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Discussion Starter #1
I've been doing a lot of research on my upcoming purchase of the Santa Fe Calligraphy with the 2.5L Turbo. I came across this video which is in Korean but you can get English subtitles:

Reddit Post about the SmartStream 2.5L Faults

He is the same engineer that found the Theta II problems as well. I'm wondering if I should go forward with my purchase.

Has any 2.5L owners over 10,000KM noticed power being sapped from the system? It's a sign that the injectors, heads, and pistons are being carbonized.

Let me know your thoughts.
 

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2019 Santa Fe Ultimate 2.0T HTRAC
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Whoa, that is bad! The issue is worst than the Theta II. The good thing is the oil level increase in 2.0T is now a decrease in the 2.5 lol
 

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I believe the sonata has used the 1.6 turbo version for a year. I didnt see any complaints in that forum. Certainly is food for thought as even the hybrid uses smartstream technology. Some people think it might not affect American made Hyundai and Kia’s. Hope the YouTube is wrong!
 

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2020 Santa Fe Limited 2.0T Awd
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I've been doing a lot of research on my upcoming purchase of the Santa Fe Calligraphy with the 2.5L Turbo. I came across this video which is in Korean but you can get English subtitles:

Reddit Post about the SmartStream 2.5L Faults

He is the same engineer that found the Theta II problems as well. I'm wondering if I should go forward with my purchase.

Has any 2.5L owners over 10,000KM noticed power being sapped from the system? It's a sign that the injectors, heads, and pistons are being carbonized.

Let me know your thoughts.
I'd be surprised if there are any owners with over 10, 000 km already. The vehicles are just getting into showrooms.

I looked at the video and find it kinda hard to believe. They usually have powertrains in test mules years before it is released. If this problem exits, Hyundai must have did little to no real-world testing of this engine. I find that kinda hard to believe with all the issues associated with Theta II that costs them lots of money. I guess in a perfect world they would have learned their lessons and revised all of their processes to ensure the new engine has better quality and more reliable than the predecessor.
 

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Discussion Starter #5
I'd be surprised if there are any owners with over 10, 000 km already. The vehicles are just getting into showrooms.

I looked at the video and find it kinda hard to believe. They usually have powertrains in test mules years before it is released. If this problem exits, Hyundai must have did little to no real-world testing of this engine. I find that kinda hard to believe with all the issues associated with Theta II that costs them lots of money. I guess in a perfect world they would have learned their lessons and revised all of their processes to ensure the new engine has better quality and more reliable than the predecessor.
It looks like they did do testing and obviously found some faults. They increased to oil capacity for the vehicle by 0.6L of oil and increased the length of the oil sensor to give a broader range before having the sensor go off. They also dropped the maintenance interval from 15K to 7.5K and in North America 6k. The quicker the oil change the less loss is noticed.

I’m trying to figure out which 2.5L SmartStream they are taking apart because the North American engine now uses 6.8L of oil vs 5.8L in the video which was originally 5.2L.
 

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Thanks for the video.

It looks like the engine was a non-turbo, which has its design differences, e.g. according to wiki compression is 13:1 in 2.5 and 10:1 in a 2.5T.

The story sounds very familiar to 2.4 GDI Theta II problems, combustion had lots of carbon with stuck rings and dirty injectors, resulting in heavy oil consumption (1q per 300mi in my case) and shaky acceleration due to improper fuel mixture. Hyundai increased oil spec and replaced dipstick. Not sure why this spirals back in Theta III after so many lessons.

I haven't heard of many issues with turbo engines though.
 

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Discussion Starter #7
Thanks for the video.

It looks like the engine was a non-turbo, which has its design differences, e.g. according to wiki compression is 13:1 in 2.5 and 10:1 in a 2.5T.

The story sounds very familiar to 2.4 GDI Theta II problems, combustion had lots of carbon with stuck rings and dirty injectors, resulting in heavy oil consumption (1q per 300mi in my case) and shaky acceleration due to improper fuel mixture. Hyundai increased oil spec and replaced dipstick. Not sure why this spirals back in Theta III after so many lessons.

I haven't heard of many issues with turbo engines though.
I watched the video again and I think you hit the nail on the head. It’s the high compression ratio in the non-turbo. So it looks like the turbo shouldn’t suffer the same fate.
 

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2020 Santa Fe Limited 2.0T Awd
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I meant testing before the engine approved for production and is released to the consumer. It looks like this testing was done after the engine was already released, and they took steps to conceal the defects.

I wonder though. Turbo engines usually have more blow-by than NA engines, so I would expect them to see more of this issue than NA engines.

6.8L of oil is a lot of oil for a 4 cyl engine. I guess this is why a lot of people say not to by a completely redesigned car or refresh where a brand new powertrain is introduced in the first year. They still have kinks to work out.

If you go through with the purchase. Please keep us updated. If these problems show up,, Hyundai will be in for another round of lawsuits and government fines. I imagine this round of lawsuits would be a lot more costly. Punitive damages are gonna be hefty.
 

