Well, it's been a while since I heard anything related to cleaning out the carbon on our engines. I want to see what are peoples thoughts on the matter.

Earlier today I applied the water treatment to my s5 gtu while being very conservative with the water I would let it ingest. Before the treatment it would misfire at idle once in a while, seems better and smother now.

 

if there was issues with it people would have listed them long ago. as long as you follow the recommended procedures it does help remove carbon which may or may not be beneficial to the lifespan of the engine, depending upon how it does finally die.

i've been doing water decarbs for nearly as long as i've been working on rotaries and i have never had it cause any problems(with one unknown possible exception). the only one time it was brought into question was on one engine that died several weeks after the car left, where the engine seized up but i would bet that the seals in that particular engine were already well beyond gone as 2 rotor pulses were already extremely low and the decarb did not help it. that particular car sat beside a house for years with the intake manifold off of it, so it already had a bullet with it's name on it.

in most cases the cars ran slightly smoother and burned cleaner with lower emissions.

 

Excellent

Both of my rx-7's run great and I am a bit paranoid about sudden engine death, i have used the water treatment with great success on 4 of my previous cars, but ever since I got my Turbo II, I did some research and read a few mixed reviews on the topic, the last thing I want to do is damage a car with barely 86k miles

 

the only bad reviews are by those who have never done it, done it properly or just want to argue.

i have also never seen oil contamination through the process either, so oil changes after service are optional.

 

ive done it before and did notice that my compression on both housings slightly increased. i actually used over a gallon and half. the smell that came out the tailpipe was terrible tho.

 

Nice to see this topic opened again. Over the weekend, I converted the sub-zero start assist system on my old '88 vert (180k) to water injection for internal steam cleaning. Ran compression tests with Rotary Diagnostic Systems tester before and after.

I'm working on a write up for the project, but long story short, the old girl is off life support. Looks like I can delay the engine rebuild until after I finish installing a T2 drive train.

The 2-rotor compression tester from Rotary Diagnostics Systems is very cool!

 

Looking forward to the write up

 

+1 on that It seems this topic has been dug out of the ground, some new (and old) members could benefit from some fresh tests

 

i also have a digital compression tester now so i will run some tests of my own, when i get to it.

 

one of the techs at the Mazda dealership told me about an Rx8 that came in with a low power complaint.

they compression tested it, and it was in the 7.7 area. anything over 8 is passing.

the service writer, sold a decarb, so they did a decarb, and compression went up to 8, 8.1. which passes.

car came back a month later with the same problem, and they replaced the engine.

so what did we learn?

carbon cleaning actually does do something. we also learned that if the engine needs seals, cleaning the carbon out does not change this.

 

the renesis isn't a great comparison point though, compression figures on the early engines are usually fairly consistent where the renesis could lose 10psi over a month's time just due to wear. in a renesis i would follow up the treatment with premixing for a tank or 2.

 

To j9fd3s and RotaryEvolution - both of you are forum vets with a lot of knowledge and experience. There are a lot of older threads about the uselessness and removal of the sub-zero system. A few mention using it for internal steam cleaning. Likewise, there are several older threads about internal water / steam cleaning. I have not seen any how to's for converting the sub-zero system for this purpose. This will be my first tech write up. Are there any guidelines for structure, content or 'expert' review before posting? Or do I just throw it out there and see if anyone calls BS?

 

What are the reccomended mileage intervals to do this. Or is it not needed if the car is driven hard enough to keep it burnt out? When my engine I rebuilt went at 147K it was pretty clean. What depsits it had were mostly a creamy brown or tan color. I wonder if this could save some engines as I'm sure the culprit of my first engine's demise was a chunk of carbon that broke off and locked it up as it was full of the black nasty stuff.

 

there is a guy on the Rx8 forum who did a nice steam cleaning thread, he got a borescope and took before and after pictures.

i think generally it is nice when you can present something like a lab paper in high school biology, you want a theory, the test and then some way to quantify the results.

so you'd say something like, i wanted to use the sub zero system as water injection, so i tested the flow rate and found... and then after looking at whatever i decided that....

it seems to depend on how you drive, i have an FD friend who basically only drives the thing @wot (he has a video maxing out the speedo), and when he pulled the upper intake the runners were spotless.