-CON-

Hi! So I have this project I am working on right now, I am building a semi-peripheral port engine with a third spark plug just like on 787B Le Mans race car, and all cermet coated internally, just almost like 787B race car.



And my question is> I heard that peripheral ported rotary engines make unbelievable power at the high rpm, but why not at low rpm? What causes the P-ported engine to have such low power at low rpm?

And if turbocharge the P-ported engine will it still have the power only at high rpm like the N/A P-ported engine?

Will the drive ability be better on the turbo P-port engine than on N/A P-port engine, or the same?

Is it even worth turbocharging a P-pot engine?

What is the best ports for the turbo setup anyways?

diabolical1

iTrader: (3)

first of all i think you need to check your facts on the 787B ... i'm pretty sure it was a full peripheral port engine.

as for your first question, generally speaking, it's a matter of intake and exhaust timing and the overlap between them. the more overlap, the softer the low end. again, this is a generalization. you can manipulate size and location of the intakes and the size and shape of the exhaust to improve low end. i'll leave it at that.

your second question: as with every turbo application you can tailor your powerband if you take the time to properly choose a turbo that will fit what you want and tune accordingly. that said, if low end is of utmost importance, then you may want to express that to your engine builder and possibly use some other type of port or port combination. adding the torque curve of a turbo does not change the fact that the engine still has more overlap than other port types.

third question: drivability is subjective, so i'm leaving this alone. all i will say is that the builder has some space to manipulate the overlap when cutting the ports, but there is only so much that can be done. a peripheral is a peripheral and overlap is the nature of the beast.

fourth question: only you can answer this one.

fifth question: "best" for what?

Aaron Cake

iTrader: (1)

Sure you are.

The 787B is a full peripheral port 4 rotor race engine, with a dry sum oil system, multi-part eccentric shaft, variable intake trumpets and of course the famous three spark plugs.

Do you have any idea how monumental the machining is going to be to put a 3rd plug into a set of stock rotor housings? A hole will need to be bored (like you would do for a peripheral port) and a sleeve inserted (again, like a PP). But then that sleeve would need to be tapped (no big deal) and SEALED AT BOTH ENDS. The outside can be welded easily enough, but the inside is exposed to combustion pressure and must seal against the chrome surface of the rotor housing. Welding that is going to be a very tricky affair, considering the sleeve will be of a dissimilar metal. Make the sleeve out of steel so you can weld or press fit into the wear surface and you end up with it being unsealable to the outer housing. Mazda cast the housings for the 787B as a custom job.

And then you need to find an EMS system to control all those ignition channels and support two levels of split. I don't think something like that even exists for less then $20,000.

Do your research on coatings. They tend not to fair very well and few high HP rotary cars are running them.

It depends on the porting. Generally speaking, overlap hurts low end. The more overlap, the less low end due to poor velocity and charge dilution. But keep in mind that many NA peripheral port engines make more midrange power then an equivalent side port, and obviously much more high RPM power.

A turbo peripheral port will depend on the turbo to make it's power, so it's powerband will depend entirely on the turbo. On the plus side the overlap will allow you to spool huge turbos very quickly. And you'll need a large turbo to prevent choking the engine.

Better.

For you, no.

There is no best.

-CON-

Thanks guys for your reply! I just need to hear from someone else s point of view.

As for housings and the plates it is all already done coating, grading, and lapping, the P-port is all ready done and so is the third spark plug. There is no going back for me now, no matter what anybody says, the money was already wasted, so I just got to go forward and finish what I stared and see what the results later.

I know the specs of the 787B car I just pointed out some similarities.

rotarygod

iTrader: (1)

Oh snap! Owned! Sorry Aaron!

That's pretty damn cool. I've never seen anyone actually get the 3rd plug locations machined. Mazda moved the dowel pins in this location to accomodate the 3rd plug which is easy to see why as you can't get yours in now.

7dust

iTrader: (14)

^^^ What he said.

g14novak

iTrader: (1)

Oh snap! Haven't seen a project like this on here in a while. I need to come over here and troll the new member section more often...

Well since your 1st and 2nd question have been answered pretty well, I'll chime in my opinion on the 3rd-5th.

3rd: The drivability IMO would probably be smoother on a turbo application, but it depends on the rest of the setup of the car and what your use to.

4th: Is it worth it to turbo a P-port engine... this one is all personal opinion. How much power are you trying to make with this car? Does it need to meet any certain standards to be street legal or meet a certain tracks specifications?

