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post #1 of (permalink) Old 07-26-2019 Thread Starter
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Is Carbon Build Up a problem?

I have been recently hearing a lot of talk about Gasoline Direct Injection (GDI) engines building up carbon really bad after about 30k-75k miles and my GDI engine has 113k. I never noticed my car (Impala with the 3.6L V6) was direct injected till I lifted up my hood and at the engine cover and it stated clear as day, direct injection. I’ve saw pictures/videos of Ford’s/Kia’s/Hyundai’s with about 75k miles with the GDI engine carbon’d up, I’m not sure if mine has this problem but if so what are some SAFE solutions to get rid of it? (I’ve heard some solutions can clog up the Catalytic Converter.) I haven’t seen a Chevrolet dealer that offers a cleaning service, only other brands. I change the oil frequently, drive mostly highway, and only Top Tier Fuel. The only thing that I do wrong is excessively idling all the time.
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post #2 of (permalink) Old 07-27-2019
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Originally Posted by jayawest View Post
I have been recently hearing a lot of talk about Gasoline Direct Injection (GDI) engines building up carbon really bad after about 30k-75k miles and my GDI engine has 113k. I never noticed my car (Impala with the 3.6L V6) was direct injected till I lifted up my hood and at the engine cover and it stated clear as day, direct injection. I’ve saw pictures/videos of Ford’s/Kia’s/Hyundai’s with about 75k miles with the GDI engine carbon’d up, I’m not sure if mine has this problem but if so what are some SAFE solutions to get rid of it? (I’ve heard some solutions can clog up the Catalytic Converter.) I haven’t seen a Chevrolet dealer that offers a cleaning service, only other brands. I change the oil frequently, drive mostly highway, and only Top Tier Fuel. The only thing that I do wrong is excessively idling all the time.
What do you mean you're using top tier fuel? You're not using 93 octane are you? Because that's just throwing money down the drain for no benefit whatsoever.

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^ If you're concerned about intake valve coking you can plumb in a quality oil catch can. RX (RevXtreme Motorsports) and/or Elite (available at JDP Motorsports) are 2 good options.
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post #4 of (permalink) Old 07-27-2019
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What do you mean you're using top tier fuel? You're not using 93 octane are you? Because that's just throwing money down the drain for no benefit whatsoever.
From The Owners Manual:

Fuel
Use of the recommended fuel is an
important part of the proper
maintenance of this vehicle. To help
keep the engine clean and maintain
optimum vehicle performance, we
recommend using TOP TIER
Detergent Gasolines. See
www.toptiergas.com for a list of TOP
TIER Detergent Gasolines.

93 Octane will give some performance benefit as the computer will advance the timing further. The owners Manual states to use 87 Octane or Higher, with 87 Octane being the low limit.
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post #5 of (permalink) Old 07-27-2019
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Originally Posted by Bowtie396 View Post
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Originally Posted by RobHazmat View Post
What do you mean you're using top tier fuel? You're not using 93 octane are you? Because that's just throwing money down the drain for no benefit whatsoever.
From The Owners Manual:

Fuel
Use of the recommended fuel is an
important part of the proper
maintenance of this vehicle. To help
keep the engine clean and maintain
optimum vehicle performance, we
recommend using TOP TIER
Detergent Gasolines. See
www.toptiergas.com for a list of TOP
TIER Detergent Gasolines.

93 Octane will give some performance benefit as the computer will advance the timing further. The owners Manual states to use 87 Octane or Higher, with 87 Octane being the low limit.
You won't receive any performance gains. Unless you raise the compression, you will not see benefits of using premium gas. Seems the owner manual means top tier gas as in gasoline that contains a certain level and type of detergents. It does not mean it recommends you using 93 octane. Higher octane just allows gas to handle higher compression without igniting prematurely. They contain the same exact energy content, so higher octane won't produce any more power. You're wasting money.

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Last edited by RobHazmat; 07-27-2019 at 10:42 AM.
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post #6 of (permalink) Old 07-27-2019
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You won't receive any performance gains. Unless you raise the compression, you will not see benefits of using premium gas. You're wasting money.
RobHazmat, You obviously do not understand modern engines. This engine is already at a 11.5:1 Compression Ratio. (Direct Injection Allows This) It is also equipped with a knock sensor. When the computer advances the ignition & valve timing it brings it the point just before spark knock occurs, with 93 Octane, it can advance timing much farther as 93 Octane has a higher resistance to spark knock. It's not all about compression.

