Hyundai Theta II Engine in Newer Years

Originally Posted by KrisZ

With direct injection fuel can be injected at any point during the cycle. All manufacturers have different fuel injection timings and lengths, but one thing is common, all of them do not use a single fuel injection time anymore.

So with multiple injection and variable exhaust and intake valve timing, all sorts of things are possible there weren't before.
However I don't think any if that can be used to somehow direct the fuel in order to clean the intake valves.

Well technically it's only got 2 strokes to be injected. It's either during stroke 1 or stroke 2. But I don't see during what stroke would opening both the exhaust and intake valves simultaneously occur?.. just so fuel could swim upstream to wash a valve??

There's positive cylinder pressure during strokes 2 and 3 but you wouldn't open the exhaust valve then otherwise you get no "boom". Stoke 1 is a vacuum.. that leaves stroke 4..but the problem with stroke 4 is there's no fuel left to clean anything

[Linked Image]
 
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Using the Mazda SkyActiv system as a point, KrisZ is correct. Fuel can be injected at any point in the cycle. It can also be injected multiple times as well. The computer controls the sequence.
 
Originally Posted by PimTac
Using the Mazda SkyActiv system as a point, KrisZ is correct. Fuel can be injected at any point in the cycle. It can also be injected multiple times as well. The computer controls the sequence.

I said I agree on that.. that's not a point of contention with me. My question is, using the supplied picture, can you tell me during which stroke both of the valves are supposed to open (overlap) to create a positive cylinder pressure, so fuel could be sucked up into the intake manifold to "wash" the IV's???
 
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Get the camera and never look back. You'll have dodged a bullet with that horrible theta engine. Just don't be surprised when you see what they give you want to trade in because it will knock you in the dirt. The trade-in on these things is just about as bad as it comes as I know all too well. It's still better than trying to keep one of those running with an engine the fact that I literally can't be cured.
As a matter of fact I dumped my Hyundai turd 13 sonata for a 2018 Camry with a four banger. No I don't find anything that unusual With the transmissionthe transmission. When you first drive one they take a while getting used to you it's got some kind of a learning algorithm. After you get to know each other it's an occasional missing a gear If you stomp on it. Some people it drives not me I hardly notice.
 
Originally Posted by smc733
Thanks for the input so far. I have been doing dealership oil changes (OEM Filter + Semi Syn) every 5k miles. The engine has always sounded rough on cold starts, but the metal noise I am hearing is new this year (and what has made me start looking back into the Theta II issues).

Here's a short clip of a cold start:
https://streamable.com/s/e0dts/huxw


If that's your engine in the video then your engine has already been replaced.
 
OP, your engine noise sounds normal. Just the typical GDI buzzing noise and I also heard what sounds like slight piston slap. Piston slap on a cold engine is quite the norm these days. I wouldn't worry.

My 2018 Sonata also does the "chuggle" startup every now and then since new. A coworkers 2017 sonata did the same chuggle startup (no longer owns the car), and a friends 2019 Santa Fe as well. All have done it since brand new, all 2.4 theta II engines. I guess it's "normal".

Concerning loud knocking knocking sounds, there is a 2015-2017 sonata in my neighborhood and on a recent cold morning at around 24 degrees F it was knocking very loudly. It wasn't piston slap, it sounded very much like a rod knock and I was able to hear it about 200 feet away. Recently I saw a 2016-2018 Kia Optima burning oil on acceleration, blueish white puffs of smoke every time the car accelerated from a stop, it was a 2.4 model.

As for campaign 953. My 2018 had the recall done and it went into limp mode on the drive home from dealer. The fix for mine was a new knock sensor harness. Limp mode cuts RPM to a max of 2K rpm and rough max speed of 62mph. Transmission shifted really hard and felt like it would stall. Acceleration was practically non existent.
 
Originally Posted by Mad_Hatter
Originally Posted by PimTac
Using the Mazda SkyActiv system as a point, KrisZ is correct. Fuel can be injected at any point in the cycle. It can also be injected multiple times as well. The computer controls the sequence.

I said I agree on that.. that's not a point of contention with me. My question is, using the supplied picture, can you tell me during which stroke both of the valves are supposed to open (overlap) to create a positive cylinder pressure, so fuel could be sucked up into the intake manifold to "wash" the IV's???





