Just another harebrained idea

[Gollum]

Without getting into a rant, let me just say that I, along with most race bodies, consider Mazda's 13b to be a 2.6 liter. Keep that in the back of your head for later.

 

 

Okay, I've had a million crazy ideas and I've been bold enough to share a few on this forum. A few of my crazy ideas have actually lead to something, while most fall by the wayside, but if I never share then I never even give them a chance to flourish. So here's the latest that's been mulling around my head.

 

So we know engines can be coupled together in various ways with success. We know the Z engine bay is quite long. People have talked about putting two V6's in to make a wicked V12 combo. Well, here's a 1-up ya idea. Why not try to squeeze THREE 13b rotary engines into a S30 chassis? Easy 200 whp each that will still drive nice on the street, which means easily reach 600+hp total, with 7.8 liters, and should be able to make around 500 ft lbs to the wheels.

 

In order to make them fit the coupling would have to be very tightly spaced. Much tighter than these two rotary engines in this thread

http://forums.hybridz.org/index.php/topic/58126-multiple-engines

 

I'm picturing something more like that way those two flatheads are joined in that thread, but kept as short as possible. If you can get the engines nearly butting plate to plate I think all that goodness would fit.

 

Considering you'd only need one alternator, one larger starter, one flywheel, one clutch, and so forth that the total package weight might be as low as a comparable displacement big block, but the weight would of course be quite low slung.

 

I think the best part of this idea, is that you can get 13b cores for so cheap. If you can do the machine work yourself on a lathe & mill (even if it's by hand, not fancy CNC machines) then the total cost could actually be lower than what it takes to build a comparable BBC, which has kind of always been the standard to many people for affordable big power numbers. Another crazy aspect is that you can easily enough get a 13b to 250+whp if you don't mind it idling at 1500+rpm. Adding it up theres quite a lot of power potential, and all with a mostly flat torque curve. You can also run carbs, or EFI and get good results.

 

 

So there you go. Might be a bit crazy for most people, but I know if I had the means I'd have some motors in my garage to play around with.

[rayaapp2]

With all the effort, why not just cnc a billet crank and stack the rotors in one setup. Use all stock parts minus the crank. The 20B Cosmo engine does that with 3 rotors. Provided your willing to put the effort into the redesign and have a friend with the tool access?

4 rotor motors have been discussed on other forums, and Ive actually seen a few in the works and one completed on one of the rx7 FD/FC forums.

Personally I hate the chrome sealing surfaces. Though I can offer no improvements for that design other than a higher nickel content or something. Most folks prefer to focus on the seal issues though.

I actually have blueprints for an American version of the rotary engine(predating the Wankle design by several decades) that Ive been dying to build, but dont have access to materials or tools to do so at this time.

 

Rotary performance mods are expensive though. Like a real bridge port... to have those done correctly it will cost $$$. Its much like grinding a cam. Anyway a large turbo instead of extra 6 rotors would be nice as well.

 

4 rotor engines

Here's you 6 rotors

Mazda had a hard enough time keeping 2 rotors together, but I suspect that was partially due to emissions mandates forced upon them. If you run them dirty as they like to be ran they might hold up a bit better. My speculation of course, but backed by the 60K mile full overhaul recommended intervals on most of the early Rotary engines. But boy do I love the idea of being able to stack extra cylinders on for added displacement if 2 werent enough... Its not like you can cast a couple of extra cylinders onto your existing inline and make it a V12... Well at least most folks wouldnt dream of that.

 

Its just to bad the stock eccentric shafts arent already setup to be stacked with coupling system to stack almost as many as you wanted within reason in a single case.

 

Ray A.

Edited September 15, 2011 by rayaapp2

[Gollum]

That's exactly the issue, how many of us actually have access to affordable CNC time? I sure don't. It doesn't even matter if I could engineer it correctly, the machine costs are just plain prohibitive.

 

A crank output to snout flange can be made with relatively simple methods using widely available tools, which is why stacking them externally seems like a neat idea.

