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Old 01-27-2009, 01:30 AM   #1
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Default Carbon build up, why does it happen?

why does carbon build up on valves/pistons ect?

Google turns up alot of preventative things that suggest ways to avoid major build up but im still stumped as to why it builds up and how it can be so strong.

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Old 01-27-2009, 01:50 AM   #2
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why does water make ya pee? it just does
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Old 01-27-2009, 12:37 PM   #3
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Quote:
Originally Posted by thesnowboarder View Post
why does carbon build up on valves/pistons ect?

Google turns up alot of preventative things that suggest ways to avoid major build up but im still stumped as to why it builds up and how it can be so strong.

Discuss
carbon is a byproduct of the combustion of hydrocarbon-based fuels.

ideally during combustion, the hydrocarbon is recombined with oxygen to form CO2 and H2O. Since a car engine isn't ideal, there are byproducts of combustion. your fuel contains other molecules and the air is not pure oxygen so there are sulfur and nitrogen compounds produced for example.

also, in the non-ideal engine, not all of the carbon is converted into CO2. some of it is converted to CO (carbon monoxide) or left unburnt as raw hydrocarbons, or can't find a dance partner in the combustion chamber and remains pure carbon soot. this happens primarily when there is not enough oxygen for complete combustion. ie running too rich.

so you have raw carbon floating around in your motor as part of (rich) combustion.

now, normally the carbon will remain suspended in the exhaust gas and just get blown out the tailpipe (and onto your white bumper), but some people dont like to open 'er up and drive around slow all the time. the lack of exhaust flow isn't as good at evacuating the carbon in the chamber and it sticks to whatever's in its path out--the piston, chamber, ports, valves, exhaust, whatever.

so there's two primary things you can do to reduce carbon in your motor:

1. tune it properly (not excessively rich) to avoid producing carbon.

2. run that **** hard (high rpm, high load) to blow it out.
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Old 01-27-2009, 01:05 PM   #4
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How is a rainbow made? How does the sun set? How does the posi-track on the rear end of the plymouth work? it just does!
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Old 01-27-2009, 01:26 PM   #5
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How is a rainbow made? How does the sun set? How does the posi-track on the rear end of the plymouth work? it just does!
Look POZ-queen, why don't you put your rainbow flag out on your townhome?
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Old 01-27-2009, 02:09 PM   #6
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How is a rainbow made? How does the sun set? How does the posi-track on the rear end of the plymouth work? it just does!
they are both powered by the ignorance of the masses.
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Old 01-27-2009, 03:29 PM   #7
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"so there's two primary things you can do to reduce carbon in your motor:

1. tune it properly (not excessively rich) to avoid producing carbon.

2. run that **** hard (high rpm, high load) to blow it out."

Or- #3. drain the coolant and overheat it like you wanna kill it.

I blew my heater hose on the highway and had to replace a warped head. I was amazed at how clean the piston tops were. Had about 140K on the motor at the time and was expecting a thick carbon coating. Pleasant (as pleasant as can be for the circumstance) surprise...
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Old 01-27-2009, 04:03 PM   #8
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You can remove the carbon build up with a few different methods, as well. A couple of the more popular used to be dribbling a small quantity of cool water into your running (hot) engine or doing the same with a little automatic transmission fluid.. Both supposedly cause the carbon to dislodge and exit the combustion chamber.

Additives containing oils (Marvel Mystery Oil) will leave some carbon deposits on the stems of your intake valves. So will leaky valve stem seals.

The additive Techron developed by Chevron was created to assist in the removal of carbon deposits and is available in one of their off the shelf bottles. Toyota had a run of engines that had a tendency to develop heavy carbon buildup in the mid '90s and had Techron listed as an approved cure in a TSB. If that didn't work they had to pull the head, and warranty folks don't like to spend money they don't have to (Toyota also had a bad sludge problem in a particular V6 around the same time).

