Peter F

Has anyone tried to clean out the combustion chambers with the old injecting water into the intake with engine running?
Results and any advice on procedure to avoid hydrolocking to share?
Where did you hook up the water tube?

example found on ricer cleaning: http://www.youtube.com/watch?v=tt7IY0keOD0

/Peter

AO

That looks WAY scary! I would never try that in a million years... unless it's with someone elses engine. Hey Enzo...

Schocki

WTF!

Cleaning the combustion chamber should be done on the track!
My cars always run a lot better after a couple of miles on the Autobahn. Especially for the old 911, a huge difference!!!

Bottom line: Drive it hard (sometimes) and you will be just fine!

Mrmerlin

Peter, wait.........If the water injection isnt done correctly you can damage a piston/ring/cylinder/rod. .Why not instead try to add a can of Techron or similar fuel injection /intake system cleaner, I couldnt imagine that a 928 engine would need any carbon removal , since the fuelinjection,intake system is so effecient, granted there will be a small bit of carbon on the tops of the cylinder head and piston top but ...............What are you trying to achieve? lets say that a piece of carbon breaks off and jams into the cyl wall then it takes out a ring land, then it scores the cylinder.Vs just leave well enough alone, if its running good dont try to fix things. just my 2 centz

Jfrahm

I have done this with water, as have some friends. Not on the 928 though. Several people I know have done the same thing with seafoam. No ill effects. A concern I have is with water pooling in the intake somewhere and then a slug of it getting to the motor at some inopportune time.

The idea with the water is that you get the engine cracking hot before doing this and then the small amount of water will flash to steam and clean the chambers. If you have seen how clean a cylinder can get due to an HG leak it's the same effect. I do not think I'd run more than a liter or so though the motor at one go as after the first bit the head temp is probably too low for the steam cleaning to be effective.
I would suggest running for a while without the water to let the temp come back up. Some sat the water can find it's way into the carbon deposits and then flash to steam, exploding them. An engineer I know uses this procedure on bike engines before teardown to decarbon them. I hate scrubbing/scraping carbon myself. Trouble is if I'm tearing an engine down it might well be too broken to do this to.

After all that I would not go to WOT before driving around at very moderate throttle for a while in hopes of getting any pooled water out of the manifold. You'd need to get what, 60cc of water in the wrong place at the wrong time to hydrolock, that would be pretty difficult at the flow rates this procedure uses unless you really turned up the dumb.

-Joel.

Courtshark

Water cannot be compressed. If you have any doubt about your ability to inject water vapor rather than even a tiny, but whole, droplet of water, do NOT attempt this. I run water injection on my 88 SPG as a means of reducing the charge air temperature for my 25 psi of boost. I use a .7mm (yes, point-7) nozzle injected into my intercooler before the throttle body that is driven by a 100 psi pump with a pressure accumulator and pressure switch activation (boost pressure controls the operation; it doesn't come on before 5 psi). Without something comparable, you run the risk of hydrolock, or, even worse, throwing a rod right through the block (among other maladies).

A bottle of injector cleaner, or fitting a test pipe so you can run 110 octane race gas, are good options. Also check with your mechanic to see if they can do a B&G Powerflush for you. If not, tell them to get the tool, or buy it yourself (not sure if B&G sells it retail, though). It's cheap, easy, and very effective for in-engine cleaning.

Lizard928

actually I have done this many times on various cars over the years, including a couple of 928s.

Driving it hard does work wonders, but on our sloth like speed highways it just isnt that practical.

I do it alot differently though, I take a small vacuum line like the one off the front dampner in the 928, and have the engine held at roughly 3000rpm, I normally use a litre coke bottle or something like that filled with water, and just put the vacuum line into the water.
This acts just like a carb and as the water gets pulled in just past the throttle plate it vapourizes due to the air turbulance.
I have never pulled apart a german engine that has had so much carbon in it that a chunk would fall off and bugger up a cylinder wall or lodge a valve open.

