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Scoot 4-rotor FD featured in Nov. Import Racer!

Old Nov 2, 2004 | 07:42 AM
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Thumbs up Scoot 4-rotor FD featured in Nov. Import Racer!

quick magazine specs:

12A based N/A peripheral 4-rotor with custom designed 3-piece eccentric shaft

4 individual 46mm slide valve throttle bodies in a CF ram air induction box

8 550cc FD injectors

lightweight 12A rotors with 3mm apex seals

twin Power FC's with Commanders with twin crank triggers at 90 degree offset

custom SS equal lenght 4-1 header

pressure variable exhaust bypass (muffled at low throttle, open at WOT)

tons of other stuff

475hp at 8000
345 lbs-ft at 6000

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Old Nov 2, 2004 | 09:05 AM
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two pfc's? how the **** does that work?
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Old Nov 2, 2004 | 09:09 AM
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That's gotta be tricky, but I imagine you have 1 PowerFC for the first 2 rotors and another for the rear 2. I guess just as long as you program them the same, you're good to go.

I figured they'd be making more horsepower than that, although that's nothing to sneeze at!

Dale
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Old Nov 2, 2004 | 09:59 AM
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Why would you put 3mm Apex seals in a N/A engine?
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Old Nov 2, 2004 | 10:28 AM
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Originally Posted by Dwood432
Why would you put 3mm Apex seals in a N/A engine?
More than likely have changed the compression ratio....but more importantly.....why not?
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Old Nov 2, 2004 | 10:31 AM
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Originally Posted by dcfc3s
That's gotta be tricky, but I imagine you have 1 PowerFC for the first 2 rotors and another for the rear 2. I guess just as long as you program them the same, you're good to go.

I figured they'd be making more horsepower than that, although that's nothing to sneeze at!

Dale
Japanese love using domestic products, and nobody knows the PFC better than Scoot, but I do scratch my head at this. Surely there is some kind of after-market ECU that could run this beast without the complication of two ECU's. Those numbers are probably whp. I've got a few videos of the Scoot car on my site. Check them out here!
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Old Nov 2, 2004 | 10:34 AM
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Originally Posted by 95R2-89TII Ground Zero
More than likely have changed the compression ratio....but more importantly.....why not?

For the same reasons I kept the stock seals in my single turbo motor.
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Old Nov 2, 2004 | 12:14 PM
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Originally Posted by dcfc3s
That's gotta be tricky, but I imagine you have 1 PowerFC for the first 2 rotors and another for the rear 2. I guess just as long as you program them the same, you're good to go.

I figured they'd be making more horsepower than that, although that's nothing to sneeze at!

Dale
Dale,

I think pfc#1 controls rotors 1,3 and pfc #2 controls 2,4.

A 2 rotor fires every 180 deg.
The 4 rotor in the 787 and 792 fires every 90 deg.

Rotor #1=0 deg
Rotor #2=90 deg
Rotor #3=180 deg
Rotor #4=270 deg

Of course they could have joined two two rotor e-shafts end to end in which case your theory would be correct.
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Old Nov 2, 2004 | 02:40 PM
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Originally Posted by CCarlisi
Dale,

I think pfc#1 controls rotors 1,3 and pfc #2 controls 2,4.

A 2 rotor fires every 180 deg.
The 4 rotor in the 787 and 792 fires every 90 deg.

Rotor #1=0 deg
Rotor #2=90 deg
Rotor #3=180 deg
Rotor #4=270 deg

Of course they could have joined two two rotor e-shafts end to end in which case your theory would be correct.
but the question is (or at least my question is) how do you get the two computers 90 degrees out of phase with each other, and how do you keep them sinked up? would one computer need some sort of signal from the other one(to stay in phase), or could they work indepepdently?? im just wondering how exactly to accomplish this feat? could you use two crank angle sensors with one 90degrees behind the next (i dont remember if thats what the computer uses to compute when to fire... im not really knowledgeable when it comes to aftermarket... or any ECU;s for that matter)
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Old Nov 2, 2004 | 02:50 PM
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Originally Posted by RotorMotor
could you use two crank angle sensors
Bingo.
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Old Nov 2, 2004 | 05:44 PM
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Just quoting myself from the very first post....
Originally Posted by neit_jnf
twin Power FC's with Commanders with twin crank triggers at 90 degree offset
YOU NEED TO READ!!

Last edited by neit_jnf; Nov 2, 2004 at 05:46 PM.
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Old Nov 2, 2004 | 06:28 PM
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Originally Posted by neit_jnf
Just quoting myself from the very first post....

YOU NEED TO READ!!
hehe oops... its been a long day. so i wonder if there is any worry about the 90 degree advanced one becoming miscalibrated at all, or if its a pretty safe system?? also you would need to update the maps in pairs correct? if one map never loaded properly id think you would have some bad problems. either way, seems to be a good way to run a 4 rotor... too bad the 3 rotor is phased at 120 degrees. so basically get 2 PFC's... connect each sensor to both unit... and get 2 crank angle sensors and offset one 90 degrees... sounds doable. now if only i could get a 4 rotor crankshaft id be set haha
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Old Nov 3, 2004 | 02:27 AM
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I wonder if you can buy the whole package from Scoot.