If i ever have the head off of an engine, I will gently remove the heavier carbon before reassembly. It creates nasty hot-spots that will cause detonation. But I prefer to "tune it right" and "run that **** hard."

And the posi-track never did work in a Plymouth...
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Old 01-27-2009, 04:09 PM   #9
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just run your car at the track at least once per month for two hours per track day. That's what I do.
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Old 01-27-2009, 04:24 PM   #10
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Here is a nice writeup someone linked a thread on a local board for me:

Carbon Build-Up

Im not concerned about buildup since my car sees 7k just about ever on ramp its driven on. Im trying to understand why it happens. Thanks for the input guys. Keep the info comin!
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Old 01-27-2009, 04:33 PM   #11
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Its crazy how many people never put the needle in the red. Whenever I drive or ride with people from work, they all like to tell me that I'm going to blow up the motor. It revs that far over for a reason, lol. Another guy I work with told me "there is no reason to rev a car past 4k rpm." I can't fathom a car that doesn't see the full rpm range daily...it revs that high for a reason.
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Old 01-27-2009, 04:39 PM   #12
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I feel the need to contribute two fun facts to this thread.

My 153k mile 1.6 motor revved much faster on heel-toe shifting after I ran water through a vacuum tube into the intake.

A bunch of my friends fouled plugs when they ran "purple" at Hallett last year, even the FI cars. They fouled them on the way home, when they were cruising with race-fuel. I believe two cars fouled plugs so bad that they wouldn't even run.
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Old 01-27-2009, 04:54 PM   #13
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Hustler, may i ask how much water you sucked through the vac line? I recently picked up an 88 audi 90 quattro that i'm suspecting heavy buildup and am considering the water trick to see if it helps at all.
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Old 01-27-2009, 05:09 PM   #14
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Quote:
Originally Posted by hustler View Post
I feel the need to contribute two fun facts to this thread.

My 153k mile 1.6 motor revved much faster on heel-toe shifting after I ran water through a vacuum tube into the intake.

A bunch of my friends fouled plugs when they ran "purple" at Hallett last year, even the FI cars. They fouled them on the way home, when they were cruising with race-fuel. I believe two cars fouled plugs so bad that they wouldn't even run.
just from the race fuel?
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Old 01-27-2009, 05:14 PM   #15
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Quote:
Originally Posted by thesnowboarder View Post
Hustler, may i ask how much water you sucked through the vac line? I recently picked up an 88 audi 90 quattro that i'm suspecting heavy buildup and am considering the water trick to see if it helps at all.
1.5 liters or so. Try multiple vac ports to try to get water in each cylinder. Just slurp in a little water at a time...don't plunge the tube in.
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Old 01-27-2009, 05:15 PM   #16
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I've done it with a quart jar of water on a v8 a few times. Be careful not to give it too much too fast or it will screw up you engine (hydro-lock, bad news). You also want to pick a line that will give you good distribution to all cylinders. Think where the water injection guys put their nozzles.

I revved the engine up by hand (engine needs to be good and hot to work) and poured as much in as it could stand without it dropping below 2500 rpm.

Not very technical...
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Old 01-27-2009, 05:16 PM   #17
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Quote:
Originally Posted by mazda/nissan View Post
just from the race fuel?
if not then its a remarkable coincidence.
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Old 01-27-2009, 05:21 PM   #18
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Oh, yeah, and if you still have a cat on your car, that's where the carbon will end up when you are finished.

You might check that out when you are done. Good time to gut the cat and add a simulator for better breathing.
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Old 01-28-2009, 02:23 PM   #19
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Quote:
Originally Posted by hustler View Post
just whine about your car and how it will fail at the track at least twice per month for two hours per track day. That's what I do.


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Old 01-28-2009, 05:04 PM   #20
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GM sells a wonderful over-the-counter carbon remover. Can't recall the name, but it looks something very similar to ATF; I've been told you can even use ATF to do the same thing..... Suck it up via the vacuum tube, as already mentioned...
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