Renesis engine issues finally identified?
 

I originally posted most of this in a different thread in the disucssion section before I realized that this is probably something that everyone should study up on. In a moment of rotary clarity I think I figured out why the Renesis dynos inconsistently, has inconsistent mileage numbers reported, has people reporting random engine failures, has dealerships telling people they need new engines even though they seem to run, and why people that premix have seemed to report better mileage. It all has to do with one thing. The oil metering system. The new setup on the updated engine for 09 and the same system on the 16X led me to this conclusion. It's so simple. I've know all of this for years and yet I've never actually tried to tie it together. Until now. Keep in mind this is all a hypothesis on my part and nothing more. It is my personal interpretation of what is happening based on the facts that I see.

The updated Renesis for 09 had added 2 more oil injectors. Take a look at the 16x pictures and you'll see how they are now done. The 4 on the engine now are in the same place. There is now 1 in the middle of the housing but not directly between them. It's a little higher up on the housing. This way the middle of the apex seal gets lubricated. This is how it should have always been done as the middle is where the apex seal is hottest and needs the most lubrication. The 13B engines had their oil injectors centered on the housing but only 1 on each. On the 1st and 2nd gen RX-7's there was also an injector in each primary intake runner on the lower intake manifold. This way oil got mixed with the air well and directly lubricated the center of the apex seal.

The reason why the Renesis has both of it's oil injectors pointing diagonally towards the sides is actually to lubricate and cool the corner seals which now get exposed to hot exhaust gasses. They don't on a peripheral port engine. The downside to this was that some of this oil doesn't get burned nearly as well as it does getting injected directly into the center of the housing. This could lead to the side seals getting carbon locked. This led to the development of the wedge shaped side seal on the Renesis that helps force carbon out of the side seal grooves. The effects of this oil injection technique issue is still seen on the Renesis however in the form of carbon buildup in the intake and exhaust ports.

Since much of the oil metering goes towards the sides of the rotors and little actually lubricates the apex seals where they need it the most, they have a tendency to warp a little bit and wear faster. This can have multiple issues. An obvious one is potential engine longevity. Another issue is compression. As these seals get too hot and warp slightly, they don't seal as well and the engine doesn't build the dynamic compression ratio that it should have if the seals were lubricated properly. This is most certainly one reason why there are inconsistent power numbers from various cars. Along with this, mileage may also suffer to an extent. This hypothesis seems to be reinforced by the fact that many people that premix tend to get better gas mileage. Their apex seals are lubricated properly. These engines also show less wear upon teardown.

The oil metering pumps on the RX-8 also seem to be inconsistent. Some people report little to no oil consumption from the OMP. This is only making the apex seal issue worse. While the engine may run for a long time this way, fatigue is slowly setting in. Nothing may be noticable as power may only be down slightly. At some point this fatigue may rear it's ugly head all at once in the form of a broken apex seal. This too seems to be supported by the randomness in which engines have been reported to fail.

Also take oil temperatures into account. Too high oil temperatures aren't good. The oil in a rotary rejects about a third of the total engine heat. That's alot. If the apex seals are already too hot, and additional engine heat is going to be exagerrated even more. Not good news on the apex seals.

When you put all of this together you can really paint a good picture as to what has been going on with all of the power irregularities on the dyno, the mileage inconsistencies that are reported, the engine failures reported, and the engines that dealers have said need to be replaced even though the cars seemed to run fine to the owners. It all fits together and is tied to the location of the oil metering jets.

The solution seems obvious now. Lubricate the apex seals where it's needed most. The center. They are keeping the oil metering jets that are already saving the corner seals but now they are finally dealing with the apex seals. The rotary was always a very reliable engine. Why? The RX-7's lubricated the center of the apex seals. The race engines all use premix which also lubricates the center of the seals. Proper attention yields reliable results. We could even go so far as to tie in a correlelation with the people that report flooding issues more easily than others as that too is compression related.

The apex seals apparently just get enough oil to be fine. This assumes everything works properly though. Any little issues at all can change this in a hurry. A few degrees in engine temp from overly hot oil, an improperly working oil metering pump, etc can all lead to issues. Some issues may be minor and as such may lead to minor power or compression losses. Other more serious issues may kill the engine entirely.

