TeamRX8

iTrader: (25)

Funny how you never seem to think that the same is true when others find gains you claim aren't there.


.

RotaryMachineRx

iTrader: (1)

Hehehe

and

EricMeyer

That's interesting. We MAY have seen a 1 improvement but those tiny numbers are just so hard to swallow on a chassis dyno. So many variables even when you closely try and measure and control them all. We typically see about a 1% or less variation in each of our motors or approx 2 hp. Almost always see 150 ft lbs +/- 1

I'm curious. We've seen more power deviation from the side seal SPRINGS. Generally we see about a 2%+ power loss after a 3 to 5 hour long test or race events. And up to a 5% loss (or 10 hp) over 12+ hours. This is after we return from a event, dyno on the same dyno under the same conditions (temps, fuel, tire pressure, clean plugs....). We then yank the motor and tear it down and go right to the side seal springs. Some of them see about .001 of wear on a spring peak or valley in only a few hours of engine use. There is usually one or two springs that will have a peak or valley that shows .002 wear with over 5 hours of use. With more engine hour use we see more even or consistant wear on most all the spring peaks and valleys.

Why all this hub bub? Because I was wondering how I would go about testing power differences on an engine using various end gaps. Using the same side seal springs after a dozen or so hours in the scenarios mentioned above would not get us back to our typically peak power numbers so we would be off by a few to start (when using the same springs). On the other hand, to test the gap/shape/both would require someone to work the seals, run the motor, pull them, put in a diff cut/shape and repeat process using a very lower hour spring (assuming they see the same issues we do with said spring) or put in a new spring. That's a lot of time and effort to confirm this.

Just curious.

As I sort of eluded to above, D.D. and Rob have tried poking around with this before and found no appreciable gains either. One of them did find some interesting findings when using dual springs and taking .010 off the bottom of the side seal itself. If we're talking a hp or two gains then I think we are back to how consistant is your dyno testing methodologies. We typically approx 1% variances or inside of 2 hp from motor to motor to motor and STD correction.

EricMeyer

If I knew the controlled conditions of a dyno test and a little bit about the folks and how they went about setting up their tests then I would welcome somebody with a zillion year old dyno chart to share their data. Your assumption about what else was done to an engine assumes that something different was actually done to it. There are people out there that compare apples to apples ya know.

Charles R. Hill

iTrader: (7)

All I am doing, Mr. Meyer, is asking you to delineate the standards by which you believe all these things to be adjudicated and discussed so we can all do so in the most objective way possible.

That is incumbent on people who wish to place themselves in certain positions of leadership, whether here or anywhere else, lest one be just another of the unwashed masses.

As for comparing apples-to-apples, some of us do. Great explanation on the side seal spring issue, btw. Pretty detailed stuff.......

olddragger

iTrader: (3)

over the years I have had the fortune of speaking with Eric, spent a little time with his crew, seen his cars run, seen his lap times etc.
I dont think there is a member of this forum that has done more RD on this engine in NA form.... period. And believe me his success's are fact based. He data pile is unbelieveable.
His enviroment is different that those of us on the street doing the occasional track day and also from us that are forced inducted, but still there are a lot of things that can be shared.

I find his findings on the side seal springs to be be very interesting. I cant help but wonder if Mazda changed them somehow on the S2 model. They do have a different part number, but that may not mean anything?
Thanks for posting that up Eric.

Charles R. Hill

iTrader: (7)

1) Agreed, and anyone else wishing to become part of that cadre held in such esteem should be held to the same high standards. That is all I am saying.

2) Exactly, and contexts outside of racing are sometimes more difficult to deal with.

3) So do I.

MazdaManiac

iTrader: (3)

I think anyone that has actually taken a motor apart has noted the unusual wear of the side seal springs.
It is, unfortunately, pretty obvious.


They didn't. They are identical. I have all SII sealing components in my current motor.

