[currantredGT]

The octane rating is a measure of a fuel's resistance to knock under pressure. The "compression ratio" of an engine is a static figure that represents the difference in cylinder volume between bottom dead center and top dead center. It doesn't necessarily represent anything about the actual pressure in the cylinder. The 1.6L engine might have a compression ratio of "only" 10.5:1 (I believe it's actually 10:1), but it's also turbocharged, and it's really disingenuous to ignore that. Yes, a Forte GT with the 1.6T engine will run just fine on 87 octane fuel, but it will make even more power on 89, 91, or 93 octane fuel. Modern engines use advanced variable valve timing, fuel injection, and electronic ignitions to allow this, but what is typically happening with 87 octane fuel in a turbocharged engine is that you are taking a more powerful engine and de-tuning it so that it will still run properly without detonating. Many automakers advertise the power generated with 91 octane fuel (Ford with EcoBoost engines, for example, where they actually note the reduced hp/torque figures with lower octane fuel in the owner's manual), but Kia has apparently taken the route of advertising the 87 octane power rating, which is pretty impressive at 201hp (just over 125hp per liter). Since 87 octane or higher fuel is what they specify, they have seemingly made the choice of deliberately under-rating the performance of their 1.6T engine for whatever reason. In any case, it makes the Kia Forte GT an exceptionally good value for its price point, and a very fun car indeed.

I would like to share some of my input that I've been able to "log" with 2 simple devices: an OBDII scanner along w/ car scanner app for iphone, and a dragy perf. meter...
Coming from a car that RECOMMENDED 93 octane for better performance, and doing some "research" on the 1.6t engine prior to buying the Forte, I decided to continue on w/ fueling up w/ 93...

Did a few runs/pulls 0-60s, 45-65, 20-60, 80-100 mph plus a few others, 1/4 mi, 1/8 mile...cool. Quick car.

After 2 1/2 months of fueling up w/ 93, I decided to try out 89 octane...

There are NO differences between 89 and 93....at all. None that dragy can show. Taking into account variations in temperatures and DA, of course. I am at sea level.

Back when I was running 93 octane, the car scanner app "logged" 226.76 hp @ 55F, on 89 octane the app logged 221.65 hp @73-77F... Granted, I do not know the accuracy of the OBDII scanner in proving engine HP, seem pretty accurate for other values I occasionally track, and 220-227 at engine would equal ~182-192 at the wheel...

I don't know if there are any differences between the 2020 and 2021 Fortes, (I don't think so), but at least that's what my '21 is showing me.

 

[ZiggyM5]

The part I hate is that when you fuel up the message on the gas pump says: "May contain up to 10% ethanol". I take that to mean it may be 5%...6%...10%...12%...13%...15%! All depends on how much ethanol the delivery truck filler felt like putting in it...

Hummmm.... that doesn't sound good at all. 😱

 

[ForteGT2]

Hummmm.... that doesn't sound good at all. 😱

It does say "MAY CONTAIN"...LOL!

 

[ZiggyM5]

It does say "MAY CONTAIN"...LOL!

Yeap. "MAY. " That's scary!!!!

 

[jsblanch]

The part I hate is that when you fuel up the message on the gas pump says: "May contain up to 10% ethanol". I take that to mean it may be 5%...6%...10%...12%...13%...15%! All depends on how much ethanol the delivery truck filler felt like putting in it...

It can't be more than 10% ethanol if the sign says "May contain up to 10% ethanol." I'm pretty sure they don't actually need a sign, though, and that any gasoline can be up to 10% ethanol. When was the last time you saw a sign for any grade of gasoline that actually told you that it didn't contain ethanol? I haven't see one in years, I think.

 

[ForteGT2]

It can't be more than 10% ethanol if the sign says "May contain up to 10% ethanol." I'm pretty sure they don't actually need a sign, though, and that any gasoline can be up to 10% ethanol. When was the last time you saw a sign for any grade of gasoline that actually told you that it didn't contain ethanol? I haven't see one in years, I think.

Now doubt the amount of ethanol is scientifically controlled...

Local Citgo has gas with no ethanol...advertised too.

