Carbon deposits

[JD@af]

So I did a ~2,500-mile check up on my new engine, and I've got fine, black carbon deposits on my plugs, most likely from running too rich. I still need to get my fuel pressure reduced, and I plan to finish this task this evening, so hopefully that will eliminate this rich condition (idle fuel pressure has now pushed its way to about 51 psi!). However, even if this fixes the problem, my friend Dave reminded me that the carbon deposits that my plugs exhibit exist on all surfaces of my combustion chamber, and that they don't just go away.

Is this correct? And if so, any methods of flushing out these carbon deposits, short of a tear-down to clean off the quanch pads, valve faces, and piston domes? Thanks in advance, especially for entertaining a question from someone who is supposed to answer questions, not ask them...

[drift]

a fuel pressure regulator would be a bad way to go. you'll reduce the idle pressure, but in turn it will reduce pressure across the rpm band... not good.


get a fuel controller... you can adjust fuel at set rpm points throughout the rpm range.

[JD@af]

Thanks Drift. I actually already found answers elsewhere. For supercharging, this is a good solution, as I have a rising rate regulator (Cartech 20007) to increase fuel pressure as intake manifold pressure increases. This problem is pretty much in check now.

[drift]

next time please post any significant mods your motor has, as it definitely helps in diagnosing and helping to find a solution to the problem.

[drift]

since u mention using a boost dependant fuel management unit to control fuel, you should consider going with a different boost combination. i know that the Vortech system commonly uses a 12:1 FMU for turbo kits... 12psi fuel to 1psi boost.

if this is the case, i have found that this is usually way too rich... a 10:1 would be preferable, or even an 8:1.

also, with that much stress on the fuel return, the fuel pump may have a shortened life expectancy, due to too much stress. the regulator solution you have will help by reducing overall rail pressure, but would probably be better solved by converting your FMU... if that's possible with your unit.

[JD@af]

You're absolutely right. I've always resisted using a signature file, as I dislike cluttering my posts with lots or crap at the bottom. However, it may be time to give in to the dark side. Here's a link with my current set-up:

http://www.automotiveforums.com/vbulletin/t9084.html

Check my post towards the bottom of page 1.

Also, soon I will be installing a Bosch fuel pump that can support ~700 horsepower, and a Speed Pro stand alone ECU, so my current set-up, admittedly far from perfect, is just a temporary fix so I can drive and enjoy my car until the next step.

[Deercat]

Hi,
there used to be a very expert website dealing with Ford Probes and their kin where they gave a detailed procedure for "ENGINE DECARB". Unfortunately, this site is no more...
As far as I remember, you just feed a 1/2 can of the decarb solvent (at a slow rate so the engine does not hydrolock!) directly into the intake manifold after the throttle, then shut off the engine and change oil and filter rightaway.

Something along these lines.
Please do not take this too literally, I am only saying that this is a legitamate procedure which was recommended for the Ford/ Mazda 626 V6 engine (I had it done once by the dealer) and that it was claimed to be genarally applicable to all gasoline engines.

You will find a lot of stuff if you search for 'engine decarb procedure' using Google.

Len

[fritz_269]

Once you've fixed the richness problem, one of the easiest and best ways to get a lot of excess carbon out of the combustion chamber and headers is to simply run the engine hard.

Bring your car fully up to temp (15-20 min of normal driving) and then find a long and lonely stretch of highway. Slow way down and drop it into second gear just above stall RPM. Floor it and take it to redline, hold the RPMs right at redline for 10 seconds or so. Then roll off the throttle and coast all the way back down to where you started. Repeat. About 5-6 of these runs should take out most of the carbon by superheating it and providing ample air flow to oxidize it and sweep it away. Do this in 3rd gear instead of second (longer pull) if the road is safe enough for that speed.

Make sure to keep an eye on the water and oil temp and listen for detonation, as the point of this exercise is to get the chamber as hot as possible.

Another common technique for getting rid of heavy deposits is water quenching. Warm up the engine fully, then park it and pull off the intake. While revving the engine, spray a mist of distilled water into the throttle body with a clean spray bottle. The shock of the cool water hitting the hot carbon will cause it to fracture and flake off.

The Endyn site also has a fix for the high idle fuel pressures that FI engines end up with (even with a rising rate regulator):
http://www.theoldone.com/articles/regulator/
There are a bunch of posts on thier bbs about it too.
:smoker2:

[JD@af]

Thanks for all the help guys I've already lowered my fuel pressures via the Endyn FPR mods (I dropped from 51 to 36 fuel psi at idle.. I'm debating whether I want to try and drop it any more by enlarging the pressure relief hole), and my plan for increasing engine heat is to use a fuel additive called Marvel Mystery Oil. I'll put my dirty spark plugs back in, check them after some long drives with Marvel Mystery Oil added, and if they're clean, I'd say I'm golden. Seems like a safer way to build combustion chamber temeratures than revving the engine like a madman! I'll post to let you know how it works.