MazdaManiac

iTrader: (3)

Example, please?

olddragger

iTrader: (3)

Oh i know there was wear, but the inconsistance of the wear, the short period of time it takes and the fact that this is occurring on such a prepared engine is what I find very interesting.
I know Eric has been fighting side seal spring life expectancy for a couple of years and has tried many, many different things to try and improve it.
I cant help but wonder on the factory balanced etc engine what is happening?
But i apologize to the op---I dont mean to threadjack.
Back on topic

EricMeyer

Ask that another way and I'll give it my best shot. Not sure what your asking me to define--dyno procedure?

And thanks Denny.

-E

AAaF

Did you see a noticeable difference i oil temp with rotors coated? And would you recommend this for NA applications?

EricMeyer

This was an interesting effort. A reputable source suggested we try these and we did. At the time we were looking for more power and they wouldn't tell us WHAT we were buying---only that it was the hot ticket. Imagine my surprise when I opened the box and found coated rotors. We saw no power differences nor appreciable temperature gains or losses.

My experience/our team's experience has been that the weak link in the engine is the side seal spring. The more power we make the higher the Exhaust Gas Temperature and the higher the EGT the faster the spring weakens. A conversation with a very, very smart rotary engine guy who has forgotten more than I'll ever know said something interesting about this effort. He said that the ceramic coating would be retained in the combustion event as it is reflected or absorbed less into the rotor and therefore the EGT SHOULD be higher (which is the opposite of where we wanted to go). To say this another way---coating on the rotor flame face lessens the heat into the rotor for the oil to cool it. This now higher combustion temp expels through the exhaust ports at these higher temps. We don't use them.

This same smart person suggested that it might be interesting to experiment with some type of coating only on the little exhaust scallop on the edge of the rotor that the hot exhaust gasses travel near/over. Never tried it.

Like anything, you'd need a controlled environment to test these things. I don't know how we would do this with the oil temps. In otherwords, how do you hold all your inputs stable and then watch to see if the oil increases or decreases. I THINK you'd do a back to back to back to back with motor swaps at a track on a constant temperature day driving the same lap times (or something simulated on the dyno) and analyze the heck out of the oil and EGT relationship. I'm not so sure that watching the what might be the lowered oil temps allows you to lean these things out to make more power because the EGT's should get even that much hotter. So in the end they didn't seem like something we could try something with or see benefit from. Perhaps I'm all washed up and haven't a clue. This was our experience. We were looking for power at the time and ended up with these things. I wouldn't reccomend it. Are the RX-7 guys experienced with this? I know they have done a zillion more things with these engines over the years than the RX-8 crowd.

olddragger

iTrader: (3)

Does the rule book restrict any cooling jacket modifications?
Are you allowed to cool the fuel? Fuel rail?
are more springs being affected on a particular side of the rotor.
Coolant as it passes the exhaust ports is not picking up that much heat.
I always wondered about converting to a single pass coolant system instead of the double pass like we now have.
Same kind of situation, in a way, that some recip guys fixed by doing a reverse coolant flow mod.

Please disreguard---on second thought I am sure you have covered any and all of this--sorry op

Highway8

iTrader: (11)

Good info.

Maybe the side seal springs would benefit from a ceramic coating. ????

Charles R. Hill

iTrader: (7)

I was/am asking for you to specify your preferred method of accurately evaluating the efficacy of various side seal gaps and we will do our best to adhere to those standards and report/discuss our results as time goes by. If we all adhere to the same standards, the discoveries will be more accurate and data more useful.

RIWWP

iTrader: (2)

Using a brittle and non-flexible material to coat something that has to flex in order to do it's job isn't going to work.

Either the spring wouldn't move or the ceramic would keep cracking/come free, etc...



You have a point though. If it's the heat that is destroying them, IS there a material that is flexible that can take the heat?

Highway8

iTrader: (11)

I didnt even think about the flexibility. A quick google search shows many companies claiming to have ceramic products that will flex. Standard ceramic coatings flex less then 1% but some claim up to 15%.

AAaF

Excellent feedback.

