Is Carbon Build Up a problem? - Page 2 - Chevy Impala Forums
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post #16 of (permalink) Old 07-29-2019
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Here in KY, 93 octane is a minimum of 60 cents higher than 87. But getting back to the original question about carbon deposits. The buildup happens on the valves, not so much in the combustion chamber. The direct injector sprays fuel into the cylinder, so normal deposits that buildup on the valves don't get washed off liked they did with port injection, or throttle body injection, or way back when, carburetors. Repair shops offer an upper intake cleaning service that will clean them, or you can do it yourself. There are youtube videos that show the procedure. I've not done my 2015 yet, but it's only got 34K miles, & still runs nice and smooth.
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post #17 of (permalink) Old 07-29-2019 Thread Starter
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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.
I use 87 (regular) not premium.
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post #18 of (permalink) Old 07-30-2019
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when they replace my spark plugs (yea whoever designed that really sucks) they called and said do you want intake cleaned. how could i resist

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166K on 2014 Blue Ray Metallic 2LTZ with 19s and nav. sadly new trans at 140K. Used to own 1995 DCM SS with only 260K!
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post #19 of (permalink) Old 07-30-2019
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Originally Posted by luckydriver View Post
when they replace my spark plugs (yea whoever designed that really sucks) they called and said do you want intake cleaned. how could i resist

How much did that set you back?
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post #20 of (permalink) Old 07-30-2019
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How much did that set you back?
my mind is telling me 125 or 150. i shoulda asked for pics

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166K on 2014 Blue Ray Metallic 2LTZ with 19s and nav. sadly new trans at 140K. Used to own 1995 DCM SS with only 260K!
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post #21 of (permalink) Old 4 Weeks Ago
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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.
From my understanding/reading it seems as though without a tune you won't see much of a difference in performance running the 93 octane. One of the other members said that he was still seeing a decent amount of knock retard even running the 93 octane. I've viewed a few different forums addressing this issue as well as I was looking for ways to boost power without going heavy on mods and many have them have stated they aren't seeing really any performance boosts from running 93 octane in the 3.6 lfx vvt. The ones that say they do don't really have anything other than anecdotal testimony to support their claims. Does the knock sensor advance timing very slowly? Or should it have things figured out after a tank of premium goes through it? Is their anything else in the sensor/engine system that might prevent the motor from taking advantage of the higher octane?
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post #22 of (permalink) Old 4 Weeks Ago
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Here is a brand new article just posted by Car and Driver on this very subject (high vs. low octane gas):

https://www.caranddriver.com/reviews...dodge-charger/

They test different fuel octane levels in four different cars. Power in every car increased with higher octane fuel - anywhere from 8hp to 20hp depending on the car.

But again, whether or not this extra performance is worth the extra cost of the higher octane gas is a decision that only you can make. Also, just becuase the car is creating more HP on the dyno, doesn't always translate into better 0-60 numbers either (as shown in the article) - there are many other aspects that play into that.

I guess this article illustrates that any advantage of higher octane fuel really depends on the specific engine/car - and how it's tuned from the factory.

For me, especially since I don't put that many miles on my cars anymore, I like to use premium. The extra costs is not going to break the bank and I like knowing that I'm getting the most performance I can from the engine. Also, at least with the way GM tunes their cars (where it starts wtih the high timing tables and reduces the timing when it sees knock), I would think that less overall knock would be better for the engine - so I'd like to avoid as much knock as possilbe. Even though the engine computer quickly reduces timing to stop the knock, that initial knock still happens.
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post #23 of (permalink) Old 4 Weeks Ago
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Originally Posted by jtrosky View Post
Here is a brand new article just posted by Car and Driver on this very subject (high vs. low octane gas):

https://www.caranddriver.com/reviews...dodge-charger/

They test different fuel octane levels in four different cars. Power in every car increased with higher octane fuel - anywhere from 8hp to 20hp depending on the car.

But again, whether or not this extra performance is worth the extra cost of the higher octane gas is a decision that only you can make. Also, just becuase the car is creating more HP on the dyno, doesn't always translate into better 0-60 numbers either (as shown in the article) - there are many other aspects that play into that.

I guess this article illustrates that any advantage of higher octane fuel really depends on the specific engine/car - and how it's tuned from the factory.

For me, especially since I don't put that many miles on my cars anymore, I like to use premium. The extra costs is not going to break the bank and I like knowing that I'm getting the most performance I can from the engine. Also, at least with the way GM tunes their cars (where it starts wtih the high timing tables and reduces the timing when it sees knock), I would think that less overall knock would be better for the engine - so I'd like to avoid as much knock as possilbe. Even though the engine computer quickly reduces timing to stop the knock, that initial knock still happens.
I'd be interested in an article that directly tests the 3.6 lfx motor from GM. The test that seems to matter the most from your article is the naturally aspirated v-8 in the Dodge. Which yielded pretty much no gain in performance running 93 octane compared to regular fuel. I would assume the results would be the same for our cars.
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post #24 of (permalink) Old 4 Weeks Ago
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In your previous post, you were talking about people coming to conclusions without any "evidence" - yet that is *exactly* what you are doing here by assuming that a 3.6L V6, 11.5-1 compression ratio, direct-injected engine, in a car marketed as a "family sedan" and made by GM - would have the same results as 5.7L V8, 10.5-1 compression ratio, pushrod, port-injected engine, in a car manketed as a "performance car' and made by Dodge - would both have the same results. :-)

The engines in the V6 Impala and the V8 Charger are VERY different - as is the stock tuning and the primary "audience". Just because they are both naturally aspirated really means nothing. The Charger is tuned for "performance" from the factory whereas the Impala is tuned for "comfort" from the factory. I'm sure the Charger is tuned more aggressively from the factory, trying to get every bit of performance out the car as possilbe becuase of it's audience.

