Just reading the engine specs on a 2013 Kia Optima Hybrid I have. Says it has 13:1 compression ratio with multi-port fuel injection. I was under the impression only DI could support such high compression. And it runs on regular gas. Explain.
13:1 compression ratio on regular gas?
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13:1 compression = high octane fuel.
They can put knock sensors and adjust the timing via ECM but, that guarantees nothing.
Russian roulette. Are you game?
They can put knock sensors and adjust the timing via ECM but, that guarantees nothing.
Russian roulette. Are you game?
Is it Atkinson cycle? They often have a higher compression ratio but can still take regular 
Hyunkia engines are Atkinson Cycle, so they may have a physical compression ratio that's 13:1, but due to the intake overlap on the compression stroke the effective compression is lower or something like that.
I don't believe Hyunkia does that, I only know of Toyota, Ford, and VAG doing that.
Yes it is. Does that mean when under load it won't maintain 13:1? Only at cruise or coasting?Is it Atkinson cycle? They often have a higher compression ratio but can still take regular
The intake valve is open during part of the compression stroke making the actual compression ratio lower but the expansion ratio higher during the power stroke, which is supposed to gain efficiency compared to using an equal compression and expansion ratio, I guess when you compare an equivalent engine using the otto cycle with a lower compression ratio equivalent to the effective compression of a comparable Atkinson cycle engine, there's still more power the could be extracted from the expansion during the power stroke but you run out of stroke and have to exhaust thus losing efficiency that is afforded by the Atkinson cycle..
With an Atkinson cycle engine, you will never get close to 13:1 ever due to most of the compression going out the intake valve on the compression stroke.
13:1 compression is just a measurement of quench the combustion chambers have BEFORE any valve overlap, etc.
There’s static compression ratio which is the 13:1 you are referring to and is the one you see in the specifications for any manufacturers motor. Then you have dynamic compression ratio which is when the engine is running. Two different beast entirely.
and mitsubishi. they go even further, it's essentially always running port injected and under certain conditions runs DI aswell
Hyundai does MPI + DI now.
The engine in the original poster’s car is indeed a MPI engine. Hyundai/Kia only used MPI on their hybrid engines for quite some time.
If the manual says it can run on regular you will be fine I had a 2007 Audi A6 3.2 which had 12.5 compression ratio. I ran it on regular for 148k miles and no issues. Manual said regular was fine. On the other hand my 911 says premium only and that is what I use.
the malaise era jag v12s were 13:1 or 12:1 depending on the market and you could run them on regular gas all day long if you retard the timing with the distributor.
it all depends on the head design and advanced knock control makes this a lot easier for sure
it all depends on the head design and advanced knock control makes this a lot easier for sure
I'm also surprised at how far port injected gas engines go in terms of compression
My Camrys MZ V6 does pull hardest on 93 octane, but at a comparatively low 10.8:1
I remember older Ford hybrids ran the Atkinson cycle, and even older Mazda's (929/Millennia) ran the Miller cycle
My Camrys MZ V6 does pull hardest on 93 octane, but at a comparatively low 10.8:1
I remember older Ford hybrids ran the Atkinson cycle, and even older Mazda's (929/Millennia) ran the Miller cycle