5th: Best ports for what? Are you trying to have the car run smooth? Do you want it to go so fast you can barely stay in your seat? This is all depending on what you want. Larger ports are going to yield more power at the cost of drivability.

diabolical1

iTrader: (3)

well things are a bit different building a semi-peripheral motor. you're mixing/splitting advantages and disadvantages between two different port types. i wish i had more answers for you on this, but the truth is i'm kinda forging my own way on my own semi-peripheral project as we speak.

EDIT:
hell, as it stands now, i should be asking you questions because you seem to be a bit closer to assembly than i am. LOL - which only goes to show you can never stop learning and you never know who may teach you.

i have never been inclined to try a far trailing setup, but now that you've undertaken that burden, what are you doing with the dowels?

Aaron Cake

iTrader: (1)

You should have posted those pictures in the first place.

Honestly, I do think it was money "wasted". While the 3rd spark plug is very cool (exactly how was it done, by the way? Looks like a press fit sleeve....) I don't think you'll see any benefit at all by having it.

Since you are going semi-peripheral, your engine will act much like a large bridgeport. It will have a bit more manners and the loss of low end will be far less then one would expect.

Looks like those housings are < '86. I can't quite tell from the picture, but you filled the coolant o-ring grooves with putty?

Since you've blown away the dowels, how are you going to get oil to the front bearing? I assume some sort of loop line? And remember to seal up the oil passage in the rear iron so you're not going to get leaks.

What EMS are you going to run? As I mentiond, finding one that will allow two levels of split is going to be an issue.

Meh, I'm not too worried about being owned. What I'm baffled at is how someone could accomplish this without even knowing the basics of porting and overlap. Then again, just handing some housings to a machinest and saying "Do this" doesn't take knowledge.

(I'm not trying to be an ***, I'm genuinely trying to figure it out)

-CON-

When I say the best I mean improvement in every thing, more advantages than disadvantages and if something else batter comes along it becomes the best at that moment.

As far as it is your answer than it is your opinion, so you tall ma what the best choice would be (porting vs turbo) in your opinion. People beside what's best not science because everything is for people.

What I am trying to make? "The Fast and The Reliable'' like everybody else I guess!

About the pins> yeah I can still put 'em in, I just need to cut 'em, I know oil supply to the front baring goes through the pins, yes Argon I'm just gonna have to loop/ jump it, a lot of race engines jump that line anyways. I already made the manifold for this set up and Weber, but now I'm thinking to go with Megasquirt.

I don't wanna say I know everything about rotary because I always learn something else from someone else that I didn't know, that is why I join here.

As I said I like to hear others opinion

diabolical1

iTrader: (3)

another question ...

curious as to why you built around an older block.

-CON-

cuz its known as a heavy duty engine block, this particular block has the groove of the waterjacket on the housings instead of it being on plates, the plates dont crack.

I did take one engine apart because it had its plate cracked.

-CON-

Mazda went back to their old design of the waterjacket for the rx8 engine as well!

Aaron Cake

iTrader: (1)

Something else just popped into my mind...You've bored through he dowel castings, so you'll now have to split the dowel pin in half. This is going to be a MAJOR detriment to engine stability. Put 400HP through that thing and it will twist like there's no tomorrow. You'll need to strengthen the block at this point. The only thing that comes immediately to mind is a 1/4" aluminum plate on the bottom of the engine between the block and the pan. But to maintain the strength, you'll have to be very careful about how you cut through it to allow the oiling system to work. Or go dry sump.

Here's the thing; Porting and turbocharging are not mutually exclusive. The engine needs to be a system. Your choice in porting will be dictated by how much power you want to make (how much do you want to make anyway?), and then your turbo will be dictated by your porting. If somehow you got a smoking deal on a specific turbo, then you can build an engine to suite that turbo.

I would not suggest anything to do with a carburetor in a high overlap issue. All the bad press that bridgeports and peripheral ports get is due to carburetors, not the porting.

A Megasquirt is a good choice, but it has a very steep learning curve. Something tells me that doesn't worry you.

A Megasquirt will not run your 3 plugs per rotor. It only supports split on 4 spark plugs. Without a MSII and a router board (if the router board ever comes out) I can't think of how you will control those plugs unless you write your own firmware.

However the rear dowel castings are much, much weaker compared to the newer ('89+) engines. A bit of detonation at around 400HP and you'll crack a rear iron. And by weakening the dowel castings on the rotor housings and having to split the dowels, you've just moved this problem down to around 300HP.