That I don't know.
 
Originally Posted by PimTac

That I don't know.

Me neither, that's why I'm a bit skeptical of this claim that fuel spray is washing the IV's in a DI... even with VVT.
 
Originally Posted by Mad_Hatter
Originally Posted by PimTac

That I don't know.

Me neither, that's why I'm a bit skeptical of this claim that fuel spray is washing the IV's in a DI... even with VVT.


Your picture is missing valve overlap with VVT on both exhaust and intake valves. For example the pentastar engine in my minivan doesnt have an EGR valve valve overlap is used to get the EGR charge mixed with intake stroke. Full VVT and valve lift add a whone another dimension to engine operation. That's why we can have engines now that can operate in Otto and Atkinson cycles for example.


As far as the claim that this can be used to "wash" the intake valves, I don't think it's possible because even using valve overlap, the fuel will be fully vaporized and mixed with air, so not sure how that would help with any cleaning.

In a port injected system, the fuel is sprayed directly over the valve, so there is pressure and raw fuel doing the cleaning. That's a lot different tha having fuel and air vapor going over the valves.
 
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Originally Posted by Mad_Hatter
Originally Posted by PimTac

That I don't know.

Me neither, that's why I'm a bit skeptical of this claim that fuel spray is washing the IV's in a DI... even with VVT.




If the fuel was hitting the valves in any way it would be the faces and not the back sides where the GDI issue has been reported.

Some GDI engines have less of this problem than others.
 
Originally Posted by PimTac

If the fuel was hitting the valves in any way it would be the faces and not the back sides where the GDI issue has been reported.

Good point and makes me even more skeptical about this claim. Unless I'm missing something, and it's possible I am, I'm gonna say that this claim is...

[Linked Image]
 
Originally Posted by Driz
Get the camera and never look back. You'll have dodged a bullet with that horrible theta engine. Just don't be surprised when you see what they give you want to trade in because it will knock you in the dirt. The trade-in on these things is just about as bad as it comes as I know all too well. It's still better than trying to keep one of those running with an engine the fact that I literally can't be cured.
As a matter of fact I dumped my Hyundai turd 13 sonata for a 2018 Camry with a four banger. No I don't find anything that unusual With the transmissionthe transmission. When you first drive one they take a while getting used to you it's got some kind of a learning algorithm. After you get to know each other it's an occasional missing a gear If you stomp on it. Some people it drives not me I hardly notice.


You do realize that if you engine goes (extremely unlikely that will happen) you get a new one for free?
 
Originally Posted by Driz
Get the camera and never look back. You'll have dodged a bullet with that horrible theta engine. Just don't be surprised when you see what they give you want to trade in because it will knock you in the dirt. The trade-in on these things is just about as bad as it comes as I know all too well. It's still better than trying to keep one of those running with an engine the fact that I literally can't be cured.
As a matter of fact I dumped my Hyundai turd 13 sonata for a 2018 Camry with a four banger. No I don't find anything that unusual With the transmissionthe transmission. When you first drive one they take a while getting used to you it's got some kind of a learning algorithm. After you get to know each other it's an occasional missing a gear If you stomp on it. Some people it drives not me I hardly notice.

Fortunately, I got it for a rock-bottom price as a CPO (50% of MSRP) two years ago. The trade value I was quoted with one visit to a dealer (the Camry had body damage so I passed) wasn't terrible given the difference from what I paid for it, however, I would definitely not be happy had I paid MSRP.

Originally Posted by SatinSilver

If that's your engine in the video then your engine has already been replaced.

Because of the red dipstick? I thought that part became standard in the 2015s.

Originally Posted by Whammo

You do realize that if you engine goes (extremely unlikely that will happen) you get a new one for free?

I wasn't the poster this was directed at, but... it is a huge hassle if this happens. Dealing with a potentially dangerous failure, fighting with Hyundai to cover a rental (and probably getting stuck in a beat up Accent), waiting 6-8 weeks for the repair, submitting records (which I fortunately have neatly in a folder in my filing cabinet, and scanned to PDFs)...
 