Talk about $$$$.
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Old Nov 3, 2004 | 11:42 AM
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I for one am not impressed.

Correct me if I'm wrong, but isn't the main advantage of the rotary its inherrent smoothness and ability to sustain high RPM's, which is how it makes good horsepower for its small size? Adding rotors should increase this smoothness and internal counterbalancing (think V-12 as opposed to V-twin), so why are they not revving their motor much higher than 8000 RPM? It seems like Scoot has built this car for the wow factor alone, as evidenced by using two half-decent ECU's instead of one really good one.

If they were shooting for increased torque, why not just build a larger displacement rotary engine from scratch? It would have less parts, that should net you with less weight per displacement. Such a concoction couldn't be so difficult to fabricate, Mazda has been making rotaries for years.

-s-
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Old Nov 3, 2004 | 11:58 AM
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Originally Posted by scotty305
why are they not revving their motor much higher than 8000 RPM?
Probably because there's no benefit in turning higher rpm just for the sake of turning higher rpm, although it does impress people who don't know any better.

For it to be worthwhile, you must be able to provide enough air to keep the engine fed, and the 12A ports probably become a restriction before 8,000 rpm is reached, causing horsepower to fall off. If you could provide enough air to keep making power at 8,000+ rpm, you'd sacrifice more low end to do it. There's a balance that needs to be maintained.

It seems like Scoot has built this car for the wow factor alone, as evidenced by using two half-decent ECU's instead of one really good one.
Or, you could look at it as using two readily available and perfectly acceptable ECUs instead of trying to find or build one that will control a 4-rotor engine, a configuration never available in any production car...

If they were shooting for increased torque, why not just build a larger displacement rotary engine from scratch? It would have less parts, that should net you with less weight per displacement.
Not likely, the rotary design doesn't lend itself well to increasing displacement. You either increase the number of rotors, increasing length and weight, or you increase the size of the rotors and housings, increasing height, width, and weight. Either way, you've got a packaging and weight problem. You can't "bore and stroke" a rotary to increase displacement with no increase in package size.

Such a concoction couldn't be so difficult to fabricate, Mazda has been making rotaries for years.
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Old Nov 3, 2004 | 12:08 PM
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Couldent the Haltech E11 controll a 4 rotor, when using the right Aux outputs
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Old Nov 3, 2004 | 07:23 PM
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Originally Posted by jimlab
For it to be worthwhile, you must be able to provide enough air to keep the engine fed, and the 12A ports probably become a restriction before 8,000 rpm is reached, causing horsepower to fall off. If you could provide enough air to keep making power at 8,000+ rpm, you'd sacrifice more low end to do it. There's a balance that needs to be maintained.
There are people racing 1st-gens that turn over 10,000 rpm and make power doing it. Many of them do this with bridgeports, not even peripheral. I'm guessing that the problem is with the eccentric shaft.


Originally Posted by jimlab
...Or, you could look at it as using two readily available and perfectly acceptable ECUs instead of trying to find or build one that will control a 4-rotor engine, a configuration never available in any production car...
I would expect you to be the last person to disagree with spending extra time and effort to do things right, especially with regards to weight savings and performance.

Not likely, the rotary design doesn't lend itself well to increasing displacement. You either increase the number of rotors, increasing length and weight, or you increase the size of the rotors and housings, increasing height, width, and weight. Either way, you've got a packaging and weight problem. You can't "bore and stroke" a rotary to increase displacement with no increase in package size.

Good point; adding width and height would probably offset any advantages in torque. It is my belief, however, that the rotary engine is far from its ultimate capabilities. Whether the progress comes in the form of design improvement, new materials, or whatever else, I feel that adding a couple rotors is far too rudimentary an idea to be given so much credit.

But you can't tell me that Mazda is the only company capable of fabricating a rotary: http://www.freedom-motors.com/ builds them for use in watercraft, and I'm sure that there are plenty of other places that could make them if they felt so inclined.

I must admit that this is an interesting topic compared to most that I've seen on this board recently, but it would be even better if there were more innovative ideas being brought up. UC Berkeley has been making those miniature silicon rotary motors for a while now, who's going to push the envelope next?

-s-
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Old Nov 3, 2004 | 07:31 PM
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Originally Posted by scotty305
There are people racing 1st-gens that turn over 10,000 rpm and make power doing it. Many of them do this with bridgeports, not even peripheral. I'm guessing that the problem is with the eccentric shaft.
You're talking about half the displacement. With forced induction, it might not be an issue, but pulling in enough air through a manifold to keep four rotors happy may be an issue. It could also be the eccentric shaft, as you mentioned. A 2-rotor engine doesn't have to deal with a 2-piece eccentric shaft or turning the mass of four rotors.

In any event, there are reasons *not* to turn more rpm, just because you can. I doubt those bridgeport or peripheral port engines idle well, and I doubt they'd be something you'd want to drive in stop and go traffic every day.

But you can't tell me that Mazda is the only company capable of fabricating a rotary: http://www.freedom-motors.com/ builds them for use in watercraft, and I'm sure that there are plenty of other places that could make them if they felt so inclined.
Given enough money, time, and equipment, you can build almost anything. However, anyone building a 4 rotor from 12A parts and using two PFCs to control it is taking the path of least resistance by using readily available components. If it works, why reinvent the wheel?
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