I for one am very happy to see this new setup. It shows that they've analyzed the issue extensively and are taking care of it. What "should" we expect to see with these changes to the oil metering system? We should see more consistent gas mileage reported. We should see more consistent dyno results and the average will probably be higher than what it is now. Probably more on par with the few people that have gotten higher numbers than the rest. We should see fewer engine failures. Keep in mind I'm using the word "should" and not "will". Time will tell but I'm excited.

The one piece of advice that I'd give now that I know this is just to be on the safe side, premix!

Here is a temperature chart on apex seals. It shows the importance of oil metering in the proper location. I am also including a link to a Mazda test chart that shows the effect of oil metering on apex seal temperature as well as what the ideal ratios are for these tests.


http://rotaryeng.net/Sealtemp-verse-oil-vol.jpg

Too bad there's no real fix for us preexisting owners besides premixing. And we haven't even gotten to the bottom of the fuel pump clogging.

The fuel pump clogging issue is an interesting one as this was typically never an issue with fuel filters on pre-renesis vehicles. All I had ever heard was do not use marine 2 stroke oil for premix. That was always the general rule. I never really looked into why that was so though.

I don't want to get too far off topic, but with only a few months use on an upgraded fuel pump, my filter was filled with black goo. I was premixing with 2 stroke RP oil and some FP60 in the gas tank at the time.

I think it's also possible prior oils used in the past had residue that stayed in the gas tank and might also contribute.

At any rate, the filter clogging raised it's ugly head when I was on the dyno and was around 1/4th tank of gas left. Above 7k rpm the AFR's got lean as (I assume) less fuel was making it's way into the engine. Once the filter was replaced, the issue went away, so that's as conclusive as I can get with my issue.

I want to premix, but it's scary since going lean like that can kill my engine when in boost.

I do think that needs to be researched and figured out as well.

Well, back on topic - do we yet know if it'll be easy to drop an upgraded renesis in the older rx-8's?

If my engine ever goes, I wouldn't want to go back to a ticking time bomb.

I have a Renesis intake manifold that I bought just to play with. I might look into seeing how difficult it would be to integrate 2 more oil injectors into them but this time on the lower manifold itself like the RX-7's did it. This part wouldn't be difficult. The thing that would need to be worked out is how to tap into the oil metering lines from the omp. The other issue is that you can't take the lower manifold off of the engine without first removing the engine from the car which sucks. Maybe this is something that I should look into for people who are going to have their engine out for whatever reason anyways. I need to think about this one for a while.

the updated engines won't swap. they have a different wiring harness and pcm among other things. I'm sure its technically possible, but not a direct block swap.

I think that light premixing ~2-3oz per tank is the best solution for current owners.

As Brillo said. "Engine managment is not the same". Kinda like putting a 13B in where the Renesis is, and hoping it will just plug and play.

So what are the down falls of dumping additional "engine oil" into the intake system?
Seeings how the current OMP uses it . Would an increase in "engine oil" (through the metering system) have a detrimental effect on the apex /side/corner seals. Is there a possibility of additional carbon build up?
Mazda must not think so if they've added two more OMP injectors.
I guess what I'm getting at is why not use 5W-20 as a premix oil. Instead of say, Idemitsu?
One must remember that this is what is actually happening with the OMP injection system currently and in the past.

On my RX-7 I use a separate omp tank. I have used straight motor oil when I've run out of 2 stroke. Of course it was Royal Purple and I know it burns clean.

I think much of the current carbon issue in the intake and exhaust ports all has to do with the fact that the metered oil is being injected towards the sides of the rotors away from the combustion chamber where it can't burn off cleanly. Injecting a small amount where it will burn cleanly shouldn't prove to be an issue at all.

would upgraded cooling system (bigger radiator PLUS using synthetic oil) help with the cooling of the apex seals?

i don't like the whole idea of premix when it is KNOWN to be basically incompatible with the RX-8 fuel filter...

Is some 2 stroke oil made for oil injections systems and other is made for mixing with gasoline? That may account for the black "goo" in the tank.

I've been using marvel mystery oil for the last 30k miles, the last 8 of which have been w/FI. I have 80k total miles on the car. I put a quart of mystery oil into the motor every time I change the oil, and I add @4oz w/every tank of gas.

I'm not sure what test I could do to determine what the positive effect(if any) is on the motor, but there have not been any negative results so far. If my motor is still going strong @100k miles(@30 w/FI) I will certainly be impressed and continue to add the mystery oil.

