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Discussion Starter #1
in your opinion what is the best additive to put in the tank to decarbonize the valves and piston crowns?
 

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I have been using Marvel Mystery Oil (MMO) every other tank full. I add 2-3 ounces and hopefully this will prevent any valve concerns down the road. Seafoam, I am told is good, also.
MMO saved the day for one of our members at the smart Car Rally in Deadwood, SD. He developed a severe engine miss & through a CEL. This happen out in the middle of nowhere. The only thing I could think of at the moment to try and resolve this concern was to give the car a double dose of MMO. I added 6 ounces to a full tank, we erased the code which was a P0 300 and a after driving a few miles down the road, everything returned to normal. We used MMO religiously in that car for the rest of the trip and there were no further issues with cylinder misfiring.
 

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For the valves, unless you have direct injection, the best bet would be Techron.

To clean off the tops of the piston crowns, the best thing I've found is Mopar Combustion Chamber Cleaner. MCCC squirted directly into the cylinder and let to sit for a couple of hours took off all the carbon on top of the pistons of my Miata with over 180k miles on it, to the point where I could see shiny metal and read casting lettering.
 

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in your opinion what is the best additive to put in the tank to decarbonize the valves and piston crowns?
Just curious but why do you think you need to do this? Does the car have that much mileage? Did you do a compression test that indicated an issue?

Since we have to run premium I'd just top up the tank and take it for a good run down the highway.

I'm not a big fan of using an additive unless they are absolutely necessary.
 

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I think I saw it in an '09 Mercedes manual, but if one does not use Top Tier Premium there is a prescription to use additive, and I believe it is of the Techron type....
 

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Discussion Starter #9
anyone heard of BMG products

it is not a high mileage car and all internal combustion engines build up carbon deposits, especially on the exhaust valves and piston crowns.

it's just a maintenance to keep it from too much build up. i have used Techron over the years but just wanted to see what everyone else used.

one idea i am toying with but cannot figure out where to put a switch that is accessable while driving like on the shift lever but it is too short and has to be a momentary switch. thats what is holding me up. in WW2 (my dad was a bomber mechanic)bombers used 55 gallons of water in a drum on take off then jettison the drum. water kept carbon build up down and allowed them to run full boost on the superchargers and advance the timing for max power because of weight and shorter runways. i used it twice on cars in the past. and one time tore the engine down to install an aggressive cam for a supercharger and the engine was just like new. the water cools the intake air making it denser then turns to steam and slowly dissolves carbon. when i had a PT cruiser turbo. several guys set a system up like this and reported favorable results (i had already been doing it for years but in mine i ran 50/50 alcohol and water). the trick is to not overload the engine or it can contaminate the oil).

i know this is no high performance engine but i have always believed engines were built and could easily be improved on (thats why there are aftermarket parts).

i'd love to drive the limited edition (for $52000...wow) that has 123hp. boy what a sleeper!
 

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Just curious but why do you think you need to do this? Does the car have that much mileage? Did you do a compression test that indicated an issue?

Since we have to run premium I'd just top up the tank and take it for a good run down the highway.

I'm not a big fan of using an additive unless they are absolutely necessary.
I feel strongly that the valves and piston tops should be de-carbonized. This little Mitsubishi engine lugs alot if you drive it in automatic mode. We can debate about the subject until the next century.There will always be someone for doing it and some of us against it. I tore my engine down for a misfire code on cylinder 3. My Fortwo was previously owned by an elderly gentlemen and he did not take very good care of it. I tore the engine down at 36,700 miles and here is 2 pictures of what I found.






So for me and my side of the argument, the proof is in the pics. These engines are prone to carbon. Now whether the fellow ran hi-test gas or not, I do not know. We have argued every point of adding or not adding additives to the fuel and oil. There are even those that argue about whether it carbons up and as to why or why not and a million other points about the whole situation.
So I say to you, just look at the pictures and if you worry about your valves looking like this then get yourself an additive and use it religously. If it doesn't matter to you, then don't. You may never get a misfire from faulty valves and burned seats and many don't. But if you had to go through what I did at 36,000 miles, then a little Marvel Mystery Oil in the gasoline and a little in the gas tank occasionally makes ME FEEL better. Whether it helps long term or not I do not know at this early point. But for ME I'm not taking any chances. There were those on this forum that convinced me to do it and I like the idea. We used to rev the engine up to about 2,000 rpm and trickle water into the carburetor. That would supposedly quickly cool the carbon and cause it to break loose. Kind of hard to do on the Fortwo. Let the debate roll on. DCO
 

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The opinions of those in the automotive fuel industry say by using a top tier fuel, valve deposits should be practically eliminated for non-DI engines. This has come from different people on different automotive forums, and I've seen high mileage engines used in a high performance manner with very clean intake and exhaust valves.