Even in the old days you could run the timing more advanced with higher octane gas, you just had to change the timing yourself with trial and error. Higher Compression also necessitated the use of higher Octane gas but is not the only reason for it.
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post #7 of (permalink) Old 07-27-2019
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Originally Posted by RobHazmat View Post
You won't receive any performance gains. Unless you raise the compression, you will not see benefits of using premium gas. You're wasting money.
RobHazmat, You obviously do not understand modern engines. This engine is already at a 11.5:1 Compression Ratio. (Direct Injection Allows This) It is also equipped with a knock sensor. When the computer advances the ignition & valve timing it brings it the point just before spark knock occurs, with 93 Octane, it can advance timing much farther as 93 Octane has a higher resistance to spark knock. It's not all about compression.

Even in the old days you could run the timing more advanced with higher octane gas, you just had to change the timing yourself with trial and error. Higher Compression also necessitated the use of higher Octane gas but is not the only reason for it.
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post #8 of (permalink) Old 07-27-2019
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What are you a little kid ? Go buy a basic Automotive Text Book and learn something. I have been a mechanic and engineer for 25 years, and people like you are BS because you think you are a Know-It-All.
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post #9 of (permalink) Old 07-27-2019
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What are you a little kid ? Go buy a basic Automotive Text Book and learn something. I have been a mechanic and engineer for 25 years, and people like you are BS because you think you are a Know-It-All.
So youre aware of the OAR that limits the range of the knock sensor which won't allow it to advance the timing to even matter? Also, just to entertain your opinion, let's say it does advance the timing to make a difference with 93 octane. What benefit are you really getting? Maybe 1-2 mpg increase if you're lucky? More realistically you'd be getting somewhere in the .3-.5mpg range increase. So cool, you're upping your gas mileage anywhere between 2-10%, but now spending 25-35% more in gas.. so tell me? Did you just improve your performance or nah? Because your mile per dollar just went wayy down.

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post #10 of (permalink) Old 07-27-2019
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I am aware that the OAR (Octane Adjust Ratio) is a creation of Ford used with EcoBoost Engines.

The Ford Mustang with the 2.3L On 87 Octane it makes 275 HP, on 93 Octane it makes 310 HP, this is all done by the PCM advancing valve and ignition timing based on input from the knock sensor and other readings from various sensors.

Getting better MPG is not the purpose of advancing the timing, it is getting more power, I do not understand why the rant about MPG as it has nothing to do with it. The PCM can advance the timing as it sees fit based on input from the knock sensor unless a limit is imposed in the software.

As usual you do not know what you are talking about, just trying to prove that you are a Know-It-All.
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post #12 of (permalink) Old 07-28-2019
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It has been shown that the 3.6L DI LFX engine does produce more power and get better gas mileage with higher octane fuel. Like mentioned, the computer starts with the timing from the "high octane" table and reduces it down towards the "low octane" table timing as it experiences knock. It *will* experience more knock on lower octane gas, which means it will lower timing. Less timing = lower performance. The more knock it detects, the further it lowers the timing (until it gets to the timing value in the "low octane" timing table. It also "remembers" the amount of knock for a certain amount of time via a "knock learn" value.

More timing = better performance. The lower the amount of knock (and knock retard), the better.

Whether or not squeezing that last bit of performance from the engine is worth it to you or not is a personal decision.

This is all clearly visible by logging the engine parameters with something like HPTuners (which I've done). I definitely saw more KR on lower-octrane fuel. You can also watch how the Knock Learn value impacts things.
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post #13 of (permalink) Old 07-28-2019
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I've tried the higher octane in my 14 LTZ 3.6. If I'm climbing mountains and fighting the wind I see a slightly better gas milage after a tank or two. But no where near enogh to justify 20-30 cent a gallon price increase. I get up to 34mpg @ 75 using 87 octane top tier gas. Now paying just a few more cents per gallon for that is justifiable in my humble opinion.
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post #14 of (permalink) Old 07-28-2019
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I've tried the higher octane in my 14 LTZ 3.6. If I'm climbing mountains and fighting the wind I see a slightly better gas milage after a tank or two. But no where near enogh to justify 20-30 cent a gallon price increase. I get up to 34mpg @ 75 using 87 octane top tier gas. Now paying just a few more cents per gallon for that is justifiable in my humble opinion.
Getting better MPG is not the main purpose of Higher Octane Fuel or Advancing the Timing, it is getting more power, although there can be a rise in MPG depending on how you drive it.
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post #15 of (permalink) Old 07-28-2019
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In my region, 93 octane is 50 cents/gal higher than 87 octane. That's considerably more than just a few cents per gallon.
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