Miata Mailing List: May 1996, Message #82
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   From: RSAlder@aol.com
Subject: Re: Water to remove carbon?
   Date: Thu, 2 May 1996 07:08:58 -0400

In a message dated 96-04-28 21:41:53 EDT, IO20017@maine.maine.edu writes:

> Remember the old trick of pouring a Coke bottle of water
>down a carburator to remove carbon from valves and cylinder
>heads?  Despite the effectiveness, I figured fuel injection
>had made this process impossible.  However, it was suggested to
>me that a small vacuum line from the intake manifold could be
>placed in a cup of water....slowly injesting the water and
>performing the same cleaning trick.  Any of you backyard
>mechanic types ever done it this way?  Any guess what size
>suction line will keep me from destroying the engine?  Anyone
>want to try it first and post the results!  =)
>

Mike,

Thanks for the note, which jogged my mind into a into, what for me passes for
thought.
I took you up on your offer.

I have an Aerodyne turbo in my 90 Classic Red and from the start, have had a
knock problem.  A call to Corky Bell elicited a suggestion to try the old
hot-rodder trick (his words not mine) to try to romove some carbon deposits
which may be the cause of the pre-ignition.  It is possible to pour the water
into the air filter mounting on the turbo and I tried it but stopped before
using much water...didn't seem to work too well.  The water seemed to
accumulate in the connector tube from turbo to plenum.

After reading your question, I put a "T" in the hose which feeds my
vacuum/boost guage from the take-off just aft of the throttle body on the
plenum and led into the cockpit where I could put it into a two quart water
bottle belted into the seat.  I used a hemostat to restrict the flow to where
the engine did not hesitate at idle with the tube sucking air. Got on the
freeway and up to ~3800 rpn in 5th and stuck the tube in the water and drove
that way for about 5 miles or somewhat less than 1 quart H2O.  The engine ran
a bit rough that way but I didn't have to use much more throttle to maintain
speed and I really didn't want to get into boost for obvious reasons.  

Driving home from the freeway I had "opportunity" to put my foot in it on
occasion and based on  those limited tests, I would have to say that, yes, it
works.  I have the J+S knock sensor and I can easily tell when it senses
knock and takes a big chunk of advance out of the initial spark advance.  I
did not feel that happening and didn't hear any pinging (knock is a much
better description of the noise made under boost) even though it was an 85
deg day.  The engine seemed to feel smoother under boost.

So, yes, it can be done without damaging anything and IMHO, does work.  More
testing, of course, will be necessary.  I'll keep you informed if you would
like.

BTW, the tube used was 1/4 in. plastic which came with my drip irrigation
setup... but it needs to be pinched down substantially.

Ralph Alder
SoCal 90 Red A
Team Classic Crank (the engine--not me)