3.3TT What is “mid phase air intake Continuous Variable Valve Timing (CVVT) system”?

[TheBeginning]

Saw this on the Korean Genesis website for the G70 regarding the 3.3t . It states “mid phase air intake Continuous Variable Valve Timing (CVVT) system”. Is this any different than a normal CVVT system?

 

[TheBeginning]

Link

Genesis G70 – Luxury Sport Sedan | GENESIS

Explore Genesis G70 Shooting Brake, our most versatile model to make any ifestyle more luxurious. Sporty meets practical with high-performance driving and a spacious interior. | GENESIS

www.genesis.com

 

[Thomby]

Not sure what the "mid" would refer to here. A lot of variable valve tech refers to "cam phasers", the actual mechanisms at the front of the camshafts that use oil pressure to rotate or phase the cams relative to their baselines.

Kia/Hyundai have docs that explain the 4 scenarios it adjusts for (low speed/low load, low speed/high load, partial throttle, high speed/high load), but I've never seen "mid phase" referenced. Maybe something lost in translation or relating to the continuous adjustment (vs. older system like VTEC that had two discrete cam profiles).

Hyundai Genesis - CVVT (Continuously Variable Valve Timing) System Description and Operation - Exhaust Emission Control System

www.hgenesisdh.com

 

[TheBeginning]

Not sure what the "mid" would refer to here. A lot of variable valve tech refers to "cam phasers", the actual mechanisms at the front of the camshafts that use oil pressure to rotate or phase the cams relative to their baselines.

Kia/Hyundai have docs that explain the 4 scenarios it adjusts for (low speed/low load, low speed/high load, partial throttle, high speed/high load), but I've never seen "mid phase" referenced. Maybe something lost in translation or relating to the continuous adjustment (vs. older system like VTEC that had two discrete cam profiles).

Hyundai Genesis - CVVT (Continuously Variable Valve Timing) System Description and Operation - Exhaust Emission Control System

www.hgenesisdh.com

Thanks for that link, that’s a good resource. Nowadays, it seems rare to find a car WITHOUT vvt. Some auto makers are expanding on the concept, though with variable valve lift or variable valve duration. I’m curious if the Hyundai system is doing something like that.

Interestingly, I found a patent for the Hyundai system system, but the status is abandoned

US20150377087A1 - Middle phase continuously variable valve timing system with intermediate lock pin and cam torque response control and method thereof - Google Patents

A method of controlling an intermediate lock pin and cam torque response for a continuously variable valve timing system with is disclosed. The method includes entering a cam phaser control mode for controlling the middle phase CVVT when an engine starts, or performing lock pin chattering of a...

patents.google.com

 

[rtv900]

Thanks for that link, that’s a good resource. Nowadays, it seems rare to find a car WITHOUT vvt. Some auto makers are expanding on the concept, though with variable valve lift or variable valve duration. I’m curious if the Hyundai system is doing something like that.

Interestingly, I found a patent for the Hyundai system system, but the status is abandoned

US20150377087A1 - Middle phase continuously variable valve timing system with intermediate lock pin and cam torque response control and method thereof - Google Patents

A method of controlling an intermediate lock pin and cam torque response for a continuously variable valve timing system with is disclosed. The method includes entering a cam phaser control mode for controlling the middle phase CVVT when an engine starts, or performing lock pin chattering of a...

patents.google.com

I wouldn't think a single car would possibly exist without it these days. VVT tech was in economy cars over 20 years ago.
plus I'm pretty sure it does vary lift and duration. Wouldn't be all that great if it could only shift the same profile forward or back

 

[Thomby]

I wouldn't think a single car would possibly exist without it these days. VVT tech was in economy cars over 20 years ago.
plus I'm pretty sure it does vary lift and duration. Wouldn't be all that great if it could only shift the same profile forward or back

I think it's a matter of diminishing returns, same reason we haven't seen solenoid valvetrains (infinitely variable for timing, lift, and duration) take over: because while the initial gains of adding (say) an intake-only system with one profile for low and one for high rpm might be pretty big, subsequent gains from adding the exhaust side, making it more variable via cam phasers, then lift/duration just don't improve things a ton more.

 

[oddball]

Yeah, it's just a bad translation. That patent filing is likely what they were trying to say. "Traditionally", a VVT phaser relies on oil pressure to control the alignment of the cam. There's no oil pressure when the engine starts. Looks like they found a method to manage the startup sequence until oil pressure is reliable.

Variable duration and variable lift is VERY hard. Well - *variable* is hard. *Alternate* is not. There's a bunch of engines that have two cam lobes for each valve - one with more lift and duration than the other - and usually an oil-based control mechanism with different rockers/followers to select which lobe is active.

