherjorge
5 months ago
Reply to  EVDesigner

Excellent point

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