iSki123

Hey guys, I've seen a lot of threads being passed out on water decarbing a rotary engine. I don't really want to buy the spark plugs as of right now.. Or a new catalytic converter. Heard some word that with water decarbing you don't need to disconnect your cat, sensors or need to replace already good spark plugs. Has anyone done this before? Should I know about some downsides before I do this? I mean, only thing I'd be worried about is the heat the steam would generate. But that's about it... What tools/type of hose is necessary for a job like this?

Any thoughts?

- iSki123

Edit:

Here's a video I found on water decarbing an RX-8. He users WD-40.. I could assume that'd foul your sparks...

9krpmrx8

iTrader: (46)

Decarbing is BS and does nothing to prevent carbon build up on a large scale in the Renesis engine.

iSki123

Well, Rotary engines like the 13B burn lots of oil and collect carbon like crazy. I try and redline my vehicle every now and then. But by the time I redline it in 1st I'm already going the top speed limit here! (4 SPEED FTW)

I think a decarb might help, If it doesn't.. That's fine too! H2O is a free decarb tool. ;D

9krpmrx8

iTrader: (46)

Yep, it might also wash off the oil film and cause damage to your irons and seals too.

nycgps

iTrader: (1)

H2O decarb does work, but you have to premix heavily before you start it.

iSki123

Premix my fuel? Or the H2O going into the vac lines? It all goes to the same place either way you look at it!

viprez586

iTrader: (5)

See here. Premix, or add it to the chemical. I recorded beneficial results.
https://www.rx8club.com/do-yourself-...8/#post4401036

Yep, whichever you prefer. Personally I'd premix the chemical or H20.

iSki123

Yeah,I guess it wouldn't kill to try and put a little 2 stroke in the h2o I'm using for the decarb. The thing that baffles me though is this:

Oil doesn't mix with water, the time it takes for the h2o to become steam is basically a milisecond. The car would've been running for at least a good 5 minutes before injecting the solution. The rx8's oil injectors would've been lubricating the seals by that time! H2o doesn't mix with oil at all.. So steam shouldn't rid of the oil, but it will remove most of the carbon in the engine. Now the reason why people take precaution when seafoaming 13B engines is because at startup with a cold engine the rx8 doesn't lubricate very well! Also the seafoam DOES rid of the oil inside of the engine, due to the fact it'd be sitting there for a long period of time cleaning the engine internals. Now, since I'd be working with an already lubricated and running engine I guess this would be a precaution I wouldn't have to take? Correct?

^^ I could be completely wrong with this. Just a n000b assumption.

9krpmrx8

iTrader: (46)

Yeah I am sure the premix will hold up fine mixed with a chemical, And it won't mix with the water......

Do what you want man but you have no data to support that this does anything at all. It's all risk and no reward.

I have seen plenty of regularly "decarbed" renny's apart and they all had a lot of carbon build up. The best thing you can do to reduce it is to try and use good quality gas all the time, change your oil often, and drive the car hard to insure the engine gets up to full temperature on a regular basis. And even then the effort is mostly pointless but IMO, it helps (if your engine is healthy otherwise).

The people saying they saw good results doing the decarb procedure are right up there with people who say their idle improved and their engine runs smoother after they started premixing or the people that say their cars starts better and runs smoother after a grounding kit install.

BlackSunshine280

Meh, Just use some 30% nitro glow fuel as premix 1gal/tank the extra temperature will keep the carbon out and youll gain hp and you would be in fact adding oil to your fuel. The hotter exhaust will flame cut your ports too giving you a free port job!

In all seriousness now. Im with 9k on this subject even an absurd decarbing regimin say...2x per tank will not eliminate the carbon buildup in your engine. Youd be better off using your $ keeping your ignition system nice and happy.

j9fd3s

i used water for mine, it made no difference, but i feel good.

9krpmrx8

iTrader: (46)

That's kind of how I feel about my SOHN and running Idemitsu. It was a huge waste of time and money on my last engine (died of failed coolant seal) but it makes me feel good, So I still do it on my current engine

viprez586

iTrader: (5)

Quoted from the link, incase you didn't see the results I posted/ click the link.
I guess I did nothing to this car and it still runs as shitty as it did before I touched it? I must be lying certainly.


Tell ya what, I know the guy who bought this car, I told him it needs an engine. I'll de-carb the living **** out of it before he pulls it, then I'll tear it down and post pics.

paimon.soror

iTrader: (15)

^ wouldn't prove anything really ... to prove decarbing actually does something you would need a before and after .... everything else is just moot. Don't expect that decarbing removes every ounce of caked carbon from your engine.

Mr_Pieper

Damn. I thought this was about de-crabbing.

RIWWP

iTrader: (2)

Yes, before and after are the critical things needed. "Don't expect that decarbing removes every ounce of caked carbon from your engine" is very accurate, but the flip side of that is: "just because it doesn't remove everything doesn't mean it removed nothing."

I really need to get around to doing that actual test. I've had a USB borescope and new set of plugs to test out various methods for a few months, but the clutch failure delayed me and the holidays were too busy... maybe I can do it this weekend. Have to find a place that won't get my neighbors pissed at me for smoking up the neighborhood (all retirees in a home owner's association).

I expect the actual results to be somewhere between the two extremes, as usual.

