accelerating hard to clean out carbon build up? - Toyota Nation Forum : Toyota Car and Truck Forums
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#1 Old 08-22-2012, 11:37 PM
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Unhappy accelerating hard to clean out carbon build up?

I am going to pose this to you guys, I do routine maintenance on my friends car, including routine throttle body cleaning and it gets a fuel injector cleaner every so often (Techron). And I have taught my friend to drive her car efficiently from stop signs, to improve gas mileage. but she came to me today and said that when her mom drives her car one in a while, and when she does, she does hard accelerations to over 4,000 RPM before the car shifts, and she said I am lucky to hit 3,000 when I accelerate from a stop before it shifts... Her mom said you have to do this frequently (weekly) to "clean it out" referring to carbon build up...

Now my friend does drive on open 55 MPH roads for 50 minutes a day, 4 times a week and doesn't make to many short trips, and she said she is taking a hit on her MPG when her mom does this kind of behavior to her 1995 Camry 2.2, and wants to know if her mom have a valid concern or if she should tell her to stop it.

I guess her mom feels she doesn't drive the car aggressively enough to keep carbon from building up. There has not been any issues with the car regarding idling or anything...

I welcome any comments, I almost think her mom may have some old school tendencies in her, but I'm not sure. But I don't want to advise, want to get a consensus.
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#2 Old 08-23-2012, 12:14 AM
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4 grand once in awhile certainly wont hurt it.

But I agree, I wonder about the validity of "blowing out the carbon".

I'll say, I've had the head off a few engines. All 80's and newer stuff, except for one, a 65 Mustang that is/was mostly original. However in all cases true mileage was unknown (due to motor swaps, or in the mustangs case, odometers that roll at 99,999).

The Mustang had the worst carbon build-up of them all. I mean easily twice/three times the carbon. It also had 3x the sludge, though that could be from sitting for 10+ years. So from my own personal experience, I'm going with...

Todays engines, oils, and gasoline do not suffer from carbon like the old tech did. Maybe if you only did short trips (not warming it up fully) then maybe they'd carbon up.

I wonder what an machine shop/engine rebuilder would say?

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#3 Old 08-23-2012, 10:06 AM
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No, running an engine at high RPM doesn't do anything to remove carbon.

Carbon build up can come from a few things, running the engine with wrong fuel/air mix(most common), dirty fuel, leaky valve guides/rings allowing oil into the cylinder.
Carburetor engines allowed owner to "run rich", so they ended up with lots of carbon issues, lol.
"and blowing out the engine" with high RPM was usually not engine carbon coming out, it was exhaust system carbon build up coming out.
Water injection removes carbon build up but it must be done right.

Fuel injected engines don't have the owner accessible fuel/air adjustments, so tend to run with the correct mixture, sensors do fail, so they can run rich, but just not as likely.

Mom, grew up with carbureted engines and probably got that "blow out the carbon" from her father, which didn't apply then either, but Daddy knows best, lol.
I would just let "sleeping dogs lie" on this one, getting between a mother and daughter for a few bucks in fuel would not be a wise decision IMO, lol.

Running higher octane fuel doesn't remove carbon either.
Octane rating is the compression point at which the fuel will ignite without a spark.
If your engine has the compression to run 87 octane then that's what you should use, 93 octane won't run "cleaner" or give better performance, thats not what the 87 or 93 numbers are about, they are compression ratings not "power" ratings.
There is the same amount of "energy" in a gallon of 87 octane as a gallon of 93 octane.
If you have a high compression engine 87 octane will ping or knock as it ignites on its own before the spark, this would reduce engine power, it is a mechanical reduction in power not related to "fuel power", the 87 fuel ignites on the up-stroke so takes power away from the crankshaft, instead of on the down-stroke adding power.
Higher Octane fuel needs to have more "complete strings" of fuel, so it doesn't pre-ignite.
The higher the Octane the fewer "incomplete strings", so the more expensive it is to produce.
"incomplete strings" give the same power as "complete strings" by volume, "incomplete strings" just ignite easier, which happens under higher compression.

The Octane number is a common myth/misconception, it is not about power...it is about compression.

The more expensive fuel treatments do clean light carbon build up off pistons and valves.
But a light carbon build up is not really an issue.
I just did the head gasket on a '97 2.2L with 180,000k, wiped the carbon off with a damp rag, so hardly any, no fuel treatments ever used, had the car since new.

Last edited by RonR; 08-23-2012 at 11:15 AM.
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#4 Old 08-23-2012, 10:21 AM
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There is something called the "Italian Tuneup". The name comes from Ferrari mechanics racing customer cars on tracks to clean them out.

Opinion: There is something to it. High RPM's = a flood of gas, high heat and high exhaust pressure. This could theoretically burn off and blow out some carbon, clean off the catalytic converter, etc. How effective this is gas alone can't be proven. Used with a fuel system cleaner like Techron concentrate it should work pretty good. Thats when I use additives like Techron concentrate - on long highway trips.

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Last edited by leakyseals; 08-23-2012 at 10:22 AM.
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