 

Also, most of the people needing to rebuild their rotary engines every 60k are usually either force induced, running monster HP, or their engine is running dangerously lean from time to time for rotary standards. I've seen plenty of people with mild NA rotary engines make it past 200k before needing new seals. Rotary seals don't like force induction, plain and simple. They make lots of power, but the seals just don't last.

 

I'm in agreement though that emission standards have surely dictated some things for Mazda. Mazda designed high compression versions that could make a lot more power, but it would have never passed emission standards even in it's day, hence why the cavity design on the rotor has changed nearly every generation of the motor.

[rayaapp2]

Oh no, I was not stating that early rotary engines need overhauled at 60K, I was stating that that is the recommended service overhaul interval on the early ones...

 

Though I cannot remember where I picked that bit of info up at, at this point. I seem to remember it was from a legit source and it was directed at first gen rx-7 12A.

 

You could always ask Lumberjack aka Josh in Fremont about CNC. Im sure if you had the program ready that would seriously cut down on expenses. If you made them a deal and it worked out his workplace is always open to picking up things like this. They are seriously looking at doing a small project for me. The RB cylinder head oil drain with an AN fitting that isnt available anywhere. As soon as I can get a cylinder head up to them they are looking at going into production on them.

 

Anyway, it doesnt hurt to ask.

 

If you get a chance check out patent 1,224,642

I have the original copies of everything for this patent. Patent was applied for in 1914 and approved 5/1917. My paperwork is dated 1913. Someday I will assemble this family heirloom. But seriously harebrained ideas...Im all in.

[Gollum]

If you get a chance check out patent 1,224,642

 

You should see what I've been building in solidworks.

[HowlerMonkey]

7 miles per gallon best case scenario with 3x13b.

 

If they are naturally aspirated and bridgeported, then mileage goes way down from there.

 

I moved to nissans after running rotaries from about 1981 until 1990 when I left Z shop of Miami for Datsun Dynamics.

 

They are just too loud in performance trim unless you turbocharge them.....which opens up more that needs to be addressed.

 

You might get 600hp from a well done turbo II engine.

Edited September 28, 2011 by HowlerMonkey

[Gollum]

7 miles per gallon best case scenario with 3x13b.

 

I'm not going to ask you prove this, I just want to know your thinking behind it. Are you assuming MPG goes down squarely to displacement of the rotary? Because that's inherently not true with regular applications. The 6 liter LS2 can manage 30mpg highway in a S30 chassis when paired with the .5 OD T56 and a tame foot. If GM made a 3 liter V4 version I highly doubt it would reach even 25% better fuel efficiency.

 

MPG is a complex equation that I'd suggest might be even harder to perfectly predict than horsepower. The only thing that makes people shrug it off is the small window of figures. But the nuances are immense. Every factor there is to making power effects MPG, and there are other things that DON'T effect HP that will certainly effect MPG.

 

I'm not saying a 3x13b won't have pitiful MPG. I'm sure it will. I'm just suggesting that if 1x13b gets 21mpg then that doesn't mean three will use three times the fuel.

 

Now, under FULL THROTTLE I'm sure that might very well be darn near the case, minus aero and drivetrain factors. But you're not driving WOT 95% of the time you're in a car, unless it's a dedicated track car.

 

 

[rayaapp2]

I'm not going to ask you prove this, I just want to know your thinking behind it. Are you assuming MPG goes down squarely to displacement of the rotary? Because that's inherently not true with regular applications. The 6 liter LS2 can manage 30mpg highway in a S30 chassis when paired with the .5 OD T56 and a tame foot. If GM made a 3 liter V4 version I highly doubt it would reach even 25% better fuel efficiency.

 

MPG is a complex equation that I'd suggest might be even harder to perfectly predict than horsepower. The only thing that makes people shrug it off is the small window of figures. But the nuances are immense. Every factor there is to making power effects MPG, and there are other things that DON'T effect HP that will certainly effect MPG.