 

[008601]

The octane rating is a measure of a fuel's resistance to knock under pressure. The "compression ratio" of an engine is a static figure that represents the difference in cylinder volume between bottom dead center and top dead center. It doesn't necessarily represent anything about the actual pressure in the cylinder. The 1.6L engine might have a compression ratio of "only" 10.5:1 (I believe it's actually 10:1), but it's also turbocharged, and it's really disingenuous to ignore that. Yes, a Forte GT with the 1.6T engine will run just fine on 87 octane fuel, but it will make even more power on 89, 91, or 93 octane fuel. Modern engines use advanced variable valve timing, fuel injection, and electronic ignitions to allow this, but what is typically happening with 87 octane fuel in a turbocharged engine is that you are taking a more powerful engine and de-tuning it so that it will still run properly without detonating. Many automakers advertise the power generated with 91 octane fuel (Ford with EcoBoost engines, for example, where they actually note the reduced hp/torque figures with lower octane fuel in the owner's manual), but Kia has apparently taken the route of advertising the 87 octane power rating, which is pretty impressive at 201hp (just over 125hp per liter). Since 87 octane or higher fuel is what they specify, they have seemingly made the choice of deliberately under-rating the performance of their 1.6T engine for whatever reason. In any case, it makes the Kia Forte GT an exceptionally good value for its price point, and a very fun car indeed.

Knock is pre detonation. The compression at higher levels requires an octane rating that's higher so it won't pre detonate. Adding higher octane to lower compression engines will not add power. It just takes longer for it to combust which is at top dead center instead of being at its ready to fire stage lower in the stroke. It's called a power stroke in a diesel. It allows the fuel charge to burn through its entire down stroke because of the lower compression than big bore diesels and better atomization of the fuel. On the street you would not see any difference in power. The only thing going faster is the money out of your wallet.

 

[Chevrasaki]

The octane rating is a measure of a fuel's resistance to knock under pressure. The "compression ratio" of an engine is a static figure that represents the difference in cylinder volume between bottom dead center and top dead center. It doesn't necessarily represent anything about the actual pressure in the cylinder. The 1.6L engine might have a compression ratio of "only" 10.5:1 (I believe it's actually 10:1), but it's also turbocharged, and it's really disingenuous to ignore that. Yes, a Forte GT with the 1.6T engine will run just fine on 87 octane fuel, but it will make even more power on 89, 91, or 93 octane fuel. Modern engines use advanced variable valve timing, fuel injection, and electronic ignitions to allow this, but what is typically happening with 87 octane fuel in a turbocharged engine is that you are taking a more powerful engine and de-tuning it so that it will still run properly without detonating. Many automakers advertise the power generated with 91 octane fuel (Ford with EcoBoost engines, for example, where they actually note the reduced hp/torque figures with lower octane fuel in the owner's manual), but Kia has apparently taken the route of advertising the 87 octane power rating, which is pretty impressive at 201hp (just over 125hp per liter). Since 87 octane or higher fuel is what they specify, they have seemingly made the choice of deliberately under-rating the performance of their 1.6T engine for whatever reason. In any case, it makes the Kia Forte GT an exceptionally good value for its price point, and a very fun car indeed.

Finally someone who understands. This man knows what he is talking about. Everyone else is just speculating.

If anyone else is actually interested in learning something, instead of guessing your way through life, here are some resources:
Why turbo cars use lower compression ratios:

What is octane?

How ECUs work to change tons of variables on the fly:

 

[El Spicoli]

Finally someone who understands. This man knows what he is talking about. Everyone else is just speculating.

If anyone else is actually interested in learning something, instead of guessing your way through life, here are some resources:
Why turbo cars use lower compression ratios:

What is octane?

How ECUs work to change tons of variables on the fly:

Ok, I will ask - how much difference in HP is there btw 87, 89, 91, and 93. Pretty sure it is not a big gain with the higher octane.

Sent from my Pixel 4a using Tapatalk

 

[currantredGT]

Ok, I will ask - how much difference in HP is there btw 87, 89, 91, and 93. Pretty sure it is not a big gain with the higher octane.

Sent from my Pixel 4a using Tapatalk

 

[Chevrasaki]

Y'all can pretend that these 1.6T engines are lazy lumps of cast iron, but this is no Corolla. Kia have tuned this tiny little 1.6L turbo engine to produce a lot of power. The turbo raises intake pressure in the cylinder by more than 15PSI under load and adds a lot of heat. It only takes a simple google search "Kia / Hyundai pre-detonation issues" to see that they have already had to update software in older cars because these tiny 4-cyl engines with all of this tech and high compression destroy themselves trying to meet EPA regulations. Personally, I have learned too much about what causes Low Speed Pre Ignition and what it can do to your engine to feel comfortable putting 87 in a forced induction engine, or even a high compression NA engine.

For me, an extra ~$5 per fill up is pretty cheap peace of mind.