I'd really love to drop a 16X into the 8. If this was a perfect world my Pettit kit would mate right up to it so I wouldn't have to pony up for another FI kit.

I was discussing this with a mazda representative today at the Chicago Auto Show. He said the reason the 09 wiring is different is because Mazda went to an electronic OMP in addition to the 3rd nozzle. Has anybody else heard this?

The omp isn't where it used to be so it could be all electric now. I'm not sure. It has always been turned mechanically by the engine.

RotaryGod,
I'm new to all this stuff so be gentle ;)
What is two stroke oil? From what I just read on wikipedia,I dont under stand how this works with our Car (RX-8)?

Also when the Apex Seals are no longer any good, Can you just have your Engine rebuilt? Is that what you mean by "Teardown"?

So is Castro GTX ok?
What where the Engines like that used normal Oil VS RP Syn Oil like?

Is this true?
In this thread https://www.rx8club.com/showthread.p...ight=rb+premix
You say 600-1
Whats that mean? How much is that? I dont want to use too much.

If it is nolonger where it used to be and is now electronic, then this is good right? Can we add that extra thank and regulate the oil like you said in the pre mix thread? I dont know. I could be worng.


Thanks! and keep up the great work RG :)
-Gil

Personally I have been using pre-mix in both my 20B-REW + 13B-MSP engines. Having been using pre-mix in the Cosmo for 5+ years now I have not had an issue with a clogged fuel filter or a failing fuel pump.

How quickly does this "black goo" issue take to evolve.......??

Is it particular to the MSP engines only.........??

Am sure its a minor issue as pump or filter is much cheaper to replace than an entire engine.

REgards

Might just be with MSP as you and RG just stated but I dont think its a minor issue as its not just in the fuel pump. Recall some Engiens had "this kind" of sticky stuff inside there Engines too?
We dont know where the start / stop point is. So where do we start looking? How do we know? ect.

I am almost certain it is all electric now. On a side note, I was pissed though because the one of the main reasons I went to the show was to check out the 09 and they didn't even have one. They gave me some excuse that they were all in testing but come on. Its the freaking Chicago auto show and it advertised the debut of the 09 RX8 but Mazda couldn't even get one to the show. The GTR and Challenger are awesome tho!

/thread jack

One of the last ecu flashes from Mazda was suppose to increase the amount of oil injected into the engine under certain conditions. So yes, I would say that, the ecu does control the OMP.

There is no excuse for Mazda not having a RX8 at the Chicago Auto Show. It's the largest in North America and it's only 2 weeks after the Detroit show. They had a RX8 there.

Currently, I think its the stepper motor thats ECU controlled and he actual pump is driven by the motor. In the 09 I think they have changed the pump to be controlled by the ECU, also.

So RG how much premix would you recommend? I have been doing 4oz a tank.

I am still shaky on the idea of premix. However 2 oz. doesn't seem like alot and will get pretty diluted.

The idea of adding an aditional oil injector is a def. an interesting idea. a stand alone system utilizing an electric pump may be posible. basically take it away form the ecu all together... Im not a programmer so I do not know if that is possible.

I think I will get an upgraded rad. either way because cooling is a huge issue and it can only help...


2 oz. and the additional cooling capacity seems like a good idea to me .. any thaughts?

Its simple if you understand the concepts of a 2-stroke motor (Bike motor) :)

Hard to say, if it never *broke into pieces* then maybe. Cuz imagine if the Apex seal wears out, what kind of *wear* will it do to the rotor housing ? You have to take the motor apart and measure the clearance before You will know if the motor is still good or already dead. if it made any deep marks on it, its not good.


Many people use Castrol GTX without any problems, I like Synthetic because its more pure and can withstand higher heat. Which is a proven fact.

Hmm you ask if it withstand higher heat wont it burn not as clean ? Well, the temp inside a chamber can easily burn even the most 1337 Synthetic oil out there. Rotary is a hot hot hot engine so Oil cooling is very important in engine operation. Synthetic oil can resist heat better than Regular Stuff (harder thermal breakdown)


ITs simple math. We have a Tank with about 16 Gallons of fuel, so divide it into a certain number can give you a certain ratio isnt it ? :)

Electronic is good because Mazda can make *readjustment* easily.