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I wonder though. Turbo engines usually have more blow-by than NA engines, so I would expect them to see more of this issue than NA engines.
Blow-by maybe (top-to-bottom), however the video showed bottom-to-top oil propagation and burn due to piston slack and then carbon buildup.
 

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Start any new car on the dealer lot. Remove the oil fill cap and enjoy the astonishing blow-by pressure (bottom-to-top). If you can, compare with a 10-20 year old MPI car.
Dealers will say that the blow-by is normal. Of course they will.

IMO it's part of the "improvements" needed to achieve better/higher gas mileage. Less friction from the piston rings on walls, better MPG. Sure that destroys the engine in long term, but if that happens after warranty period, that's a win for manufacturers. They get to sell more cars.
 
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Start any new car on the dealer lot. Remove the oil fill cap and enjoy the astonishing blow-by pressure (bottom-to-top).
That's not blow-by. It's air being moved around in the crankcase by the backs of the pistons.
Four cylinder engines have a second order imbalance in piston motion that causes a net in and out motion of the air at twice the frequency of the crank rotation.
That's also why 4 cylinder engines bigger than 2 liters generally have a balance shaft.
If you hold the palm of your hand or a piece of paper or cardboard over the fill cap you'll see that it's not a net movement of air.
It's just pumping air in and out like a subwoofer.
SInce the late '70s I've had multiple cars with 4 cylinder engines and they all did that when the fill cap is removed.
 

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That's not blow-by. It's air being moved around in the crankcase by the backs of the pistons.
That "air" carries a lot of oil mist. The piston segments don't scrape the cylinder walls that hard anymore, to reduce friction loses (and improve the gas mileage). Some oil gets burned and some gets recirculated (and increases the carbon deposits on the back of the intake valves).
Your palm will get oily if you test that fill hole.
If you hold the palm of your hand or a piece of paper or cardboard over the fill cap you'll see that it's not a net movement of air.
Try again with the new cars. On my test on a few 2020 engines, there was a visible column of exhaust gas/oil coming straight up from that hole.
 

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Blow-by maybe (top-to-bottom), however the video showed bottom-to-top oil propagation and burn due to piston slack and then carbon buildup.
Yes. If I'm not mistaken, the video also mentioned oil burning due to blow-by gasses being reintroduced to the combustion chamber via the intake system....which a lot of turbo engines are known for. Folks usually try to mitigate the effects by adding an oil catch can. These engines are doing a double-whammy burning oil lol!

Well...at least, according to what is shown in the video.
 

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Start any new car on the dealer lot. Remove the oil fill cap and enjoy the astonishing blow-by pressure (bottom-to-top). If you can, compare with a 10-20 year old MPI car.
Dealers will say that the blow-by is normal. Of course they will.
They may get sprayed with oil mist 🤣
 

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The base model Sonata in Canada uses the same engine.
The New Kia Sorento as well.

If this becomes widespread like the Theta 2 this will be really bad. Only time will tell as people rack up more miles.
 

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That's K7 in the video with a Smartstream 2.5L GDI (in Korea since 2019). The problem I see is that entire family of 2.5L Smartstream engines is built on same block: 2.5L non turbo, 2.5L turbo, with various compression, hp, tq etc. New K5, Sorento, Hyundai models and even several Genesis models use same engine block and each has different setup depending on model. So if that 2.5L has issues in Korea, there's good chance we'll get similar issues (granted that was not a outlier defect, but inherited design of Smartsream 2.5L). This not good. Not good at all. GDI engines are prone to carbon build up, clogged intakes (literally black tar everywhere), clogged valves etc to begin with, and this new issue of prematurely failed piston rings, oil consumption - will only lead to even faster engine deterioration. Add to that huge gap between piston and cylinder wall leading to scorched cylinders (hello Theta 2 issues) and even more accelerating oil burning and carbon deposits and clogging. This looks like potential nightmare. I've seen myself an open Theta 2 engine with 60k miles - it was black tar everywhere.
Kia/Hyundai - leaders in design, interior, options for money etc, but with one major flaw - probably worst 4-cylinder engines ever made in terms of design and reliability. I wish Kia/Hyundai would have stick to their V6 like in Telluride/Palisade, that one was out since 2018 in Korea and so far not a single issue, but then again they are a better designed engines to begin with, one of the Kia/Hyundai best engines made.
IMHO Kia/Hyundai needs to drop 4 cylinder Theta series engines altogether and either go with their bulletproof V6 with Hybrid or EV.
 

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I wish Kia/Hyundai would have stick to their V6 like in Telluride/Palisade, that one was out since 2018 in Korea and so far not a single issue, but then again they are a better designed engines to begin with, one of the Kia/Hyundai best engines made.
Unfortunately the days of the V6 are numbered. I'm so happy I found an extremely low mileage 2012 Santa Fe with the 3.5L V6 back in July, but even they tend to have chain tensioner issues pop up around the 100K-120K mark. I feel terrible for people who drop their hard-earned money on a car only to have the engine fail.
 
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