You'll notice the 787B had entirely different rotor housing castings which moved the dowel locations up.

diabolical1

iTrader: (3)

heavy duty engine block, eh? well, what's done is done so take it as far as you can. i suspect if you actually turbocharge this thing, you're likely to be building it again in short order. the dowel areas are likely to crack if you didn't add dowels or use thick studs and unfortunately, in terms of structural integrity, you've probably shot yourself in the foot by using a far-trailing setup. Aaron already mentioned why, so i'll just leave it there.

for what it's worth, the painfully few semi-peripherals i've seen were ALL REW-based. mine's based on a S4 T2 block, but i'm keeping it N/A as i develop my skills and learn to tune it. this motor is strictly a learning exercise for me. by the time i think of adding a turbo to the mix, i'll build around an REW, too.

at any rate, good luck with your project. can't wait to see it running.

diabolical1

iTrader: (3)

i could have sworn i read somewhere that the far-trailing plug fired simultaneously with the trailings. i'm tempted to say that it was Rotarygod that put forth that information, but i may be mistaken.

that said, i'm just asking if the MegaSquirt signal to the trailing couldn't be split to fire the far-trailing plugs as well or is it just not that simple?

Jeff20B

iTrader: (13)

I thought L and T fired together and the late T fired later.

-CON-

I can machine engine stud holes and fit more pins through that, I even see it done by someone on this forum, I just don't remember where.

Did you actually seen that block cracked, because I never did, but I did take one engine apart that had its block cracked, and it was a 1990.

Besides all that. third spark plug can be fired at the same time as trailing. The leading coil is perfect for this mod, I will get two sparks from one coil.

I don't know much about engine management systems, about the Megasquirt I found out not to long actually.

Aaron Cake

iTrader: (1)

I don't remember. I had always thought that they fired after another split period. I'd check my Yamaguchi book but it's at home and I'm at the office.

It could be. Using two FC trailing coils connected in parallel would do the job.

I've always thought that as well.

Just do a search for "doweling" or "dowel pinning". You can add more dowels, use a stud kit, or mix and match the two. But now you are having to solve a problem that wouldn't exist if the 3rd spark plug was not there, and a stronger block was used.

In person I've only seen a few crack. I've seen a load of videos of rear irons cracking on the dyno. Ignition noise is generally the cause, which resuts in massive detonation and a cracked iron.

If you fire it at the same time, then yes, you can replace the two single output coils on a trailing ignitor with two leading dual post coils. However, are you absolutely sure they fire at the same time? I'm picturing it in my head and that looks like it's firing into the compression stroke. Guess it depends on how much split you are running.

-CON-

I think running a third plug with turbo may cause detonation faster !!

Does anyone have any Idea?

diabolical1

iTrader: (3)

okay, Jeff, this (check post 17) is where i read it. i freely admit that i didn't research it myself - wouldn't even know where to begin - so i took Rotarygod's word at face value. i would love to have the correct information on this and i don't mind doing the research if someone gave me some direction/advice as to where to find it. it has relevance to Con's project, so i'd post it here once found.

diabolical1

iTrader: (3)

as long as you take all the documented steps on intake charge heat control, then my thoughts would be if you (1) confirm when they need to be fired, (2) choose the right plug-type and heat range and you (or your tuner) (3) manage timing in a relatively conservative way, then there shouldn't be a problem.

-CON-

Here is an other thing that I just totally forgot> If you will mount the strongest engine what ever you think it is with the engine mount on the front and 400hp, see if it wont rip your pin out. Because of the twist.

Old 12 and 13b engines are mourned on the front, S4 and S5 are mounted on the center plate, and the FD's are mounted on rear plate.

I wasn't going to mount my engine on the front, but because I cant mount it any where else I am going to build a heavier oil pan and put mounts on there, change 10 millimeter bolts with 12 millimeter studs, for the oil pan, that will do the trick!

And yes it is one of the strongest blocks in the rotary family, But you do know that a lot of FC's and FD's engine fails because of the plate crack on the waterjacket groove. How often? Well I happen to take one apart because of that!

Who knows what I am talking about will back me up on this one!

Aaron Cake

iTrader: (1)

I think if you looked at later blocks ('89 and later) that would alter your opinion about how strong the earlier 13B engines are.

You're concentrating a lot on a failure that doesn't happen very often (cracked water jacket) while ignoring a failure that does happen on the earlier blocks (cracked dowel) when things go a bit wrong in the tuning.

There seem to be many downsides for alterning stock housings for three plugs, the more I think about it.

I wonder if there will be any gains?

Where in Canada are you anyway? I'd be interested in seeing the setup when it's all done.

-CON-

Central part of Canada!

The only time that failure happens is when it is twists the engine, and it twists because it is mounted on the front.