noahmrogers

Tell me its stupid or I'm missing something, but...

I am building a tube chassis car, plan is to have LSX w/ Porsche transaxle, but I don't really need 430hp and I would prefer losing a few hundred pounds.
So, I had this crazy idea about a 300whp single rotor.

Reason I'm asking on this subforum:
Looks like 91/93oct 13b PP NO-aux-inj. guys are hitting 650ish, so 300 out of 1 should work, right?
Alternatively the 91/93 PP N/A (naturally aspirated) guys hit 300whp.. which makes sense, being that 14.7psi is ambient and so running 14.7ish is 2x ambient and should double-ish power.

Anyone have a few recommendations for shops that might build and ship me a simple PP 13b? Looks like there are a few in the state and au/nz.
Billet looks cool, better than modifying?

Again, thinking about single rotor, single turbo 300w/91/15/pp/non-aux. Or I could run water I guess, that was a thing in '08, still?
Again, alternative is an LSX and I'd rather do something interesting. Best engine-building shops?

diabolical1

iTrader: (3)

welcome to the board, Noah.

single rotor:

the only company that comes readily to mind right now is Atkins

https://www.atkinsrotary.com/store/o...or-engine.html

that said, if you're serious about it, i'm sure other companies might be able to get it done for you. i know Goopy has done some pretty neat things (which i have seen with my own eyes), so he would be an option i would recommend looking into, but i'm sure any of the really hardcore rotary shops that do their own machining between here and Australia could probably manage the task.

13B PP:

you can take your pick of the trusted shops that could get one build for you. there are quite a few of them in your state, too.

Racing Beat, Mazdatrix, Pineapple Racing, Defined Autoworks, Chips Motorsports, etc.

the list is in no particular order.

Billet is cool, but with an arrhythmia-stimulating cost and i don't see why you would need to go that route with what it sounds like you plan to do.

lastphaseofthis

iTrader: (8)

well they(billet builders) hit 1600 in a 2 rotor drag car compound turbo, if you are doing drag as well, you could go for more then 300 if you are pp with turbo. 430 sounds sound about right. lsx power, half the weight.

noahmrogers

sounds like not 91 octane
I'd like to chat with them if you have a shop recommendation


Thank you and I did see Atkins, but I assumed because its equivalent of a 600+ 2-rotor that it would need to be built from scratch anyways.

I saw some discussion on multi-piece e-shafts, so I assumed there were a number of builders that I could talk to about a PP housing and billet ends with a 1/2 shaft, seems pretty straightforward as you imply.
The LSX world is full of a million crate engine options, whereas in the rotary world it seems like everything is in pieces/parts.
I'll start calling shops.

New questions:
Is there any consensus on ECU setup?
In typical engines, RPM is limited by valve mass, what is the reason rotaries can't top out at limit of the flame-front, the speed the fuel burns (20k rpm?). What's the weak point?

diabolical1

iTrader: (3)

you basically have "crate engine" options with rotaries, too. it's just that you're probably not going to see them in a Summit catalog. you can get assembled engines from any of the shops i mentioned earlier, and there are others,

management will be completely up to you. there are many good options out there.

as for RPM limits, weight (rotors) and shaft flex are the issues you will begin to encounter once you are able to move beyond certain levels.

noahmrogers

I take back my question about max RPM.
Some simple physics suggests the flame speed limit is something like 9,000 rpm.

Beyond that torque drops off, but its getting into flamethrower territory.
Most piston engines will have something like 8cm of stroke.
The rotary has something like 15cm (divide by 1.5 for eccentric shaft spinning that many rotations in one power+exhaust).
8cm*2strokes*6000rpm piston = 15cm/1.5e:r ratio*9000 rotary.

Lots of 1 rotor research leads me to believe it would be pretty easy, basically bolts, balancing, and shaft...
... but I think I'll stick with a classic 13b and low boost for now.
I like megasquirt, I'l'l look into it.

RXBeetle

Have you been following the Team Boosted 356 build? Turbo 1 rotor Porsche 356 replica.

noahmrogers

I definitely saw it, looks cool.

If they can hit 300 on 91octane... that would be a big deal.

mikey D

noahmrogers

MODS!

But seriously, let's compare:

LSX:
450lbs
430hp
$9000 new.

13b
180lb long block / 75lb turbo kit / 45lbs acc.
~300lbs
430hp
$??? built

This assumes clutch, flywheel, and transmission mass are the same.
They get heavier with torque, not power, but the number is close enough.

So is 150lbs worth the pain?
My thinking is in my case yes.

My car is 1500lbs so 150lbs is 10%.
That would be like losing 300lbs from an FD.
Or having 45 more hp.

This doesn't include the fact that we've been discussing 1 rotor, which is 100lbs less.
So lets compare the 2 cars.

1400lbs single rotor vs 1650lbs erod
rotary is better because:
15% mass delta
10% rollover threshold improvement
add e85/water/meth injection and turn up the boost to exceed LSX hp.
more compact, fewer parts, cheaper rebuilds for track.

Would you pay $10k to lose 15% weight and get 10% lower center of gravity (actually rollover %)?
I think most people that do coilovers and control arms are paying more for less benefit.