Cylinder deposits are more difficult to prevent and eliminate, but tend to also have a much smaller effect on engine performance. I know of one instance of an engine used for numerous track days that broke a valve spring after about 20k miles and not long after a dyno run that showed minimally decreased power output from new. The inside looked pretty rough with carbon caked on the piston crown but output was not affected much.


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I feel strongly that the valves and piston tops should be de-carbonized. This little Mitsubishi engine lugs alot if you drive it in automatic mode. We can debate about the subject until the next century.There will always be someone for doing it and some of us against it. I tore my engine down for a misfire code on cylinder 3. My Fortwo was previously owned by an elderly gentlemen and he did not take very good care of it. I tore the engine down at 36,700 miles and here is 2 pictures of what I found.






So for me and my side of the argument, the proof is in the pics. These engines are prone to carbon. Now whether the fellow ran hi-test gas or not, I do not know. We have argued every point of adding or not adding additives to the fuel and oil. There are even those that argue about whether it carbons up and as to why or why not and a million other points about the whole situation.
So I say to you, just look at the pictures and if you worry about your valves looking like this then get yourself an additive and use it religously. If it doesn't matter to you, then don't. You may never get a misfire from faulty valves and burned seats and many don't. But if you had to go through what I did at 36,000 miles, then a little Marvel Mystery Oil in the gasoline and a little in the gas tank occasionally makes ME FEEL better. Whether it helps long term or not I do not know at this early point. But for ME I'm not taking any chances. There were those on this forum that convinced me to do it and I like the idea. We used to rev the engine up to about 2,000 rpm and trickle water into the carburetor. That would supposedly quickly cool the carbon and cause it to break loose. Kind of hard to do on the Fortwo. Let the debate roll on. DCO
My dad was a great believer in Wynn's Friction Proofing and he owned multiple automobile repair businesses. So I'm not totally adverse to using additives, granted much of it is in the synthetic oil I run in our cars these days vs back then when we were getting dino oil in metal cans. The premium gasoline we get up here contains additives that reduce carbon build up as well.

In your case 'My Fortwo was previously owned by an elderly gentlemen and he did not take very good care of it.' I can see the use of additives, granted the issue may have been using cheap gas, and not giving the motor a good run once in a while. My primary concern is that using some 'cleaners' could strip the cylinder walls of lubrication and this could lead to scoring though again I think each individual situation will have it's own unique solution. So I think it really depends on a lot of factors, off the top I suspect that car was driven very slowly, maybe short hops so it never really warmed up and maybe went long intervals between oil changes. Btw do I really want to go 15,000km between oil changes as the info on my bottle of Syntech states?

I'm not saying don't use additives and actually given the really long intervals between changes that I'm seeing these days it probably makes more sense since you would be reinforcing what is already in the oil. But in TR's case I was questioning whether it was actually necessary. As opposed to just putting in a tank of the highest octane premium and then giving the car a good squirt down the highway.
 

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Discussion Starter #15
i think it is likely that all internal combustion engines will develop carbon deposits from a hydrocarbon being burned. will additives help, sure they will. could an engine run fine without removing the deposits, sure but you will never feel it if you don't because you are so use to the feel of the car. but why not help your motor stay at it's optimum best. you can't burn anything and not have carbon left over...look at ashes from a fire.

i had forgotten how someone told me to trickle a 50/50 mixture of trans fluid and water (shaken up real good...not stirred lol)down the carb at high rpm then turn the motor off after awhile and let it sit. needless to say we didn't have to worry about mosquitoes that night (looked like a dozen smoke bombs went off). and that was supposed to remove carbon but boy was that fun. looked like a smoke screen being laid down by a WW2 destroyer during a sea battle. anyway enough banter, i am just a preventative maintenance nut
 

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i think it is likely that all internal combustion engines will develop carbon deposits from a hydrocarbon being burned. will additives help, sure they will. could an engine run fine without removing the deposits, sure but you will never feel it if you don't because you are so use to the feel of the car. but why not help your motor stay at it's optimum best. you can't burn anything and not have carbon left over...look at ashes from a fire.

