rotarygod

MSII is really nothing more than a daughterboard upgrade for the MS. All I have to do with my unit is to remove the chip and plug in the daughterboard in it's place. The newest version of the MS board whihc is v3.0, has the ignition circuit built in. I had to build mine. No big deal though. It's all basically the same unit.

Currently the rotary specific code does not work on the MSII since it is slightly different software but that will be taken care of very soon.

MS was written in assembly language. The MSII can be written in C which will make it much easier for many people to work with.

brillo

Nice show of suppport on the MS forum guys, if you haven't posted yet please do, we want to keep the thread and the idea at the forefront of everyones minds over there.

Were getting close to having a solution, and the software folks overthere may kill two birds with one stone, giving us ignition control and non wasted spark mode.

rotarygod

Everyone's support on the MS forum is doing wonders! When I tried to ask for some help as an individual on the exact same topic a month ago, I wasn't given alot of consideration as a sole individual. Now we might actually be getting somewhere.

The code might actually get written this week that will allow us to keep the stock RX-8 coils working. This in itself is a good thing and definitely makes life easier. It would also mean that I can tune in negative timing split which is still a relatively unknown black art of rotary tuning.

It was suggested that the RX-8 code will be embedded in the MSII software. The guy doing it is currently working on getting the MS software for the rotary code adapted over to MSII use and while he is doing it he might just write the RX-8 code in with it as well. It does mean that I will have to do the MSII daughterboard upgrade to my unit but that's fine with me. MS is an 8 bit ecu. MSII becomes a 24 bit. Just to let you guys know, the stock RX-8 ecu is a dual 32 (64)bit unit.

Keep up the support over there. Drop in a comment every once in a while if you can. Lets keep that thread going on the front page where it gets lots of attention. It seems to be working. This is exactly how the Neon guys got their code written. Enough people asked for it and it just appeared one day but it was all because of the amount of people that wanted it.

Thanks to everyone who is helping out. The real hero in this project is the guy who is willing to help us out with the coding. Without him we wouldn't get very far very fast. I'm just responsible for supplying my own Megasquirt to the project and knowing how to tap it into the system. Brillo is responsible for spending a few necessary research bucks as well as being my bitch and letting me mess with his car! Without Ken and the others at the MS forum, we'd be stuck with a fuel only ecu upgrade so they deserve far more credit than we do.

dodo_croatia

I have a question.
Will it be possible to use the extra features of MegasquirtnSpark-extra Firmware. http://megasquirt.sourceforge.net/extra/index.html
As i see that additional hardware that has to be built is not hard to make, so why not, i see a lot of interesting features.

rotarygod

You can use it for whatever you want. You could integrate in knock control, boost control, shift lights, auxiliary port control, nitrous control, wideband tuning, etc... to it. It isn't quite as easy as just running a new wire though. MS was designed as a basic bare minimum system to keep it cheap. The kit comes with what you need to get a car running good off of it. It does not have all of the circuitry needed to do alot of the additional features. Those little circuits need to be added. The reason they did it this way is so you only purchase and build what you need. When you are paying for aftermarket ems systems, you are also paying for alot of features that were built into the unit that you may never use. That's a waste of money. The nice thing with this is that all of the extra features are in the software so when you build the little driver circuits, it is all there ready to be used. These little circuits are usually only a few dollars in parts every time you want to add one. Image how much the kit price would go up if you had to build all of these extra features you may never use. It's a really nice way of doing things. Pay for what you need and nothing you don't. Too bad they don't all work this way.

dodo_croatia

I was plannig to put megasquirt in my ae86, but at the end I didnt put ITB so i am running stock ecu. Then was the first time I read something about MS. At first glance to me it was just a cheap EMS, but now i see that that system is cheap an has ALOT of potential. I am glad that you guys are helping to make it work on rx-8.

btw. At the end will you use MS2 or MS?

MintyFresh

added my 2c worth of support on the MS board. Unfortunately short of offering a free website there's little else i can do thats useful.