I know, Thanks RG :)



Oh, For some reason, my mpg stays about the same no matter if I premix or not, my 8 has been burning oil since day 1. I have a working OMP I guess. Cuz some people like MM, before he swap his OMP out, it hardly burn any oil.

My car burns about 1 quart every 1K-1.5K miles (or less, depends on my driving style) b4 the recall flash, now it burns at least 1-1.5 quart every 1K-1.5K miles for sure.

Dear Rotarygod,

First of all, thank you very much for sharing with us your always wise knowlegde. In this particular case the lesson is about the "probably-no-so-good" lubrication system we have got for our beloved renesis engines.

As for premixing, we know that the fuel pump (and particularly the fuel filter) is the weak part as it tends to get clogged quite frequently. In this regard here in Spain, there are some members of the www.club-rx8.com (inlcuding myself) who are considering the fuel pump as a wear part that must be replaced at some point in time.

Fortunately the fuel pump "kit" is not a very expensive part, just about 150 USD + replacement cost so as soon as the first sympthons of fuel starvation happen, the fuel pump gets replaced.

By the way, where have you got the info about the new OMP and new oil injection system for 09 RX8 ? :) it has not been published oficially yet :)

Best regards

jird20

Fuel pump is ALWAYS a wear part that must be replaced at certain point. This applies to every car.

But its just that our pump sux and need service sooner than most cars out there :(

I had a few chokes a while ago. might have to do with my colder plugs. but anyway Im planning to replace my fuel pump b4 I reach 50K miles. Im @ 39K now.

Look at 16x engine and its tech papers

As far as I know, the 09 model will be equipped with a (revised?) 13B-MSP.

I think rotarygod and some others around here know many more things about the new car than we do :lol: . I am afraid they have to be tight lipped for the time being... but sometimes they somehow release some partial information to us :)

This might be the case about the new OMP. Am I right Fred?

Cheers

jird20

while i dont disagree with you on the metering pump issue (ive driven a couple 8's that made apex seal noise) but having both taken statistics (loooong time ago) and worked at a mazda dealership, would disagree with blaming the metering pump for all of the inconsistencies.

a lot of it is the owner/drivers of the cars. if you took a sample of any performance area of any car you'd find it "inconsistent" too. mileage for example, varies with the driver, topography, weather, fuel quality, etc etc.

or even the dealership part, in the 3 years i was there, we changed 1 rx8 engine. why? because it was leaking coolant externally. we had one more that tested with low compression, but mazda WOULD NOT let us change it. they made us put coils on it, which fixed the compression problem (i know! if i didnt see it i wouldnt believe it)

so back to the metering pump issue. yes, i think its weak too. ive driven a couple of cars that made apex seal noise. the seals make a scratchy noise when they dont get lubed right. this is troubling, as theres no obvious "fix"

First of all, thank you for your very interesting post.
A part from the new third injector versus premixing what do you think about making two different oil circuits? one for engine and parts cooling and a tank filled up with 2stroke oil for injection? I know this is fairly used on aircrafts but i've seen a kit or two for sale made for our Renesis.
Thank you very much :)

Synthetic oil with several ?'s
 

:Eyecrazy: About the subject spoken earlier i thought you couldnt use sythentic oil? The dealershiop said "rotary must not take synthetic", but if some of you are using it with no porblems i might think about it my self. Oh yeah thanks rotary god for the post, much help. Also, in time should i think about pre mix. I have 55k on my 04 am I going to run into problems with my engine. The reason I ask is that my shop guy mentiond some thing similiar which was stated above. I am the lay person (excuse my lingo) for this subject, but he said that there was a machine or some thing that mixed the gas and oil and he recommended "premixing". He said if this machine goes out "good luck, amigo"I was frusterated thinking of the subject:banghead:. Any who if you all know please tell.

I agree that it doesn't explain everything. I do think it explains many things though and that's what is important. Keep in mind this is still just a hypothesis and in no way can I absolutely claim that it is in fact to blame for these things. It seems to be pretty well founded though based on what we know and what Mazda is doing to deal with the issue. At the very least the topic is worth studying further.