 

I'm not saying a 3x13b won't have pitiful MPG. I'm sure it will. I'm just suggesting that if 1x13b gets 21mpg then that doesn't mean three will use three times the fuel.

 

Now, under FULL THROTTLE I'm sure that might very well be darn near the case, minus aero and drivetrain factors. But you're not driving WOT 95% of the time you're in a car, unless it's a dedicated track car.

 

Its weakness and its strength is lack of torque. It also runs dirty. Torque is a major factor in MPG. Then add into the equation the port event(no valves) and what you will have to do to it to get it to make horsepower will be the opposite of what is needed for low end torque. Rotary engines are a different animal. The only thing in common with a conventional reciprocating Otto cycle engine is the 'Otto Cycle' itself(4 stroke). I do not grasp it fully either, but Ive been playing with them for several years. Just dont tell my family I touched anything Mazda(They WILL dis-own me). I had an 87 turbo II for a while that was Barbie pink and I nick named it Zoom Zoom Boom.

 

So if one engine gets 20MPG. You still got to feed the other 2 with extra mass(and still short on torque) to turn to couple them together. EGR might be a significant help with MPG during cruise so the mixture can be leaned out.

[Gollum]

Its weakness and its strength is lack of torque. It also runs dirty. Torque is a major factor in MPG. Then add into the equation the port event(no valves) and what you will have to do to it to get it to make horsepower will be the opposite of what is needed for low end torque. Rotary engines are a different animal. The only thing in common with a conventional reciprocating Otto cycle engine is the 'Otto Cycle' itself(4 stroke). I do not grasp it fully either, but Ive been playing with them for several years. Just dont tell my family I touched anything Mazda(They WILL dis-own me). I had an 87 turbo II for a while that was Barbie pink and I nick named it Zoom Zoom Boom.

 

So if one engine gets 20MPG. You still got to feed the other 2 with extra mass(and still short on torque) to turn to couple them together. EGR might be a significant help with MPG during cruise so the mixture can be leaned out.

 

All totally makes sense. I never expected to get 30mpg, so please don't read it that way. I was simply asking for more details on the though process.

 

If I had to make a completely uneducated guess I'd estimate at average combined tanks ranging from 14-20mpg. 7 seems retartedly low, but then again it will be a VERY different setup that anyone doing would probably care less about the MPG attained.

[rayaapp2]

I would honestly believe it to be lower than 14mpg.

If you had 3 bone stock in good condition 13B's tied together, Id guess 14mpg would be on the high side no averages taken.

 

they are rated at a combined 17mpg 15city/21hwy in a late 80's rx7

That is if you run 3 EFI 13B setups and you dont convert them all to carbs.

Throw MPG out the window on these.

 

Still for the cost of 3 13B engines(ones that will not require major work) I think you could get your hands on a 20B 3 rotor, get slightly better mileage for any kind of actual street driving and reduce the complexity of the whole thing. Id be stoked to have a Cosmo engine in an early 240z. 3 rotors and a big turbo and your keeping the weight way down like this. Id venture a guess that the 20B weighs in close to the stock L24 maybe a little less. The 13B is very light. Without the exhaust manifold or alternator 1 strong guy can pick the 13B up by himself.

[ZR8ED]

I've seen a hot rod where they bolted/welded two big block v8's to make a v16. Ever see a tractor pull? 5 and 6 5000hp big blocks all working together...Ok I'm getting a bit silly here, but hey why not?

[Gollum]

Where do you think I first got the idea of multi-engined cars? When my parents got satellite TV back when I was 12 years old I watched almost nothing but car shows all summer long. As much as I hated nascar, circle track, sprint car, tractor pulling, etc it all ended up having an effect on me. It was all racing and was about 1,000X better than anything else I could find on TV

[HowlerMonkey]

 

 

A man with his priorities in order.

 

 

Car and driver did it in 1985

 

Edited October 1, 2011 by HowlerMonkey