The funny thing about internal combustion engine dynamics is that the precise valve opening/closing event timing, especially overlap, has a huge effect. So changing the overall cam timing can have a massive effect on the engine, even without changing the lobes themselves. And since most engines have separate intake and exhaust cams, the overlap can be altered. Most VVT systems are doing something crazy like 20+ degrees of swing!! In ye-olden-days, moving a cam by 4 degrees was considered a major change to engine dynamics.

VVT gets a ton of advantages and they can package it in a small and reliable system. The alternate-lobe systems are a little wonky so I doubt they'll stick around much longer, if they are at all now. Maybe Fiat still does it? There's not enough need to figure out fully variable valve control.

Konigseggeessiiggeee promised to have solenoid controlled valves in an engine, what, 5 years ago? Some day...

 

[TheBeginning]

I wouldn't think a single car would possibly exist without it these days. VVT tech was in economy cars over 20 years ago.
plus I'm pretty sure it does vary lift and duration. Wouldn't be all that great if it could only shift the same profile forward or back

That is what a basic VVT does. Simply advance or delay the valve lift event, but does not change the cam profile (lift, duration, etc). Many companies have added on to this, like VTEC, which switches to a different cam profile above a certain RPM. That way they can have an engine with good fuel economy and operability around town while also allowing the engine to breathe at high RPMs.

I think it's a matter of diminishing returns, same reason we haven't seen solenoid valvetrains (infinitely variable for timing, lift, and duration) take over: because while the initial gains of adding (say) an intake-only system with one profile for low and one for high rpm might be pretty big, subsequent gains from adding the exhaust side, making it more variable via cam phasers, then lift/duration just don't improve things a ton more.

There are a few systems out there that do exactly that. Off the top of my head:

Fiat Multi-Air: It uses a small hydraulic spacer between the camshaft and valve. Most of the time hydraulic pressure inflates the spacer and results in normal valve actuation. Under certain conditions, the Fiat engineers reduce the hydraulic pressure, causing the spacer to collapse resulting in early closure of the valve or reduced lift. Not the best system in my opinion since it only reduces valve opening. From experience behind the wheel, the engines feel laggy.

BMW Valvetronic: Really cool system which uses a lead screw to vary how much the cam can lift the valve. Combined with their VVT system, VANOS, BMW can completely control airflow with the intake valves. Since gasoline engines only function in a narrow air fuel ratio band, the best way to control engine power is by controlling how much air can enter the engine. Just about every engine does this with a butterfly valve which can restrict airflow entering the engine. BMW on the other hand can control airflow completely with the valve train. This makes the engines far more responsive due to less distance between ambient air and the cylinder. Also, efficiency is improved due to lower pumping losses.

There are a bunch more valve lift control systems out there which companies have invested large sums of money into.

 

[Thomby]

Fiat Multi-Air, BMW Valvetronic

Right, I'm aware of Multi-Air, and the fact that it's been in a small handful of cars in 15 years, none remotely performance oriented. Same deal with Koenigsegiggsegiggseg as @oddball mentioned...they put it in a couple multi-million dollar cars but it hasn't worked its way down, likely because it's significantly more expensive/complicated but there just isn't that much left to optimize vs. a decent traditional VVT system.

BMW's Valvetronic/VANOS is an interesting exception, by being so much closer to a fully continuously variable system, and one that's been in a ton of cars (models + units). Probably due to the fact that they figured out (as I understand it) a reasonably straightforward way to build onto what existing camshaft tech already does, vs. completely reinventing the wheel.

 

[TheBeginning]

Right, I'm aware of Multi-Air, and the fact that it's been in a small handful of cars in 15 years, none remotely performance oriented. Same deal with Koenigsegiggsegiggseg.

Konigseggeessiiggeee promised to have solenoid controlled valves in an engine, what, 5 years ago? Some day...

Seemed like koenigsegg freevalve concept has a low return on investment. Small power returns compared to just turning up the boost.

That reminds me of this really interesting video of a guy who fabricated a solenoid actuated valve train for a Miata. Figured you two would enjoy it, linked below.

Video

 

[Thomby]

Seemed like koenigsegg freevalve concept has a low return on investment. Small power returns compared to just turning up the boost.

That reminds me of this really interesting video of a guy who fabricated a solenoid actuated valve train for a Miata. Figured you two would enjoy it, linked below.

Well compared to completely fixed valve timing/lift, going to a fully variable setup would be a big improvement. But I think that similar to other potentially game-changing tech (Wankels, rotary valves, CVTs), modern engines have had so many decades of incremental or "good enough" tweaks and refinements that even a "better"/ideal solution just doesn't have much benefit left to capture (but does introduce cost, complexity, etc).

Have not seen the Freevalve Miata, will add to my list, thanks!

 

[Devin]

Seemed like koenigsegg freevalve concept has a low return on investment. Small power returns compared to just turning up the boost.

That reminds me of this really interesting video of a guy who fabricated a solenoid actuated valve train for a Miata. Figured you two would enjoy it, linked below.

Video

That's pretty cool