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Originally Posted by smc733
Originally Posted by Driz
Get the camera and never look back. You'll have dodged a bullet with that horrible theta engine. Just don't be surprised when you see what they give you want to trade in because it will knock you in the dirt. The trade-in on these things is just about as bad as it comes as I know all too well. It's still better than trying to keep one of those running with an engine the fact that I literally can't be cured.
As a matter of fact I dumped my Hyundai turd 13 sonata for a 2018 Camry with a four banger. No I don't find anything that unusual With the transmissionthe transmission. When you first drive one they take a while getting used to you it's got some kind of a learning algorithm. After you get to know each other it's an occasional missing a gear If you stomp on it. Some people it drives not me I hardly notice.

Fortunately, I got it for a rock-bottom price as a CPO (50% of MSRP) two years ago. The trade value I was quoted with one visit to a dealer (the Camry had body damage so I passed) wasn't terrible given the difference from what I paid for it, however, I would definitely not be happy had I paid MSRP.

Originally Posted by SatinSilver

If that's your engine in the video then your engine has already been replaced.

Because of the red dipstick? I thought that part became standard in the 2015s.

Originally Posted by Whammo

You do realize that if you engine goes (extremely unlikely that will happen) you get a new one for free?

I wasn't the poster this was directed at, but... it is a huge hassle if this happens. Dealing with a potentially dangerous failure, fighting with Hyundai to cover a rental (and probably getting stuck in a beat up Accent), waiting 6-8 weeks for the repair, submitting records (which I fortunately have neatly in a folder in my filing cabinet, and scanned to PDFs)...


FWIW: Kia may be doing things differently than Hyundai but my new long-block engine replacement in Dec '18 was NO hassle. Took 10 days, they required no records (which I do have), gave me a 2019 Optima to drive as a replacement and it was all at no charge. I got a forever warranty (unlimited miles, unlimited time, all owners) to boot. I paid for a new serpentine belt but that was at my request to change it. They even moved over all my bolt-on modifications. I am a happy camper. YMMV.
 
Originally Posted by WhizkidTN

FWIW: Kia may be doing things differently than Hyundai but my new long-block engine replacement in Dec '18 was NO hassle. Took 10 days, they required no records (which I do have), gave me a 2019 Optima to drive as a replacement and it was all at no charge. I got a forever warranty (unlimited miles, unlimited time, all owners) to boot. I paid for a new serpentine belt but that was at my request to change it. They even moved over all my bolt-on modifications. I am a happy camper. YMMV.

Good to know. I am going in on Saturday for an oil change and have asked them to check out the hard start/knocking issue (which many have noted is likely normal, but this appt was set up before this thread). It would be great if I could get ahead of the replacement before a highway breakdown, would make things much easier. In the event I got a replacement, I too would definitely want to pay for a new serpentine belt and possibly water pump.
 
Originally Posted by Mad_Hatter
My question is, using the supplied picture, can you tell me during which stroke both of the valves are supposed to open (overlap) to create a positive cylinder pressure, so fuel could be sucked up into the intake manifold to "wash" the IV's???

The overlap period is at the end of #4 and the start of #1.
As the piston passes by TDC the exhaust valve closes and intake valve opens.
Leftover exhaust gasses in the cylinder are at exhaust manifold pressure, which is greater than intake manifold pressure.
 
Originally Posted by smc733
Originally Posted by SatinSilver

If that's your engine in the video then your engine has already been replaced.

Because of the red dipstick? I thought that part became standard in the 2015s.


I don't believe that's the case at all. Red should mean long block replacement. How did the oil change at the dealer go?
 
Heard nothing but horror stories about my Triton 5.4l 3v Ford engine.
Heard Horror stories about my Hyundai 2.4 Thea engine.
Both run great.
I had a 2001 GM 5.3l with the cold start knock.
Great engine no problems.
Keep the oil clean and drive.
If you drive a zillion miles there`s a point you need to look at residuals.
Being cheap is a crap shoot.
I would not trade over anxiety.
That too is a crap shoot.
If I used my vehicle to make a living Id shop for a good dealer who will stand by me Regardless the brand.
 
Last edited:
The Direct injection sounds like a diesel with the hood open.
My 2017 Santa Fe is like that.
High pressure injection normal in my mind.
 
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