Good work RG & Brillo and thanks to Ken et al for helping you out

rotarygod

All I need to do to use MSII is to unplug my current chip from the board and plug in the new MSII daughtercard. Then just change software. That's it. It's the same basic board with an upgrade. That makes it easy. This is one reaso I love the MS platform. When a new version comes out, yours isn't obsolete. You just upgrade it.

olddragger

iTrader: (3)

Glad the MS2 will work better! I thought it might make it a little simpler for our car with its 64
bit's!
Quick question to RG --If you do try the negative split timing will the rotor itself need motifying?
Does the renisis have a fireslot (hope I said that right)in the rotor?
This is getting good.
Olddragger

brillo

no modification is necessary, in fact our cars already run in negative split at idle. its no different that adjusting the timing in a positive split

MS II is not 64bits, its 24bits. Our stock dual ECU's are 32bit each.

olddragger

iTrader: (3)

Hello Brillo
Great work yall are doing man. Thats what I intended on saying although in backreading i realize I stated that in a confusing way. Our cars 32 bit x 2.
Our cars already do a negative split at idle? Dang I didnt know that. Why is it set up that way? Hmmm. Damn and i wanted to get a good nights sleep.
Olddragger

rotarygod

It's all about emissions. Negative split lets you run leaner. I could get really technical and explain why to you but I'd have to have a rotor and housing in front of you and actually show you. Lets just say that the a/f ratio entering the engine gets leaner but the a/f ratio when burned in negative split mode is still the same. Sleep in that one! The more vacuum you have, the more negative split you can run. The less vacuum you have, the less you an run. You can not run negative split with positive pressure.

swoope

iTrader: (5)

rg,

just found out that the pull for the great am beer fest. is the first of sept. i have some being pulled for you.

yes this is off topic, but is the support i can provide!!!!!!

it will be labled fragile incect parts.

beers

rotarygod

That's awesome!

swoope

iTrader: (5)

^^^^^^
let me know if brillo is into this also!!!!!

beers

rotarygod

We spend alot of time at the St Arnolds brewery so I'd say he's pretty well into beers too.

swoope

iTrader: (5)

get him to send me an address.

i might be at the gabf in denver in oct.

i should have the stuff out about 3rd or 4th of sept.

beers

olddragger

iTrader: (3)

RG
You are sadistic man. Say WHAT? Just when I think i am beginning to understand something.
Ok then--on the renesis the side port increased vacumn --right? This is getting to be as confusing as trying to tune a 6 pack of webers.
Think I'll join the beer club and wait for an eureka moment.
Olddragger

rotarygod

It really has nothing to do with porting. It has everything to do with engine load. Confused yet?

tuj

RG: regarding the negative split. I think I know why this works. As the rotor passes the leading plug, its creating a vacuum, pulling the charge across the rotor face. But at low loads, this vacuum is weaker so the charge is not concentrated at the rotor face. Therefore, by firing the trailing plug first, the combustion forces the mixture towards the leading plug and rotor face, where the leading plug can then ignite and more completely burn the mixture.

Is that it?

olddragger

iTrader: (3)

Yea --what he said. But wouldnt that put more heat on the trailing plug at idle since it's part in the thermodynamic cycle would increase over normal?
Yea I bet it does have to do with rotor decompression/compression. with that in mind is the stock rotor accuate on it's decompression leading edge/apex seal distances. Probaly so.
I feel like a kid in school and thats a good thing.
olddragger

rotarygod

It's not due to creating a vacuum that it works. You need to think about the shape of the rotor. It has a dish in it. As the rotor rotates towards the smallest point which is where the plugs are, the air in the chamber due to the shape of the chamber gets pushed down into the dish to move past that small hump shape in the chamber. The problem is that due to the shape of it and the way the rotor moves, the flow goes through the dish from bottom to top as the rotor spins. In others word, for a moment the air inside the chamber reverses direction. Due to this movement, more of the air/fuel mixture is on the trailing side of the dish as the plugs fire. The a/f ratio is only important where the mixture actually explodes and nowhere elde. Since the leading plugs fire first, they are missing alot of the air and fuel initially and making power based on the small amount that initially ignited. This leaves the trailing plugs to do mostly cleanup work to burn the rest of this.

By firing the trailing plug first, we are igniting the a/f mixture where it is at it's thickest. This means we are firing it at a richer state that if we fired the leading plug first, even if the total a/f ratio entering the engine stayed the same. In other words, we are igniting more air and fuel at the same time just by altering where the main firing plug is located. Since the a/f ratio only matters at the plug as anything else in the engine is basically waste, this means we can run a leaner a/f ratio and send it into the engine with the same results. Another benefit of firing the trailing first is that it't ignition will send the flame front and the gasses in the chamber back in the proper forward direction through the dish where the leading plug can be used to play cleanup. This leaves less waste, makes us more efficient for fuel consumption, makes more power, and less emissions. Mazda actually does this on the RX-8 now but only at idle.