i had forgotten how someone told me to trickle a 50/50 mixture of trans fluid and water (shaken up real good...not stirred lol)down the carb at high rpm then turn the motor off after awhile and let it sit. needless to say we didn't have to worry about mosquitoes that night (looked like a dozen smoke bombs went off). and that was supposed to remove carbon but boy was that fun. looked like a smoke screen being laid down by a WW2 destroyer during a sea battle. anyway enough banter, i am just a preventative maintenance nut
TR there's nothing wrong with preventative maintenance. I do it too and sometimes I go overboard, but Max is my car and my responsibility. Parts are not the easiest to find and it's only gonna get worse. The engine in our Fortwo is actually considered a high performance engine because it does have a compression ratio of 10 to 1. That high of a compression ratio is the reason they tell us to run premium gas in it. Can you run regular in it? Sure. But if there's detonation the ECM is gonna retard the timing. If it gets carbon built up it effectively raises the compression which leads to detonation which also causes the ECM to retard the timing. When the timing retards, performance suffers, and with only 70 hp I don't want to lose any of it. Retarded timing also causes an engine to run hotter. We don't want that on the Fortwo either. Carbon deposits can have little protrusions that heat up red hot and ignite the fuel mixture before the spark plug has a chance to. That is a no no too. It's all just a matter of checks and balances as the old saying goes. Are we splitting hairs? Maybe. But it sure is fun to talk about and debate! DCO
 

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Many years ago when I worked on cars (Chevrolet Dealer), we had a gm solution (can't remember the name) to decarbonize engines, but because of all the smoke it produced we would not do it when the customer was watching, but I have to admit the cars seemed to run smoother after all the smoke cleared. Additives discussion will be like talking 'oil', everyone will have their own opinion, in my case I use Techtron approx. once a month.
 

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I feel strongly that the valves and piston tops should be de-carbonized. This little Mitsubishi engine lugs alot if you drive it in automatic mode. We can debate about the subject until the next century.There will always be someone for doing it and some of us against it. I tore my engine down for a misfire code on cylinder 3. My Fortwo was previously owned by an elderly gentlemen and he did not take very good care of it. I tore the engine down at 36,700 miles and here is 2 pictures of what I found.

So for me and my side of the argument, the proof is in the pics. These engines are prone to carbon. Now whether the fellow ran hi-test gas or not, I do not know. We have argued every point of adding or not adding additives to the fuel and oil. There are even those that argue about whether it carbons up and as to why or why not and a million other points about the whole situation.
So I say to you, just look at the pictures and if you worry about your valves looking like this then get yourself an additive and use it religously. If it doesn't matter to you, then don't. You may never get a misfire from faulty valves and burned seats and many don't. But if you had to go through what I did at 36,000 miles, then a little Marvel Mystery Oil in the gasoline and a little in the gas tank occasionally makes ME FEEL better. Whether it helps long term or not I do not know at this early point. But for ME I'm not taking any chances. There were those on this forum that convinced me to do it and I like the idea. We used to rev the engine up to about 2,000 rpm and trickle water into the carburetor. That would supposedly quickly cool the carbon and cause it to break loose. Kind of hard to do on the Fortwo. Let the debate roll on. DCO
As I have said before.
'A picture is worth a thousand words'
The proof is right there in the pictures.
I don't know if our engines are direct injection or not, but I have read about carbon build up with LEXUS and AUDI direct injection engine. Same problem with our Mitsubishi engine ?

Carbon Buildup on 250/350 IS Direct Injection Engines? Problem ...
https://www.clublexus.com › forums › 5...
Jun 29, 2011 - 4 posts - ‎3 authors
Was reading about the carbon buildup issues with gasoline direct-injection engine cars and Audi was the worst of the bunch ... But the Lexus IS line was also cited as having carbon build-up problems
 

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Almost certainly, the Mitsubishi engine is not direct injection. DI only really became mainstream about 2011 or 2012, and came with engine redesigns which increased compression ratios and fuel pump pressures, so pretty significant changes which would have also increased power outputs.

Those photos show a vehicle which has been poorly maintained, and not run using a top tier gasoline. While the "Top Tier" branding may have started off as a money making certification, it has come to be accepted as a standard which ensures that consistent use of those fuels results in minimal deposits, both on the valves and in the combustion chamber.

DI engines don't have unburned fuel with the detergents running past the intake valves, and engines in poor maintenance won't burn cleanly, resulting in the relatively cool intake valve building up deposits as it opens and is exposed to the combustion byproducts. It's kind of a necessary evil for the advantages that DI provides.


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+1 on running top tier gasoline. I've been running Shell's premium and find my smart has really good highway performance for a little motor.

Here's a brochure discussing the fuel, obviously some of it is marketing hype but a lot of additives are going into todays fuels....

http://www.shell.ca/en_ca/motorists/shell-fuels/shell-v-power-nitro-plus-premium-gasoline/_jcr_content/par/textimage_bf52.stream/1496353254694/d0d78c792ea2c65bb4fba405f70f0269d5378d4cd22b3daa967b09f164ad1c73/shell-v-power-nitro-plus-premium-gasoline-brochure-en.pdf
 
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