9krpmrx8

iTrader: (46)

Sure, if you cared less about an engine you could fill it with seafoam and let it sit and then deflood it and start it and sure some carbon would be broken down. But your cat would be clogged, your plugs fouled, and you would likely ruin the coolant seals as well as destroy the protective oil film on your hard parts and saturate the oil with carb cleaner/seafoam/whatever. But yeah you would get rid of some carbon.

Look up my thread on the Mazda reman we recently pulled apart with 22,000 miles on it. The rear housing and rotor were still good and had a **** ton of carbon build up on them. That engine was decarbed before it was brought to us in an attempt to improve compression. The front rotor and housing had little carbon build of course because the mangled seals did a good job of removing it while bouncing around in the combustion chamber. The car was not maintained well at all and it showed in many ways.

Karack

and you know that the decarb was done well? and it was water or seafoam?

every engine i have torn down with water injection had zero carbon buildup, even after 50,000 miles at much higher horsepower levels and dumping much more fuel than naturally aspirated engines.

as RIWWP said, don't expect a single treatment to get much carbon off, it is a multi step process. i have been doing H20 treatments on rotary engines for years(including renesis) and have never had any ill effects from doing them at all. you just have to watch your exhaust temps and not cook the underside of the car or overheat the cat severely.

will it make your engine like new again? probably not, but in most cases the engines did respond with slightly better compression/vacuum.

in most cases i run about a gallon of water through the engine, 1 rotor at a time in 16oz intervals off the lower intake ports which have capped ports there. this unfortunately will not touch your 5/6th port sleeves which do also carbon up and can cause issues with armatures breaking off the sleeves and going through the engine on sticky actuators, which is where seafoam upstream comes in.

it beats sitting there waiting for the car to not start one day..

i do not much care for the PCV system on the renesis which tends to pollute the intake with oil. i prefer atmospheric venting through a catch can, this helps keep less carbon from building up in the port actuation systems but i would suggest premixing and/or doing a full intake decarb before installing a catch can off the engine, otherwise the oil lubricating the sleeves will dry up and may bind worse.

RIWWP

iTrader: (2)

9k,

I agree with that. I don't think letting seafoam sit in the engine is beneficial. Faintly helping with carbon, but largely causing other problems. Just pulling an old set of plugs with carbon caking on them and sitting them in a jar of seafoam will show a very gradual dissolving of carbon on the plugs, but after 24 hours there was still far more on it than off, and the seafoam liquid was still clear enough to let most of the light through.

What I plan on testing is decarb methods while the engine is running. We know from water/meth injection on RX-7s that the internals stay very clean, so I would extrapolate that there will be far more benefit to decarbing under combustion than just sitting there. However, even high RPM neutral revs to suck the choice of cleaner through is hardly a precise measurement, and it still isn't done under load. I expect that these two factors will result in driveway ingestion decarb methods producing less effective results than a regular water/meth injection setup.

It's a pretty wide range of possibilities between the two extremes of completely ineffective (soaking) and completely effective (constant mist injection). Where in between is the question I would like to answer with the test. And I plan on using a different fluid front rotor vs rear, to see the impact of fluid choice. And unless one or both is terribly ineffective, I will only be able to test 2 fluids.

9krpmrx8

iTrader: (46)

No we don't know it was done well, it was done at the dealer (Zoom Zoom method)

Yeah and we all know everything that works on older 13B's works on the Renesis,

viprez586

iTrader: (5)

If you guys read the thread I did do before and after tests.
I made several 2nd and 3rd gear WOT passes logging peak grams/second.

Prior to the de-carb it barely hit 200. After it would consistently pull 208-210/grams per second. Not to mention the very noticeable change in overall smoothness.

Sure, a brief one time process might not do much. Again read what I did, multiple steps, using two different cleaners, over the span of 2 days letting some steps do a heavy soak and others introduced once it was warmed up.

My thought behind this is if you DO run quality fuel, oils and change the oil often,and minimizing short distance driving. Speculatively even running a SOHN adapator too, along with the de-carb process will overall as a combined effort minimize total carbon deposits.
That being said, why is it that cars that are neglected often result in engine replacement seemingly sooner? Probably because they're not following anything aforementioned.
(NOT to say well maintained cars don't need engine replacements sooner than later)

+1

paimon.soror

iTrader: (15)

Rotary Resurrection home of the budget rebuild.

Karack

coming from the dealer you can't even be sure the treatment was even done at all. i worked as a factory tech for over 10 years and some of the shadiest technicians work for the factory, or forgetful.

anyways, even they don't follow instructions most of the time. i personally labor the engine as much as possible just before it is attempting to stall itself. this allows the solutions to work the best versus being vaporized and running out before doing much of anything.

yes the renesis is built differently but many of the same principles still apply to ALL rotary engines. if your attempt is to discount the facts, i work on 8's almost daily also and i still treat them mainly the same way as the older engines. though they are much less tolerant of mistreatment and issues with the car than the older engines were.

paimon.soror

iTrader: (15)

That isn't a test ... that proved nothing more than "something" happening within the block that is all speculative. Maybe you blew away one tiny smidge of carbon that made the world of a difference, or maybe you blew away all carbon and the engine is spotless.....

Then we could also get into the debate of MAF calibration issues, condition, voltage, etc....

The question is, what is that "something" that happened ... and that cannot be proven without a teardown before and after

9krpmrx8

iTrader: (46)

G/S reading from one day to the next, from one run to the next means nothing.

Again, there is no scientific data that proves "decarbing" does anything effective. But what I do know is that it's bad for your cat, plugs, and oil. But believe what you want, it's your car.