There is a downside though. How wide this negative split is and how soon you can fire the negative plug is very dependent on engine load. This is where the vacuum level actually comes into play. At high vacuum levels (or really low pressure levels for you technical people) such as at idle, you can run a very wide negative split. As the pressure level rises towards ambient, you need to run less and less negative split. You had better be at the very least at zero split by ambient pressure but a little lower than this pressure would probably be safer. Above ambient such as under boost or the benefit of any positive pressure in the engine such as other tuning aids that take the efficiency over 100%, you should start getting into wider and wider traditional split. You should nver run negative split when under boost. You will grenade something.

This has everything to do with combustion chamber pressures. Also remember that we are dealing with dual flame fronts inside the engine too. Depending on how these interact, they can cause detonation. The chances for detonation increase as pressure increases which is why you only want negative split under vacuum conditions when chamber pressures are low.

It's a little confusing and alot of rotary tuners still don't know about this phenomenon. There is a guy in Florida running a very large streetported RX-7 with a large single turbo. Under cruising conditions when not under boost, he runs negative split. Remember he has an engine with heavy overlap that needs a much richer mixture than the Renesis does to keep running. Even with his setup, on the freeway he runs high 15-low 16:1 a/f ratios and the turbo spools faster when he steps on the gas.

I still dont' know alot of the timing secrets behind it and just how much to the extremes it can be taken. I have talked to this guy and he has stated that he runs as much as -38 degrees of negative split!!! That's downright crazy. I've never seen more than a 15 degree split used and he has doubled that in the other direction. Strange but true. Currently I have my RX-7 running in negative split. I can only get -12.5 degrees of split though as I have a rigged distributer accomplishing this. As rpms and loads increase, it tapers of to a total of 0 split. I have no positive split ever. It works really well but I can't test beyond this range with my current means. Hopefully with a new Megasquirt upgrade I'll be able to test this further. I should be able to. I also don't have my MS hooked up to the ignition right now.

The results have been promising but I really need to do alot more trial and error to see what really works and doesn't. Like I said, why it works is a little complicated and almost easier to understand by looking at a rotor and housing in person.

tuj

Thanks for explaining that RG. You rock! There certainly is a "black-art" to rotary tuning. I hate to get much more off-topic, but do you know what benefits there are to asymetrical side intake and/or side exhaust ports in terms of shape and/or opening/closing times? I'm thinking about cross-flow inside the engine.

lurch519

hey rg, i know its off topic, but i sent you a pm last week asking for you to take a look at something for me, just wondering if you could check it out for me and maybe give me some insight.

rotarygod

It isn't so much cross flow into the engine although there may be some vailidity to that. The intake and now exhaust port timing are all treated independently of each other. The primary intake port timing opens later than the secondaries across from them. This was done for low end power. By opening a little later we have even less overlap, or in the case of the Renesis more dwell, than by opening it earlier. They also close fairly early in the cycle. This means there is more time for the air that actually does get into the engine to get compressed and get utilized. We see this as more low end torque. Having a smaller port with less timing also does something very important. It keeps the intake velocity in the runners very high. Velocity is more important than volume right up until you max it out. You only add more volume when you need it. If you notice, these are the only 2 ports opened until 3750 rpm. Mazda did pretty good here. The port timing they chose was also based on tests they ran to determine which port timing configurations made most power and where. Remember bigger is not always better as I just implied. The secondary intake ports add more area which is what we need when we max out the primaries. These ports come online a little differently. They open just slightly earlier. Don't think of them as being tuned totally independent of the primaries. They are but they aren't. Confused? By opening them slightly earlier and closing them at a slightly different point, we have also changed the timing of the ports. Since they all work together in a system you need to think of it in perspective as the equivalent of a new larger single port that opens a little bit at a time slightly earlier, then gets full flow and then closes at a slighty different rate. Remember there is a certain port timing that is most benefical to a certain rpm range and that is what this does. On the 4 port and 6 port cars, these port timings for the primary and secondary ports are slightly different between engines. This is because each engine requires a slightly different powerband. The 4 port engine has less timing which implies it needs more low to midrange power. The 4 port engine also produces more power than the 6 port engine up to about 7000 rpm so you definitely can see the result of this. It is above this where the 4 port engine can't go that the 6 port engine makes it's best power. The auto transmission just sucks that gain right away on the 4 port though.

