9krpmrx8

iTrader: (46)

I am sure gas quality plays a significant role in this. This engine was NA, it did see nitrous for a bit but only a couple of bottles worth on a 55 shot.

Are you implying that it is no big deal? or no big deal on that engine considering the mileage? I have seen wear similar to that on Mazda remans with only 30k or so. This is where oil choice comes into play IMO, because my bearing looked damn near perfect and the engine only saw Mobil1 0W-40.

9krpmrx8

iTrader: (46)

I'm pretty sure this was his second engine.

TeamRX8

iTrader: (25)

how does that answer my question?

9krpmrx8

iTrader: (46)

Sorry, I believe this was his first rebuild, which was done by Mazmart. Pettit did rebuild the engine you gave him.

loewenm

Not to highjack this thread, gentlemen, but this is all quite interesting to me. I sold my '05 Shinka to someone who wanted more than I did. In the process of the sale we discovered poor compression. I was off of rotaries, until this thread. Looks like there are some (potential) fixes.

I will watch the debate rage with great interest!

RIWWP

iTrader: (2)

That's pretty broad and generalizing.

This thread simply looks at what happens inside your engine on a decarb. Even if it was 100% successful in removing all carbon from inside the engine, you still have numerous other failure methods for the engine.

So not only is this not a catch-all for engine failures, it can't even be a catch-all for 1 failure method.

Watch with interest sure, but don't take it further than it actually goes.

nycgps

iTrader: (1)

i like how ppl thinks any sort of cleaning will reverse engine wear -_-

houstonrx8er

iTrader: (8)

^ unobtanium is the key

nycgps

iTrader: (1)

^^the next RX will cost like a space shuttle ...

houstonrx8er

iTrader: (8)

wait...wasnt that shut down

olddragger

iTrader: (3)

the engine shown was a used engine ( 45 K on it) that I bought from a RX 7 guy that owns a military/commercial grade carbon fiber company. He actually built a functional carbon fiber PPF.
It was an engine he was going to use on a project that got sidetracked. This was back in 2009.
It was my second engine and used as a core when I bought a rebuilt engine from Paul at Mazmart. The standard rebuilt Mazmart engine blew (2009) when I bought gas at a spot I usually dont and it turned out to be bad. It blew while under 8 psi of boost, lead ignition timing of 21 degrees and 200 load. DUH. I know this now
Pettit built my present one, it is not a standard rebuild and Steve Kane tuned it. It is running great since Dec 2011.

back to the regular scheduled program.

HexRX

Seriously right -__-
Engine wear is just that, you cannot reverse it. You can stop engine wear, and even do things to prevent it, but it is a machine and until they figure out how to keep heat out of the engine, carbon off everything, and a good seal, engine wear will happen. It is just how much that happens and how fast it happens is up to the individual.

Karack

i did the other half version of RIWWPs test on an older engine version and noted a few compression results on a 106k mile 4 port automatic non MSP engine, the automatics always have more carbon buildup than your average 6 port and turbo engines. same basic practice, 1 gallon per rotor except i did the engine 1 rotor at a time and was a little aggressive about how much to inject.

does decarbing an engine hold water? - RX7Club.com

i'll try the same tests on an MSP, maybe my own 6 port MSP when i have the time.

cliffnotes: 1 rotor got a 5-7psi increase, the second rotor got a 4psi decrease. overall it still seemed beneficial and that is still my conclusion, though nycgps is correct, wear will determine the outcome and cannot be undone. the test still sais to me that the critical areas around the seals are being effected by the procedure otherwise compression wouldn't rise.

does it translate to an MSP engine? not exactly, you can't inject as much water into an MSP over the same period of time so it may have positive or negative impacts as the water is recycled through the overlap. the side seals being less exposed and more important on the renesis is the unknown variable.

RIWWP

iTrader: (2)

Thanks for the info. Good to see a pre-post compression test result, and I tend to agree with the conclusion you mentioned in the 7club thread.

On my next rotary, be it another RX-8 or a future new rotary, I will be doing water injection with periodic borescoping to determine if controlled volumn water delivery over an extended period of time will yield any improved results over what has been tested here. I expect that the answer to that will be 'yes', although the conditions and volume of injection will be something to figure out. For example, injection at idle? under cruise load? at full throttle? Many considerations to each, and pretty much all water injection theory is based on detonation mitigation under boost, so there will probably be some trial and error to figure it out.

Karack

water injection seems to be done best at higher RPM/engine loads but it obviously does do it's job regardless of the load put on the engine.

my FC TII is getting the engine yanked so i will be inspecting that engine, which i ran without water injection for about a year and then reactivated the system on, so i'm interested to see if the engine comes out totally clean of carbon or not. if it does then the above should be accurate.

the cars i built with water injection at boost with new engines torn down years later had 0 carbon deposits, but the injection only comes on after 5psi of boost, so there's obviously potential for carbon to stick but the injection blows it right back out.

i'm just not sure how well a factory RX8 ignition could handle that though, smaller amounts up to the point and just below ignition breakup might be best. but i can't even guess how many cc/min that would be, usually i start at 250 and move up to 500cc/min but those are on cars with stout ignitions, those cc/min examples are for turbo cars and not n/a though. 110cc/min would probably be a good starting point for a naturally aspirated setup set to come on after 5k RPMs at WOT.