As long as nothing else is changed(AFR etc), it's kind of intuitive that EGT will increase, and energy transferred to coolant as well, as long as less energy is transferred to the rotors. I was wondering if these increased temps would be a problem for other parts in the chain. So I got just the answer I wanted.

PhillipM

If the coating is thin enough, it should be able to flex without cracking, provided it has enough adhesion, you don't need a lot of flex in a thin coat. Same reason fibreglass bodywork can be coated in quartz crystal for scratch protection.
However, a thin coating is obviously going to help less than a thicker one, so...catch 22.

What are the standard side springs made from, I'd imagine a stainless alloy or are they inconel based?

EricMeyer

I don't think efficacy is the correct word for you comment so I'll share what we did and what we found.

Several years ago when we started running the Renesis we were blowing motors after a few hours of use. We couldn't figure this out. A close friend of mine builds very high end racing motors. Anything from $40K per stuff that the goes in the local Indy roundy round racing circuits to very strong spec miata motors that are legal and make great power. Bottom line is that he is a smart guy. After a few boom booms with the Renesis we started looking very very closely at the failure modes. We started with very new or brand new parts. BRAND new. I'm embarassed to tell you how many new irons, housings and crate engines I purchased. Our rebuild process involved new everything every time. We are talking using housings, rotors, e-shafts, oil control rings----all the hard parts with just a few hours from new. I think at one time we were rotating 5 new motors in the mix for our two car Grand-Am effort. We would leave for a race with brand new motors (each would be installed and sent to the same dynojet chassis dyno I've been using for about 5 years now. We would break them in for a few hours per the Mazda break-in procedure which slowly added rpm over time and record all the data on both cars via our Motec data acq systems (one for each car). So we had a ton of data for each car over dozens of engines. We would take with us two newly rebuilt spare (also with all those new parts) as backup motors. Each Grand-Am weekend would use the two fresh engines in the cars PLUS the two fresh spares we brought with us. Let me stress this so you hear me very, very clearly----we were rebuilding new or brand new motors. NO junk yard or street parts were used. BRAND new parts were used in these engines including the consumable springs and side seals. In a few cases we put in brand new apex seals in these engines with only a few hours on them to address these failures. These failures were ALWAYS the side seal clipping a port, breaking, losing compression and in a few cases delivering catastrophic results and scoring the irons (which I would later buy as new and we would re-start the rebuild process with brand new irons). I stopped adding up the dollars cuz it was sick. I remember looking at dozens of new irons and housings at one time and did the math in my head (remember, I bought these new from Mazda to eliminate any variation in the builds). So please here me in that we were isolating variables which I beleive is the question you are asking about our methodology or whatever big words you were using in your other posts.

Dyno procedures used for break-in were the same. Dyno pulls were always recorded with the diff temp above 130F because higher hp is recorded with a hot drivetrain (something I've shared seveal times on this forum). All builds were used with the same exact tune using balanced new injectors and new plugs. All were tested with the spec race gas. Lambda was .929. EGT's were recorded for both cars. Needless to say I have recorded lots of data. After about a half a dozen or so failures we finally looked at the side seal springs and realized that SOME of them were thin at either the peak or valley. For clarity for some of you that don't delve into these engines, this would be the small peak of the side seal spring that touches the bottom of the side seal and the other valley that touches the bottom of the side seal groove or seal gland. We believed these early failure modes were due to SIDE SEAL CLEARANCES so we begin calling the experts and asking what they were using. We tried those. Boom. We made them tighter. Boom. We changed the shape of them. Boom. We used the stock (brand new in every one of these situations) side seals that corresponded to the alpha characters stamped on the rotors. Boom. We bought the larger size "cut your own" side seals and tried those. IN NEARLY EACH CASE WE FOUND NEAR ZERO POWER DIFFERENCES. Might there been one or possibly two hp? Yeah. Is a dyno 100% accurate? I think not and to think so is uneducated. So that people can put this into perspective, a 1% dyno variation on a 200 hp engine is.....yes, 2 hp. How can you accurately measure a 1 hp gain when the dyno has a 1% variation. Someone would be ignorant to believe they can measure a 1hp gain. Yes we saw one and two hp differences. We (and all the very smart engine guys that have several smart employees working for them building racing motors) believe that you can't measure 1 and 2 hp---especially when your making 500 hp. 2 hp on a 500 hp is 4 tenths of a percent if my salesman's math is correct. 4 hp would be .8 if my math is correct. So sports fans---I highly doubt a mechanical device (dyno) with various inputs can measure inside of 1% (or 2 hp) RELIABLY on a dynojet chassis dyno that is well maintained.

