pp4rotor

My friend and I are looking very deeply into assembling a 4 rotor from two 13bs, we have worked out the accentric shaft adapter as well as rearplate/ adapter/ frontplate setup in the center of the motor. The hard parts are worked out, but after some more thought, the idea of opposing the shafts 90 degrees instead of the original 180 degrees came up. Does anyone have any ideas on the ignition of this beast if opposed 90 degrees as well as 180 degrees. Were actually considering running a DSM coilpack and ecu for rotors 3 and 4 with a stock 12a distributor up front with the points matched to fire leading and trailing spark at same time. This works in theory at least. Any other ideas? The motor will be carbed so no worry of coupling the ignition with fuel injection.

Also, how have the 90 degree opposed 4 rotors been balanced in the past?

Kenku

Well... ah... for anything dealing with a 4-rotor, I'd pretty much say to make the ECU do ignition, but... carbed. Points too... so the original, non-electronic dizzy. Bizarre.

It sounds like you're sticking two 13B e-shafts end to end. I guess that if you had them 180 degrees opposed, you could just have the stock dizzy fire a dual-post coil and run 2 rotors at once but... eesh. Running them 90 degrees opposed, I'm having severe trouble imagining how to do without hacking up the distributor.

Balancing... well, I can't but wonder if the front counterweigh balances out to the same as the rear AT counterweight. If so, I think in theory you could have the two engines not be opposed at all, so the vibratious that need the stock counterweights balance out.

This is completely different than how Mazda made their 4-rotors. It sounds like you're trying to join two 13Bs together, which means the 1st & 2nd rotors will be 180 apart, and the 3rd and 4th will be too. Mazda had the 2nd and 3rd rotors be 180 apart, so the middle two were essentially a 13B in terms of balance. The other two were 90 degrees opposed to the center two, and 180 apart from each other. I'm pretty sure it was only counterweighted at the ends of the engine.

There's some problems with essentially joining two engines together... it gets hard to balance things if you have the center two rotors at 90 degrees, but if you don't you don't get nearly as smooth of power delivery. A really big issue though, is length. You're going to end up needing a fair bit of room in the middle for the adapter and whatnot. Even if you didn't, a 4-rotor 13B with conventional housing widths is rather longer than a 20B and those have been shown to be a minor headache to fit into a '7. I *have* seen a 4-rotor built this way, but it was for a tube frame circle track car where length isn't a problem.

Guess I'd just advise thinking about some things a bit.

Jeff20B

iTrader: (13)

Ah, this is what you were talking about Kenku. I don't really have anything to add at this point other than to say you could join two 13Bs together with a simple CV or universal joint from shaft to shaft.

Man, now I'm all hot and bothered to hook two 13Bs together. Where to get two more 13Bs, where to get more 13Bs for cheap! Where to get etc.

pp4rotor

Definately have looked at the mazda 4 rotor and noticed our problem in balancing. If 90 degrees apposed, do you think it would be possible to simply have a counterweight on our adapter in the center of the motor between the 2nd and 3rd rotors and omit the counterweights at the front and rear?

The counterweight in that case would just be part of the adapter we are building. What if there is no counterweight, I guess it would just put a **** ton of stress on the two center main bearings and wear them out quickly. Any opinions on the counterwieight on the center of the motor alone without weights on the ends?

Actually, now that I think about it it needs counterweights on front and back much like a stock 13b. The 180 opposition balances out the center of the shaft. It still needs the counterweights on the ends. The 90 degree opposed 4 rotor would need the same thing.

Sponge Bob Square Pants

There was mention a while back of Pineapple Racing selling 4-rotor cores, ready to go, for $8500 us.
I'm not sure how good the 4rotor engines are put together, or the specs, but Pineapple does have an excellent reputation. Just another possible option.

Also, if you can get ahold of Jim Downing he can provide you with extremely valuable information, he has raced for years and built 4 rotors before with good success.

RETed

Oh, I dunno if you call his racing with his 4 rotor very "successful".


-Ted

pp4rotor

pinapple actually bought the rights and design from a guy in washington whom we are talking to currently.
his website is grannies speed shop... i can't find link now.

the basic idea is to make cost a minimum (2005 challenge) and we are now thinking that multiple dsm ignitions, which are waste spark, we can run 4 coils, each with 2 plugs coming off them, and fire two plugs per rotor at the dsame time. is there a really big problem with this?

also, this would only work with 180 phase, as the 90 phase would require the ecu to switch between the coil packs each 90 degrees, which isn't possible since the ecu has only 2 outputs.
we thought of using a relay sort of switch that would alternate the signals each 90 to each set of coils, but this is getting complicated.

so, suggestions are more than welcome, thanks for your time!

Shamrock.James

you could join them at 90 degrees, although 180 is more ideal as it removes the need for the counterweigths altogether.

wwilliam54

run 2 separate ecu's

rotarygod

iTrader: (1)

Granny's speed shop built theirs a little differently. They adapted the rear of one shaft to fit into the front of the other shaft so there were literally 2 engines end to end. Each engine fired at the same time as the other one. In other words the 1st and 3rd rotors fired at the same time and the 2nd and 4th rotors fired at the same time. Think of this setup as the rotary equivalent to a flat plane crank on piston engines. This solved many problems for GSS. This way you can use a standard ignition setup with no modifying. You could just split off the spark plug signal somehow. It is firing like a 2 rotor after all. The other thing that running both engines like this is good for is the fact that you only need a stock front and rear counterweight. No need to worry about special balancing procedures. You can also run 2 independent exhausts or run them together. There are so many neat benefits of running both at the same time. As a downside it will have the sound of a 2 rotor or 2 of them as opposed to the different sound of a 4 rotor.

Shamrock.James

i would also asume it would vibrate a lot as well, i remeber the spoon 4 rotor had some problem you might want to look into as well as it was ripping through engine mounts.

RETed

Please, it's "Scoot" and not "Spoon".
Spoon Sports makes Honda stuff.


-Ted

bill Shurvinton

I'm putting together an ignition for just such a beasty at the moment. Can't comment on the balance side, but I know the engine was balanced by the UKs top vibration expert (he does everything from car engines to industrial machinery).

There are about 5 ways of doing the ignition, all of which have merits and drawbacks. Once I have something working I'll post and let you know how it went.

Bill

Shamrock.James

LOL can't belive i fucked that up ... oh well too much F&F but yeah i meant to say scoot.

Kenku

About Downing; got a chance to talk to him and his engine builder when they were at Road America last year. They have an R26B, though not with the variable length intake trumpets. Said they bought it from Mazda around '92 and haven't had to rebuild it in about 10 years.

Definitely a Mazda one and not one they built though... well, aside from the intake manifold which I already mentioned. To hear him tell it, they don't do any development work on the things anymore, and the big big reason they're still running it is because it doesn't break.

http://ham.and.cheese.on.rye.sandwich.net/elkhart/ is some pictures I took at the races. 19 is the first of the shots of his car. Some of them get a pretty good look at the car; he was really friendly and let me get up close to it.