This does work well and there are a few spots on the 85/86 manifold that water can pool, however if you have taken the end tanks off there is normally a large pool of oil in those spots anyways and if it injested that you could see the same effects as water with a hydrolock.
Due to this I do NOT see this being an issue.
I do recommend opening the car up afterwards to allow it to breath all the moisture out of her.
It also doesnt matter if the engine is piping hot or cool the water will remain atomized just like fuel in tiny droplets and will pelt the valves and pistons which cleans them and is effectively a milder form of shot peening/bead blasting.

Imo000

I've also done this but not on a 928. You'll need a lot of water to hydrolock the engine. Remember, there are 8 cylinders so whatever water goes into the intake it gets devided by 8. Not to say that if you are not carefull it won't lock up but, if you use a small vacumm line an a bottle, it would be fine.

In that clip it apears that thre is a lot of water going into the engine but really it isn't. The rpms are up (needs to otherwise the engine will stall when the water is injected) so for each cycle there is very little water entering each cylinder.

jtrygstad

I have done this with my 80 Euro. Fantastic results. I had failed emissions several times, then Garrity told me to get a one or two liter bottle with water and pour directly into the CIS intake with the engine revved to about 3000 RPM. Did this about three times. Intially, nothing happened until water level in the intake rose up to the throttle body. Then the car barked, blowing out a huge black cloud and promptly died. (Remeniscient of John Candy's old Mercury in the movie Uncle Buck) Restarted and did it again until the exhaust belched fairly clear. Dramatically improved both emissions and performance.

I would then follow the "water treatment" with a couple of cans of LubroMoly "Ventil".

dr bob

The method of drawing water in through the manifold vacuum hose is good. If you have a hot-wire airflow sensor, you really don't want to get water going through that, so the vacuum port idea takes care of that issue. Rev the engine a little to increase flow/velocity in the manifold and there won't be any risk of puddling. Going through th evacuum tubing limits the rate that water that can be drawn in, making this a relatively safe method so long as the engine stays running.


The liquid water is drawn in, and lands on hot parts that may have carbon deposits on them. As much as we like to think that we gain performance when we get rid of carbon in the cylinders, the real benefit comes from cleaning the deposits from the backs of the valves, below the tulip section. These valve deposits severely limit air flow, so getting rid of them means better easier breathing. Anyway, as the water flashes to steam, it sucks heat out of the parts it lands on. It's that rapid change in temperature that fractures the carbon deposits and allows them to be drawn through the engine and out the exhaust. Once the water is flashed to steam, its effectiveness as a carbon remover is pretty limited.

kjurkic

For those worried about pooling, just use a SPRAY BOTTLE available from any grocery store; use on mist setting.

Ken

Peter F

Thanks guys,
just what i wanted to hear, lot's of good input on why and why not.
I'm well aware of having to be cautious and also know that an 'Italian tune up' or track day may be a good cleaning method.
I have just about got my engine to run like it should after a number of issues being fixed.
It was running very rich when I bought the car and I just don't know for how long.
So I suspect there will be some carbon build up on the valve steams and really would like to get it clean without opening the engine.
I have heard a lot about this method from guys that has been around with a lot of experience working on engines and just wanted to hear the 928 wizards opinion on how it would work on the 928 V8.
My main concern is what this might do to the catalysators, I'm running a 928Specialist x-pipe with their high flow catalysators after and don't want to clogg them up.

/Peter

/Peter

V2Rocket

carb cleaner...wont harm the engine at all and will get cleaning done in the chamber and the intake too

Fogey1

That's my concern as well. We used to do this on the air-cooled Continental V-4's that powered the kiddie trains in Zilker Park (we just dribbled water in front of the carb throat and it was sucked in). LOTS of black crap out of the exhaust and a big black spot beneath. OTOH, it worked.

Carb cleaner makes me worry about detonation.

Imo000

Nope. Carb cleaner is conbustible and pretty much all of it will burn up. I'm not aware of anything as effective as water.