RIWWP

iTrader: (2)

I'll be interested in the results.

My concern about water injection at high loads for the Renesis is that high EGTs/Exhaust port temps are a problem, and I think that water injection then will be increasing the EGTs. If I can get 75% of the benefit at lower loads, I think it would be better for the engine in the long run, and the extra miles would end up making the difference.

At idle only would still work, since there is still plenty of heat to turn the water to steam, but the lower airflow would make it harder to get into the engine still atomized (assuming injection at the throttle body) and I don't know how condensed water might affect other intake components. There shouldn't be significant time spent idling anyway.

So I'm leaning toward injecting with MAF values in the 30-100g/s range only. Something to play around with though.

Karack

water injection has always reduced EGTs, which would benefit the side seals and carbon deposits but it won't benefit power output. even with tuning you might break even in the power department but you won't gain power from it.

this was my principle for building a turbo renesis for the track but i opted to not risk it and worked out a peripheral exhaust setup with early rotor housings. even by dropping the EGTs at the ports the increase from the turbo alone far from offsets it.

the only thing i might have concern with is the side seals absorb so much heat that instantaneous cooling from the intake charge may cause them to wear at an exceedingly higher rate. but i'm probably overthinking it, the intake charge already would have shown results in this area.

RIWWP

iTrader: (2)

Certainly. I'd never expect power gains from it. The only real tuning factor that would matter would be those EGTs. Your comment there seems to be contradictory to things I've seen from other sources, where running water through the engine could get the exhaust hot enough to glow even at idle.

Fortunately, it should be easy to test with the RX-8, due to the reported rear O2 sensor temp through the ECU.

Brettus

iTrader: (2)

Some anecdotal evidence here .....

I recently started water injection on my turbo 8 . 280ccs from 12psi which it hits at between 4-4500rpm. Have not seen higher EGTs (as reported by the 02 sensor) .
Since doing that ....... she seems to run better than before even though the engine only had 10000 miles on it pre injection . Vacuum at idle is a little better and startup seems better . You could say it's my imagination but after all the miles i've done in my car I've become very attuned to how it behaves .

RIWWP

iTrader: (2)

I had seen your water injection comment in your thread, and I was hoping you would comment here

Thanks for the info.

Karack

i have noticed water injection cause the latter half of the exhaust to heat up warmer than usual but i have not noticed the whole exhaust system to run exceedingly hot. the reason being on the renesis the ECU is dumping fuel because the wideband is expecting a result and getting a false reading and then begins dumping fuel, which is afterburning in the exhaust, this is even more true if you do one rotor at a time.

if you measure your exhaust temps under heavy loads with a system working to the point of not causing engine misfires(another point of the afterburn heating the exhaust) you should see EGTs drop compared to normal readings. i use my water injection also to help cool the engine when climbing mountains on hot days.

the issue is decarbing isn't the same as working out a properly functioning water injection system to work at load. water fouls ignition, if the ignition fouls then raw fuel goes into the exhaust and ignites there instead. an inert charge of water burning with the fuel lowers the temps of everything related. this statement is probably more true than anything.

RIWWP

iTrader: (2)

Pretty much the core statement of the entire project...

Brettus

iTrader: (2)

So far i have not noticed a difference one way or the other . Are you talking major difference or just a few degrees ?

Karack

yes, i just wanted to be sure you understood. the point is to inject enough water so that it atomizes and doesn't blow out the ignition. this requires injection tuning and requires smaller amounts than with turbocharged setups because the compression is less dense.

if the ingition handles the job then you won't see those negative results.

the difference won't be dramatic but it should be notable. there's many factors you won't take into account such as ambient temperatures and the injection amounts. 230cc is not a large injection amount so the results won't be as noticeable. if you were out on a hot day and took an accurate measurement without the water and then took one with say 350-400cc you should see the results.

also if you're using the "catalyst" as an EGT probe the numbers will be even less discernable. it's just too far downstream and taking an average exhaust temp at that point. you could place probes between the turbo and manifold or at the turbine outlet, those points are where the EGTs will be in the 1600F range and also where you will more accurately find the breaking point of an engine. an ideal setup is one EGT per rotor exhaust port and then trim your fuel for each rotor to match EGT's(requires accurate instrumentation though).

i would say EGTs are even more important for the MSP than for the older rotaries, because more of that EGT % is absorbed into the sides of the rotors. the lower you can get/keep your EGTs, the better. with dual EGTs a 10% difference means life or death to an engine. but keep in mind i am also not a huge believer in overcomplication, if it works just leave it alone.

RIWWP

iTrader: (2)

Yup, entirely understood.