A K24 is nearly as heavy as an LSX, as expensive if built, and its tall, I don't think it would fit.
An EJ is heavy and not super reliable.
My thinking initially was to go with the Hayabusa GSXR1300 engine... which is more comparable to rotary weight/power/reliability.

At the end of the day 150lbs matters a lot more in a 1500lb car.
If I had a 3000lb car, I might agree LSX mass increase doesn't matter much.

But also if we're talking built engines, the rotary has 1000+hp potential, so that kind of negates all arguments, and you're having a discussion about emissions at which point I suggest you go cummins and I'll go jet turbine to extrapolate on the distinction. My goal is power/weight, not truck.

mikey D

I dont totally agree with your weight, hp and cost assumptions other than the k series being tall and overly expensive.

I still run an na 13b. Its small, light and fun.
ill be curious to see the route you choose.

diabolical1

iTrader: (3)

in all fairness, you brought the 13B into this. my entire second post (#5) was based on this part of your original post:
... because i thought you were still trying to decide. i don't see how most of what i said applies to the 1 rotor engines (what would they be called anyway? 6B? 7B?)

shift flex would not apply to it. i'm guessing your maximum RPM will totally depend on rotor weight, balance, porting and airflow.

the guys in that video did 4 bridges in addition to the turbo - all on just one rotor!, so i'm dying to see what kind of power they actually make with it. i didn't agree with their apex seal choice, but it wasn't my decision to make, so that's neither here nor there. i respect the engine either way.

_________________________

RXBeetle ~

long time. glad to see you're still around. thanks for posting that video. those guys are now one of my new Youtube obsessions.

noahmrogers

7B officially.
If they can make 300+ with a non-pp then I will almost certainly go 7B w/ PP, that's plenty.

PAC, for example, on their billet blocks, claims 40+psi, which would be 400hp in a 7B, extrapolated from the 20b and 13bpp numbers divided by 3 and 2.
Which is about right for a 1.2L piston equivalent with 45psi or ~4 atmospheres (oem air is 14.7 at sea level, +45 is 3 more); 1.2L then at 400hp is just 83hp per liter x4.
Although, I would say the conversion is 1.5x not 2x rotary:piston displacement, there is 1 combustion stroke per 1.5 revolutions of the e-shaft, compared to 1 per 2 in otto cycle.

RPM is absolutely dependent on flame speed, which is about 0.5m/s meters per second in a combustion engine. You can do the algebra as I did and find that over 9000rpm you'll be shooting a lot of unburned fuel out, which explains torque drop off. That is regardless of porting and balancing,.. which are important for efficiency and torque, and mechanical strength, but even a low-efficiency and low-torque, mechanically-weak engine could have very high RPM potential with an increase in flame speed or is otherwise limited by that.
F1 engines have short strokes to achieve high RPM, their flame speed is not higher.

My research suggests the following:
0. rotary engines are reliable but very sensitive due to seal failure
1. seal failure caused by detonation which is catastrophic in rotary engines, the primary cause is OVERHEATING (various).
2. the engines are mechanically weak just like a piston engine running at 3-4x design load, especially when overheated, so pins/dowels and other bracing is often incorporated to builds... but this not specifically related to detonation/heat failure.
3. overheating can be avoided with the following:
a. aux injection (as a form of charge cooling)
b. upgraded cooling components
c. rich mix
d. retarded timing
e. decrease pressure harmonics intake/exhaust
f. phenolic spacers
g. larger than typical turbos which compromise throttle response but are more efficient
h. ironically, running at extreme RPM so there is unburnt fuel and detonation has less time to build pressure
i. i suspect oil injection and 2 stroke mixes are acting as cooling, not wear related
j. oil cooling
k. direct injection
4. considering everything in this list, a rotary should be as seemingly unlimited as piston engines are, but with 3:2 power volume density and 3:1 power mass density.
5. crazy ideas would be direct injection of water ATDC, fixing potentially hot plug tips, or otherwise better cooling of the combustion chamber, which is the primary issue.

Alright, going to call around for parts on the 7B and work up some numbers.

KansasCityREPU

iTrader: (9)

Since owning a 2017 Colorado with a V6 @308HP, if I ever do a non-rotary swap this would be my choice. Maybe even put a turbo or two on it. The CTS twin turbo version (LF4) is 464 hp.

Type: 3.6L DOHC V-6 with Direct Injection
Bore & Stroke (in / mm): 3.7 x 3.37 / 94 x 85.6
Block Material: Cast aluminum
Cylinder Head Material: Cast aluminum
Valvetrain: Dual-overhead camshafts with four valves per cylinder; continuously variable valve timing
Fuel Delivery: High-pressure direct fuel injection with electronic throttle control
Horsepower (hp / kW @ rpm): 308 / 230 @ 6800 (SAE certified)
Torque (lb.-ft. / Nm @ rpm): 275 / 373 @ 4000 (SAE certified)

noahmrogers

LOL

We're talking 1 rotor and hayabusa, the k24 being too heavy, and you suggest this.
A 400 lb engine that is huge and less powerful than basically everything else.

Ford 1.5L Turbo (2020 fiesta?) might be a good choice.

mikey D

I'm thinking from your responses you might be in the wrong forum.

noahmrogers

I originally posted in the single turbo forum asking what kind of top hp numbers people were seeing with pump gas and if there were any single turbo engine builders... then the thread was moved.