Summary---we found near zero power differences in over a dozen engines using new parts, the same tune, break-in procedure, same bearing tolerance, balanced assemblies, new irons and housings, new seals and consumable parts (o-ring kits, springs, corner seals, etc.). I trust you now understand how we/I came to our findings. Did we mess up and did you or other find power gains? Sounds like you did. We did our procedures above and found tiny, tiny variations.

May I ask about how many engines you have personally rebuilt and the power increases you have supported in earlier posts? I would be interested to hear about your processes, testing and the results.

Respectfully,

Eric Meyer, proud team owner and RX-8 racer with over 35 or more Renesis engine rebuilds---near each one failing from side seal spring wear, loss of compression with several of them ending in side seal breakage.

olddragger

iTrader: (3)

Cant get any better than that--I dont think?

So excessive side seal spring wear is occuring? Yet it is not consistant as it is not occuring on all peaks/valleys of all seals?
To me and my little mind, that can only point to a manufactoring quality problem?
I wonder if our ss springs are made from the same material that the P port motors springs where made from? Probably?

Highway8

iTrader: (11)

Lambda of .929, thats about 13.5 AFR, correct? Is that your WOT AFR? For us street gas guys that would never work. We would have Detonation and Blown Apex seals left and right but with your race gas I am sure it helps make more power. However it must cause your EGT to be much higher and as you previously stated High EGT is what you believe to be destroying your side seal springs.

So I wonder can you run a richer AFR, more aggressive timing could you make similar power but lower your EGT and extend the life of your motor?

Looks like you were writing an answer to my question at the same time I was writing it.

EricMeyer

We haven't found any rationale as to why the failures occur where they occur. I can tell you that once one spring gets weak it will what we've been calling "cantilever" and clip the port. It will break in almost the same spot everytime---about 40% or so down the length of the side seal. Breaks it right off. This is evident sometimes in that one spring gets so thin that the spring breaks and this almost always cantilevers the spring (or whatever it does) and the spring breaks/loss of compression. We've gotten pretty good with our data acq at predicting this however every once and a while we get surprised. There is no rhyme or reason we feel as to the location of the spring thinning/failure. Personally I think the spring is going because we are trying to make as much hp as these dumb engines will make and that is one contributor. Running them wide open throttle (WOT for the new guys reading this) for 50 minutes at a whack makes a lot of heat. I haven't shared this before but we know run a much, much lower Lambda (Air/Fuel for the new crowd). The term Lambda is typically used in the road racing circles and in higher end engine tuning. Not sure when or where it started but we stopped using "A/F" terminology becuase all the smart guys we were tapping into used it. In anycase, we run a lower Lambda value to produce lower EGT (Exhaust Gas Temperature) and we beleive that this lower EGT exposes the side seal exhaust area to lower temps and therefore it lasts longer. Lowering or richening our Lambda has shown us this again and again that our engines will last longer than leaning them. You use a S___T load more fuel but she runs cooler.

I have a friend at Mazda that has access to Mazda manufacturing drawings and he has shared that the newer B revision springs changed from rev A by using a higher heat treating effort. He offered nothing else. This tells me that the Mazda engineers found out the spring needed more of the benefits that higher heat treating provided. I presume that this is longer life between failures.

Meyer out

9krpmrx8

iTrader: (46)

Great stuff Eric. Thanks for sharing. Can I ask if you ever did anything with oil pressure in your engines?