There are a few people around here that may or may not find out things a little sooner than everyone else does. I can't comment on whether or not this is in fact true though. ;)

This is not the thread for "Synthetic vs. Mineral Oil" debate. There are SEVERAL threads on the subject elsewhere

Thanks nycgps :)
For all the no0bs like me, this is a cool page I found. You guys check it out and let me know what you think
http://adam.standley.googlepages.com/home3

I think Redline SI-1 Complete Fuel System Cleaner is a good alternative to premixing.

Cleans carbon and is a synthetic lubricant.

Marvel Mystery oil as well. It's $4 for a 32oz bottle.

Idemitsu cost a bit more only like 5 bux and its 100% working ...

How does a "Noob" get 6,428 posts Dom? :Eyecrazy: :banghead: :lol:

Why does it matter?:icon_no2:
Think quality, not quantity.

I'm just screwing with him.............kind of a running joke of sorts.
Actually this is a really good thread and am reading it with great interest.

I don't look at the # of someone's posts as a good or bad thing. The thing I appreciate the most is the willingness to share experience and info around here.

You have to be able to sift through opinions, personalities, emotions...but that is to be expected when you don't have the luxury of talking face to face.

Is there a test I can do to determine if my OMP is working properly??

The sohn adapter is a for sure way to know if it's working or not. I watch the oil container (washer fluid bottle) decrease as I drive. It's been 1 quart per 1000 miles for several months now.

I know this is not a premix thread but I have noticed the crap that has settled in the bottom of the 4oz bottles of protekR and seeing that I dumped a full bottle into a clear container and noticed even more after letting it settle this may contribute to the cloging of the fuel pump problems.

I would stay away from Mystery Oil - it is a pretty good solvent, like WD-40, but as a two-stroke lube it would be useless.

I use about 8 ounces per fill of good (ISO EG-D quality) oil, to keep the ratio somewhere between 150:1 and 200:1. If you want a extra lubricant in your fuel, you need to use enough to actually do the job.

The upper limit of the qualifying tests for the best two-stroke (JASO-FD) oil standards is 150:1 - after that there is no protection at all.

Modern two-cycle oil at less than an ounce-per-gallon will leave NO deposits in fuel filters, millions of users would have found the problem long ago.


S

yes, but most of us using pre-mix also have a working MOP too. So ruuning that much pre-mix isn't necessary. I personally don't recommend more than 1/2 oz per gallon fuel (254:1) for cars with a cat converter

Personal Thoughts
 

I don't think it's a good solution. They made the apex seals tension load to float up or down to minimize blow-by. That apex seal design (i'm no engineer) i can see carb build up in the moving point were it's designed to shift minus a couple degrees at the overlap point. Then it getting stuck either on it's, or stuck at it's center making it hard for the rotor to turn over, and increase load on the rotor during initial startup. Atleast with the current design, the A stuck apex will eventually extend to perform the needed compression on startup, provided you have a strong battery and the new starter.

This is my perspective on a renesis motor that can develop buildup from the 'average driver' (Read: those that don't read this board, or have any mechanical background).


There you have it, my thoughts :eyetwitch

MMO is just distilled mineral spirits and benzene. It is not a lubricant anymore than dumping in ATF to your gas tank would be.

Its good that majority of the rx8 owners can come to this forum to talk about the issues that are apon us but in the end we have all bought into becoming Mazdas ginypigs

+1 :squint: :squint:

I'm not a dragster, i'm a marathon runner
 

I have a few questions after reading this thread.

My car history:
I have 52k miles and have been using amsoil 5w20 syn oil every 3k miles. I use 92/93 gas and check the level of oil with every fill up and add if needed. I usually going through about 1.5 quarts between oil changes. Its a 2004 and had the last recall done at 21k miles.

1. When is the average time to change the fuel filter?
2. How would i know if my oil metering system is working properly, is there some type of diagnostics test for this?
3. When do people usually change out coils?
4. Would a dyno test and compression test be a good thing to get once a year to catch early signs of any parts failing for people who have high mileage?
5. Is there certain criteria that i should look for to start premixing or should i definitely start now? I will check the premix threads to find appropriate oil and amounts depending the answer here.
6. Should i get an after market water temp gauge to make sure my engine is running correctly, i thought it wasn't really needed unless you had forced injection.

This is my daily driver and i love it. My goal is for at least 4 more years with this car and over 100k miles. If this included apex seal replacement or a new engine from mazmart so be it I mentally repaired, monetary preparation needs some work but can be done.