 

[ForteGT2]

Y'all can pretend that these 1.6T engines are lazy lumps of cast iron, but this is no Corolla. Kia have tuned this tiny little 1.6L turbo engine to produce a lot of power. The turbo raises intake pressure in the cylinder by more than 15PSI under load and adds a lot of heat. It only takes a simple google search "Kia / Hyundai pre-detonation issues" to see that they have already had to update software in older cars because these tiny 4-cyl engines with all of this tech and high compression destroy themselves trying to meet EPA regulations. Personally, I have learned too much about what causes Low Speed Pre Ignition and what it can do to your engine to feel comfortable putting 87 in a forced induction engine, or even a high compression NA engine.

For me, an extra ~$5 per fill up is pretty cheap peace of mind.

If you watch all the videos in this thread and listen to those that write about "compression ratios" you'll notice that they all talk about low compression ratios in turbo engines. Kia's 1.6T has a 10.5:1 compression ratio - THAT is not low compression! You can bet that during high load conditions the engine is reducing power by retarding the timing to prevent pre-ignition because of 87 octane gas.

 

[currantredGT]

Y'all can pretend that these 1.6T engines are lazy lumps of cast iron, but this is no Corolla. Kia have tuned this tiny little 1.6L turbo engine to produce a lot of power. The turbo raises intake pressure in the cylinder by more than 15PSI under load and adds a lot of heat. It only takes a simple google search "Kia / Hyundai pre-detonation issues" to see that they have already had to update software in older cars because these tiny 4-cyl engines with all of this tech and high compression destroy themselves trying to meet EPA regulations. Personally, I have learned too much about what causes Low Speed Pre Ignition and what it can do to your engine to feel comfortable putting 87 in a forced induction engine, or even a high compression NA engine.

For me, an extra ~$5 per fill up is pretty cheap peace of mind.

Based on my above results, Id not compare this car with a Corolla, and I don't think anyone on this comment section has made any comments about the car being lazy, to the contrary...
You mentioned in a post something about speculating...I wouldn't call testing with GPS perf. meter and using an OBDII to see check out values like boost, for example, which remain the same with either octane... speculating...what I've done is actual testing, no? Speculating would be holding on to the stance that THIS car performs better on 93...my testing proved that it doesn't - that is my main stance.

Now about reliability and any potential issues w/ these engines if you don't use 93, I wonder if Kia, or Hyundai for that matter, would still recommend 87+ for a engine that will "inevitably" fail along with offering a 10yr/100k mi powertrain? THAT is A LOT lol - wouldn't that create more money they would lose on inevitable warranty work rather than just specifying to use higher octane ONLY (91+)? I think the latter would be better and the most cost-effective option in the long run for a company, unless you want to argue that they will find ways to void your warranty? lol

 

[ForteGT2]

IMO 87 is fine! It is what Kia recommends...for normal driving. However, for people who drive their cars and only use two throttle positions - idle and WOT - a higher octane would be better.

 

[currantredGT]

IMO 87 is fine! It is what Kia recommends...for normal driving. However, for people who drive their cars and only use two throttle positions - idle and WOT - a higher octane would be better.

lol maybe if youre in constant "abuse" mode , sure

 

[Chevrasaki]

If you watch all the videos in this thread and listen to those that write about "compression ratios" you'll notice that they all talk about low compression ratios in turbo engines. Kia's 1.6T has a 10.5:1 compression ratio - THAT is not low compression! You can bet that during high load conditions the engine is reducing power by retarding the timing to prevent pre-ignition because of 87 octane gas.

Haha yeah I posted most of those videos. Retarding the spark timing is absolutely one way an engine can help prevent damage from pre-ignition. It can also change when the valves open and close, how long they stay open for, how much boost the turbo is adding, how much fuel the direct injection is spraying, etc. It's wild how many variables the computer has control over to make it run smooth in all altitudes, at all temperatures, and give better economy when cruising, plus more power when requested. I'm a nerd, I can literally read about this stuff all day.

Based on my above results, Id not compare this car with a Corolla, and I don't think anyone on this comment section has made any comments about the car being lazy, to the contrary...
You mentioned in a post something about speculating...I wouldn't call testing with GPS perf. meter and using an OBDII to see check out values like boost, for example, which remain the same with either octane... speculating...what I've done is actual testing, no? Speculating would be holding on to the stance that THIS car performs better on 93...my testing proved that it doesn't - that is my main stance.