I have datalogged my 2012 Impala with 87 and 93 octance fuel and there is definitely a lot more knock on 87 octane fuel. Less knock = higher timing = higher performance. I don't do any 0-60 timed runs or even test the car on a dyno, but generally speaking, higher octane reduces knock, which increases performance.

You also have to take the 0-60 tests in that article with a grain of salt since there is so much "human involvement". The driver may have had a better run the first time, for example. Most people would never be able to have the exact same numbers from a 0-60 run even if they do it "back to back".

What *can* be taken from that article is some evidence that higher octane = increased horsepower - without a doubt. Even the naturally-aspirated Charger was stated to gain 14 horsepower with the higher octane fuel according to Dyno tests, which are much more accurate than 0-60 timed tests.
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post #25 of (permalink) Old 4 Weeks Ago
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Originally Posted by jtrosky View Post
In your previous post, you were talking about people coming to conclusions without any "evidence" - yet that is *exactly* what you are doing here by assuming that a 3.6L V6, 11.5-1 compression ratio, direct-injected engine, in a car marketed as a "family sedan" and made by GM - would have the same results as 5.7L V8, 10.5-1 compression ratio, pushrod, port-injected engine, in a car manketed as a "performance car' and made by Dodge - would both have the same results. 🙂

The engines in the V6 Impala and the V8 Charger are VERY different - as is the stock tuning and the primary "audience". Just because they are both naturally aspirated really means nothing. The Charger is tuned for "performance" from the factory whereas the Impala is tuned for "comfort" from the factory. I'm sure the Charger is tuned more aggressively from the factory, trying to get every bit of performance out the car as possilbe becuase of it's audience.

I have datalogged my 2012 Impala with 87 and 93 octance fuel and there is definitely a lot more knock on 87 octane fuel. Less knock = higher timing = higher performance. I don't do any 0-60 timed runs or even test the car on a dyno, but generally speaking, higher octane reduces knock, which increases performance.

You also have to take the 0-60 tests in that article with a grain of salt since there is so much "human involvement". The driver may have had a better run the first time, for example. Most people would never be able to have the exact same numbers from a 0-60 run even if they do it "back to back".

What *can* be taken from that article is some evidence that higher octane = increased horsepower - without a doubt. Even the naturally-aspirated Charger was stated to gain 14 horsepower with the higher octane fuel according to Dyno tests, which are much more accurate than 0-60 timed tests.
The key words you should've taken from my comment are "would assume". That doesn't mean I refute the claim of the article. It just simply means that I would assume since they are the most similar that I'd expect the results to be similar. I'm just inquiring about information on the subject. I'm not here to argue.

I'm just saying I'd be interested in seeing testing on our specific engine to see what the results would be between octane.
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post #26 of (permalink) Old 4 Weeks Ago
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But, with the information you provided, can one assume that you could gain even more performance from E85? I understand it's a lower BTU fuel, so mpg will take a hit, but the fuel management system will make up for this by making the ratio richer correct?
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can one assume that you could gain even more performance from E85?
I dont think you will notice any performance difference, but the engine is now capable of running a less dense fuel by taking advantage of its octane rating. The injectors and fuel pump are also larger to accommodate longer injector duty cycles.

I cant run E85 in my Impala, but I can in my Terrain. My seat of the pants dyno tells 0 difference from 93 octane fuel and E85. My MPG running E85 drops about 3MPG, but the cost per mile is still much cheaper.
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post #28 of (permalink) Old 4 Weeks Ago
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Am I the only one waiting on opinions about the original question? It seems we finally got it clear that Top Tier means a higher quality/level of detergents to fight carbon build up. But like the original poster jayawest, I am curious if that is considered enough or are there recommendations on type and frequency of additional carbon buildup cleaners?

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post #29 of (permalink) Old 4 Weeks Ago Thread Starter
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Am I the only one waiting on opinions about the original question? It seems we finally got it clear that Top Tier means a higher quality/level of detergents to fight carbon build up. But like the original poster jayawest, I am curious if that is considered enough or are there recommendations on type and frequency of additional carbon buildup cleaners?

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I wish someone would answer the specific question and not refer to knocking and other things. I need clarification on the Carbon Build up concern!
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post #30 of (permalink) Old 4 Weeks Ago
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Originally Posted by ChevyGuru View Post
But, with the information you provided, can one assume that you could gain even more performance from E85? I understand it's a lower BTU fuel, so mpg will take a hit, but the fuel management system will make up for this by making the ratio richer correct?
From what I've seen, most people actually do report better performance with E85. Personally, I've never even seen an E85 pump, let alone actually ran it, so I have no first-hand knowledge about it. :-) Like you said, you'll get way less MPG with E85, but the 3.6L FlexFuel Impalas do run different timing for E85 fuel (they have flex-fuel-specific "adder" tables where it changes timing for different levels of ethanol). Some areas of the adder table (rpm/airmass table) have lower timing and some areas have higher timing. Some areas of the timing table add as much as 18.5 degrees of timing, which is a HUGE difference. It semes like low-throttle, mid-rpm areas actually reduce timing by a few degrees and the higher-throttle, mid-rpm areas have more timing.

Last edited by jtrosky; 4 Weeks Ago at 06:28 AM.
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