On the 6 port engines we have a 3rd set of ports that open up at higher rpm's. They don't do much to the open timing of the engine other than the fact that they add to the total open area of the port system and therefore you have more air earlier but their most important benefit is how late they stay open. They close at 80 degrees. The chamber is already getting smaller by this point so you would think that air would would reverse back out of the port. Alot of 2nd generation RX-7 guys leave these ports open full time for simplicity reasons and lose power below about 4000 rpm as a result of this reversion. At higher rpms, the air actually keeps flowing towards the engine as the chamber starts getting smaller. This is because air has mass and a body in motion tends to stay in motions. This inertia forces a little more air into the engine. This is known as inertial ramcharging and actually makes it possible to have greater than 100% intake efficiency. We also call this boost! Why not leave all the ports open this late though? Well that goes back to the velocity thing. Remember that this is the last port to close. All the air traveling towards the engine is traveling through this port. It has alot of velocity. There's that important word again! This high velocity allows more to get into the engine. If we had another port in the chamber that stayed open this late, our velocity would cut in half. Some would say that is OK as we have twice the ports. The thing to remember though is that energy rises at a square to velocity. If we lost half of our intake velocity, we'd lose more than half of the energy that is trying to push air into the engine through this remaining timing. That means that more port area would give us less ram charging and therefore less power. Velocity over volume until you max it out!

Exhaust port timing works in basically the same way but obviously in the other direction. Much of the same rules apply as far as velocity. The nice thing about airflow though is that you have pressure in front and behind the main pulses. In an exhaust we need to design a high velocity system to aid in chamber scavenging. We want to leave as much room as we can in the combustion chamber so we can fit in more clean cooler intake air.

As far as the intake runner lengths go, this can get even more complex. You don't design one set of runner to tune to one rpm and then another set to tune to another rpm. Some people have stated this is the way to do it on an engine that opens them sequentially. Remember that when they are all open together, the ports are in essence 1 large port. You need to treat intake tuning accordingly which means each set of runners must be tuned to the same ultimate power peak. The fact that there is such high velocity through them since some stay closed at some spots more than offests the fact that those runnes that are open at that time aren't tuned to a lower rpm. Don't worry about it. If you look at the different runner lengths though, you will see that the primaries, secondaries, and auxiliaries are all different lengths than eash other. This may get confusing since we know they are all supposed to be tuned to the same spot. Since each set of ports has a different intake timing and duration, they send pressure waves back at different times. They also resonate at different frequencies. To compensate for these differences, we need to adjust runner lengths accordingly. This means that at the desired tuning point with all the runners and ports working together, these different lengths are all tuned at the same spot. That's what is important.

You can see how porting is much more science than it is just making a hole as large as you can. Personally I feel that no one should be porting these engines larger at all. I feel that they need to be concentrating on getting the most flow out of what they have. They can be improved. Making a port larger also doesn't necessarily mean it will flow more air. It may actually flow less! It's all about velocity.

How does all this relate to crossflow inside the engine? Well at first it may appear that this is very important. Yes it does help to atomize the fuel somewhat. Then again look at a peripheral port race engine. It has a straight shot into the engine yet still runs fine. It's low end/ part throttle issues are a result of severe port overlap and not fuel mixing. You need to remember that different sides of the port open and close and then the air travels a long distance. The vertical side of the port opens first and the top edge closes last. This means there is alot of airflow direction change inside the engine. It would be very hard to make a swirl type of intake work effectively on a side port as it's rotational direction may very well reverse after it passes the port. Needless to say, avoid any "tornado" type of intake products. Then as the rotor moves and the combustion chamber changes shape, the air gets pushed down into the rotor combustion face dish and again changes direction. You can really see how the rotary loses alot of efficiency, where it does, and why. Basically cross flow effects are minimal at best. I could have saved a paragrapgh and just typed that one sentence.

I've turned this into a senior thesis on rotary engine airflow mechanics rather than a Megasquirt thread but hopefully it has answered alot of questions. It probably created more though.