Now about reliability and any potential issues w/ these engines if you don't use 93, I wonder if Kia, or Hyundai for that matter, would still recommend 87+ for a engine that will "inevitably" fail along with offering a 10yr/100k mi powertrain? THAT is A LOT lol - wouldn't that create more money they would lose on inevitable warranty work rather than just specifying to use higher octane ONLY (91+)? I think the latter would be better and the most cost-effective option in the long run for a company, unless you want to argue that they will find ways to void your warranty? lol

I absolutely appreciate the data to back up your claim. While it does contradict the claim that the vehicle will adjust it's fuel map to the type of fuel you're using and provide more power, I'm still not convinced that there are no benefits from running higher octane fuel. You may be right, and if you are, then as I mentioned, I end up paying $5 more per tank. If I am right, then I will get much more than 100K out of the engine.

IMO 87 is fine! It is what Kia recommends...for normal driving. However, for people who drive their cars and only use two throttle positions - idle and WOT - a higher octane would be better.

This is a great point, if you never drive with WOT then you really wouldn't see the benefits of higher octane, the engine would never try to make more power if it is not requested.

I am one of those "idle, and WOT" people you mentioned hahaha.

lol maybe if youre in constant "abuse" mode , sure

Is that a problem?

 

[ForteGT2]

lol maybe if youre in constant "abuse" mode , sure

They exist...LOL!

Forte GT vs world - YouTube

Kia Forte GT Vs The World - YouTube

 

[currantredGT]

Haha yeah I posted most of those videos. Retarding the spark timing is absolutely one way an engine can help prevent damage from pre-ignition. It can also change when the valves open and close, how long they stay open for, how much boost the turbo is adding, how much fuel the direct injection is spraying, etc. It's wild how many variables the computer has control over to make it run smooth in all altitudes, at all temperatures, and give better economy when cruising, plus more power when requested. I'm a nerd, I can literally read about this stuff all day.



I absolutely appreciate the data to back up your claim. While it does contradict the claim that the vehicle will adjust it's fuel map to the type of fuel you're using and provide more power, I'm still not convinced that there are no benefits from running higher octane fuel. You may be right, and if you are, then as I mentioned, I end up paying $5 more per tank. If I am right, then I will get much more than 100K out of the engine.



This is a great point, if you never drive with WOT then you really wouldn't see the benefits of higher octane, the engine would never try to make more power if it is not requested.

I am one of those "idle, and WOT" people you mentioned hahaha.



Is that a problem?
View attachment 82945

^^^that's hilarious!

I think I do some spiritedly driving I don't hit triple digits many times, though lol
But constant "abuse mode" creates more wear and tear and, at the end of the day, this is NOT a performance car, no matter how quick it is for what it is. I don't think 93 octane would save an engine from constant abuse - yes, some ppl drive like that...but it's another variable to consider for the life expectancy of any engine lol

 

[El Spicoli]

I don't want to challenge your times though I do like to open it up a bit. We have some saying use the various octanes and Kia says it is ok to run 87 octane. Call me crazy but if they thought their engines were gonna implode using 87, they would not have advised to use it.

It was a simple Q, what HP gains are obtained using the various octane rated gasoline? My point is that putting 89 rated octane gas.is not going to get you a lot more HP. I do put mid grade in mine btw.

I am not trying to beat people off the line and I don't have Civic SIs trying to race me though I do get a ton of compliments on the fire orange color and rebadging.

Sent from my Pixel 4a using Tapatalk

 

[currantredGT]

I don't want to challenge your times though I do like to open it up a bit. We have some saying use the various octanes and Kia says it is ok to run 87 octane. Call me crazy but if they thought their engines were gonna implode using 87, they would not have advised to use it.

It was a simple Q, what HP gains are obtained using the various octane rated gasoline? My point is that putting 89 rated octane gas.is not going to get you a lot more HP. I do put mid grade in mine btw.

I am not trying to beat people off the line and I don't have Civic SIs trying to race me though I do get a ton of compliments on the fire orange color and rebadging.

Sent from my Pixel 4a using Tapatalk

Lol I didnt mean to target you, or anyone, I've just been trying to prove that, based on my testing, I've not seen any differences in performance w/ this car (granted, up to 110 mph - the car is limited to 135-138 mph -Ive not reached that)...I use 89 just cuz lol I could just fuel up with 87 or 93 but Im happy w/ 89 - a happy medium I have not tested w/ 87, my guess would be about the same as 89 and 93...

Personally, I think its pretty cool that I get to say "I can do 6.31-6.4 sec to 60 sec in my car w/o 93 octane " lol considering that a Mazda 3 turbo does 5.9-6.1 sec with 93 octane ONLY (w/o launching).